burning question - HSI? [Archive]

Michael Carter

07-19-2008, 08:45 AM

I have Mike's book and it's fantastic, but the fact that nobody seems to have done it yet speaks to the complexity. Maybe I'll be the first one someday.

Or to the antiquity. Even Cessna is going to glass. After a six month search for one myself, I resigned myself to using a monitor to display flight instruments.

I don't think FS gauge manufacturers really want to offer something that no one but a handful of hobbyists will buy. And the less they sell the higher the pricetag.

Unless you are wealthy, it's going to be hard to come by one for using in FS. Especially the correct model for the aircraft you are modeling. I wouldn't buy a replica of a King HSI to install in a 727 and I also wouldn't install a Collins 110 in a 172.

cscotthendry

07-19-2008, 05:49 PM

Michael Carter

07-19-2008, 11:23 PM

More power to you. I hope you succeed.

If I could handle the frustration factor of such an undertaking I'd try it myself.

AndyT

07-20-2008, 12:16 AM

Scott, Could you post some pix of the face of the 525a? I'm wondering about something now....

cscotthendry

07-20-2008, 12:20 AM

Andy:

I could post pics, but then I'd have to kill you...

Actually, It's the HSI from FS9/FSX on the GA planes. I haven't done anything concrete as far as the internal design goes yet, just some ideas in my head as to the mechanicals.

AndyT

07-20-2008, 03:52 AM

Thats the one I was looking at. I came up with some mechanicals for all of it even the CDI. That part was tough. And I have a way to make it work also. It would plug into two slots on the Simkits CCU.

EDIT: You will need 7 servos to run it and two of them require contact brushes.

This would be a rather large unit though...
Sure you don't want to go with glass?

cscotthendry

07-20-2008, 02:31 PM

Andy:

I would really like to see your ideas on this. I think the course card could be run from a stepper motor with some differential gearing, but that's as much as I've thought about. As far as the servos, using the micro sized units would help keep the size down. PM me and let's talk more about this.

ruprecht

07-20-2008, 07:18 PM

I would love to see your ideas too Andy. I had designed it in my head and came up with the following (based on the F-16 HSI rather than the civvy one mentioned earlier in this thread, reposted from ViperPits):

- The project would need four geared steppers: One for the inner CRS/CDI plate, one for the compass card, one for the RMI needle and a fourth for the heading bug. Right there you need either four concentric axes or ring gears. Complex when constructing from hobbyist materials!
- The inner plate also needs a servo mounted on it for the CDI needle. This presents a further problem for power and signal wires that must come from the control circuitry through the hollow centre axis to the servo, in such a way that repeated rotation of the CRS needle will not twist up and wreck the wiring. You would have to look at something like a 4-signal brush contact (such as a stereo+mic miniplug). This is not counting the off flag and TO/FROM indicators on the CRS/CDI plate which would require either separate control wires (again wired through the hollow axis, needing yet more brush contacts) or you'd need to build a microprocessor-controlled circuit on the back of the CRS/CDI plate that could handle the servo and all 3 flags with only 4 input wires.

The remainder is fairly well understood with 7-segment LEDs for the miles and course indicators, solenoids for the outer off flag, rotary encoders for the HDG and CRS knobs and optical interrupters etc.

When you say 7 servos would be needed, do you think it could be built with servos? Wouldn't you need steppers for continuous rotation of the cards?

cscotthendry

07-20-2008, 07:49 PM

Guys:
Get busy scribbling. Put your ideas on paper and let me see them. I have a lathe and milling machine and the tools to cut gears as needed. Also I have a copy of the faceplate (outer facia) of the artificial horizon that could be modified (slightly) to make them look like the real thing. I'd be prepared to have a go at making a few of these if we can come up with a workable design. But lets do this offline of the forum. Go to my website, get my email address and PM me directly and let's have a go at it.

Michael Carter

07-20-2008, 07:58 PM

Please post any updates or breakthroughs on this project.

I'm very interested in following your progress.

ruprecht

07-20-2008, 08:05 PM

I will get designing. I respectfully disagree with moving it to PM, isn't the whole point to let others get the benefit of our thoughts? In the end, this is a thread specific to an HSI, so why not discuss here?

However, understand that a forum is not necessarily the best way to collaborate; if I get some time later I might throw up a Wiki and a new project on my JIRA issue tracker which you can all access, would that work for everyone?

*EDIT* Wiki page is here: http://vaaf.net/wiki2/index.php5?title=HSI this is on the VAAF forum/wiki that I co-moderate.

Scott, I've come across your site before, very impressive mate! The design in my head needs ring gears, so I had hoped you and your gear cutters would throw into this discussion! :)

cscotthendry

07-21-2008, 12:13 AM

Ruprecht:
I think the forums are a great place to get advice and solve problems, but not so great for brainstorming and just general comms.

If by ring gears you mean rings with teeth on the inside as well as the outside of the ring, then I can't do that. I can only cut teeth on the outside of things. To cut teeth on the insides requires something like a broaching machine. But if you mean a ring with smooth inside, yep, can do that!

BTW, I've bookmarked the wiki. I've never wiki'ed before so it'll be a bit of a learning curve for me. Bear with me.

Michael Carter

07-21-2008, 01:20 AM

For the inside of a ring you can use a capstan roller like those used on tape machines. Hard rubber and lasts fairly long. I've only replaced one on the tape machines I have in nearly ten+ years.

You can mount a capstan rollor on the drive end of a servo or stepper motor.

cscotthendry

07-21-2008, 02:51 AM

Hey, that's a good idea!

AndyT

07-21-2008, 03:04 AM

Ok, I've never used Google Sketchup before so I'm trying to put my idea together in 3D. The scribbles I have on paper would only confuse you.

What is our time line on this project?

cscotthendry

07-21-2008, 03:07 AM

Err Timeline? This is a hobby for me so.. whenever. BTW I'm retired so anytime's a good time for me and every day is Saturday:D

AndyT

07-21-2008, 03:09 AM

Good answer! (ding ding ding!) LOL

Michael Carter

07-21-2008, 03:10 AM

Hence the palmtrees and the tranquil sunset no doubt in the avitar image. ;-)

cscotthendry

07-21-2008, 03:15 AM

Now you're getting the idea

Michael Carter

07-21-2008, 03:18 AM

Still have 19 years to go. Probably 24 at the rate the economy is going. :roll:

cscotthendry

07-21-2008, 03:20 AM

19 Years, yow! You get less than that for robbing banks!!! LOL!

Michael Carter

07-21-2008, 03:39 AM

25 to life in the US if armed. Considered armed robbery. If old folks (seniors) or anyone under 18 assaulted during the attempt, it's aggravated armed robbery. Life, maybe with or without parole. If a death occurs intentionally, Man I, unintentionally, Man II, but that's up to the Prosecutor.

AndyT

07-21-2008, 04:38 AM

Sketchup is giving me grief.
How do I get it to draw on the surface of an object?

AndyT

07-21-2008, 05:12 AM

Ok, figured it out. When you build an object you have to build the outside of it and then draw, then make shape adjustments. They could've said something in the lessons.... :D

ruprecht

07-21-2008, 05:58 AM

racing you, but I'm using 3dsmax :)

ruprecht

07-21-2008, 08:24 AM

This is what I meant by the ring gears, and how they would work to mount the heading bug and RMI flags while still leaving an empty core for a swinging CDI servo assembly.

http://imagehost.radsy.com/unipit/hsi_ringgears01.jpg

cscotthendry

07-21-2008, 02:52 PM

Ruprecht:
Wow, that's looking pretty cool!:cool:
BTW, Here's something to consider. The course card/CDI and the heading bug normally rotate with the compass card except when being moved by the knobs. Then they move relative to the compass card. I would bet London to a brick that in the real gauge, these pointers are diven by some type of differential gearing rather than being driven by independant motors. So one motor drives all three at once and the differential gearing just sets the relative positions of the course pointer and heading bug.

AndyT

07-21-2008, 04:33 PM

Obviously you are way better at this 3D thing than I am.
Very nice idea.

Scott, I'm not sure about that, but you could be right.

ruprecht

07-21-2008, 07:24 PM

pointers are diven by some type of differential gearing rather than being driven by independant motors. So one motor drives all three at once and the differential gearing just sets the relative positions of the course pointer and heading bug.

That may well be the case mate, but we'll need a smarter head than mine to figure out how to build that! I was right with you up until the word "differential" :D

cscotthendry

07-22-2008, 12:17 AM

I've been thinking about the gearing. It'll come, it just needs some cooking time.

Westozy

07-22-2008, 01:56 AM

Ruprecht:

I intend building an HSI for my sim when the time comes. I'm planning to build the BK KI525(a?). I have a couple of plastic copies of the face for the artificial horizon in this series and plan to modify that for the 525 face. I need to work out the mechanics of it yet. If you want to PM me maybe we could collaborate on the design.

Err... Ruprecht, I see you're in sunny Brissy. Where are you? I'm on Russell Island.

Hi Scott,

My friends Joe and Nerina have bought a property on Russell Island and they own "Russell Island scoota cars". They are Perth based but will be living there after Christmas.

Gwyn

cscotthendry

07-22-2008, 02:54 AM

Gwyn

I don't know them personally, but I know of them. Some friends of mine who own the island restaraunt know them. Six degrees of separation eh?

Westozy

07-22-2008, 03:44 AM

Gwyn

I don't know them personally, but I know of them. Some friends of mine who own the island restaraunt know them. Six degrees of separation eh?

Rgr that, Nerina has been singing at the restaurant, she is currently my partner in music! I will no doubt be visiting Russell Island at some stage in the future.
I see you are a machinist capable of producing gears, I am also a machinist but only have a lathe. I have been trying to locate stock plastic gears to suit my Airbus TQs without success, would you be interested in a job producing a few for me? I want to use gears to drive the pots instead of the current drive system I am using. I'm also thinking of changing the trim indicator drive chain. Cash or trade services, no probs! I'll PM my phone # for a yak if that's ok.

Looking forward to your reply,

Regards,

Gwyn

ruprecht

07-22-2008, 03:57 AM

I've bought gears from Serv-o-link in the US as recommended by Mike Powell's book. It's obviously not the cheapest way to get gears, but they come in a good range of sizes if plastic will work for your application.
Do any aussies know what tooth pitch/PA the Jaycar gears are?

ruprecht

07-22-2008, 06:12 AM

A little more design work this evening:

http://mycockpit.org/forums/images/HSI/hsi02.jpg

Might do some more after dinner. That is based on the dimensions of a servo I had to hand, which is unbranded, though it is roughly the same size as the Futaba S3107 micro. The CDI needle sticks out about 6mm to give full travel; to reduce parallax you could mount the servo farther back from the CDI plate. It's too late for the maths right now :)

When the model's a bit more advanced, I'll publish an animation showing how it all works.

AndyT

07-22-2008, 06:27 AM

Thats nice. The problem is the servo must be further back so the From/To indicator can fit in there. It could be a couple of LEDs with a servo switch somewhere else in the housing. You will need your first set of brushes for this. To help you visualize this, add the wires to each servo, (or LED).

Also, the servo you are showing has to be attached or at least move with the inner CDI plate that will have the arrowhead on it. That whole assembly needs to be able to spin 360. This is where your second set of brushes is going to come in.

And since you are so good with the 3D modelling, how about if I forget about making mine and just comment on yours? (It's not as easy as it looks ya know... :roll: )

Why 4 outside gears for each ring?

ruprecht

07-22-2008, 06:35 AM

the servo must be further back so the From/To indicator can fit in there.

Yup that's not hard to do, the design is in my head. Or you could move the TO/FROM indicator slightly outwards from their usual position - I will cut holes in the CDI plate later to show you what I mean.

It could be a couple of LEDs

Great idea, I was thinking a solenoid, but LEDs are much simpler.

with a servo switch somewhere else in the housing. You will need your first set of brushes for this. To help you visualize this, add the wires to each servo, (or LED). Also, the servo you are showing has to be attached or at least move with the inner CDI plate that will have the arrowhead on it. That whole assembly needs to be able to spin 360. This is where your second set of brushes is going to come in.

Spot on - my thought is to actually have microcontroller-driven circuit mounted on the back of the servo/CDI assembly, so only 5 wires are needed through a brush contact arm, and it can drive the servo, TO/FROM indicator and off flag all from one device.

Why 4 outside gears for each ring?

Just supports for the main gear assemblies. Probably overkill, but with the close tolerances on the HDG BUG and RMI flags, you wouldn't want too much wobble. They should be able to rotate independently of the two other support gears on the same axis.

AndyT

07-22-2008, 06:45 AM

Sounds good.

The TO/FROM can both be on one side of the CDI needle slot. The problem here is that as you turn the plane and the CDI plate turns, so do the TO/FROM arrows. So either we create some logic that flips them on the turns or we need a different way to mount them so they don't spin.

Put a small tab between the LEDs to prevent light bleed-thru.

The flags are hidden under the outer ring which is where you have the 4 supports at. A simple shaft to a flipper/solenoid down in the housing could handle them.

