Push/pull controls

[Kerbo]

I like to build things rather than buy when I can so I am cobbling together some push/pull controls for throttle, pitch and mixture in my GA pit. After some browsing at my local Ace hardware store this is what I came up with.

Note my hi-tech prototyping methods consisting of scrap paper and permanent marker.

The pieces so far consist of:

wooden knob
3/16" aluminum rod
nylon spacer (3/16" ID, 1/2" OD)
nylon washer (1/2" ID)


The rod is a loose fit in the nylon so I need some kind of friction device, preferably adjustable. I think after some paint the controls should look and function quite well.

Is anyone else building their own push/pull style controls? What methods did you use?

[Ronson2k9]

You may want to take a look at this construction article

http://www.flightsim.com/main/howto/pushpull.htm

I'm building something similar to this but with Cessna controls instead the cupboard door handle.. Not that that's not just as good but I figure if I can get it looking like a Cessna control unit then why not give it a shot..

[No Longer Active]

Hi Wriley,

Firstly, if you plan to use a Throttle, Fuel Mix AND Prop Pitch, then your aircraft has just gone from a 172 to a 182 in 95% of cases, so make sure you really know what you want first, aircraft type wise!

Also.....

For your throttle, you have the right idea, I have used and will continue to use my three 100k slide pots to do the job, many slide pots are 60mm slide travel, but you will need to get the 100mm slide pots for realistic results, the 100mm travel pots of very very rare and are hard to find as you will need the LINEAR type, you can use either 10k, 50k or 100k to do the job, either pot will do the job.

As for the Mix and Pitch, these throttles actually have an added mechanism to the slide function, as well as sliding up and down, they also have a twist function, where you rotate the knob left and right, you do this to 'trim' the throttle as you will need to fine adjust the mix and pitch which is essential for flying both VFR and IFR and engine tuning is priority.

To get this rotate function, the only way to do it is to get a set of real aircraft mix and pitch levers, sadly you cant buy just the knobs as it is all connected to make one complete system per lever, although you can just buy the throttles knobs as the throttle does not have the rotate function. If you go down this route then you can pick a mix and pitch lever for around $80 upwards per lever!

You say that you don't like the easy way as there is no fun in it, so I guess we will probably now see these twist levers in your throttle quad lol! Give me the design if you manage to build the twist levers yourself.

I forgot to mention that the mix and pitch levers have a locking function via the button in the middle, and the main throttle is just a friction lock type!

Good Luck!

Alex

[Ronson2k9]

Okay did a bit of work..

http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/ECGCessna206FullRender.jpg

From my calculations (based on Parts manual drawing) the mean diameter of the knob ends are 30mm. To get them to function like the actual item you would need to have a bolt that is moved when you turn the respective control. This could be connected to a treaded rod that is itself bolted to the knob.

So rotating the rod moves the bolt and pushing or pulling the rod moves the bolt. This bolt would then be connected to the pot for the control input.

I plan on making the knobs out of doweling. Drilling and cutting where needed.

The mixture and prop control would function in the fashion described above the throttle however has it's fine tune as part of the mount and not as part of the knob. That one is a bit tricky to figure out but I'm working on it.

The slide for each control can be a piece of aluminum tubing with the treaded rod inside. A stopper so the control never leaves the instrument panel. I'm thinking a nylon nut and UHMW (Ultra High Molecular Weight) Polyethylene should both hold the nut and make it slide very easily on the threaded rod (could also be nylon perhaps?). The nut would be in the UMHW sandwich with just enough space to allow it to move then on the other side would be the pot which could also be held by the UMHW. You could even use the UMHW for the ports for the shaft for each of the controls. Remember the older CHYoke ;) how that would stick sometimes? So with this stuff no sticking ever..

UHMW is available in many sizes and can found at wood working tool suppliers. Used in skid surfaces for routers and other tools. I know in Canada it's available at Lee Valley Tools.

As a NOTE: you can always find a way to make a rotational pot work as a linear one it's all in the mechanics. If you think of a clock.. All you would need is gears and a toothed slide to move rotate the gear. It's a bit more work but if need be.. :)

Schematics of the throttle group to follow shortly.

[No Longer Active]

Hi, I still have my throttle quad from my last project, and have real throttles on the way, buying real throttles does save you a heck of a lot of work!

Believe me the throttle quad is the easiest part to make, Ive made em' a ton of times!

Or get the lathe going! Lol!

[No Longer Active]

Heres one way of making fake knobs:

http://alexpilot.50g.com/throttleidea.jpg

[Kerbo]

Or get the lathe going! Lol!

I came soooo close to buying a lathe today! My local Harbor Freight (http://www.harborfreight.com/) had a big sale going today and their 7x10 mini lathe was $399. But I decided against the divorce. ;-)

My cockpit is based on a 172 but is more of a generic GA single engine. Besides, there must be hundreds of different cockpit layouts for the 172, maybe one of them has a pitch control?

[Kerbo]

As for the Mix and Pitch, these throttles actually have an added mechanism to the slide function, as well as sliding up and down, they also have a twist function, where you rotate the knob left and right, you do this to 'trim' the throttle as you will need to fine adjust the mix and pitch which is essential for flying both VFR and IFR and engine tuning is priority.

