Control Stick for 3 axis push pull tube.

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blane.c

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I don't know what forum this question belongs in but most likely it will involve some tubing in construction so here it is.

Are there any successful control stick designs available that pass 3 axis control through one hole in the spar(s) of a low wing?
 

Deuelly

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Maybe something like the RV-4 where you have a 1.5 to 2 inch tube going through the spar with a bell crank on the back for ailerons. Then the push-pull for the elevator runs through the center of that.

Brandon
 

FritzW

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Are you talking about going through the main center section spar on a VP-3? ...I've got a CAD model of that somewhere
 

blane.c

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Seriously! Cool! I've been giving it some serious thought for several days, got a couple sketches but thought it might be wise to see what others have done before proceeding. I think The -3 would work well with a elevator push pull tube in addition to the aileron's and am curious about the rudder as well. I am curious about control stops, the as drawn yoke will stop on the forward weld and aft radius of the elevator control slot which seems odd so maybe the elevator and rudder stop on the servo tab limits? There isn't an obvious aileron stop on the stick or in the linkage that I have spotted yet so it may be out at the aileron itself? Have you given any thought to a controllable trim tab for any or all of the axis? Most people just want the elevator, but I am intending multi engine version with the 810cc engines and so rudder and aileron trim are desired as well. I think Evans would approve a new powerplant solution. The real engine solution with a bucket full of money is the D-motor the same weight and general size as the VW and 90hp at 3000rpm, 162ft lbs at 2500rpm for 77hp. The -3 would scoot along then.
 

don january

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I can see a push pull for elevator and ailerons going threw the front spar together with one hole but yaw control would be a trick unless you made your stick grip rotate left and right to activate bellcrank for rudder control with push pull tubes then rear spar height would be a issue along with seat bottom. Personally I imagine rudder control done without my feet would be a whole new learning curve.
 

FritzW

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I found the VP-3 stuff in a dusty corner of the hard drive. I didn't draw the holes in the spar yet but judging by the per-the-plans holes Evans was going to make I think you have lots of options.

VP-3 Center Section 1a.JPG VP-3 Center Section 2.JPG VP-3 Mock Up red.JPG
 

blane.c

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I can see a push pull for elevator and ailerons going threw the front spar together with one hole but yaw control would be a trick unless you made your stick grip rotate left and right to activate bellcrank for rudder control with push pull tubes then rear spar height would be a issue along with seat bottom. Personally I imagine rudder control done without my feet would be a whole new learning curve.
I am working on a better sketch.

This is just to get the idea.

IMG_2070.JPG
 

amv8vol

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I don't know what forum this question belongs in but most likely it will involve some tubing in construction so here it is.

Are there any successful control stick designs available that pass 3 axis control through one hole in the spar(s) of a low wing?
The wooden Jodels/Robins
 

blane.c

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I see your concept and believe it to be doable. One thing you stated was 7/8" hole OD max and that is were I believe problem will show it self.
It is tight with the rudder tube, maybe to tight. I think there is plenty of room without it. Maybe just run the other two and use conventional cables for rudder. But I want to experiment a little with all three first.
 

don january

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FritzW. The way I'm seeing it the rudder tube just slides forward and aft. So all three tubes fitting a 7/8" hole may be a problem to find a tube strong enough for the rudder tube to fit in such a tight area without flexing and causing elevator and rudder tubes hitting and binding.
 

blane.c

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Yes elevator tube and rudder tube both slide fore and aft. And it is tight in there so reason I posted. I am worried about binding. The idea would work better with a larger dia. to work with. Should be enough room to do the aileron and elevator? Put rudder control through one of the 3/4" holes or just leave it cable?

VP-3-C-11.png
 

blane.c

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VP-3 SPAR HOLE SKETCH.jpg I don't see how it would matter structurally to the spars if you removed all the material from the two shades areas? Therefore you could have a center tube dia. of 1 1/16" from the top of the 7/8" torque tube hole to the bottom of the 1/4" bolt hole. Additionally you could have a 1" hole along side of it inside the boundary of the 3/4" cable holes and the 1/4" bolt holes. A 1 1/16" hole should be sufficient for the aileron torque tube and the stabilator push pull tube to pass through it, the rudder push pull tube could run along side in the 1" hole? Providing I am interpreting this correctly and the hole layout is for both spars?
 

BJC

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It is possible to feed 1/8” control cable through 1/4” or 5/16” holes using nylon or HDPE guides bonded in place. The limitation is that the cable must be fed through the guide before any fittings are attached, and reasonably good alignment is needed.


BJC
 

don january

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Blane. C You could do as I did and run your Rudder cables over the top of the front spar via a small pulley in front at top of spar with cable supported with guides along the inside of Fus. but as BJC says you must feed cable threw all guides before hooking up one or the other end. I fastened pedals and did final assy. at the rudder.
 

blane.c

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The as drawn for the cables is good. I am speculating on the push pull stuff as a modification, one thing is that one of the pulleys for the cables for the stabilator is mounted outside on the stern, It is kinda' cool in one way but just odd in another and just another moisture and critter entry in the end.
 

blane.c

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The stabilator design on the -3 lends itself to a push pull. It just looks like it should be hooked up that way vs. cables. The rudder not so much, but it could work easily enough. The aileron is push pull off the torque tube as drawn.
 

FritzW

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Have you given any thought to a controllable trim tab for any or all of the axis?
One of the guys on the VP group came up with a clever trim idea for the stabilator. It was years ago and I couldn't find his drawing but it looked something like this:

Swap the fixed mounting bracket on the rear face of the stern post for a bellcrank on the front face. Run a bowden cable to a trim control in the cockpit (a vernier or jack screw).

I need to make an accurate drawing to get the geometry right....
VP Trim.jpg
 
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