The dual yoke presented a challenge as there is very little information around on how to do this. Most dual yoke sims are designed by builders utilizing column yokes emulating larger aircraft. The telescopic style yoke for GA aircraft is almost non-existant from a sim builders point of view so some creative engineering had to be undertaken. Here is my resolution to the problem.
Once again the emphasis was on simplicity and ready availability of hardware. No welding or special tooling is required except for a hand drill, hacksaw, drill bits etc. Obviously if you have more sophisticated tools it will make your job easier.
I purchased a 2m length of 25mm (1″) aluminium tube from the hardware store and cut it in half. After unsuccessfully attempting to manufacture bearings out of plastic plumbing fittings, I lashed out on this job and bought “pillow block” bearings to mount the axle. This part of the build is too important to put up with inadequate mechanics. These are oil sealed bearings with two grub screws in each one to lock the tube inside. They mount inside a metal mounting block and fit beautifully snug on the 1″ tubing. The end result is very smooth rotation even with tension on the aileron connector pulleys. Both axles mounted on the elevator mechanism. Two pulleys were manufactured using heavy duty threaded plumbing fittings with a notch cut out to accommodate the cable locking nut. 2mm galv wire is lightly tensioned using a turnbuckle to provide unison aileron movement.
I tried a number of different methods to have both yokes move in unison and this is what I ended up with, and it works a treat. Two heavy duty drawer slides I had from an old school desk were used as runners. They contain bearing races and when lubricated provide very smooth movement. Here you can see one of them fully extended. They give a maximum of around 450mm (18″) slide which was more then enough for my 300mm (12″) requirement. To join them together I used a piece of 16mm (5/8″) melamine trimmed to provide a balance between strength and weight. Then the yoke centre poles were attached in their bearings to provide aileron movement (here shown with old plastic bearings now replaced). Springs are used to provide elevator centering and tension.
The combination of the heavy slides, timber support and the 15 degree angle mean that it has a heavy feel about it but the springs counter this a bit. My old yoke had too little damping and felt far too light. If too heavy, my options are to add heavier springs or reduce the incline of the system. The elevator provides a total of 300mm movement from full pitch up to full pitch down. This approximates the movement of a real aircraft. Galv wire is locked into the pulleys using the insides of an electrical wire joiner. A turnbuckle provides tension adjustment.
Now for the electrical setup. Here is the elevator pot with simple wire linkage. For and aft movement of the yokes turn the pot. You can also see the black aileron stop which stops the yoke being turned full circle. This gives a total aileron rotation of about 120 degrees from full left to full right….plenty! This is what I came up with for the aileron control. Using some aluminium bar, wire and a few lego pieces and it works a treat! The wire is bent like that so that it doesn’t hit the black aileron stop when turned full right aileron
A closer view of the beautifully engineered aileron pot linkage. Due to the rotational movement of the yokes translating into only a small movement at the axis, I needed to have some gearing to adequately rotate the potentiometer. This system uses some of my sons old construction toys materials to do the job. As he’s now a physiotherapist I don’t think he’ll miss them!