Stick Cable Exit Location

[MauiLvrs]

Deciding where to place the cable exit holes on the stick...
Reviewing the location of where many builders placed the hole seems to be mid distance between the fulcrum and the end of the short end of the stick. Applying basic physics, this would seem to be the location of the highest amount of stress on the stick.
Not to start a war like the primer wars ... but it seems that the hole location should be on the other side of the fulcrum to be places where the stresses are lower.
Wouldn't the location with the lowest stresses be as far away from the fulcrum on the long side of the lever arm?

 

[apkp777]

What cables?

 

[pierre smith]

Hi Dave...

..on our -6 we simply went straight out of the bottom in a clear plastic, protective sheath.

Regards,

 

[Camillo]

Yes, bottom.

In pilot stick, I made a hole at 45?, below up/down force solder joint.
A friend of mine made me notice that it is OK to make it exit downward. So, since I did not cut the hole in copilot stick, I made a downward exit, there.

 

[Steve]

no hole

I only have the 2 PTT wires inside my sticks. I ran them out the stick bottom between the rod end bearings. I didn't use one but a protective plastic sheath at the stick bottom end is a good idea. Perhaps at the next condition inspection.

 

[apkp777]

Ah, the stick wires (cables). I exited through the bottom. Protected the wires with "snake skin".

 

[rv9av8tr]

Stick wiring location

I ran my PPT wires out the side of the stick, right at the fulcrum point. Has the least amount of rotation on the wires at that point. Used the smallest size MS bushing in the hole.

 

[kentb]

Hello Dave

Like most I ran my out the bottom. Protect it and give a little slack. No problem after 3 years of flying.

Kent

 

[MauiLvrs]

Like most I ran my out the bottom. Protect it and give a little slack. No problem after 3 years of flying.Kent

This was our first thought too... But stuffing a 1/4 bundle of wires between the rod bearings caused a little bit of concern. Both from chafing and the rare possibility of causing a jam/binding in the aileron movement.

In pilot stick, I made a hole at 45°, below up/down force solder joint.

Which lead to this option that we are considering. Used by many builders and also seems to be trouble free. But started thinking about the physics involved and thought that it may be on the wrong side of the pivot point to minimize the forces.
F1D2=F2D2

http://en.wikipedia.org/wiki/Lever
So on the RV, if you place the hole half way between D1 (3 inches) and apply 100#s force the force at D2 (12 inches) would be 25#s. The force at the hole (1.5 inches) would be 50#s
If the hole was on the other side of the pivot point at the same 1.5 inches the force would be 1/8th the total force or 3#s. The math seems nice and all... But in practice when you're prying on a huge rock with a 2x4 why does the board seem to always break at that point and not on the other side where the forces are much higher?


Which leads you to option 3...

I ran my PPT wires out the side of the stick, right at the fulcrum point. Has the least amount of rotation on the wires at that point. Used the smallest size MS bushing in the hole.

which is exactly what we were thinking next... Except for the compression forces in the tube itself, the force is 0. Ideal... 0 force and doesn't move much. Except for the compressive forces. In reality the steel is probably so strong in relation to the forces involved in an RV that it can't break in any case...

Think I try and fit the wire bundle out the bottom and see how bad the squeeze is tonight...

 

[apkp777]

Uh, I don't think you need to worry about the structural strength being compromised by a small hole drilled for the wires. Those control sticks are pretty heavy duty. I am pretty sure you'd rip the hinges off the aileron spar long before a stick failure. Besides there's two of them anyway. Run them out the bottom and protect em with spiral wrap, snake skin or heat shrink. My concern wasn't the sticks, but the 26 gauge wire that they used for the servo control wire. Wire tie the whole bundle every 3" to keep it stiff.

 

[Camillo]

Which lead to this option that we are considering. Used by many builders and also seems to be trouble free. But started thinking about the physics involved and thought that it may be on the wrong side of the pivot point to minimize the forces.
F1D2=F2D2
[omissis]
So on the RV, if you place the hole half way between D1 (3 inches) and apply 100#s force the force at D2 (12 inches) would be 25#s. The force at the hole (1.5 inches) would be 50#s
[omissis]

Actually, when I wrote below fulcrum, I intended below push/pull fulcrum but above roll fulcrum. So, wikipedia image is not representative, since I made my hole well on the left of D1 segment.

 

[PaulR]

Out The Bottom

So I have two Tosten grips which have, I believe, 11 wires. I don't have the wings on yet as I'm still at home. Is there really room to go out the bottom of the stick with this many wires?
It looks like there could be some binding between the hiem fittings going that route.

If anyone has some pictures of the wiring under the floor pans, particularly of the sticks, I would sure appreciate seeing them. I've searched the threads here and found a couple, but more is better for me.

Thanks and Merry Christmas!

 

[rv9aviator]

Add another vote for seeing pictures of wiring coming out of the bottom of the stick, I am installing the Tosten grip as well.

 

[MauiLvrs]

... Is there really room to go out the bottom of the stick with this many wires?

Yep.... I covered them in two layers of heat shrink and passed the pilot out the bottom...

The copilot need to be removable, so I drilled a hole above the joint.
Have to work on finding photos....