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Control stick Mic wiring, Preferred method?

R

ron sterba

Well Known Member
(QB9A) Was wondering about the preferred method of ( Mic and Auto pilot disengage ) wiring out the base of the control stick to the panel? I'm thinking a 3/8" hole and rubber grommet 1" from bottom on forward side of stick. Your comments please as my RV is being built with the preferred methods of Vansairforce members. Just bought two conductor 22 gauge in a jacket, one jacketed for each Mic and Auto Disengage buttons from Pacific Coast Avionics.

Thanks and always much appreciated!
Ron in Oregon
 
cable out the bottom

The above posted thread has a great deal of information about this topic already. However, You might think about all of the comments about weakening the stick by drilling a hole in it. I have the Infinity stick grip that has a large blue cable with all the bundled wires running down straight out of the bottom of the stick. I found it unnecessary to drill any holes in the steel stick. There is plenty of clearance and I allowed for all the necessary movement of the stick from stop to stop in every direction by doing so and eliminated any potential weakening of the stick.
 
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washer

For anyone choosing the welded washer, the easy way is to buy a foot of the next size larger 4130 tube, .058 wall thickness, and cut a washer out of the tube. The optimum washer should not be round, but should be teardrop on top and bottom as installed on stick. Round washers welded all the way around set up undesirable stresses in 4130 that can lead to cracking.
 
I have the seven-button RAC stick grip. I ran mine through a 1/4" reamed hole with a snap bushing. Below the gusset weld, above the pivot point. The wires are covered with shrink-tube.

FP09122012A0004R.jpg


I haven't finished the routing yet, but this is the direction I am headed unless i find something better (just temp zipties for now):

FP09122012A0004X.jpg


FP09122012A0004Z.jpg


FP09122012A0004Y.jpg
 
Hi Colin, Looks like you have a good relief on the exit from the stick.Nice job, ties look good. I went with two buttons on the stick, one PUSH TO TALK and a auto pilot disengage . Keeping with the KISS principal you know.Decided today I needed a new project so I started on the Engine baffles. At least I feel like I'm doing something again rather out thinking myself on the electrical. Merry Christmas.
Ron in Oregon QB9A
 
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ron sterba said:
Hi Colin, Looks like you have a good relief on the exit from the stick.Nice job, ties look good. I went with to buttons on the stick, one PUSH TO TALK and a auto pilot disengage . Keeping with the KISS principal you know.Decided today I needed and new project so I started on the Engine baffles. At least I feel like I'm doing something again rather out thinking myself on the electrical. Merry Christmas.
Ron in Oregon QB9A
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That is funny because I also was getting tired of the electrical and have spent the last few workdays on the engine baffles.
 
WingsOnWheels said:
I ran mine through a 1/4" reamed hole with a snap bushing. Below the gusset weld, above the pivot point.
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Colin, that's definitely not the preferred method.

You've drilled a hole at the most stressed location in a primary control system component. The hole further increases local material stress by roughly a factor of three. I'm sure you're not the first to drill a hole there and certainly won't be the last, but it's still not a good idea.
 
DanH said:
Colin, that's definitely not the preferred method.

You've drilled a hole at the most stressed location in a primary control system component. The hole further increases local material stress by roughly a factor of three. I'm sure you're not the first to drill a hole there and certainly won't be the last, but it's still not a good idea.
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Do you have any data I can review to substantiate that claim? Have there been any reported failures and that point below the top weld of the gusset? I would think the area at the most risk of failure would be at (or adjacent to) the butt-weld line, above the top gusset weld, or below the bottom gusset weld.

Where would you suggest the wires exit the control stick (ie, did you run any wires to yours, where do they exit). I'm certainly open to better solutions.
 
WingsOnWheels said:
Do you have any data I can review to substantiate that claim?
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You will not have difficulty finding basic beam equations and stress concentration equations for holes.

Without question, the stick is weaker now than as delivered to you. I have no interest in specific analysis to determine exactly how much less strong or fatigue resistant it might be. The point is that builders should never weaken a primary control component...in particular when there are good alternatives.

Where would you suggest the wires exit the control stick (ie, did you run any wires to yours, where do they exit). I'm certainly open to better solutions.
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Obviously one choice is out the bottom. The second choice is to thicken the material at the stress concentration, the standard method being a welded patch around the hole, preferably diamond or long oval in shape. My own (RV8 front stick) has a diamond reinforcement cut from a tube one sleeve size larger.
 
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DanH said:
Obviously one choice is out the bottom. The second choice is to thicken the material at the stress concentration, the standard method being a welded patch around the hole, preferably diamond or long oval in shape.
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A third option, at least on the RV-10 stick, is down the back. I am not familiar with the other model's stick configuration to know if this applies to them as well.

Image-7068012-82023156-2-WebLarge_0_3d3ec545fec35e03d0c61974b085dddd_1


Then cover with your favorite material, like:

Image-7068012-91825239-2-WebLarge_0_059e69e6877172fd6a4f94c40c3d8daa_1


These were taken from Geoff Comb's build site.
 
DanH said:
Obviously one choice is out the bottom.
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This is what I did. Works fine. Though I don't have any pictures handy.

Ron, I should have some time after the holidays if you want a second opinion on electrical stuff i'd be happy to go over it with you. I did recently wire up a stick grip with way more connections than yours!

Cheers!
 
Ditto on out the bottom. I just used a piece of spiral wrap on the cable to prevent chaffing. I also made triple sure there was nothing for it to snag on.
 
Bob and Brain nice jobs, James I'll take you up on the electrical visit. Well its looks like I can get a section of plastic flex out the bottom. And a as previously mentioned the phone cord style, you know the curly Q type,you take the cable out the bottom of the stick and you wrap the cable around a pencil and you get a spring looking style that will endure many movements. So I think that's the route for now. Man I thank you all for participating in the thread! Merry Christmas!

Ron in Oregon
 
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