I forgot to mention that the mix and pitch levers have a locking function via the button in the middle, and the main throttle is just a friction lock type!


That is good info, thanks. If I ever get some machining tools I may have to tackle that. Why pay $80 a pop when you can build your own? 8-)

[No Longer Active]

Why pay $80 a pop when you can build your own

Lol, for me, its because I have no workshop, shed or garage, everything I make is made in my living room or bedroom, and yes that does involve a lot of hoovering of the carpet!

[Ronson2k9]

It's not so much the layout that decides the equipment but the equipment that decides the layout. Depending on the power plant you have in your Cessna that will let you have what controls you want to have. Avionics and so on are a personal choice but again there needs to be accompanying room for the hardware in the plane to let you put that in there.

You couldn't see a weather radar in an Ultralight as there is very little room. If you follow.

So depending on the engine selection? That will give you the engine controls. I would recommend you take a look at the 172's for sale on various sites to see what is out there. Often times more then cars aircraft have a lot of owner personality in them. You will find things you perhaps wouldn't expect if you are primarily looking at the Cessna site for info.

When you find the one you like? Then go through it's specs. Take a look at it's MIP as it's almost always there for you to see. Perhaps not in high res but good enough to pick out equipment. That's what I did. I 'Shopped' for the aircraft configuration I liked and now I'm going to reproduce that as best I can with a few added things as well. As I can't have everything I want and there are things you need to have because it's a sim.

Been doing a bit more work in the drawings of the Cessna engine control group.

I have 2 drawings. One that is a 'white' print (the opposite of the blue print). That is 1:1 scale when printed. The other is a color rendering of the ECG (Engine Control Group) for the Cessna 206.

http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/Cessna206ThrottleGroupBP_Fullsize.jpg

http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/Cessna206ThrottleGroupOrtho_rndr1.jpg

You should be able to take any measurement you want straight off the white print. Parts almost all be made out of wood except the moving bits what are the actual control surface.

From the looks of the real instrument the throttle is a stainless steal and the other two are a brass rod.

As mentioned from Wriley you can use nylon for those parts as best as can be found. Would give smoother/quieter operation. All rods have a cam on the outside of the MIP so there is support for the rod in it's entirety outside panel. Leaving all the room needed for control mechanics on the inside.

They look simple enough but in some ways if you want full function are a bit tricky to set up. I do think that the nylon threaded rod should work quite well for the both types of movement both rotational and in and out.

Only questions are the extent to which the movement is controlled or where all the stops are..

- Is the fine control infinite (going the length of the control) or is it limited to a few turns? My guess is it's infinite.

From pictures it looks like the throttle can come out about 3 inches or 7.5cm if you include the length of the cylinder 10.5 to the interior of the panel and the stop on the exterior rod. The interior nylon control rod would be that plus length of controller pot.

Working drawings of the complete control setup coming next..

[kermit]

80 $ a pop,
don`t think so ,I bought mine original cessna throttle, mixture and prop rpm including cable for only 20$+ 10$ P&P in total on Ebay.
I have put 100k slidingpods (a 3,95 euro) mounted on selfmade aluminium holders and connected it on my simkits CCU2 .
note Simkits is asking 245 euro ex VAT a piece for the same device.
And you can`t beat the original,
greetz

[No Longer Active]

80 $ a pop, don`t think so

Very much so, maybe you get them on ebay secondhand, $80 from aircraft spruce in UK at the moment!

[No Longer Active]

Ron, thanks for the drawings, so how exactly are you going to make the knobs?

Cheers,

Alex

[kermit]

Thats the charme of ebay
You can buy items on monday for 2 $ and just a few days later you have to pay double /triple for the same item

take a look at this just copy and past,
http://cgi.ebay.com/ebaymotors/Mixture-and-Throttle-Cables_W0QQcmdZViewItemQQ_trksidZp3286Q2em63Q2el1177QQhashZitem35a3e2ad60QQitemZ230382808416QQptZMotorsQ5fAviationQ5fPartsQ5fGear

This is 2nd hand but even that looks better then selfmades, and when you are take your time in account for making them, what will be cheaper?
I know that making your own stuff is a part of the pleasure but I like the original look.
greetz

[Ronson2k9]

You haven't seen mine yet.. hehe

I agree the actual item is always good to have for many reasons. There are times though that even if you can get the real one converting to use in FS or finding them can sometimes prove difficult. I'm always hunting though..

A note on the Throttle: You had mentioned Alex that there is a friction lock on the throttle so that ring just beyond the knob isn't for adjusting it's for locking the throttle? I didn't know that. Now I don't have to worry about getting that to adjust the throttle as I had thought it would need to do.

Now that I know the dimensions of the controls I'm going to see what I can find if doweling comes in that size or not? If not I may end up using polymer clay to make them. I'll have to make a mold first but that shouldn't be to hard. Like you I don't have a lathe so it would be hard to do on a drill press or I could try your idea.. Looks pretty promising too.

It would be cool to get the release to work for the prop and mix controls. I may have a spring loaded 'dummy' version or try to get it working as it should but then I could be going a bit over the top prototypically speaking. I know I want the fine adjust though that makes sense from a flying standpoint.

