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[No Longer Active]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..



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:

[Kerbo]

Or get the lathe going! Lol!

I came soooo close to buying a lathe today! My local Harbor Freight 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?

[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.





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..