AndyT

07-22-2008, 06:50 AM

ruprecht

07-22-2008, 06:51 AM

Ah - now I see the problem. You're picturing a King-style TO/FROM e.g.http://www.esmofly.net/HSI-esm.jpg whereas I'm picturing the F-16 style e.g. http://home.priorityonesystems.com/hsi/HSI_layout.jpg :)

Should be straightforward enough to mod the design for either.

ruprecht

07-22-2008, 06:53 AM

Also two of the support gears can be used to connect the front panel knobs to. Or would we want them to go to a pot somewhere to feedback the position info? If we build position sensors into the rings, then we can connect them directly.

The approach Mike Powell used in his book is to have the knobs as rotary encoders, which drive the steppers to position to ring, rather than have the knobs geared directly to the ring. I'm gunna go with what I know for now! :)

AndyT

07-22-2008, 06:56 AM

Ok, I see what you mean. Yes, should be pretty easy to handle either.
This is beginning to sound like a combo of the two you have pictured above.

The encoders are perfect for the knobs.

ruprecht

07-22-2008, 07:12 AM

Can anybody figure out the gear trains? The big gears have 120 teeth, and it would be nice to gear them to commonly available 24- or 48-steps/rev stepping motors so that we can move the rings in 1/2 degree or maybe 1/4 degree steps?

AndyT

07-22-2008, 07:42 AM

We need a position sensor on each main gear so that when it powers up, it can calibrate itself. All we have to do is have either a small tab that breaks an optical sensor or trips a micro switch when it hits the 360 mark. Then the software can do the math on its own. Once its done that, it can set itself to the whiskey compass.

cscotthendry

07-22-2008, 04:05 PM

Ooohh...Bit of a stretch calling me a machinist ;) I have the machines, but the talent is pretty raw. Nonetheless, I think we could probably work something out in trade services. Don't want to do cash as that implies I'm open for biz. I'll phone tomorrow. Today's full on with the boat.

cscotthendry

07-22-2008, 04:41 PM

Ruprecht:
Love your drawings mate. Here's some practical considerations. The CDI needle needs to be elastically attached to the servo. Servos can rotate through about 180 degrees and from experience, when the sim is first powered up, there's always the chance that a servo will run feral. If the pointer is rigidly mounted to the servo, you'll get some damage at worst or some mis-alignment at best.

I like the idea of using LEDs for the to/from flag. Simple and elegant.

Gear trains are straightforward. At 48TPI, just divide the number of teeth by 48 and that is the working diameter of the gear. Halve that and you have the working radius. Add the working radius of the two gears that must mesh and you have the centre distances. Your gears look great in the 3DS, but you don't need to be that fancy. Just draw circles at the appropriate working radius.

The three gears you have in the drawing are going to be difficult to "home". As you've discussed, we'll need some kind of sensors on the gears. If we use opto-interrupters, there will need to be a LOT more space between the gears. Another option is to place small magnets on the gears and position reed switches around the periphery of the gears.

Also, the gears/compass plate/CDI card/Heading bug carrier need to be supported somehow.

I know all this sounds like criticism and it is, but constructive criticism. We'll get there with this.

BTW, I have a copy of the actual facia of one of the BK gauges and it's a bit frightening how small this unit is and how much stuff has to go inside.

ruprecht

07-22-2008, 08:01 PM

The CDI needle needs to be elastically attached to the servo.

Good thought, noted.

Gear trains are straightforward.

I've got it sorted in terms of fitting the gears together, I meant more the gear ratios. For instance, it would be nice to be able to move the CDI assembly in half-degree steps. If I have a 12-tooth gear on the pinion of a 48 steps/rev stepper, and mate that directly to a 48-tooth gear on the CDI assembly shaft, 48 steps will give me 90 degrees of shaft rotation, or 1.875 deg/step. So what different and/or intermediate gears are needed for 0.5 deg/step?

The three gears you have in the drawing are going to be difficult to "home".

I've got something in my head about where to put optointerrupters, will get that into the design tonight.

Also, the gears/compass plate/CDI card/Heading bug carrier need to be supported somehow.

Also in my head ;)

No worries at all with constructive criticism, this is a collaborative process.

AndyT

07-22-2008, 09:50 PM

We need to know the RPM and the smallest step the servo is capable of to determine the correct gear ratios.

ruprecht

07-22-2008, 10:19 PM

Given that all 4 major axes (compass card, heading bug, RMI needle, CDI assembly) need to rotate continuously, I don't think servos are viable. Servos have only a limited range of movement, we really need to be looking at stepping motors. Servos are ideal for the CDI needle and the glideslope indicator, with only limited (~ 90 degree) range of movement required.

Even the highest performance aircraft can only turn at about 20 deg/sec. I'm not sure how fast you can get common 48 steps/rev steppers to turn, but at 1/4 degree steps, 20 deg/sec equates to 80 steps/sec or 80Hz. Is that possible? Given that Mike Powell's book (henceforth BSAI for simplicity!) talks about accelerating through 250Hz to 1KHz (pp 192), 80Hz seems like it should work easily.

AndyT

07-22-2008, 10:49 PM

Most servos have a small tab that keeps them from 360 movement. Break it off and there you go. But I agree that steppers are likely a better choice.

And as small as this unit is likely to be, I think 1 deg steps will be more than enough resolution.

cscotthendry

07-23-2008, 03:07 AM

Whether we use modified servos or steppers we still need to have a home sensor. However, steppers allow you to predict where the driven gear is at any given time. Modified servos work on the priciple that 1.5ms PWM signal centers or stops the servo rotation, A narrower pulse causes the servo to turn one way and a wider pulse the other way. The problem is that you don't know how far the servo has turned unless you couple an additional feedback mechanism such as a rotary encoder or some other type of encoder. Now you're getting really complicated and then steppers look a lot simpler.

If you have a 48 steps/rev stepper and you want .5 degree res, then you need to get 720 positions on the driven element. You just need a combination of gears that gives you 720/48. It works out that a ratio of 15:1 will give you that. This can be accomplished a few ways. You could have a large gear with 180 teeth and a pinion on the stepper that has 12. Or you could have a divide by three followed by a divide by five. This could be done with a compound gear.

The problem with a 180 tooth gear and a 12 tooth gear is the overall case size and the size of the stepper motor. If you position even a small stepper at the radius that a 180 tooth gear will demand, You will find it probably won't fit within the required profile of the instrument. However, we can use multiple gear shafts to offset the stepper. This makes the construction more complex, but only a little.

While you're sketching, have a scope around at steppers on the net. We'll need a source of cheap steppers all the same size. I bought a batch from a company called Futurlec, but they're not terribly prompt suppliers to do a project from. But they are CHEAP. I've seen some criticism of them in some forums, but my experience has been generally that they are slow, but basically honest. BTW, my steppers are 40 steps/rev. and they're an excess stock.

Also, if at all possible, look for units that already have a 48TPI pinion mounted (around 12-14 teeth).

Hope this helps. You guys are doing a great job tossing this around. I'm confident that we can come up with a workable design.

ruprecht

07-23-2008, 03:16 AM

While you're sketching, have a scope around at steppers on the net. We'll need a source of cheap steppers all the same size.

Jaycar carry this one: YM-2751 48 steps/rev (http://jaycar.com.au/products_uploaded/YM-2751.pdf) though I'm sure our american cousins can get steppers cheaper than AUD $19 each!

ruprecht

07-23-2008, 03:18 AM

PS I am about to do an order to Serv-o-Link for some gears for the Altimeter project in Mike Powell's book - if any aussies want some gears and want to split the shipping, let me know before thurs night.

ruprecht

07-23-2008, 03:49 AM

Just been sketching the gear trains in my "pit book" :) I think I have it sorted:

For the main ring gears (x 3):
- components: 48 steps/rev stepper, 1 x 12 tooth gear, 1 x 36 tooth gear, 1 x 24 tooth gear, 1 x 120 tooth gear, idler shaft.
- assembly: the idler shaft has a 24 at one end and a 36 at the other. The 12 is mounted on the stepper. the 12 mates to the 36 for a 1:3 ratio, and the 24 (at the other end of the idler shaft) mates to the 120 ring for 1:5 ratio.
- result: 48 steps gives 1/15th rotation, or 1/2 deg/step.

for the CDI:
- components: 48 steps/rev stepper, 1 x 60 tooth gear, 2 x 12 tooth gear, 1 x 36 tooth gear, CDI shaft, idler shaft.
- assembly: a 12 on the stepper, a 60 on the end of the CDI shaft (with the CDI assembly at the other end), idler shaft has a 36 and a 12. Mate the 12 on the stepper to the idler 36 for 1:3, and the idler 12 to the CDI shaft 60 for 1:5.
- result: 48 steps gives 1/15th rotation, or 1/2 deg/step.

Thanks for the help on the gearing, now to see if the gears will fit inside. I feel like I'm on an episode of MythBusters - "Hobbyist HSI - it can't be done!". Hoping to bust that myth!

AndyT

07-23-2008, 04:17 AM

I just had a great reason for making layered gear rings and I got interupted and now I lost it. It had something to do with embedding position sensor triggers.

So before I forget, we can use flexible drive shafts for some of the elements. Ever see a Dremel with the Flex cable hooked up? Same principle.

AndyT

07-23-2008, 04:22 AM

After spending two days on this, I have a much better understanding why BK charges $15,000 for an HSI. I don't even want to think about what Simkits would charge.

And by the way,
By posting the development process in the forum, we are making the designs that result public property and not avialable for any person to patent or copyright.

Michael Carter

07-23-2008, 09:39 AM

Collins are even higher. But they have a couple more functions as well.

ruprecht

07-23-2008, 10:24 AM

quick update:

Have added H21A1 optointerrupters for the main ring gears. Had to be careful that the flag had a full range of movement, and still not convinced the flag on the compass card won't cause some problems with the 7-segment displays and off flag mechanisms.

Also added cutouts for the glideslope indicators, and mounted servos in positions that might work. Am using 0.5" and 1.5" spacers as used in BSAI.

http://mycockpit.org/forums/images/HSI/hsi03.jpg

AndyT

07-23-2008, 06:23 PM

Ok, Lets move the optical sensors to the opposite corner because the rotary encoders need to go where you have them now. (or just rotate the picture..)

Since this is a combo unit that fits many planes, I guess we can lose the outer facia ring that the BK unit has.

Now if you please, add the encoders and the 7 seg displays in the corners. That way we will know if the proper clearance exists or if we need to modify the ring flags with a greater bend.

Can we get a detail shot of how you have the inner servo connected at this point?

This is looking good. I imagine there are a few out there ready to build as we design. :D

AndyT

07-23-2008, 06:30 PM

Hmmm... If we add just a squidge of space between the rings, do you think we could fit the opto-interrupters between them? That way they do not interfere with the encoders or the 7 seg displays.

My largest Simkits instrument is about 5" deep, so we have plenty of room yet.

cscotthendry

07-23-2008, 06:55 PM

Ruprecht:
Love ya work mate! Here's a suggestion for the optos. If we drill a hole in each ring gear the optos can be moved up to straddle the gears and save some space.

Another practical consideration as far as the materials for the gears. Consider the standard thicknesses of metals. I'm not sure what the thicknesses are for brass (expensive in the sizes needed) but aluminum (aluminium for the Aussies watching) cover a pretty wide spectrum. 3mm is a nice thickness to work with but I've made gears successfully from thinner stuff.

The problem with thinner stuff will be the attachment of the bug and course pointers. As it appears in your diagrams, it looks like you've attached them to the inside edge of the gears. We might be able to make a tab on them and fold them and attach them to the face of the gear, but that adds thickness to the gear which needs to be accounted for, as far as the optos are concerned.

One more practical consideration, we'll be home building these, so try not to make the tolerances/clearances too tight. That makes them really hard to build.

Lastly (for now) for rotating bearings or concentric shafts, it's hard to go past the little brass tubes that you get in the hobby stores. I'm not really familiar with the sizes of the metric ones, but the imperial ones go from 1/16" upwards at 1/32" intervals and the slide inside one another very nicely and freely with minimal play or wobble. The wall thicknesses are just under 1/64".

Keep going mate your drawings are looking fantastic. I myself would prefer the BK style, but hopefully we'll be able to mod your mechanicals to suit the different style.

cscotthendry

07-23-2008, 07:03 PM

Guys:
I just had an idea for mounting the ring gears. Imagine the ring gears meshed with 4 small gears of the same thickness as the ring gear. Imagine these small gears positioned at 90 degree intervals (even three at 120 degree intervals would do). Now imagine that each of these gears rotates freely on a fixed shaft mounted to it's plate, but most importantly...Each small gear has a washer on both sides of it that overlaps the ring gear thus retaining the ring gear while the little gear acts as a bearing.

AndyT

07-23-2008, 07:12 PM

HA! Thanks Scott! I had that idea for drilling the hole the other day but as usual, my grandaughter chose that moment to ambush me. Apparently I have 'Climb on and beat on me' tattooed somewhere on me. So, thanks to her, I had forgotten that one. And the layered gear idea I had was a rather complex method of always knowing the exact position of the gear.