[Kerbo]

Great drawings Ron, keep up the good work. Are you measuring the real thing or just designing by guesswork? Either way they look fantastic.

I'm using cheap wooden cabinet pull knobs until I have the time to make something better.

[Ronson2k9]

Great drawings Ron, keep up the good work. Are you measuring the real thing or just designing by guesswork? Either way they look fantastic.

Well it's my best guess. First I took the drawing of the C206 MIP from the Parts manual and going on the 79mm gauge I then figured the number of pixels to the mm in my drawing which is 2.34 then I measured the diameter of the controls and divided by 2.34 that's how I came up with 30mm diameter per control. Give or take a mm. The diameter is as close as I can get. The other parts are based on good ref photos.

I got the working drawings up next. That shouldn't take to long to do should be done tomorrow.

The mixture and prop control (if on the C172) are a bit different then the 206 as there is just a thin flange over the port to the instrument panel. For some reason it's much larger on the 206. The throttle though is the same.

As you can see from this photo.
http://commons.wikimedia.org/wiki/File:Cessna-172-trim-control.jpg

You can't see the actual control but the flange over the MIP where the control goes through is there. It is for the mixture control BTW. Looks like this 172 is amphib float equipped from the gear button you see there. I've seen them so I know there out there if you are perhaps thinking of of going on the water yourselves.

http://www.baumannfloats.com///images//randompics//fullsize//cessna172m_onstep.jpg

This is the photo I'm getting all my primary data from.
http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/Cessna206cockpitwiki.jpg

Photobucket reduced the size to about 1/10 it's actual size .. If you like I can email you the full version?

This is the pit I'm building after though
http://www.airliners.net/photo/Cessna-T206H-Turbo/0403998/L/&sid=9745f89be8d7440691e852b5e59ca2ff

I'm almost tempted to build the whole sim in Blender (the software I used for my drawings) but I'd rather build it for real.. hehe. It can make great drawings in 2 or 3D. It's pretty amazing software.

[Ronson2k9]

I have the working drawing complete. This is for the Prop Pitch but the same principal should work for others as well.

http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/PropPitchControlWD.jpg

All measurements are a bit transitory given your equipment. The pot I used for the drawing had a total movement of 60mm which would be perfect as the total movement of the control is 75mm.

You could use a nylon bolt for the nylon rod if a rod can't be found. You would have to remove the head as you need the threads to turn within the slide holder. You could go with a cotter pin approach to connect the nylon rod to the brass tubing. Using a pin vice and small drill bit 1mm perhaps drill two holes through the tubing and rod and then run a piece of piano wire through the holes rounding it back so it doesn't snag on anything.

http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/cotterdetail.jpg

UHMW will work best to keep friction to near zero. That should let the nut slide when the bolt/rod is being rotated and slide easy when pulling/pushing.

The control rod should have support from inside and outside the panel so it can't move in any other direction except that of in and out.

For the C172 that may mean putting extra UHMW on all sides to the bolt then becomes the support as well. Could be a good idea in all instances so long as you can remove that later if anything needs to be replaced.

UMHW comes in many forms including tape. So you can build the holder out of wood if would like or aluminum angle lengths and tape UMHW to it. This could be preferable to screwing or trying to glue it together as UMHW is a wax it can't be glued very easily. Glues can bought but they are pretty pricey. So drilling and bolting is perhaps the best way to connect all the pieces if going with the solid UMHW material. There is the tape though so you could make the holder out of masonite (hard board) and then tape the surface where the bolt will ride. The masonite parts could be glued together with wood glue. UMHW both the solid form and tape can be bought at Lee Valley in Canada the tape is $12.00cdn a roll. There are many other contact surfaces in the simpit that could benefit from that tape (eg: yoke/rudder) making it a pretty good investment.

If you're outside Canada you can find UMHW Polyethylene mostly at woodworking supply shops. It's used in tooling and making jigs for woodworkers. It can be worked like wood (cut drilled sanded). It's best to use carbide tipped tools to work with it as that will leave a cleaner relief. It's quite rigid as well. I've never come across any that would flex in any way. So you don't need to worry about it flexing.

This pretty much concludes my tutorial. If anyone has any other thoughts or improvements feel free to pass them along.

[Kerbo]

Ron,
Could you explain how the fine adjust nut works? I can't get my head wrapped around it. It seems like the nut would need to slide for normal operation but remain fixed in order for the fine adjustment.

Thanks

[Ronson2k9]

Sure no probs.

The nut would slide back or forward as you TURN the control. The nylon rod turns as you turn the control moving the nut to one of it's extremes. So you can slide the nut back and forth by pull/pushing the control and rotating the control also moves the nut but much more slowly giving you a fine adjustment. As fine as the pot will allow of course. The guard is there to act as a wrench kind of keeping the nut from turning as it slides. The UHMW is to make sure the nut never binds on the guard.

In looking at the cotter pin option for connecting the threaded rod to the brass control rod. I should be able to find a nylon washer with sleeve as a stopper (plumbing parts section of hardware store) for both ends of the threaded rod. If not it shouldn't be hard to make one. A large enough outer and inner diameter bushing/tubing would work very well too. That could be put on the outside brass tube at the juncture between the brass & threaded rod with a cotter pin going through all 3 items at once...

