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I had several problems with commercially available yokes. The cheaper ones don't have the travel real yokes got, only about half. This applies to the pitch as well as the roll axis. 18 cm from full down to full up elevator. Aileron axis travel is 180 degrees from full left to full right, as measured in a Piper Archer. The expensive ones aren't much better. Exceptions are possible as I may have overlooked one or two. Usually the yoke is just that, and I wanted more features, more like some products which are becoming available nowadays. I wanted switches for battery, alternator, engine start, all the lights, gear, flaps trim, etc.
I needed some donor hardware. I chose a game pad Yes indeed...Not the first thing you expect to be a donor game control especially for a yoke. But the Logitech rumble pad has 5 axes, on 2 joysticks and one throttle. Plus a lot of buttons, which I could use for a lot of functions. And I had already used other Logitech devices. I want to stick to one manufacturer to prevent problems with drivers, etc. The rumble pad gave me one other very interesting possible feature, a stick shaker! The game pad has 2 motors in it with off center weights on it. If I would be able to incorporate this in the yoke I would have several nice gear or stall effects. I first tested the rumble effects with the device intact. After disabling the control forces I had a very acceptable effect. A little rumble on takeoff roll or after landing, a nice gear up thump and subtle gear down click and the stick shaker worked well in the jets. But that would be the icing on the cake!
The painted box with holes to mount the switches, etc. The wood used is 9 mm plywood.
To save height I wanted to position the roll spring horizontally instead of vertically. Which was not a problem after all. Depth on the other hand was. A spring takes up a lot of space when not stretched. Mine had to be about 10 cm long unstressed to be able to extend to up to 30 cm total. This is needed to accommodate the 18 cm travel and still be under a little tension in full up or down position. I attempted to position the springs from left to right inside the box and use a cable to connect them via rollers to the yoke rod. It did not work well, the rollers caused so much friction that this was not a viable option. I tried a different approach, to place the springs diagonally. That way when the spring is not under tension it is parallel to the front or rear of the housing. When fully extended it runs diagonally across the box.
This diagonal spring set-up saved me a lot of space and I could get a travel of 18 cm in a box with outside depth of 25 cm (the wood is 9 mm thick). Also the spring was able to be extended in full up or down deflection without being over stretched while still being under a little tension in the other position. It did cause a bit more friction in the rod guidance, but I came up with a solution for that. More on that later.
Roland used a threaded rod to attach everything to; this seemed like the way to go. Nuts can be modified and turned into mounts for all kinds of things. The pitch springs will be attached to a bolt in the middle of the yoke rod. This bolt serves more functions. It will also be used for the roll spring and the link for the pitch potentiometer. All this on one bolt? By soldering a plate to it you can enlarge its surface and provide a space for all kinds of things, and you can solder threaded rods to it as well.
The yoke rod consists of the threaded rod on the inside and an aluminum tube on the outside. (I am now thinking of replacing it with chromed steel for a smoother feel and less wear.) Nut 1 holds the tube in place as well as nut 2. Nut 2 also has a piece of threaded rod attached to it which in turn is connected to the roll spring. Nut 3 has been smoothed on the inside so the treaded rod can move freely in it. There are two pieces of rod attached to nut 3. One to connect the pitch springs and the other which runs along the guidance bar. The roll spring is attached to this bar as well. The guidance bar prevents the rod with the roll spring to turn but lets it move back and forth. The blue lines are nylon spacers to let nut 2 and 4 turn smoothly against nut 3. To let the yoke rod move smoothly I used nylon rings where the rod enters the box. These are mounted on the outside of the box.
This is nut 2 with the roll spring.
This is nut 4 with the plate and rods. The hole in the plate is where the roll potentiometer goes. The roll stops are also visible. These stop the rod on nut 3 from going too far. On the bottom you can see the connection and part of the pitch potentiometer strip. If you look close you might see that the inside of the nut is smooth.
Here's a picture of the assembly.
The gears are some kind of nylon-like plastic. I had to enlarge the holes in the gears, which is hard to do if you have to drill a 12 mm hole. The hole has to be in the middle otherwise the gears will wobble. I failed. So I had to fix it. I modified a washer to hold the gear on the yoke rod centered. The hole for the potentiometer axis was made just a little too small so it does not need additional fastening.
This shows the gear wheel and the tapered washer to keep the gear wheel centered.
This is the guidance bar. The notches are where the roll spring is attached. To let it run smoothly I used 3 small ball bearings (not visible). Two to prevent it from moving along with the roll of the yoke. These are adjusted so there is no play but no extra friction either. The guidance bar does not need lubrication but needs to be clean. The third ball bearing is used to counteract the pull of the pitch springs. That one is just visible on the far side. It can be adjusted by turning the bolts on either side of the aluminium plate. The guidance bar needs to be exactly parallel to the yoke rod for it to work.
The completed yoke box. Rumble pad and toggle to momentary circuit board on the left. Game pad and a second toggle to momentary circuit board on the bottom on the right. The pitch spring set-up can be clearly seen. The pitch potentiometer sliding strip can also be seen.
So to make a long story short I used a real Piper yoke for my project. It was the most expensive part but well worth it. It had a tube fixed to it which had to go. I made a round wooden block to fill the hole and made sure it was a perfect fit. Attaching the threaded rod was a bit harder. I needed heavy duty washers to keep the wood from being crushed. The whole thing needs to be firmly tightened so it does not give way when under stress from the roll spring.
Shown here is the yoke with horn extension on the left horn. Also the telephone type cables which provide the connections for the buttons on the yoke are visible. An external solution may not seem very tidy but it can be found on most real GA aircraft with buttons in the yoke.
Shown here is the other side of the yoke. The washer is clearly visible. The connector is still on the telephone wire; I use it for easy disassembly or maintenance. The female type is installed in the box.
This was made from copper alloy sheet. I was kind of proud after finishing this. The hole in the front side is for the original push to talk button which I installed but it is not functional. On the top are holes for the a/p and f/d functions. The big hole is for the pitch trim.
The yoke after the completion, I would add the extra switches at a later stage.