EDIT: I like the three at 120 better. Just as sturdy and less to build. So the washer is basicly a bushing to keep the spacing correct.

cscotthendry

07-23-2008, 07:18 PM

Roger that and less gears to cut. ;)
The washer is a spacer and retainer.

ruprecht

07-23-2008, 08:44 PM

Is this what you meant by the support gears? The washers are standard steel off the shelf, and the shafts are 1/8" and 3/32" brass tubing. The gear is a 12-tooth.

http://mycockpit.org/forums/images/HSI/mountingGear02.jpg

Trevor Hale

07-23-2008, 08:52 PM

Guys, keep up the great work. You are making history as you progress here.

ruprecht

07-23-2008, 09:00 PM

Thanks Trevor.

Guys, while I focus on the modelling (around my day job and other pitbuilding activities!) it would be very helpful if you could collect standard dimensions for the components we will be using. Things I'm thinking of are:

- rotary encoders
- 7 seg displays
- sheet metal
- LEDs

etc, anything you can think of. I am working in mm to 3 decimal places. Remember, use commonly available stuff, not random stuff from your "bits box".

cheers lads

ruprecht

07-23-2008, 09:14 PM

Ok, Lets move the optical sensors to the opposite corner because the rotary encoders need to go where you have them now.

I kept the rotary encoders in mind when I positioned them, I thought the 7-segs needed more room than the encoders. I think there's enough room, it will depend on the dimensions of the encoders.

add the encoders and the 7 seg displays in the corners.

Next on the list :)

Can we get a detail shot of how you have the inner servo connected at this point?

Nothing connecting it at the moment, all in my head.

ruprecht

07-23-2008, 09:22 PM

optos can be moved up to straddle the gears

If necessary that can be done. I'm concerned about separating the ring gears too far as it extends the length of the bug and RMI indicators which will give us grief in the end if they start to droop. Let's see if there's enough room as is, then revisit.

3mm is a nice thickness to work with but I've made gears successfully from thinner stuff.

Coincidentally, I have worked using 3mm gears right from the start :)

One more practical consideration, we'll be home building these, so try not to make the tolerances/clearances too tight. That makes them really hard to build.

Trying, but there is a limit to how hamfisted we'll be able to be :) This is quite a precision instrument! We could always scale up to a 4" model to give us more wiggle room, but that affects gearing and all sorts of things.

it's hard to go past the little brass tubes that you get in the hobby stores

picked up a selection of these yesterday at Mr Toys :)

I myself would prefer the BK style, but hopefully we'll be able to mod your mechanicals to suit the different style.

I think the hard part is in the mechanicals, the look of it can probably be easily modified to suit almost any model once we've got the basics down. I'm working on the F-16 HSI a) because it's what I know, and b) because I know there is a big community of people over at ViperPits just screaming for it!

AndyT

07-23-2008, 09:44 PM

In milimeters to 3 decimal places? I'm going to have to find my calipers...

Here is an encoder.
http://www3.alps.com/WebObjects/catalog.woa/E/HTML/Switch/Encoder/EC11/EC11E15244B2.html

ruprecht

07-23-2008, 09:48 PM

We may not always achieve accuracy, but when we stop trying we guarantee it won't be accurate :)

Michael Carter

07-23-2008, 09:55 PM

I sort of though this was going to be a 4" unit.

You'd have a lot more space to work with.

ruprecht

07-23-2008, 10:46 PM

Here is an encoder.

Cheers mate - BSAI uses the Bourns 3315Y-1-006 - dimensions for that one would be awesome too.

ruprecht

07-23-2008, 11:49 PM

first snag:

http://mycockpit.org/forums/images/HSI/7segs.jpg

The rotary encoders work really well, but the 0.3" 7-segment displays are too big and occlude the compass ring. This is based on the DigiKey 67-1416-ND single digit module. Couple of options:

- Find a smaller commonly available 7-seg module, probably 0.2" or smaller, and preferably in a 3-digit block. Best option. There is a candidate here (http://australia.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6165260) but they are $21.30 each!
- Redesign to 4" to make enough space. Not my favourite option due to the redesign work required.
- Dispense with the 7-segs altogether. Will piss off the F-16 community and leave you only analog displays of CRS and HDG BUG information. Workable option.

Whaddya think?

*EDIT*

OK I tried it with the Kingbright KCSA02-127 0.2" SMT single - and it JUST fits if I relocate the top mounting hardware. There's about 2mm or clearance to the opto flags with the relocated hardware, so it's all good.

http://mycockpit.org/forums/images/HSI/7segs2.jpg

So here's a challenge guys - find these or similar 0.2" 7 segs at a reasonable price for 6!

AndyT

07-24-2008, 03:57 AM

Ask and you shall receive:

http://www.bourns.com/pdfs/3315.pdf

Can I have a 3/4 side view of that last shot?

Ok, Try this:
Since the LEDs are SMDs (Surface Mount Devices for you non-electronics types reading this) we can put them on the face of the front plate and cut holes for them in the final faceplate. They fit and if the faceplate is 3mm thick, they will be flush with it. AND they will not be interferring with the rings behind them at all.

ruprecht

07-24-2008, 04:00 AM

Another update, I'll explain later:

http://mycockpit.org/forums/images/HSI/hsi04.jpg

*EDIT* OK I've dispensed with the optointerrupters and the flags, they're just too big. It was suggested above that magnetic reed switches or the like would be better, I think that's a great idea. Any suggested items, with dimensions and/or datasheets would be awesome.

I've added another large gear for the CDI assembly, and shown how it fits together. I decided to do it this way as it's more rigid and precise then the folded-metal approach, but it is heavier. There will be a brush contact shaft running through the middle of the gear which also mounts it on a 608 skate bearing or similar, again to aid rigidity and ensure it rotates precisely in the centre of the assembly. The CDI servo control board will be mounted on the rear of the CDI gear. There's about 20mm of space between the gear and the plate behind it for the board.

PS dimensions on commonly available steppers would be sensational.

AndyT

07-24-2008, 04:46 AM

We can get the LEDs from mouser for $2 each which is about as cheap as we are going to find them I think.

I understand the 4th ring is the mount frame for the CDI Arrow plate. Nice. It will fit right thru the center of the others and is strong enough not to bounce around because it's ultimately held by the same mount gears. I might make it 5 or 6 mm in thickness though because it has to bear the weight of the servo along with all the rest of the hardware.

WOW! Steppers are costly. I'm looking...

ruprecht

07-24-2008, 05:02 AM

We can get the LEDs from mouser for $2

This really gives me the irrits - same product, same manufacturer, 10 times the cost in Aust. That's economies of scale for you.

AndyT

07-24-2008, 05:15 AM

http://www.portescap.com/Repository/...r_01042007.pdf

And what it looks like...

AndyT

07-24-2008, 05:22 AM

When we are done, we can figure something out on parts and shipping and such...

ruprecht

07-24-2008, 05:25 AM

mhmm... US$19 for a 20 steps/rev motor... this one (http://jaycar.com.au/productView.asp?ID=YM2751&CATID=&keywords=stepping&SPECIAL=&form=KEYWORD&ProdCodeOnly=&Keyword1=&Keyword2=&pageNumber=&priceMin=&priceMax=&SUBCATID=) is about the same price and 48 steps/rev?

AndyT

07-24-2008, 05:32 AM

This one is $17 US and 48 steps.
http://www.portescap.com/Repository/Documents/26M048B_Can_Stack_Gear_Tr_01032007.pdf

Take your pick.

ruprecht

07-24-2008, 06:01 AM

That's the one. Awesome. They don't ship outside the US, so we might need you to buy 12 and on-ship 4 each to me and scott!

For the electronically minded, here's a challenge: design a microcontroller circuit within the following constraints:

- fits on a circular circuit board < 60mm dia.
- has only 5 inputs: data ground, data +, data -, power ground, power (5 or 12V)
- ideally uses a PIC flash microcontroller (e.g. PIC16F648A)
- can control a micro servo through roughly 90 deg movement, plus three separately controlled LEDs
- MAY be a daughterboard with a larger separate motherboard, but must conform to the input limitation above
- is suitable for home fabrication (so keep the traces at a reasonable width) or consumer board shop (e.g. PCB123, ExpressPCB)
- please supply Eagle or PCB123/ExpressPCB layouts

*EDIT*
- Contains some sort of protection to ensure the servo does not move unpredictably at startup. Possibly prevent power being supplied to the servo until a stabilising pulse train is active?
- Has approx 10mm dia hole in the centre of the board for a shaft to pass through.
- has holes for 3 #4-40 mounting screws
- supports ICSP so we don't have to disassemble the whole instrument or pull the chip to update firmware

Who's up for the challenge? :)

AndyT

07-24-2008, 06:08 AM

Lets limit it to Express PCB since I have that one also.

AndyT

07-24-2008, 06:16 AM

Hmmm..... Check this out....
http://www.futurlec.com/Mini_SMCC.shtml

ruprecht

07-24-2008, 07:37 AM

One for the stepper gurus: will the L293D bipolar H-bridge driver (600mA) be able to drive this stepper (http://www.portescap.com/catalog/78.pdf)? (note the 12V bipolar version).

Westozy

07-24-2008, 09:11 AM

Hi guys,
Re - tubes, bushes, rollers, axles etc, I can make what you need to any size and post them over. This is a great project growing on our pages and it would be good to see a working prototype!
(Tip - break apart old printers, they are a great source of small mechanical parts).

Gwyn

ruprecht

07-24-2008, 11:24 AM

OK my brain hurts - but the drive shafts are in. I had to change the gears because they wouldn't fit. 32 on the (48 steps/rev) stepper drives a 48 on the idler for 2:3, a 12 on the other end of the idler drives the 120 for 1:10. Total 1:15, 0.5deg/step for all 4 rings. You can see the dual-axle shaft on the left of the instrument drives the front two rings, and the other on the right drives the rear two.

I had to remove the glideslope servos as there's just no room. Maybe we could do it with LED bars? Can someone get me dimensions on a 5- or 10- LED bar?

Remaining is the axle and brushes for the CDI assembly and the circuit board. Then: over to you guys :)

If anybody has 3dsmax9 please let me know, I need you to inspect the model to pick up any errors. Where's Mr Powell when you need him :) Couldn't have done this without inspiration and information from your excellent book sir.

http://mycockpit.org/forums/images/HSI/render6.jpg

Mike.Powell

07-24-2008, 11:35 AM

One for the stepper gurus: will the L293D bipolar H-bridge driver (600mA) be able to drive this stepper (http://www.portescap.com/catalog/78.pdf)? (note the 12V bipolar version).

Looks good to me.

VERY interesting project!

Matt Olieman

07-24-2008, 03:01 PM

Please folks :) :) :) Upload the photos in the gallery and link them in the forum rather then outside of MyCockpit.org. Otherwise it takes forever to load up a page.

I've moved all the CAD drawings to MyCockpit.org. NOW LOADS INSTANTLY!!!! :) :) :)

Matt O.

cscotthendry

07-24-2008, 04:36 PM

Hi guys:

Sorry for my absence. I'm in the middle of selling my boat and there's work to be done that keeps me out all day. I'll be offline for the rest of the weekend probably.

Whew!!! I miss one day and you guys have filled three pages of stuff...GREAT WORK!!!

Seriously here's some things I see.

I see that you've added a fourth gear and stepper. If we can get rid of it I think it would be better from a reliability/simplicity point of view. I agree with the guy who designed the blackbird "Simplicate and add lightness"

The washers for the retainers/stepper can be easily custom made. Also we can make them from delrin which will make them slippery and smooth.

Please let's don't go to 4". The only thing that I think would push us there is accomodating lots of steppers and I'v already aired my opinion on that.

Reed switches are 13mm long and 2mm diameter with axial leads. The exit of the leads is VERY fragile so allow about 20mm width total to keep the bend in the leads away from the body.

Sourcing parts from the US. I have a friend in Texas who is quite willing to source stuff and ship it for me. I'm sure that if we offered him an HSI, he'd fall all over himself to help.

I only have Protel99 for PCB, but I see Andy has put his hand up for that. Good one Andy.

Don't buy stuff from Futurlec. They are honest, but slow. Also they only seem to deal with runout stock so supply may not be guaranteed.

For stepper drivers for small steppers, it's hard to go past the FAN8200 from JAMECO. At 80 odd cents they're cheap as chips ;) They can drive unipolar or bipolar steppers so they're very versatile. Unfortunately, they're through hole devices so if we need 4 on a board, that's a lot of real estate. Another reason to get rid of that extra gear/stepper.

Ruprecht: What can I say about your drawings. Mate I'm just speechless in awe. I do have a suggestion though. You could squeeze some space out from between some of the gears and maybe bring back the glideslope servo. I think also that the GS could be done with one servo, we might just have to make a fiddly bit of metalwork for the arms. But that's OK. I really think the glideslope capability is essential.
*EDIT* Instead of squeezing space out from between the gear plates, maybe if you added just a little space forward of the plate in front of the steppers, the GS servo(s) could go there??