At the end of the threaded rod
- stopping the nut from trying to climb off the end of the threaded rod

At the beginning of the threaded rod
- stopping the nut from trying to slide the threaded rod off the brass rod
- stopping the brass rod from coming out of the MIP.

The stopper itself can't be a nut as that would prevent the control from turning. I had thought it could have been at the beginning but remembered that. Further the stopper and cotter pin mean outer diameter has to be less then the nut to keep if from binding in the guard. Glue could be alternative if you can find one that will hold nylon to brass ?? Hence the cotter pin.. hehe

So a bill of materials would be.. (per control)

Nylon Bolt and Nut
Brass or Aluminum tubing
UHMW tape/solid pieces
100k linear slide pot
Wood or Wood Rod (doweling max dia is 1" the control calls for 1-3/16") :(
- I may be able to find stair stringers that are that diameter or a little bigger though?

I'm waiting for someone to come over to the house today but after I'm going to hunt down the bits.. and start putting them together.

[Kerbo]

The nut would slide back or forward as you TURN the control. The nylon rod turns as you turn the control moving the nut to one of it's extremes. So you can slide the nut back and forth by pull/pushing the control and rotating the control also moves the nut but much more slowly giving you a fine adjustment.

Why would the nut slide and the control rod not move in/out when you turn it? The only way I can see this working is if the force to move the control rod in/out is greater than the force required to move the pot. Are you relying on the friction of the control rod bushing, where it goes through the MIP?

[Ronson2k9]

Okey...

The nut will not rotate as it is attached to the pot control arm (drill a small hole in the side of the nut for the control arm). The control knob is secured to the nylon rod via set screw and or glue to keep the rod and control knob as one solid structure. So when you turn the knob the rob turns too. That means the nut on the pot has to move. It will move if you pull on the rod or if you turn the rod the nut doesn't turn only the rod.

The pot is secured in the guard which is itself secured to the MIP.

So..

Pot + guard attached to MIP (so that you can if needed remove the pot later)
Nut attached to pot so nut can't turn. This will cause the nut to move should you turn the rod.

The guard is there to help prevent the nut from turning. Just a bit bigger then the outer diameter of the nut so the nut can slide but not turn. If using UHMW that will make that even more so as it's super slippery plastic.

Rod can turn or slide either way the nut moves the pot. Either incrementally or directly.

Hope that helps

[Kerbo]

So when you turn the knob the rob turns too. That means the nut on the pot has to move.

Why would the nut have to move?

When you turn the rod it is just as likely the rod will slide in/out (and the nut not slide) as it is the nut will move (and the rod not slide). There has to be some force stopping the rod from sliding to get the nut to move the pot when you turn the rod. That force is my confusion. :)

Think of holding a bolt with a nut threaded on it in your hands. The nut is in your left hand and the bolt is in your right hand. Now turn the bolt with your right hand. Does only your left hand get pushed? No, because the force against each hand as the nut travels on the bolt is the same (all else being equal).

If you are planning on the friction required to slide the rod through its mount being great enough to overcome the force of the nut sliding the pot (thus causing the nut to slide and not the rod when the rod is turned) that is fine. I am just trying to get your design clear in my head. :?

Sorry for being so dense!

[Ronson2k9]

Yep your right I hadn't thought of that. Okay.. So to get the nut moving we need to keep the rod from moving during the rotation.. Working on it.. Remember the button on top of the knob.. We know that's to keep the rod from moving when not pushed in. So that must release something in the cable to allow it to slide freely.

What could I use to keep friction high when rotating but low when push pulling that could be activated by a push button. Non of them simple options.

- Separating the rotation from the push pull via CAM.

- Spring loaded release.

- Electro magnet (always on until you push the button to turn it off)

- Turnbuckle. Rod has threads going in opposite directions. If you have a nut at both ends turning will bring then together or spread them apart. Like a wood clamp where the turning brings the end together.. Trying to think of what kind of thread that is.

Wood clamps keep coming to mind for a solution to this though.. I'm still working on one perhaps you have some thoughts..??

[Kerbo]

I don't have any bright ideas yet. We need to know how a real one works because some bright engineer already figured this out. :D

[Ronson2k9]

I dare say they aren't going to give their engineering drawings for a shot at duplicating their controls. Cutting open one to find out how it works probably not a good option. I would use it first.. hehe..

Difficulty is that the hole thing has to move.

Okay is possible to route two pots through the same control. 1 could be for the push pull and one could be for the fine tune. 2 50k's for instance. The only problem with that would be in order to have the full movement of the control the turning pot would need to be fully engaged (turned).

I think I have it .. Worm Gear...

Beauty of this is you can rotate to get a movement and you can push pull to do the same movement. The resistance to being pulled is greater then being turned (theoretically). Or if resistance is still pushing the control out. We could use the two pot method in this case it perhaps is a bit easier to set up.

Essentially what the nut on the rod is - is a worm gear. If you think of the nut as a gear.

It would be cool to have the linear pot cancel out the the rotating pot when getting close to either end. Reduced the amount the rotating pot effects the total output voltage.

