Bill Wightman
Well Known Member
Problem: How to run the wiring out of your control stick(s) when Vans says its bad to put a hole in the wall of the tube, especially near the pivot point.
Here's the warning from Vans:
Any hole anywhere in the control stick will reduce its strength. The nearer this hole is to the pivot point of the stick (where the bending forces are higher), the greater will be the severity of the strength loss. Van's recommends that builders do not drill holes anywhere in the control stick, particularly near the pivot point. Generally, the accepted routing for electrical signal wires is through the opening on the bottom of the control stick.
So now we have a problem that nearly 100% of RV builders must face: how to run the wires out the stick, and most of us don't want to run them out the bottom of the stick for reasons explained elsewhere. Also, there's no "opening" at the bottom of the RV8 stick mentioned in the warning from Vans.
This problem was also discussed at length in another thread when a builder asked how to route wires out of the control stick. Since nearly all of us have wiring in the control sticks these days, a solution is needed.
Solution: The solution is to use a reinforcement "washer" around the hole. The purpose of the washer is to reduce and disperse stresses around the hole in the stick.
This work-around assumes 3/8" diameter hole is necessary to route control stick wiring into the stick. The location analyzed for this work-around is 3/4" up from the longitudinal pivot axis of the stick (the pivot bolt). The hole may be placed on the front, back or side of the stick.
The "washer" used to distribute stress is 4130 steel, .050" thick, and has an outer diameter of 5/8". As mentioned, the inner hole is 3/8" diameter. The washer should be rolled into a radius so that it fits the stick tube's 1-inch outside diameter. To carry the stress loads, the washer should be welded around its outer and inner edges. Edit: Its not recommended to braze 4130 (see post below)
Exploded view of RV8 front stick tube with washer
The resulting tube with washer will have very close to the same bending strength as the tube with no hole in it. Smooth the inner edges of the hole after the washer is fastened. There may (probably are) better ways to do this, but this is one solution that will work.
Here's the warning from Vans:
Any hole anywhere in the control stick will reduce its strength. The nearer this hole is to the pivot point of the stick (where the bending forces are higher), the greater will be the severity of the strength loss. Van's recommends that builders do not drill holes anywhere in the control stick, particularly near the pivot point. Generally, the accepted routing for electrical signal wires is through the opening on the bottom of the control stick.
So now we have a problem that nearly 100% of RV builders must face: how to run the wires out the stick, and most of us don't want to run them out the bottom of the stick for reasons explained elsewhere. Also, there's no "opening" at the bottom of the RV8 stick mentioned in the warning from Vans.
This problem was also discussed at length in another thread when a builder asked how to route wires out of the control stick. Since nearly all of us have wiring in the control sticks these days, a solution is needed.
Solution: The solution is to use a reinforcement "washer" around the hole. The purpose of the washer is to reduce and disperse stresses around the hole in the stick.
This work-around assumes 3/8" diameter hole is necessary to route control stick wiring into the stick. The location analyzed for this work-around is 3/4" up from the longitudinal pivot axis of the stick (the pivot bolt). The hole may be placed on the front, back or side of the stick.
The "washer" used to distribute stress is 4130 steel, .050" thick, and has an outer diameter of 5/8". As mentioned, the inner hole is 3/8" diameter. The washer should be rolled into a radius so that it fits the stick tube's 1-inch outside diameter. To carry the stress loads, the washer should be welded around its outer and inner edges. Edit: Its not recommended to braze 4130 (see post below)
Exploded view of RV8 front stick tube with washer
The resulting tube with washer will have very close to the same bending strength as the tube with no hole in it. Smooth the inner edges of the hole after the washer is fastened. There may (probably are) better ways to do this, but this is one solution that will work.
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