Finally, I just don't believe the work you guys have done on this. I can hardly wait to get started on the parts.

*EDIT* Ruprecht, I don't think we need the fourth gear. The course pointer will ride on the CDI plate.
*EDIT* I just had another idea for the GS pointers. mount them on cables and make them slide up and down. Put a pulley at the top and bottom and drive the cable from the servo. Then the servo can be mounted in any orientation.

ruprecht

07-24-2008, 07:24 PM

http://www.mycockpit.org/photopost/data/500/render7.jpg

Guys, a quick explanation of a few things:

4 rotating elements are required. Compass card, heading bug, RMI needle, CDI assembly.

I could dispense with the fourth (CDI) gear, but what would I replace it with? In the end, the assembly must rotate. As it stands now, all 4 rotating elements work exactly the same way, same gearing, same everything. I agree with "simplicating" (did Dubbya work on the SR71? :) ) but IMHO making one rotator work differently is "complificating" :) Accept that it means more work for our esteemed gear cutter though :)

Re Delrin, mate do you have an Australian source? I've had no answer from Aircraft Spruce's local distributor.

Agree on avoiding 4" unless it becomes impossible otherwise. Not least because of the redesign work required!

re board space, the only circuit board that will be tight will be the swinging CDI board. the rest we can split over multiple 3"x3" boards if necessary. I'd prefer to use the RS422 architecture from MikesFlightDeck rather than depending on any specific manufacturer's control hardware, if that's at all possible?

I'll pick up some reed switches today hopefully, just so I have one handy for prototyping.

Referring to the numbered sections in the pic above, I agree we could probably save some space in sections 2, 3 and 4 now that we've dispensed with the optos. However until we've figured out the position sensing and are sure there's enough room, I'll leave it as is. I can always compress things later, but I'd hate to do it now and have to undo it because of unforseen requirements.

I think it's important to keep section 1 as shallow as possible to maintain the "look" of the instrument. Obviously there's a minimum depth dictated by the CDI needle, which in turn is related to the CDI indicator arc radius, dictated by how far back the CDI servo is. 3/8" will do for now :)

Sections 2,3,4 and 6 are 1/2" deep. Section 5 and 7 are 1" deep. Section 5 is reserved for the swinging circuitry mounted on the back of the CDI gear (gear 4), to be modelled when my mouse shoulder stops hurting!

The problem with a single arm for both glideslope indicators is that the arm must, at some point, stretch horizontally across the width of the instrument with some range of vertical movement. I'd welcome suggestions, but I can't figure out where to fit it unless you move it right back beyond section 8, in which case flexion in the armature will give us accuracy problems. A LED bar is a "simplicated" solution and not one for the purist, but it's an option. Possibly as you say Scott, extending section 5 to 2" might give us enough room. The pulley idea is an interesting one, I had thought along similar lines with a toothed belt and worm gear, but dismissed it as too complex. Maybe you could sketch something and I can then model it?

Thanks for the kind words. I am trying very hard to accommodate all suggestions, I understand this is a community project and am resisting the temptation to just design it the way I want! Part of the reason for doing CAD is that it reveals things that just won't physically work, and much of the trial and error I go through when modelling isn't visible in the end result, but many lessons are being learned and I'm trying to document them here. Please be patient with me, I'm doing this around my day job and my young family :)

ruprecht

07-24-2008, 08:19 PM

Matt, thanks for the tip on the images. I was hosting them on my own Apache server hanging off my broadband, so no wonder it was slow for y'all! And no wonder my bandwidth got hammered last night when you featured the post on the front page :D

Cheers

Trevor Hale

07-24-2008, 08:24 PM

no wonder my bandwidth got hammered last night when you featured the post on the front page :D

Cheers

I would like to introduce you to the Power of MyCockpit.org LMAO.. :mrgreen:

AndyT

07-24-2008, 09:16 PM

WHOA! I get a few hours sleep and we lose the optical sensors! How did that happen? And why?

ruprecht

07-24-2008, 09:21 PM

They are too big (causing sect 2,3,4 to be deeper than necessary) and the interrupter flags conflict with the driver shaft. Reed switches and magnets are a neater solution I reckon?

AndyT

07-24-2008, 09:27 PM

Ok, so we get rid of the interupter flags and drill a hole in the gears, then straddle the sensors over the gears themselves. Uses less room between gears than the flags, is more accurate, and we can test for an 'open' instead of a 'close' to get our reading.

Its the simplest solution. If we have to lengthen the case by an inch, then so be it. We knew going in this would be a larger than normal instrument, and we NEED some kind of sensors. Mounting magnets and reed switches while it sounds cool, is needlessly complex to my thinking. There is the issue of mounting the magnets on the gears themselves in a way that over time they do not get dislodged or even fall off completly. Drilling the hole is easy and simple.

Try putting them in the way I suggest and see what we get.

AndyT

07-24-2008, 10:08 PM

By the way, Stagger the sensors slightly. Do not put the one right behind the other. That way they take less room. I meant to add that above.

ruprecht

07-24-2008, 10:12 PM

I'm not sure mate, here's my thinking. Overall length is not a worry, the thing that worries me is the distance from gear 3 to the faceplate. That is the length of the RMI flags, which are thin strips of metal. That distance is currently about 30mm.

Mounting the optos between the gears will add, I'm estimating, at least another 10-15mm. that takes the RMI flag length to 40-45mm. if those flags sag, or suffer repetitive bending stresses during stepping, they will eventually conflict with the heading bug flag and tear each other apart, necessitating a quite difficult repair. remember that the steppers don't move the flags smoothly (in an analog way) they move them digitally, one half-degree step at a time. The longer the flag, the longer the intertial moment of the flag head and the more repetitive stress it encounters.

My thinking is that we need to *reduce* the gear 3 - faceplate distance as much as possible, not be thinking about making it bigger. I'm all ears, but I think the above is a valid concern given the tolerances involved?

Michael Carter

07-24-2008, 10:24 PM

I can see that there is no room in the housing for this, but many HSI's use a rotating drum with the CDI needle fixed to the drum rather than the needle swing back and forth across the dial face.

That's probably not an option at this point.

ruprecht

07-24-2008, 10:33 PM

BSW, I think I know what you mean and yes all I have to do is quickly model it. I've just been focused on the gear train so hadn't done it yet. I really need to do an animation to show people how it all hangs together :)

AndyT

07-24-2008, 10:34 PM

Ok, I'm not sure we are on the same thought here, so let me add in a simple sketch and this:

What is the strength of aluminum versus the weight of the bugs that will have to be held? Inconsequential. The shaft of the flag mounts can be larger than what you have drawn because it will all be hidden behind the faceplate and CDI plate. This is not a problem we need to put that much worry into.

What are the measurements I have question marked in the sketch? These are your sizes for the plate distances.
Sorry, I did not label my sketch very well....

ruprecht

07-24-2008, 10:42 PM

ah, you're a genius. Let me measure up the opto for you and see if it will work.

We were definitely not on the same page, I'm a visual person :D

-- rup

*edit* Ok it appears there IS room to do it like that, depending on distance x in the attached diagram. So long as x < about 3.5mm, we're gold with 3mm gears. the tolerances are quite tight (1/8 mm either side of the gear) which worries me a little, but the optos could probably stand some grinding out without dying.

The H21A1 optos are near as dammit a half-inch wide, so the existing spacers can stay! sweet as. Little bit of rework to position the gears in the longtitudinal axis, but that's no biggie.

AndyT

07-24-2008, 10:59 PM

One more scribble for you to address your concerns about the bending of the shafts.
The shafts have the same curve as the inside of the gear. The shape is triangular to increase the strength and durability. With this design, no bending should be possible under normal use.

AndyT

07-24-2008, 11:01 PM

We can always move the index hole closer to the edge of the gear.

P1IC

07-24-2008, 11:03 PM

Hi, guys. I have just found this thread, and it’s very interesting to me, since I have just started to design an instrument panel for my own (steam gauge of course) IFR procedures training simpit, based on stepper motors and PICs.

I started with the altimeter because it seemed to have all the nasties in there that I would encounter in many other instruments - like multiple 360 degree rotation, a knob for tweaking, a subscale, a couple of high-res needles. No CDI of course, which is an additional complication, but I decided I could get to that later when I came to VOR / ILS design. I hadn’t planned on HSI!

Then I found this thread, and started (prematurely) thinking about the problem.

For what it’s worth, I have taken a different approach to you guys (maybe because I don’t have “The Book” that you all rave about, so I’m on my own there, which I hope you will believe is not necessarily a bad thing, since I’m not constrained or influenced by the ideas in there, whatever they are).

I’m intending to use needles visibly up front, combined with clear plastic disks on to which I’ll paste cards, subscales and the like, and I’ll also use these for zero location behind the visible faces. So the problem recently announced here about having no room for the various LED zero point indicators does not exist in my design. I just use one pair of IR devices, shining through all of the discs, behind the visible instrument face, each with its own mask (a bit of tape, probably) to blank out the IR, and I can program the pics to zero each disk in turn.

There’s plenty of room for that (using a 3" instrument face), and my 3-D design mockup using Cinema 4D XL 7 shows that this will work. For the altimeter I use three small stepper motors at $3 each (Futurlec, whom I hate just like you, and Sayal in Toronto, whom I also hate, but what’s a guy to do?), and some plastic worm gears and gear wheels for the drives, which I obtained at very low cost on eBay, so no machining of gears is required (although I do have a lathe and a mill, just in case).

However, the reason I’m posting this is in response to the problem of having a rotating card on which must be mounted a motor which controls the position of the CDI, and the resultant need for brushes to overcome the problem of twisted wires.

Nonsense, he cried! :D The design you guys are working on already involves PIC microcontrollers, and so you can solve your issues entirely in software. Remember, write once, use everywhere (to paraphrase the Java launch blurb). If you require a design with complex hardware requirements, everyone suffers and output is reduced to a quality-threatened crawl. Create a design where the software does the work on a (relatively) simple hardware platform, then write the software once, and you can produce hundreds of accurate gauges. And each simpit requires quite a lot of these devices.

If you drive the CDI by means of the angular position of a cog wheel, probably then driving a pulley arrangement (a bit of thread around a shaft :cool:) then of course whenever the carrier card rotates, the CDI will move because its driver cog will rotate too. But not if you program the CDI cog to compensate. After all, you do know what the new position of the carrier card is going to be, right?

So the carrying card moves, and the CDI is commanded to compensate, so that it stays fixed in its commanded position.

Now, what happens if the carrying card rotates through say 100 times 360 degrees? It doesn’t matter, and your software will not crash through the limitations of an 8-bit microcontroller, because the delta values you feed in to the CDI will not actually be part of its control structure. You are just re-adjusting the zero position of the CDI continually.

Sorry for the lengthy post! :oops:

ruprecht

07-24-2008, 11:11 PM

Hi P1IC, welcome to the thread. I'm very interested in your suggestions, but as stated above I'm a dumb helo pilot and need pictures to understand things :) Can you sketch how you think you could design an independently rotating CDI assembly without the use of a brush contact rotor? The problem as I see it is not rotating the assembly itself to match rotation of the compass card (easily done in firmware as you say) but mounting a servo on that rotating assembly to give you a localiser bar. That is what requires the brush contacts in my book.

AndyT

07-24-2008, 11:13 PM

P1IC, I'd love to see pix of your design if you are willing to share them. 3D is better of course. It sounds like a novel solution but I have questions the Pix will answer.

No problem if you don't have the book, its not a requirement. But it is very close to the 'standard' way instruments are built and when done, you have a very high quality instrument that perfectly imitates the original. (Well, almost perfectly)

Once this design is finalised, it will be fairly easy to duplicate for nearly anyone since we are using off the shelf parts, with the possible exception of the gears which can be sourced fairly easily.

Thanks for posting and adding to our progress!

cscotthendry

07-25-2008, 12:43 AM

Ruprecht:
It would be better if the optos were all in line, then they could all be mounted on one piece of circuit board. Like Andy, I would prefer to keep the home sensors as optos. With the reed switches, I've found that you have to home them from either clockwise or anticlockwise. Also they're a bit inaccurate so there are some calibration issues as well as accurately placing the magnets on the gears. Not to mention them falling off (possibly).

Re: The RMI pointer?? I'm not familiar with the F16 gauge, but on the BK gauge the course pointer is just an extension of the CDI needle. It doesn't rotate independently of the CDI. Additionally, the CDI card rotates in sync with the compass card except when the course is being changed. Ditto for the heading bug.

P1IC: welcome to the thread. I didn't quite work out what you were suggesting, but I'd sure like to see some drawings of your ideas. Like Ruprecht, I'm a visual person. However I agree with the sentiment of making software do as much as possible. Having said that though, the whole thing could be done with a small color LCD but that's not really what we're trying to achieve.

Ruprecht: When we get down to cutting gears and bits of metal, we gotta get together. I'm sure there will be a thousand details to sort when we start making metal shavings. At that point your skill with the CAD package is really going to be crucial.