Probably what we could be looking at here is a rack mount throttle group with PC board and 3 sets of pots.

The linear one would change from having nut to a simple bushing to allow the rod to turn but not pull through.. The worm gear would be prevented from moving laterally but be allowed to turn. So the driving gear would have a hole with a key way to get it to turn.

Or we could work it so the button turns off the rotating pot as it's (push button to pull/push control). That brings about a possibly different thinking all together. Both pots work independent of each other. Then you would need a form of memory so that one can act on the others last position. Doing in logic what I've been trying to do physically.

I'm pretty sure you could put both pots in series and have a cumulative effect on voltage. The control wouldn't be that accurate in as much as you have two positions and combined they equal the output. So those two positions would change from time to time to equal the same output making for inaccuracy when using the control. Weather or not that inaccuracy is a problem depends on the amount of fine tuning that is permitted that is the percentage of change due to turning. If it's not very much then it's not so much a problem. Hold on a sec that would happen in the real control too. As you could fine tune back to a position you had first slid too. That being the case the actual control must move when turning. Otherwise it would get out of 'tune' when you did that over time?

Any thoughts now??

PS: We could just forget the whole fine tune thing and go for the straight push pull only.. Eliminating nearly all this stuff.. and about half if not more the cost of construction.

[Ronson2k9]

Rethink.. Again:

That bushing moving the pot and the screw action moving the control got me thinking again. What if the nut didn't move the pot but a bushing did. Then the nut could hold the rod till you turned it. We would need to change the amount of hold preventing the nut from sliding when you want to pull/push the control. Or provide enough constant resistance so that you still slide the control including the nut..

I'm thinking UHMW again this time though you want to make it as resistant as possible. Working at from the other direction. You still want it slide but under force. A bit more engineering involved yet.. I'm getting closer though.

The nuts job is to allow the turning of the rod to move the pot.. That's all it does. So we need a way to add resistance to the push pull to stop the from moving the nut... Need to separate off the resistance to turn the rod from the resistance to pull/push the rod. So one can be greater then the other slightly.

New drawings will be on the way I think I've got it licked this time.

[Kerbo]

Someone mentioned the button on the mixture knob locks the control in place. Does this then allow fine tuning by turning? I've always been an armchair pilot so have no idea how the real stuff works.

[Ronson2k9]

I think it would be pretty easy to grab the knob with your fingers and pushing in with your thumb release the control then push or pull. I think it stays locked as a natural course and is released when pushing the button..

That said I think I found a solution to the friction problem that keeps the design pretty much the way it is now.

We need a tube to go around the threaded rod that is free floating rotation wise at the contact with the control knob. So long as the threaded rod is able to turn within that tube the tube can then be acted upon for friction purposes.

I got new drawings on the way.

[Kerbo]

I got new drawings on the way.

Sweet!

What software are you using for the drawing and rendering? If you mentioned it I apologize for missing that.

[Ronson2k9]

It's Blender..

http://www.blender.org/

It's a GPL 3D modeling studio.. I use it for a lot of different things including sci-fi modeling and artwork but lately I'm mostly using it for flight sim stuff. You can import FSX aircraft into blender but so far there isn't an export - there still working on one.

Speaking of the Cessna throttle group.

There are a few options with the control function in how we'll set up the controls.

Option 1
- The control will stay in position till you pull/push on it. Turning the control will give you a fine tune but will not physically move the control.

Option 2
- The control will move when you push or pull or turn the knob and still give you fine adjust.

Option 3
- This applies to the other 2. You can position the threaded rod and pot so that you can adjust as soon as you move the control. That is the threaded rod extends out past the pot at it's off/zero setting. So the pot is farther away from the back of the MIP and the adjustment nut is half way down the possible threads it can move along. This will let you pull and adjust back if you like or adjust forward without pulling on the control. I was thinking that would be a good option as you may want to fine tune at any position. Of course you can only move the adjustment from zero forward to begin with but once you have moved it you can then adjust right away.

Option 1 and 2 require two different set ups so it's important to decide which you would like first.. I've got option 1/3 on the drawing board right now. I have option 2 in sketch form but haven't incorporated 3 in that yet.

[Ronson2k9]

Well I got the design done.

It will take a few more parts to add the added tuning function but I think I did it as economically as possible.

The primary principal is the friction brace. That will keep the friction to move the pot arm/control nut much less then to move the control itself. There is a free floating tube that will not turn I'm hoping. Steps can be taken to ensure that doesn't happen but they perhaps aren't that necessary. It's okay if the tube turns but would be better from a wear and tear standpoint to keep it just moving in one direction.

Control Knob...

http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/PropPitchKnobGhost1.jpg

The knob is made from wood and can be drilled to form the shape of the Prop Pitch control. On the inside are 2 drilled holes one small hole to accept the fine adjust rod and stopper (to make sure the threaded rod turns when you turn the knob). The larger one to hold the brass control rod. It will float inside the knob with two plastic bushings helping to keep it from turning when you turn the knob for fine adjust. I'm hoping the friction brace will help keep the brass rod from turning as well.

This is Knob Cross Section.
http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/PitchKnob_CS2.jpg

Onto the back end.

This is behind the MIP or perhaps if you like can be installed in a rack mount plate (making for easy adjust or repair if needed).

I'm working from the 3" through of the pot as a guide so that is the maximum length the control arm can move including the fine adjust. As yet I don't have the actual items on hand so can't offer dimensional info but you can get the idea of the working and make your measurements based on your materials.

As the outer control tube is free floating the friction brace can work as hard as you would like to hold it in place without preventing the fine adjust from working. I even built in an adjustable friction brace so you can set the amount to your liking.

http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/PropPitch_RComp1_Labelled.jpg

FRICTION BRACE

I figure I would make that out of a masonite sandwich with 2 rubber washers the same inner diameter as the outer diameter of the OCT (Outer Control Tube). Then cutting them and removing about 1/8 chunk from them this will allow them clamp adjusting the friction on the OCT. The sandwich is to hold the washers in place. The 'Bread' is 1/8" larger then the OCT diameter and the 'Meat' of the sandwich is the outer diameter of the rubber washers. The brace is then glued together (making the sandwich). Then cut in half and sanded on the edge of the friction area to give room for the clamp to work. The brace is drilled and with the rubber washers inserted it's slide into place in the brace brackets.

The rest of the design is pretty much what I've talked about before. There is added mounting plate (wood) so you can bolt it from the front of the MIP. That screw does double duty holding the Pot Guard and Pot as well. Which is screwed from the inside out. Remember to counter sink the screws so the control nut has free passage.

This would probably be a lot more effective as a worm gear and transmission as that would let you set the travel distance and eliminate most of the work but more complex to design. Parts perhaps harder to find.

There is some sheet metal in this design but you could substitute wood if you like.

If anyone has any questions or suggestions pass them along please. I'm hoping to begin building one of these this weekend so I'll be able to bring some parts lists and dimensional info hopefully.

Ron

[kermit]

Hi,
As soon as I have my cockpit installed I can make some pictures of a exploded view of a orginal Mixture controll
regards Henk

[Ronson2k9]

Hi,
As soon as I have my cockpit installed I can make some pictures of a exploded view of a orginal Mixture controll
regards Henk

If you could tell us what the actual control does. Not to say that we don't know what they are for but how the control acts when in use. That would be quite helpful too.

It would be cool to get the actual control and hook it up. I wouldn't want to cannibalize it though. I'm thinking the section I have where the pot is located would work just as well with the control cable instead of the rod that is the design now.

It's a bit of a hit and miss to the measurements as it all depends on what I can find at the hardware store to build it with. To that end it's the same for everyone else too. Once I get some of the materials though. I'll be able to put numbers to the drawing to take some of the experimentation element out of the design.

I still think a worm gear would do a much better job. I just don't know where locally I would find it. It would need to be small enough to fit in the space but big enough to do the job. Rotary 100k pots are easier to find though so you gain on that but perhaps loose on the other.. hehe..

[kermit]

It will be up for sale shortly together with a prop rpm control and throttle all orginal aircraft hardware,
I have purchased a real cockpit section of a Cessna 172 with the orginal controlls logbooks and other hardware , but still waiting on delivery.
I have already had the control opened up for adjustment to a pod and for my own curiosity:D

The innertube has a smal metal ball that locks thru a small hole to the outerhousing(that has a threaded inside wall and that in combination with the ball works as a fine adjustment) when the pushbutton with a small long pin isn`t pressed.

When the button is pressed the metalball sinks in a little dent on the pushbutton pin, so the innertube is releasing itself from the outerhousing.
on the innertube they have connected the cable that goes to the carb or mixturevalve.

When the button isn`t pressed , a smal spring under the knob will push the knob with pin back,
therefore locks the ball under tension between the innertube and the outerhousing.


I have connected that cable who is free turning on the innertube to the pod
greetz

[Ronson2k9]

Pretty cool.. Love to see pics of your new 'hardware' when you get a chance. I know if I got something like that I would want to dig right into it.. It's a good idea to take some pics though just so you have a record of where you started from.

That information on the controls is a bit more detailed that I had been hoping for. I was mostly wanting to know..

How far the handles pull out?
How many rotations there are before it requires a movement by pulling?
Actual measurements of the controls as I'm only guessing from my parts manual?
Does the control move in and out if turned?

That kind of thing. I could be interested in your controls when you have them available as there are many here that would be I'm sure? Depending on where you live and so on??

If I could get the data on them before you sell though that would be really quite cool..

Thanks in advance?
Ron

[kermit]

Hi Ron,
I will make pictures when I`m collecting the cessna, uptill its in working order.
Here some more details about the controls, I bought the controls from ebay and made them work with the Simkits CCU.
Simkits is asking 265 euro ex vat a piece for them,I did it for less

Mind before I could us them I had some pods go up in smoke and flames before I could figure out the connections, After 3 days you could still smell the burned pods:grin:

How far the handles pull out?
its now being limited to the pod being 6 cm full in to full out, but can go to 8 cm
But the CCU has calibrated to full in and full out, with Flight one`s cessna 172 you can really fine tune the controlls

How many rotations there are before it requires a movement by pulling?because off the above limitations (6cm) 26 turns full in to full out
pulling is not a part fine tuning, it goes from 0 to 100 % motor-rpm without the need of pulling.