*EDIT*Ruprecht with respect to clearances in the optos, no problem, just make the gears thinner. 3mm at the sizes we're working is WAY overkill anyway. You could take them down to 1.4mm no problem.

Cheers

ruprecht

07-25-2008, 02:49 AM

Re: The RMI pointer?? I'm not familiar with the F16 gauge, but on the BK gauge the course pointer is just an extension of the CDI needle. It doesn't rotate independently of the CDI. Additionally, the CDI card rotates in sync with the compass card except when the course is being changed. Ditto for the heading bug.

The CDI is on NAV1/ILS and the the CRS pointer is, as you say, affixed to the CDI card coaxial with the CDI indicator in its centre position.

The RMI flag is exactly that - an RMI. an independent pointer that points to the VOR tuned on NAV2 (with no course information other than direct bearing-to/from).

I suppose you could make it work as an ADF instead in software by using the NDB bearing tuned on ADF1 instead of the VOR bearing on NAV2. Could even include a VOR/ADF toggle on the instrument I guess! Maybe for version 2 :)

cscotthendry

07-25-2008, 03:43 AM

Ruprecht:
OK, I've got an RMI gauge that has a pointer that does that. But it only has the card and the pointer not all the other stuff as well. I guess then that modding your design to the BK will mean reducing some of the functionality (which is just fine by me :D)
Given what you say, it was inevitable then to have four gears involved. No matter though as you've done the hard stuff fitting it all in.
Just thinking on it though, I would rather have the GS bars than the extra VOR indication. VOR 2 could always be done on a "conventional" RMI (another project???)

ruprecht

07-25-2008, 03:51 AM

Ruprecht: When we get down to cutting gears and bits of metal, we gotta get together.

No worries mate, that would be great. PM me if you're going to be in the city during the week, I can meet up for lunch and show you over the model.

I reckon we'll be able to make shavings pretty soon - if you wanted to get started cutting some of the 120-tooth gears I reckon they're pretty much set in stone now once we've settled on a width.

Re the gear width, the reason I went 3mm is to give it a little bit of wiggle room with hobbyist construction so even if they're off a bit they will line up with mating gears pretty well. Let's make a call on the width so a) I can finalise the CAD on the gears and b) you can get cutting. I vote 2.5mm if the material is available.

ruprecht

07-25-2008, 03:57 AM

Ruprecht:
OK, I've got an RMI gauge that has a pointer that does that. But it only has the card and the pointer not all the other stuff as well.

Yup the only place I've seen a combined HSI/RMI is in military aircraft (or on civvy glass). One's initial aviation experiences tend to drive one's preferences for life - I still have trouble with the "pendulum" style VOR gauges and fixed-card ADF, but give me an HSI/RMI and I'll navigate head-down all day :) For the same reason I resist GPS, as I learned IFR doing NDB approaches! Old school!

On the BK, my intention is to proceed with the current design to finished stage to "prove the concept" and then branch it for the BK. I will build the F-16 style, if you guys build BK style (minus the RMI ring) it will be a good proof that the design can be adapted to most any HSI. If the firmware and circuit supports an RMI, it's a simple thing to just not connect that stepper.

cscotthendry

07-25-2008, 04:18 AM

Ruprecht:
Yep I agree. If we do the hard one first then it's easy to take stuff out. Also I agree with your sentiments about the D'Arsonval movement based VOR gauges. Never liked the look of them. When I first started working on airplanes they were the mainstay and I always thought they looked icky.

What's this "you guys" build the BK;) You're in too deep now. BTW are you interested in having a go on the mill and lathe? I could probably use some help when we start to make the parts. Besides as I mentioned before there will undoubtedly be changes needed for the practical construction and I sure would like to have you on tap to thrash out the design.

Anyway, If we do the military version that we're working on and then convert it to the BK style, we should have the market pretty well covered. We'll make millions ;) Have you picked out your new house yet? I've got my eye on the new Bugatti.

AndyT

07-25-2008, 04:24 AM

Money? Theres money involved?? Hmmm... I think I'll buy a new Cessna with the G1000 installed... Gotta go low and slow.

ruprecht

07-25-2008, 04:39 AM

lol, the smiles on the faces of all the happy pitbuilders as they power up their HSI will be all the reward I need :D

of course, my own Bell 47 or Spitfire would be nice too. With an HSI.

Actually to be serious for a sec, I think if we pull this off we will be inundated with requests to supply detailed instructions, plans and cut gears for folks. We should start thinking in advance what our response to that is - personally I am happy to make plans in user-friendly format but have no interest in building complete units for sale. eMachineShop, Serv-o-link and the like should do a roaring trade in the gears. It would be nice to find someone with a CNC machine to cut the plates though - the thought of hand-milling them leaves me cold.

ruprecht

07-25-2008, 04:46 AM

What's this "you guys" build the BK;) You're in too deep now.

OK let me rephrase: WE shall build an F-16 style for me and 2 BK style (or whatever you prefer) for your guys :)

And I'd love to have a crack at the milling if you're prepared for bits of the mill to go flying around the workshop :) I have 2 left thumbs when it comes to metalwork - to be fair I'm lucky to have any thumbs left at all!

AndyT

07-25-2008, 04:47 AM

As long as I'm dreaming, the Cessna would be for work and this baby http://www.tecnamaircraft.com/BrP2006T.pdf is for pleasure. In the meantime, I'll be happy with a BK style version.

ruprecht

07-25-2008, 04:53 AM

Well if we're dreaming, I see you and raise you this: http://www.avtechgroup.com/

AndyT

07-25-2008, 04:57 AM

Yep. Saw that one too. They discontinued work on it for lack of money. Too bad. It was scheduled to be only 3.2 mil each.

AndyT

07-25-2008, 08:29 AM

At any rate, I'd like to see the new 3Ds of what we have so far.

ruprecht

07-25-2008, 09:57 AM

Been flying tonight mate, no 3ds work. Showed my brother how to fly the Kai Tak checkerboard IGS in a Baron :) Love that same-cockpit multiplayer!

P1IC

07-25-2008, 10:39 AM

Thanks for the welcome! Actually I haven't drawn out my thoughts for the CDI yet - and I can't do it right now, since I'm moving house, and today is the day I de-commission my computers! Sucks.

However, just so that you know I'm not all full of BS, I've attached three images of my altimeter design, hopefully showing how I have arranged for the opto indexing.

Once I'm settled in my new home and paid an arm and a leg and the sale of my firstborn to pay for satellite internet access, I'll get on to the CDI thoughts I have, and try to explain it visually.

But knowing the speed at which you guys work, you'll have finished the project by then!:)

(I haven't uploaded attachments to this forum before - I hope it works!)

cscotthendry

07-25-2008, 02:48 PM

P1IC:
Love the idea with the worm gears. I worked this out just a few days ago and realized that you can get really high ratios with very small gears. BTW for 48TPI gears, a 1.75mm pitch thread is your friend. Fits exactly.

Oops looks like I put the cat amongst the pigeons mentioning money, LOL

AndyT

07-25-2008, 06:34 PM

By the way, for our readers who do not know what 'The Book' is, here is the link to it.

http://www.mikesflightdeck.com/mfdbooks.htm

(Hey Mike, That'll be a dollar for the advert. LOL )

ruprecht

07-25-2008, 09:04 PM

Tasks for modelling this evening:

- reduce gear thickness to 1.4mm
- expand divider plate thicknesses to 1.2mm
- position optos
- adjust shafts, support gears and driver gears to suit
- check plate dimensions are 3.24" not 3" (we might have more room than we think!)
- model the CRS needle affixed to the CDI plate

Anything else, please advise before tonight. Also please advise: what thickness should the divider plates be? I'm working on 1.2mm (18 gauge) as that's commonly available in hobby/electronics stores here.

AndyT

07-25-2008, 09:12 PM

Don't forget the thickness of the outer casing.
Actually, I would use 1.5 mm gears just because.
18 gauge is fine for the divider plates.

cscotthendry

07-28-2008, 04:30 PM

Hi all:
Here's the latest. Ruprecht and I are going to get together over lunch and discuss the developments so far. I have his 3dsmax model in DXF form and will be translating that into a more precise CAD package. 3dsmax seems to be great for visualization, but doesn't do the things needed for manufacturing. So this topic will go quiet from my end for a while, while I translate ruprecht's model (with a few improvements) into Solid Edge.

I'll keep you all posted on the news as I progress this gauge.

ruprecht

07-29-2008, 06:03 AM

And to add to Scott's comment above, I'm trying to keep my head above water with work atm and the HSI is slipping down the list. The situation should be smoother in a week or so. Progress is occurring, never fear.

ruprecht

08-01-2008, 07:48 AM

Scott and I had a great catchup the other day and, amongst many other things related to the HSI, had a think about our influences with this project.
We should really acknowledge the work of Mr Felipe Lopez Gerola from Bilbao Spain. He put together some amazing 2d drawings of a hobbyist HSI which, when I came across them on Viperpit, inspired me to visualise the instrument in 3d from hobbyist materials.
There are many people we would not be at this place in the design without; Felipe, Mike Powell, and all the amazing and talented builders out there. Here's hoping we can get this instrument done and give something back to you all.

cscotthendry

08-03-2008, 11:18 PM

Well I've started to transfer the design into a CAM friendly package called Solid Edge. Along the way, I've started to think about the jigs and machining fixtures we'll need to make the parts. As a proof of concept and to help me learn Solid Edge, I designed a machining fixture to make the gear for the heading bug.

cscotthendry

08-03-2008, 11:21 PM

I've started modelling standard parts for the construction. One of the things we'll need is servos. I've settled on the Hitec HS-55 as the modelled standard servo and created a model for it.

AndyT

08-04-2008, 02:00 AM

Nice work guys. I'm working on the driver circuits that go inside the housing. Just block schems for now till I get some more precise measurements from Scott.

cscotthendry

08-07-2008, 01:07 AM

Modelling, modelling modelling:D
I needed a reference for the positions of the control knobs etc so I modelled the BK facia

AndyT

08-08-2008, 05:58 AM

Looks good. I like the 'FlightSim Avionics'. What is DG? Directional Gyro?

cscotthendry

08-08-2008, 06:04 AM

Flightsim Avionics is my company name. I've registered a .com with Planet Domain for it too. So that's ready when the time comes.

It's actually DC for Direct Current vs AIR for air ;-) In the pic it also looked a bit like BC to me, but it's not that either. If you look closely at the lettering it is actually extruded from the front surface.

I have an RFQ in with a local plastics company for getting moulds made and a production run of about 100. Just to see what it would cost.

P1IC

08-15-2008, 01:25 PM

Hello again guys. Probably way too late, as I suspected, but it has taken toooo long to get Internet access here at my new address. Satellite, unfortunately.

Anyway, I said I would post my thoughts on a system which avoids the need for brushes in the CDI section. Four pics. Pic A shows the arrangement for moving the CDI indicator across the back panel (where all the TO, FROM etc stuff is, not shown here for clarity). This is a back view looking behind the CDI backing panel. You can see the white CDI needle strung between the two lines of cord.

When the red cog is spun, the green shaft through it also spins, driving the cords and moving the needle. Here I am assuming the green bits are fixed to the frame, ie. the CDI doesn't rotate (yet).

Pic B shows the drive arrangement in red for the CD needle. The stepper applies torque through the worm gear to the red shaft which turns the original little cog.

Pic C shows the arrangement for turning the CDI, through the green shaft. What you don't see in this pic is that the green shaft is fixed at its front end to the CDI assembly. Running the green stepper turns the whole CDI assembly including the little red cog - and this is where the problem lies.

If the green motor runs, the red cog will spin around the red drive system, making it turn and causing the needle to move. We don't want that, so whenever we turn the green drive we also need to turn the red drive the same amount in the same direction, so that the needle stays in the same position on the CDI face. So no brushes are needed. It's all done in the PIC software.

Pic D shows a bit more clearly how the assembly looks with the CDI drive cage mostly fleshed out. Of course, the rollers for the cord are grooved pulleys (I didn't draw them like that for simplicity) and the wrap of the cord around the driving shaft is more involved than shown here, but not difficult.

cscotthendry

08-15-2008, 05:56 PM

Hey that's a really neat idea. I see some issues with the physical construction, but nothing that couldn't be solved.

ruprecht

08-15-2008, 07:58 PM

P1IC

08-15-2008, 09:46 PM

Definitely an intriguing approach. How would you do TO/FROM and OFF flags? If my understanding is correct, turning the green stepper causes the whole cage to rotate. If you had flags on the cage, they would require some sort of wiring (whether you use solenoids, LEDs or whatever) and wouldn't the wiring wind up?

Just trying to understand, possibly you've already thought of the solution (or indeed, possibly I've totally misunderstood!).

Cheers

No, you are correct, that is the same problem, and it's solved in exactly in the same way. The flags might be controlled by solenoids or steppers or whatever, but if you drive these coaxially from a shaft concentric with the existing ones, and rotate them exactly as with the CDI, they will work just like the CDI assembly. No coiled wires, no brushes.