Actual measurements of the controls as I'm only guessing from my parts manual?Do you want all the measurement? I will do that tomorrow if I have the time

Does the control move in and out if turned
Yes ,when turned the control moves in and out

greetz

[Ronson2k9]

Cool and thanks. I had a feeling about the controls moving in and out as that would also tell you where the control is set. 8cm is about 3-1/4 inches at full so the 2-1/2 inches is good too. I had earlier thought of the control moving when turning. It will take a bit of re-write of the design to get it to do that. I think I can design it to do that though.

The outer tube would move the pot and the control nut would stay stationary. Then when you turn the rod that moves the control and the outer tube as well as the pot.

Looking forward to your C172 pics.. and those of the controls?

[kermit]

You have to make sure that the outertube stays put,
it is your controll body that has to be fastened to the in the instrument panel ,
take a look on the simkits-site and look for the control, that the way I did it
greetz

[Ronson2k9]

Okay.. In the previous design the control would be able to rotate and do a fine tune but the design kept the control stationary . We have found out from Kermit that this is incorrect from a prototype standpoint. So there is just a little work to get it to move the control as well when being turned.

A few things will stay the same. It's basically all the same parts with a few added on.

THE FRICTION BRACE

I deleted the friction brace. However given the difficulties with the CHYoke at times it might be a good idea to add a UHMW/Nylon washer to both sides to make sure the rod can move smoothly through the port in the MIP

BRASS CONTROL ROD

This is now where the pot movement will be coming from. So you will need to lengthen it so it can move the full length of the pot travel. You will need two stoppers and a bushing/eyelet (for the POT connection). Besides holding the bushing/eyelet in place for the pot control. One is also to stop the control rod from sliding out of the MIP.

THE THREADED ROD

This is now going to move the control when you turn or push/pull the knob. You will still need the nut to be free travel but you want more resistance on the nut so that when you turn the knob it moves the control and POT are as well. The threaded rod need not go all the way to the knob if you can't find threaded nylon rod. You can find nylon bolts that could serve in this instance they would need to be perhaps 4+ inches long to allow for securing to the control rod safely.

You can use an eyelet instead of a drilled (stopper with set screw removed) bushing so long is the out diameter is less then that of the control nut and the inner diameter is big enough to slide over the tube.

THE CONTROL NUT.

In this instance the nut is no longer connected to the pot arm. That pot arm connection will from a stopper on the brass tubing. The nut now will move the entire control when you turn the knob. You want to increase the resistance on the nut to move by clamping the nut in the guard a bit harder then in the previous design.

I also can perhaps replace the UHMW with masonite (shiny side to the control nut) so you can have more friction on the nut but not too much as the control nut must move when being pulled (unlike in MK1 when it moved as the control was rotated). The only friction in this design comes from the nut. So in many ways it's a simpler design. UHMW should give a more solid feel (resistance will be constant) so if you can find it could be worth using over the masonite.

-------------------------------------------------------------------------

This version although more prototypical is a bit of a balancing act to get all the frictions to work with each other. As there is more happening in that regard.

In Design 1 (Friction from..)

Friction Brace > friction from moving the pot/control nut

In Design 2 (Friction from..)

Threaded rod + control rod > Pot arm travel/control nut

Hopefully I haven't confused everyone.. :)

I'll make up a drawing of this design too as it is a bit easier to understand that way.

Edit: This is the new drawing.
http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/PPC_MK3_Comp.jpg

Both designs should work well.. I now it's just a question of building them.

I'm thinking because of the challenge and the prototypical nature and the added benefit from knowing where the control is set the second design stands out pretty strong.. That's the way I'm going to make mine anyway.

Just for fun.. The parts manual shows them not evenly spaced but I think I can manage them if they are..
http://i416.photobucket.com/albums/pp244/Ronson2k3/Cessna%20T206H/CessnaThrottleGroupCR_JFF.jpg

I did enjoy the brain bending on this design.. If you have any questions or other comments feel free. Photos of my build will be up shortly.

[Kerbo]

I found these little diagrams that help understand the locking mechanism for the controls with a button and provides some important dimensions.

http://www.acsproductsaz.com/790ball.htm
http://www.acsproductsaz.com/790.htm

[Ronson2k9]

Thanks and cool.

I got the measurements pretty darn close I'd say. Given that I was working from a blow up of the MIP in C206 Parts Manual. Some of the other stuff I got from photos. There is a 3" travel on the linear pot so you really can't make that longer. Most if not nearly all of the build is out of wood except the brass tubing and the nylon rod. I tried finding that Home Depot but they didn't have it. There is a fixture place that sells industrial fixtures I had went to before for another project. I had forgot about but found again when looking. All they sell is nuts and bolts and stuff like that. Including a complete selection of Nylon. Don't know if I can threaded rod in that but a long enough bolt will do. I tied it at Canadian tire even though it was the wrong size and it's so smooth it will work perfectly for this.

My model is drawn to scale BTW that is the computer model I have. It's 1 BU (Blender Unit) to each cm so it's no problem making a 'Scale' drawing of it.