Actually, one stepper will serve to display TO, From, Inactive. It's just a matter of angle of rotation in a window to display the required icon. This would save on the number of coaxial shafts involved!

Coiled wires just don't work. What if your aircraft is held for an hour in a hold, circling clockwise every four minutes? Your wires are toast. And brushes are iffy in a digital environment. They might be OK, but I prefer the software solution. Plus all the mechanical issues involved in carrying all the motors around with you as you rotate the various bits. Testing required!

Of course as you have seen, there are still issues to resolve. Mainly, how to display the RMI heading card and the heading bug in front of the whole assembly. I really REALLY don't like the rim-drive approach which has been published here, because of the mechanical complexity - having a lathe and mill, I can cut gears along with the rest of you, but I'd rather not! The answer has to be in software.

I prefer a coaxial drive system, but the CDI cage kinda puts a stopper on that for driving the flags, OBS and bug.

I haven't tried it out yet in 3D, but I think we can provide coaxial drive from behind the cage with stand-offs outboard of the CDI back plate on each display disk (which sit in front of the CDI assembly), allowing the CDI assembly to rotate freely inside with no coax shaft interfering with the CDI needle (or, in the case of an ILS, needles). But I hate it, because it's mechanically complex, with fine tolerances.

The rim drive system was incorporated into one of the designs I had for general instruments like RPM, ASI, and the like, with a simple DC motor driving the rim with a rubber sleeve to provide some traction, and a pot centrally feeding back its position - and, incidentally, the pot shaft supported the disk which made it mechanically very simple, and it worked OK (for angles of rotation less than about 240 degrees), but in the HSI we have no access to the centre forward of the CDI, and the angle of rotation is infinite, so rim drive plus a zeroing strobe driven by a stepper may be the only realistic solution.

But I worry about slip, just like with the cord arrangement in my cage suggestion - but maybe it's not an issue. With pot feedback, slip is irrelevant, but with open-control like a stepper, slip is a real issue. Gears work, but I hate them on the rim! Sorry.

I also worry about going outside the standard instrument cage, and driving a rim would seem to need a stepper out there beyond the edge.

By the way, my pics don't show that each channel has a strobe disk at the back, connected to the appropriate drive shaft, with one single LED/Photocell firing backwards through all strobe disks and monitoring all channels for zeroing, with one zero blanking pad on each disk. Software sorts it out.

But maybe there's a better solution? I'm actually sure there is - it's just a matter of finding it. More questions than answers!

AndyT

08-15-2008, 11:45 PM

A 90 degree worm gear would get rid of all the string and pulleys which I don't care for. That gives you direct drive for the CDI needle.

I've got the general direction you are heading with this design. Its going to be 12 inches deep into the panel using this layout.

There is nothing wrong with rim drives, quite often they are the best design for the application. How they are implemented is the thing. In our case, the drive is well inside the instrument casing.

Also, we do not have to use 'brushes' as brushes. We should use a slip ring here. They are made for this kind of application.

What happens if your strobe disks get out of synch with each other? The software will fail and the instrument becomes useless.

I seem to get that you are not mechanically inclined and tend to shy away from those type of solutions. Nothing wrong with that, but there are somethings that software should NOT do.

cscotthendry

08-16-2008, 04:54 PM

P1IC:
I have some suggestions for your design, hope you don't mind me butting in.

The CDI pointer in your diagram looks like it would scrape on the face of the CDI plate. You could solve this by shaping the attachment to the cable so that the needle sits forward of the cable and protrudes past the face of the CDI plate. Looking side on to the needle, think of a squarish C shape.

For the home position sensor on the needle stepper, if you set the gearing such that it only takes one (or less) turn of the gear driven by the stepper worm, then you could have an optointerrupter straddling that gear and just have a hole in the relevant place in the gear.

The interface between the worm gear and the straight gear will be a small issue to solve as well. There are two options which are a) cut the teeth on the straight gear at the appropriate angle for the worm or b) mount the steppers at an angle to the straight gear. If you mount them straight and with straight cut teeth, there will be a fair bit of wear intil they "break in" then you might get a bit of backlash in the movement.

Apart from the issues that Ruprecht raised, these are the issues I saw with the construction. As I said, they're solvable. Rup's issues may be a bit more difficult though.

P1IC

08-16-2008, 07:38 PM

A 90 degree worm gear would get rid of all the string and pulleys which I don't care for. That gives you direct drive for the CDI needle.

I don't care for it either! I'm not familiar with 90 deg worm drives - could you describe these?

I've got the general direction you are heading with this design. Its going to be 12 inches deep into the panel using this layout.

Actually, the dsign as shown in Pic 4 is only 3.2 inches deep from the front of the panel to the end of the longest shaft.

There is nothing wrong with rim drives, quite often they are the best design for the application. How they are implemented is the thing. In our case, the drive is well inside the instrument casing.

Excellent. I suppose you place the motors in the corners. I can do that too in my design. Good thought.

Also, we do not have to use 'brushes' as brushes. We should use a slip ring here. They are made for this kind of application.

OK. I was avoiding these, not just because I don't like the thought (silly me) but also because it means carrying the drive system around. Maybe that's not an issue.

What happens if your strobe disks get out of synch with each other? The software will fail and the instrument becomes useless.

If the drives get out of sync, that's probably because of lost pulses or slip. I said I am concerned about slip, but I haven't commented on lost pulses in a stepper. I don't know how common that is!

But if things go wrong in hardware or software, the instrument is useless no matter what the design is. I agree that this system relies on sync between the channels - and if that gets screwed, then physical damage can result in my design. Not pretty. So maybe some end-stop sensor which shuts down the instrument if it goes AWOL?

Anyway, how do you solve any problem with any mechanical or software glitch? They will happen, and it's not just my design which is the issue!

I seem to get that you are not mechanically inclined and tend to shy away from those type of solutions. Nothing wrong with that, but there are somethings that software should NOT do.

Actually, no. I have fairly good mechanical building skills using my mill and lathe and a few other gizmos. I just think that if I get a design wrong in software, the fix is relatively painless. If I get it wrong in hardware, I have to start over :roll: .

P1IC

08-16-2008, 08:00 PM

P1IC:
I have some suggestions for your design, hope you don't mind me butting in.

Not at all! I'm here to get ideas, just like everyone.

The CDI pointer in your diagram looks like it would scrape on the face of the CDI plate. You could solve this by shaping the attachment to the cable so that the needle sits forward of the cable and protrudes past the face of the CDI plate. Looking side on to the needle, think of a squarish C shape.

I thought that the positioning of the string pulleys (which protrude beyond the front of the backing plate) would place the needle off the face. Maybe the angle of the 3D image doesn't show that.

For the home position sensor on the needle stepper, if you set the gearing such that it only takes one (or less) turn of the gear driven by the stepper worm, then you could have an optointerrupter straddling that gear and just have a hole in the relevant place in the gear.

The opto-interrupter is used on the shaft - or rather, on a clear plastic disk strapped to the shaft. And yes, the sizing of the various drive components require less than one rev for full deviation, so that there is no confusion about the zero point. Agreed.

The interface between the worm gear and the straight gear will be a small issue to solve as well. There are two options which are a) cut the teeth on the straight gear at the appropriate angle for the worm or b) mount the steppers at an angle to the straight gear. If you mount them straight and with straight cut teeth, there will be a fair bit of wear intil they "break in" then you might get a bit of backlash in the movement.

Actually I have got bags of plastic gears and worm drives really cheap from eBay which mesh perfectly, and I will be using these for my instruments. And backlash will not be an issue because of the high gearing inherent in worm drives. Slop of less than one tooth will not be visible on the CDI needle.

Apart from the issues that Ruprecht raised, these are the issues I saw with the construction. As I said, they're solvable. Rup's issues may be a bit more difficult though.

I replied to that post, but maybe you still see issues there? Thinking again about the to / from / inop flag, that's behind the backing plate, so there is no problem about the mechanics. A clear plastic disc (I will use plastic Petri dishes, 90mm diameter, 40 discs for $8, they come sterilised, but that's not really important :p ) with the same drive system as the other indicators will (hopefully) work OK. A set of windows in the backing plate will reveal the icons when they are rotated in to the correct position.

But as AndyT said, any loss of sync is a real problem. Not for the to / from / inop system, which simply fails to display correctly, but it's a problem for the CDI needle, which may go out of range if sync goes belly-up, and wrap itself around the backing plate with extreme prejudice. So my thought is, under what circumstances might that happen?

ruprecht

08-16-2008, 08:25 PM

I will use plastic Petri dishes, 90mm diameter, 40 discs for $8, they come sterilised, but that's not really important :p )

Genius! Where do you get them from?

P1IC

08-16-2008, 09:28 PM

Genius!

Thanks you!

Where do you get them from?

I was looking for clear plastic discs for some time when I stumbled upon these.

http://www.indigo.com/science-supplies/gph-science-supply/petri-dish.html

There is some work required to cut off the rims, which will be required in many (but not all) applications, but if the application suits keeping the rims on, the lids fit over the bases quite nicely so that the two faces can be really very close together while still having both rims available for rim drive. Needles and suchlike can be pasted on quite easily. Getting a good needle cut out of paper is probably harder than cutting off the rim! :(

I picked two sleeves up in Waterloo, but they also mail out.

Regarding cutting off the rims, I've been quite successful with a Dremel tool with a sharp pointed cutter. The plastic (polypropylene) melts a bit, but I think if I make a jig for rotation using my lathe and a sharp cutter I can get a pretty good circumference cut for rim drive if I need that. Testing required! As always.

cscotthendry

08-16-2008, 10:48 PM

AndyT

08-17-2008, 02:00 AM

any loss of sync is a real problem. Not for the to / from / inop system, which simply fails to display correctly, but it's a problem for the CDI needle, which may go out of range if sync goes belly-up, and wrap itself around the backing plate with extreme prejudice. So my thought is, under what circumstances might that happen?

A power surge on power up.

The 90 degree gear is actually called a Bevel gear. Or you can do it like this:

P1IC

08-17-2008, 10:17 AM

A power surge on power up.

The 90 degree gear is actually called a Bevel gear. Or you can do it like this:

Thanks. When you said 90 deg worm drive to remove the need for the cords and pulleys, I thought you meant a long lead screw arrangement with some right-angle drive on it. I am familiar with bevel gears (and I'm looking for plastic ones to interface to my existing gear collection - good luck with that, I hear you say :roll: ).

With the bevel gear, how do you drive the needle without cords? Looks like you still need to translate shaft rotation into linear movement.

P1IC

08-17-2008, 10:21 AM

P1IC:
Re missed pulses on steppers. This only happens (in my experience) for one of two reasons. a) there is a binding on the stepper that is greater than the torque produced by the stepper or b) the pulses are applied faster than the stepper can physically react. The first is a construction/tolerance issue that is a real devil. The second one is easy solved.

Using worm drives, a) may rear it's head from time to time because of the sliding type contact between the worm and the gear. The obvious solution is...

… not to use worm gears? I'm hoping that the gearing ratio provided by worm gears will mean that very little load will be applied to the driving shaft upstream from the instrument. And being hard plastic the sliding friction is low. Yet more experimentation required!

cscotthendry

08-17-2008, 05:49 PM

P1IC

08-17-2008, 09:39 PM

P1IC:

Sorry, My bad. I didn't mean that was the obvious solution. What I thought but didn't say was ...grease. Specifically, I was thinking of that white stuff you often find in toys.

BTW, while it sounds like I've been critical of your designs, I actually think you've been quite innovative. I didn't mean to sound critical, in my clumsy way I was trying to be helpful. I'm a problem solver. I see the world in terms of problems to be solved.:roll:

Yes, Grease Is The Word - hey, someone oughta make a song outa that! :D

And you're right about the issues. Sometimes when people (ie., me) get totally into one line of thought, the little problems get ignored. The overall "brilliance" of the concept blinds the designer to the shadows lurking inside. It takes other people looking at it from the other side, where there is less reflected glory, to see these, and then it's really important that they point them out.

Even then, there is the temptation to make quick-fix patches over the issues, rather than looking to see if its maybe the overall concept which is flawed. Like my suggestion that some end-stop sensor on the CDI needle would signal an out-of sync condition, shutting down the instrument and saving the mechanics. That's clearly a fudge, and the overall concept may fall because of it.

That's what I like abut this thread - this critiquing happens on nearly every post, and no one gets offended.

Michael Carter

08-17-2008, 09:51 PM

"Even then, there is the temptation to make quick-fix patches over the issues, rather than looking to see if its maybe the overall concept which is flawed."

Tell me about it. I've spent more wasted hours on my e-lab bench than I care to say, and then the next morning (or afternoon) a different approach resulted in the desired solution.

You guys working on this HSI are way out of my league mechanically and mostly electronically, but the same thinking on different levels can produce outstanding results if you can think outside the box.

Explore new directions and ideas that you never considered befrore.

Just a thought from a non-degreed mechanical Boeing Skunk Works engineer.

P1IC

08-17-2008, 10:38 PM

Just a thought from a non-degreed mechanical Boeing Skunk Works engineer.

Listen to this guy! An icon in flight simulation, belittling his contribution. Skunky, you're tops. :D

Michael Carter

08-17-2008, 10:55 PM

P1IC, you give me too much credit. I'm mostly a an electronics experimenter (ICBM Tech) and hardware fanagler (parts fixer).

I just use, and do, what works. You won't find many drawings in my shop. But there are a lot of squares, calipers, and rules along with the machines.

You just have to build something every now and then even if its not for the sim. Engineering in in your blood, even if you didn't study for it. :D

AndyT

08-18-2008, 12:04 AM

I used to have a stack of 'Engineers Notebooks' for electronics and building trades. I wish I still had them. They had formulas and diagrams for almost everything you could think of.

cscotthendry

08-18-2008, 03:05 AM

The overall "brilliance" of the concept blinds the designer to the shadows lurking inside.

Ho ho, been there DONE that! The surest way I know to trash a "brilliant" idea is to try and build it.;-) Even so, it's still a useful thing to think outside the box as often as possible.

Seriously, I don't think the synchronization issue is going to be as big a problem as you suspect, as long as the mechs work smoothly, are reasonably balanced, don't require excessive grunt from the steppers and you don't pulse the steppers too fast. That sounds like a big ask, but it's not really. Just due care and attention to detail... The usual process of making things.

You say you have a lathe and mill, so I'm looking forward to seeing your progress on this. Please post some pics of what you're doing and consider setting up a website for your project if you haven't already.

AndyT

08-18-2008, 03:37 AM

Ok, Here comes another Andy Scriibble...

P1IC, Try this:

P1IC

08-18-2008, 09:48 AM

I don't think the synchronization issue is going to be as big a problem as you suspect, as long as the mechs work smoothly, are reasonably balanced, don't require excessive grunt from the steppers and you don't pulse the steppers too fast. That sounds like a big ask, but it's not really. Just due care and attention to detail... The usual process of making things.

I agree. Time will tell!

You say you have a lathe and mill, so I'm looking forward to seeing your progress on this. Please post some pics of what you're doing and consider setting up a website for your project if you haven't already.

Actually i have started a website, not uploaded yet, with the intention of tracking progress. But at this stage I'm still on the drawing board, and I decided that I would wait until my first instrument was running before going live (just in case the whole thing is a bin-job!)

And of course I wanted to wait until after the move to our new home, with the change of ISP - and now of course I'm up to my [nevermind] in unpacking, with Her Indoors keeping a beady eye on me lest I get side-tracked, as I do.

Now, just where did I put that soldering station…

P1IC

08-18-2008, 09:58 AM

Ok, Here comes another Andy Scriibble...

P1IC, Try this:

Cool :cool:

I like the idea of a rack and pinion. If I can find a rack to interface to the cog sets I have, that would be just excellent. I'll do a search.

Or I could cut a rack (or ten) with my mini-mill. Just as soon as I get the workbench built, the mill and lathe set up, the kitchen remodelled, the electronics workstation assembled, the satellite TV installed, the cats fed, the grass cut (again - have you guys had much rain this year? Here in Canada it is just as wet as my old place in Scotland, only warmer)…

cscotthendry

08-19-2008, 12:23 AM

Her Indoors keeping a beady eye on me lest I get side-tracked...

Wot!? Get sidetracked onto flightsim stuff from unpacking!?!?! Unheard of!:roll:

cscotthendry

08-19-2008, 02:19 AM

Hot off the press. Don't look too closely. I made a couple of mistakes on these first gears.

ruprecht

08-19-2008, 09:46 AM

So long as everyone's posting their work, here's what I was doing tonight - working on a mounting bracket for the CDI servo. One of the best things in Solid Edge is the ability to unfold sheetmetal assemblies, makes them very easy to cut and fit.

P1IC

08-19-2008, 10:14 AM

Hot off the press. Don't look too closely. I made a couple of mistakes on these first gears.

They are just gorgeous! :D

cscotthendry

08-20-2008, 07:02 PM

OK, Here's the solution! What solution? What was the problem?...

Boring the centres out of the ring gears was a very tedious operation. On the test set, it took 2 hours to bore a 20mm drilled hole out to 60mm through 9mm thickness. What a pain! Quick as a flash you say "Holesaw!". Sorry wrong answer. Holesaws just jam in the soft aluminium, and driving a 55mm holesaw takes a) A lot of torque and b) puts huge loads on the material and the equipment.

Some time ago I fabricated this rig for making mould masters for my throttle quad knobs. It did the trick very nicely and a) It doesn't flog the guts out of any of the machinery, b) it took about 5 minutes to charge through 9mm of metal and c) it doesn't turn the cutout metal to complete waste. The best part is, the disks that come out of the centre could be used later to make smaller gears.
Take a peek.

ruprecht

08-20-2008, 07:46 PM

Nice work mate. Attached, all the gears we'll ever need for the CAD.

cscotthendry

08-20-2008, 10:43 PM

Yeehaw! Now that's a compound gear if I ever saw one.

cscotthendry

08-21-2008, 01:26 AM

OK, here's attempt #2. Still a minor problem with it. I must have wound the dividing head against the backlash before cutting the first tooth-space as the last tooth ended up a little wider than the others.

ruprecht

08-22-2008, 03:04 AM

OK, all CAD and no cutting metal makes rup a sad boy. So, refer to my Servo Bracket CAD above.

I really need a custom former for this as some of the bends aren't as high quality as I'd like. But overall it works nicely and with a bit more refinement in tooling they will come out true.

It's also gratifying to see it "just work" when you build it totally from the CAD.

AndyT

08-22-2008, 03:29 AM

If this keeps up, we are going to have a working HSI pretty soon. ;) :D

Padraig

08-22-2008, 05:59 AM

Hi guys, I was talking to Andy about this not to long ago, but I simply didn't have time to write the PIC code for the microchip controller, but what I can offer is any type of laser cutting or engraving that might be required for the gauge if needed.

ruprecht

08-22-2008, 06:27 AM

You're my new best friend Padraig! Can you mail me at james (at) radsy (dot) com to let me know what sorts of material you can cut and what format you need the files in? A laser cutter/CNC was one thing we were hoping to get access to to make some of the trickier pieces.

And my company is based in Eire so I might even get over to visit ye sometime!

slainte

James

Padraig

08-22-2008, 06:40 AM

phil744

08-22-2008, 08:16 AM

I tell you somthing chaps ive been reading through all this and i have to admit I am amaized at how you are going about this and the speed of development on what I am sure will be a stunning little product, When its ready I may even revert back to a 747-200 rather than a -400.

Keep up this stunning work chaps and you all know what I am good at so if I can help at all let me know.

BTW, IPC PCB design engineer on Orcad 16 and +10 years of using Solid edge;)

AndyT

08-22-2008, 01:43 PM

Phill,

Please feel free to help out with a nice PCB design. You will not hurt my feelings!

cscotthendry

08-22-2008, 04:59 PM

Hi all:

I would just like to say thanks to Padraig and all the others for their support and offers of help. We really will build these things, but it's not going to be a quick process. We're doing designs and testing building things as you've seen from the pics so far. Some things will work, others may not.

I guess what I'm saying is please don't expect this is going to happen in a week or two. We still have a lot of work to do to make building these things feasible.:)

Padraig

08-22-2008, 10:22 PM

Hi all:
I guess what I'm saying is please don't expect this is going to happen in a week or two. We still have a lot of work to do to make building these things feasible.:)

Thanks, but im not looking for gauges, I just thought that free laser work might be handy towards your project if needed. Either way regardless of time and what not, Im looking forward to seeing your team with a finished product that you all can be proud of.

cscotthendry

08-22-2008, 10:41 PM

Thanks, but im not looking for gauges, I just thought that free laser work might be handy towards your project if needed. Either way regardless of time and what not, Im looking forward to seeing your team with a finished product that you all can be proud of.

Did that man say free? Now you're talking my kind of prices.;)

Seriously, we do appreciate the offer. I hope you won't regret making it as we will most likely take you up on it.

Padraig

08-22-2008, 10:44 PM

Did that man say free? Now you're talking my kind of prices.;)

Seriously, we do appreciate the offer. I hope you won't regret making it as we will most likely take you up on it.

LOL, well now, I meant in helping you make your prototype gauge not a hole army of minions of gauge panels. I simply wouldnt have the time.

cscotthendry

08-23-2008, 06:02 PM

Padraig:

I never really thought you were offering to do production run stuff :)

BTW, can your laser cut sheet metal? Say aluminium at 1.4-1.6mm thick?

P1IC

08-26-2008, 10:07 AM

I know this is now irrelevant :roll: but following AndyT's suggestion to me about using a rack to control my CDI needle, here's my design updating my earlier post of several millennia ago :grin:

The loss of these horrible pulleys and cords is a real relief! And the design is also much simpler to build. Thanks, Andy. I can also use this in VOR and ILS instruments. :cool:

Matt Olieman

08-26-2008, 10:15 AM

Nice work!!!! Looking fantastic :) :) :) Can't wait to see this in action :) :) :)

Matt Olieman

Padraig

08-26-2008, 11:00 AM

Padraig:

I never really thought you were offering to do production run stuff :)

BTW, can your laser cut sheet metal? Say aluminum at 1.4-1.6mm thick?

If its that small then I might be able, but I don't know to be sure, I am still waiting on it to arrive to my port which should be any day now. I have already received some CAD drawings but I think its the face plate. Also, what thickness do you want the face plate in ? I have 3mm Acrylic in clear, white, black. or I could go up to 5mm or 8mm.

cscotthendry

08-26-2008, 03:58 PM

Padraig:
Mostly it's the little fiddly stuff that's hard to machine on a milling machine with manual controls. I don't think there will be any "heavy duty" cutting involved. it's just small parts as I mentioned, from light gauge aluminium sheet < 1.6mm thick. (Take a look at the heading bug on the Bendix style HSI)

For my part, I'm still at the development stage so the drawings are not finalized. I'll send all the drawings to you at one time rather than in dribs and drabs. Is that OK?

Padraig

08-26-2008, 04:26 PM

cscotthendry

08-27-2008, 12:01 AM

Hi all:

Today, I'm trying out gear options and positions. To make it easier to visualize, I did this. I'm sure you'll all agree that it looks pretty speccy (even if it isn't going to be built like this.

AndyT

08-27-2008, 04:01 AM

P1IC,

You are quite welcome. We can still work on your design also. Nothing wrong with having another design handy.

Scott,

As soon as you get some finalized specs I would like a copy so I can begin work on the interface.

cscotthendry

08-29-2008, 03:07 PM

Hi all:

Here's a progress update on the design of the Bendix style HSI. It looks fairly advanced, but it still has a way to go.

Andy there's still a lot that isn't settled yet so no drawings for you at this stage. sorry.

Trevor Hale

08-29-2008, 04:08 PM

This is awesome. How the heck is someone going to be able to build that. it is so frigging small.

Great stuff though.

cscotthendry

08-29-2008, 05:34 PM

cscotthendry

09-12-2008, 03:30 AM

Hi All:

Here's an update, just so you know I haven't given up. The design is starting to look like something useful although still a long way from complete. As it stands, it will have a resolution of 1/4 of a degree which translates to 1440 steps per revolution.

AndyT

09-12-2008, 03:38 AM

Yes Martha, it WILL fly....

cscotthendry

09-29-2008, 01:47 AM

Still plodding...

We seem to have lost Ruprecht.

AndyT

09-29-2008, 01:57 AM

He'll be back. He just has life interrupting right now.
Looking good Scott. How far are we from needing some controllers?

Padraig

09-29-2008, 08:03 AM

Trevor:

Actually, the design is strictly not a "home build" thing unless the "home builder" has a lathe and milling machine with the accessories to cut gears.

We may produce it as a kit or complete. In any case, there's still a lot of work to do to make it feasible. The parts in it are small, but in kit form it should be within the abilities of anyone familiar with a screwdriver and soldering iron to build.

The most costly parts are going to be the visuals like the bezel, knobs, compass ring and CDI plate. These will have to be professionally made or finished.

If your project is going to hit the market on a mass scale in the future, then I can supply you the proper knobs, face plates and what ever else you need in this area, they will be professionally done.

If you even need different gears you can send me prototypes and I can manufacture these also on a mass scale if needed.

AndyT

09-29-2008, 05:23 PM

Looks like we have a factory team assembling!

cscotthendry

10-10-2008, 03:06 PM

OK, Looking close to the finishing line now. Andy, I'll send some details via PM later today about the circuitry required and the board dimensions.

Padraig

10-10-2008, 05:27 PM

OK, Looking close to the finishing line now. Andy, I'll send some details via PM later today about the circuitry required and the board dimensions.]

Wow, those 3D renderings look fab, are these going to be prebuilt ? becasue looking at those renderings it looks very complex for the average simmer to build?

cscotthendry

10-10-2008, 07:46 PM

]

Wow, those 3D renderings look fab, are these going to be prebuilt ? becasue looking at those renderings it looks very complex for the average simmer to build?