I'll take the drawings (links you posted) and check them against mine and make changes as needed.

It would be cool to get the release button working. But remember we are working with wood here. The button install would need to come before anything else. I had thought of the electro magnet as a way to release the friction on the control rod. You could almost use a bicycle brake system if you wanted to. Hooking up a cable to button. It would make it pretty complex then though.

Could make it a fake though maybe. That is the button depresses but doesn't do anything more. Would need to add a spring to the interior of the knob and a cap and button of course.

What do you think of the idea..

1 - Make it work using an electro magnet?
2 - Make it work using bike braking?
3 - Make it look like it works with a spring?
4 - Make it a non moving button?

Personally I like #3.. Would make it a bit harder to build but not to much harder. This only applies to the Prop and Mis controls...

[Kerbo]

I'd be happy as long as it looks and acts like the real thing. For my sim I am going simple for the throttle/prop/mixture controls for now and will revisit them later. I have too many pieces started already. ;)

[Ronson2k9]

All righty.. I'm thinking that will require a spring and a cap on both ends of the knob. The cap on the back end can be the faring though. That will require the control rod to be attached to the faring and not inside the knob (need room for the spring and button - also trying to keep it simple).

I was thinking of putting the rod in there anyway (well attaching it to that). Just didnt' want the control coming apart when being pulled. So will need some good gluing to get this right.

For the button I was thinking maybe a twist top bottle top (if the dimensions are right) probably not though. So a piece of sculpted doweling will do the trick I'm thinking. Well 2 of course. There are lots of things you can do to nylon but one if the things you can't is Paint..

We can put the button on a pin (piece of doweling) that will both hold the spring in place and keep the button going straight in and out. Could be easier then trying to hollow out the button so that it can accept a larger diameter spring. I'm thinking the real one pushes on something in the control anyway. It will act like the spring in a ball point pen with out the click.. (I don't think it locks open in the real one). Could use some UHMW plastic tape around the pin to make sure it never sticks to the socket it will fit into. Always not be ready for such things. In this case as when it's closed .. It's closed.. So no going back when knob has been assembled. Unless I put a nut in the end of the knob and a threaded rod to connect the two parts.. UGGG.. There should be a way to get it together without glue.. To save making more knobs and stuff. Probably with metal parts in this time as you want them to stay together till you unscrew them .. You don't want the knob coming off the faring when in use.. hehe A little bit of locktite should take care of that. I'll see what I can come up with...

The knob is getting more complex now hehe..

I'll be back later with a new cross section and dimensions now that I've got the info from those sites you hipped me to.

[Kerbo]

I'm looking forward to what you come up with, keep us posted.

[Ronson2k9]

Well this is what I have so far.

Side Cutaway Ortho
http://i416.photobucket.com/albums/pp244/Ronson2k3/PropPitch_KDCutaway.jpg

3/4 Cutaway Ghost Ortho
http://i416.photobucket.com/albums/pp244/Ronson2k3/PropPitch_KDGhostedCutaway.jpg

So far it's an enclosed design as it's a question of getting the two main parts to mate and still let it come apart. Also I don't want to tempt it coming loose inside as turning (push/pulling) could cause over time. So while building it to come apart to fix also means that it can come apart at anytime.. While an enclosed design has more strength it also means that you would need to be prepared to rebuild if need be. I myself don't think that you would but you never know..

Basically the design incorporates a spring for the button.
- Button is on a shaft that is partially prevented from full insertion by the knob and full retraction by the washer and screw. It is also under tension that should keep the button from sagging.

Precise drilling is a must and is perhaps done first before anything else. The knob can then be held in place while details are created. Then the other parts are added as the knob is assembled and painted.

When looking at the drawings from the site they seemed a bit less accurate then I had originally thought. They don't quite give enough detail to show the size of the knob. As there are ridges and bumps you can only guess if they are included in the drawing so The length from MIP to the tip is what would be the most accurate.

Myself I'm working on the assumption that all the knobs when pushed all the way in are at the same length from the MIP. It just seems to make sense to me. They are different sizes and of course textures. Should be able make easily if you have a drill press and a good set of bits. Forstner bits would be preferable if you have them for the interior drilling anyway.

Addons to the design.

The pocket that the spring sits in could be susceptible to binding on the spring when pushed..
- You could add an exterior collar around the spring that is free floating in the pocket so the spring doesn't bind
- Beveling the pocket could also work to that end as well.
You would need to augment the diameter of the spring pocket to accommodate.

Still to do.

Need to find a way to lock the tubing/threaded rod into the flange that is holding them. To keep the knob from turning them loose. A keyway could work or a set screw that goes all the way through from the outside. Being able to hide that though would be something I'd want to do.

Care must be taken to make sure all parts line up correctly
- Brass tube
- Knob Flange
- Knob
- Knob button

If any of them are out of position that would be bad. That's why drill first and detail after. If you mess up the drilling you haven't spent all that time detailing.. Not that we aren't all talented people. A small jig to keep everything in position to do the detail work would make that a hole lot easier/safer. A countersunk piece of ply with a carriage bolt should do nicely.
Any other thoughts bring them on..

Drawing with measurements to follow - baring any suggested changes..?

Ron