Padraig:
Yes it is rather complicated looking. That's why the design has taken a while to get right.

I've simplified most things and if you were able to look closely at the components, you'd see that the only complicated parts are the ring gears and the front bezel. The gauge is designed as 5 main sub assemblies: The compass heading bug set, the CDI set, the forward stepper motor set, the rear stepper motor set and the circuit board. All these mount into a frame that holds the alignment and spacing of the assemblies. For the kit builders, they will build each sub-assembly separately and then assemble the sub-assemblies to the frame.

My intention was to sell these as built or as a kit. I realised fairly early in the design that this would not be a candidate for home-building due to the complexity and precision required. Most of the parts have been designed to be made on a manual lathe and milling machine. But some parts are odd shapes and sizes that would make them a bit fiddly to cut out, hopefully that's where you come in. :wink:

AndyT

10-11-2008, 02:27 AM

Scott, Got the PM. I'll start putting pencil to papyrus.

cscotthendry

10-11-2008, 03:22 AM

Scott, Got the PM. I'll start putting pencil to papyrus.

LOL, But shouldn't that be Quill to papyrus?:wink:

AndyT

10-11-2008, 04:17 AM

The cat ate my quill. I'd use a sharp burnt stick, but I'm not allowed to have a BBQ much less a fire where I live. And besides, do you have any idea how much ink costs these days? ;) Of course with the price of gas, I could likely trade a few drops for a gallon or so of ink...

cscotthendry

10-11-2008, 04:21 PM

Was the quill still attached to the bird when the cat ate it?

AndyT

10-11-2008, 05:49 PM

Nah. This cat has lived inside all her life and freaks out when taken outside. Any birds she attack are toys.

cscotthendry

11-13-2008, 01:36 AM

It's been a while so I thought I'd better let you all know what the status is. I'm still here, and still working on the HSI. I had a bit of a setback with my software and had to re-install it and re-draw the HSI. *sigh* Anyway, after a nice holiday in New Zealand, I now have the model re-drawn and can start to think about moving to the next phase which is designing machining jigs. When I start to make the jigs and some test parts I'll have some pics to share.

AndyT

11-13-2008, 01:51 AM

Now we know what you were REALLY doing in Kiwiland looking at the picture...:D

cscotthendry

07-10-2009, 01:25 AM

Hey all:

I'll bet you thought I was gone. Well, I'm still here and I'm still working on the HSI. I won't bore you with the history of all the edits and re-designing I've done since I last posted but there has been a lot of work in this. I have the design to where I now believe I will be able to build it with my basic machine tools.

I hit a milestone today of sorts. I made the first real bezel. I started out with a piece of aluminium 90mm by 85mm by 10mm thick and whittled it down to what you see here.

Originally I intended to try to make these to sell. I realize now that, that was unrealistic. The amount of work required to make one would make the price prohibitive. The bezel alone takes a good 6 hours to make.

Anyway, I'm reasonably happy with the results. The finish is a bit rough, but since the crown ring and front opening are cut with a router by hand and not with the mill, the depth of cut varies just a bit here and there.

Mike.Powell

07-10-2009, 10:38 AM

You're setting the bar pretty high for the rest of us, Scott. That is outstanding.

cscotthendry

07-10-2009, 11:52 AM

Mike:

Thank you. Credit where it's due, it all started with your book.

cscotthendry

07-13-2009, 02:02 AM

Here's a bit more progress. I've made most of the internal mount plates. I did a test fit of the mount plates, just to be sure everything is in order.

cscotthendry

07-17-2009, 12:14 AM

More progresshttp://www.mycockpit.org/photopost/data/500/P1060464.JPG
This is the stepper mount plate. Almost everything seemed to end up mounted on this plate. The bearing in the middle is for the slip ring connector.

ruprecht

07-17-2009, 01:15 AM

That's looking absolutely brilliant mate!

cscotthendry

07-17-2009, 02:11 AM

Rup:

Long time no see. How's the house going?

ruprecht

07-17-2009, 02:56 AM

We ended up buying rather than building, have finally got the cockpit back together and building a few more bits before the flight sim expo in October. Hope to see you there, and check out the world's first sim HSI!

cscotthendry

07-17-2009, 02:59 AM

Hope to see you there, and check out the world's first sim HSI!

Roger that on the first, fingers crossed on the second!

ruprecht

08-18-2009, 10:35 AM

Scott, where did you end up getting your steppers?

cscotthendry

08-18-2009, 03:34 PM

Rup:

I bought a batch from Futurlec
http://www.futurlec.com.au/StepperMotors.jsp
They were cheap as ...

These guys seem to sell runout stock or something. They're very cheap. Not good communicators, but from my experience reliable suppliers, if a bit slow.

BTW, an update for those watching this. Progress has been a bit slow of late as I've started taking flying lessons and have bought a microlight trike. I still intend to continue the HSI project as and when I get the time ... but I've been a bit distracted lately. ;-)

ruprecht

08-18-2009, 09:54 PM

Ah brilliant, just ordered 5 of the titchy ones. Thanks Scott, and have fun on your trike!

cscotthendry

10-02-2009, 01:49 AM

G'day again:

Progress on this has slowed a bit. I've purchased a flexwing microlight (we call 'em trikes in Oz) and I've started flying lessons. I solo'ed on Wednesday and now I just have to complete the rest of my 20 hours to get my license.

Anyway, here's some progress pics. The markings are just sticky labels to get an ide of how it will look. THe finished item will have screen printed markings and look a lot better.

Enjoy.
http://www.mycockpit.org/photopost/data/532/thumbs/HSI_Progress3.jpg ('http://www.mycockpit.org/photopost/data/532/HSI_Progress3.jpg') http://www.mycockpit.org/photopost/data/532/thumbs/HSI_Progress2.jpg ('http://www.mycockpit.org/photopost/data/532/HSI_Progress2.jpg') http://www.mycockpit.org/photopost/data/532/thumbs/HSI_Progress1.jpg ('http://www.mycockpit.org/photopost/data/532/HSI_Progress1.jpg')
PS: I'll be going to the OzFlightsim Expo next weekend and I will be bringing the HSI if anyone is interested to have a look at it.

ruprecht

10-02-2009, 03:04 AM

Bravo Scott!

And congrats on your first solo - you'll never forget it. See you at the expo.

cscotthendry

10-06-2009, 01:30 AM

I made a little progress on the CDI assembly today

http://www.mycockpit.org/photopost/data/532/thumbs/HSI_CDI_Progress2.jpg ('http://www.mycockpit.org/photopost/data/532/HSI_CDI_Progress2.jpg') http://www.mycockpit.org/photopost/data/532/thumbs/HSI_CDI_Progress.jpg ('http://www.mycockpit.org/photopost/data/532/HSI_CDI_Progress.jpg')

The first pic shows the CDI gear and the standoffs that attach the CDI faceplate. The second pic shows the CDI plate and the top and bottom of the CDI pointer

Kerbo

10-06-2009, 10:24 AM

This is looking great Scott. Thanks for the update.

cscotthendry

11-17-2009, 01:33 AM

Yeah yeah, it's been a while. I've been flying so the poor old HSI has been neglected of late. I finally got a round tuit and made some more parts for the HSI.
http://www.mycockpit.org/photopost/data/532/thumbs/P1070135.JPG ('http://www.mycockpit.org/photopost/data/532/P1070135.JPG') http://www.mycockpit.org/photopost/data/532/thumbs/P1070140.JPG ('http://www.mycockpit.org/photopost/data/532/P1070140.JPG') http://www.mycockpit.org/photopost/data/532/thumbs/P1070137.JPG ('http://www.mycockpit.org/photopost/data/532/P1070137.JPG')

I've added the gear trains for the CDI, Compass rose and Heading bug. I've also added the gears on the rotary encoders and the shafts for the control knobs. I've made the hinge bar and mounts for the glideslope pointer arms (on the back plate) and finally, the hinge mounts for the flag arms (on the stepper plate).

Enjoy

737NUT

12-03-2009, 04:10 PM

Question, Why not write a code and use the stock internals driven by PIC or or other interface. I think it would be easier to do this electronically and code versus mechanical?

theodoretoby

06-08-2010, 12:53 AM

cscotthendry

06-20-2010, 01:02 AM

I'm still working on it.:oops:

lenco12

09-17-2010, 02:00 AM

Hi.....,

I can offer you some good advice. Always be clear in what you are asking for when you post to a forum. I hope my advice is helpful for all your future endeavors.

hockey sticks (http://www.morrant.com/hockey_equipment/hockey_sticks/4519_0c.html)

Question, Why not write a code and use the stock internals driven by PIC or or other interface. I think it would be easier to do this electronically and code versus mechanical?

Leo Bodnar

09-17-2010, 06:33 AM

Question, Why not write a code and use the stock internals driven by PIC or or other interface. I think it would be easier to do this electronically and code versus mechanical?
Answer, Typical HSI uses galvos for flags and needle but synchros for knobs position sensing and driving the mechanical dial. Galvos can work from a regular DAC signal. But each synchro has a rotor coil and three stator coils that usually designed to work with 400Hz AC.
To use syncrho as a motor you have to feed rotor with a 400Hz sinewave and supply 3-phase sinewaves to three stator coils with shifted phase in relation to the rotor. This is hardly a trivial task. To use synchro as a position sensor one needs to supply 400Hz AC to rotor and simultaneously sample outputs of three stator phases. Then resolve the rotor position through vector algebra calculus.
:)
By the way I have a 737 HSI that I intend to drive without any internal modifications. It has 9 synchros and 6 galvos. It is a pet project of mine so moves very slowly (but successfully) so far.

Good luck with your progress, Scott! It looks very impressive so far.

cscotthendry

09-19-2010, 11:17 AM

Leo:

Thanks for the encouragement. Lately, I've neglected the poor HSI in favor of flying. I PROMISE I'll return to it soon and get it finished...Honest. :)

In the mean time.. keep us posted on your progress with the real HSI.

Leo Bodnar

09-20-2010, 09:57 AM

No pressure Scott :) but you've gone too far to stop now!

I have found that my HSI uses an induction AC motor (skewed squirrel cage type) to drive the compass card (and everything else with it.)
It has 5 windings - I guess few of them are for tacho purposes... But we will get there!

lencoo12

09-25-2010, 02:18 PM

Check out simkits (www.simkits.com). They don't have a HSI (yet) but talk to them maybe they have a solution.

Using Easy Guage you can program your own HSI for FS9. I've heard they are working on a new version that allows you to create guages for FSX also but I've no more info on that.

jan_eddh

11-10-2010, 03:22 PM

Yippieh, just got a reasonable priced wrecked KI525A on e..y, I just hope I can get this to work without too many internal modifications. After I have it in hands I probably pop up with zillions of questions

dc8flightdeck

01-13-2011, 12:57 PM

Tony used a real HSI in his F-4 Phantom sim. Video is here. http://www.youtube.com/watch?v=bS7kWIT3fKo

He used 400Hz AC to power sychro senders that are wired to the HSI synchro receivers. He opened some simkits instruments (Gyro Compass and NAV1) and uses their servos to spin the synchro senders.

The needles are conrolled by pots that are also linked directly to servos.

One major complication with using real instruments is the different approach by each manufacturer to make their intstruments. They may look very much the same on the outside, but often work very different from each other on the inside.

Leo Bodnar

01-13-2011, 03:13 PM

dc8flightdeck

01-13-2011, 05:03 PM

Fascinating video!

Any hint where the jerky movement comes from - simulator, servos, mechanics or synchros?

Synchros are low torque devices - they are usually used as feedback senders and to drive light stuff like needles as receivers. Typically HSI card or ADI ball would have a geared DC or AC motor to create movement and then a synchro or resolver in a feedback loop. Interesting how Tony got around that. I assume he does not use feedback synchros to drive the mechanics.

Cheers
Leo

In this case the jerky movement comes from the servo. Airline instruments dampen out the signal and makes for very smooth movement. However aerobatic instuments are very sensitive and and dont dampen out rapid movements. Check out the video on my 737 webpage and you will see how smooth the ADI runs compared to the Phantom's ADI
http://blueangel.site90.net/1_7_737-200.html
For the 737 ADI we had to use signal amplifiers and it was a very involved project.

These units in Tony's F-4 have synchro receivers inside them that drive the motor's position. Normally a remote gyro fitted with synchro senders would feed the ADI or HSI with synchro signals. Instead of a gyro he used servos to spin synchro senders. The motors are provided with power on seperate pins.

I happen to work on gyros for the ADI on T-34's and they operate bassically the same as a Phantom ADI with synchro senders built directly into the remote gyro unit.

Of cource modifying a ADI, HSI, or DG the has a gyro mounted directly in the can rather than mounted as a remote unit in a completely different project.

My F-4 Phantom sim is loaded with sychro driven engine instruments, no motors used in the loop at all which is nice. I just have to take the time to get them working.