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rudder cable interference

P

pt17

Member
After final fit of rudder I have fabricated 1 and a half inch rudder links (F-6119) and my rudders are placed in the mid position. When the rudder is at full extention Left or Right, the rearward pedal rises to such a height that causes the rudder cable to bind in the snap bushing closest to it.The centre line of the bushing and the cable line up OK when rudder is centralised, but when the rudder pedal moves aft the cable moves well above the line of the snap bushing.
At present, when the pedals are fully aft, the start of the clevis on the cable just enters the snap bushing. The only threads I can find suggest placing tube on the cable, but this still has the clevis much higher than the bushing.
Is there another solution to this problem? Thanks
 
I had that problem and corrected it by making the copilot side pieces a little longer so that the pedals are parallel. It might be affected by where you place your rudder bars as well.
 
Make sure the rudder stops are set correctly for the maximum throw. The cables are the some length regardless of what the position of the pedals, so that is not an issue. Only the link length changes. I remember mine where close as well, but the stops prevented the cables from entering the grommet. The depth at which the rudder is set into the VS, the adjustment of the hinge eyebolt, can affect the cables and the rudder throw. Consider moving the rudder into the VS to give you more cable into the cabin, thus more clearance.

Hope this helps,

Roberta
 
The further forward the pedals are the less acute the cable angle from the gromet to the pedal attach flange will be. The less acute the angle, the less apt the cable will bind. Also, the neutral position of the pedals and whether they are canted rearward at the base will affect this angle. However, I do agree with Roberta and first make sure your stops are not allowing you to exceed the rudder position limits. I remember with mine I was not totally happy with the cable / gromet geometry and ended up putting a plastic sheath over the cable to help minimize the binding tendancy. I've never noticed any binding while flying or taxieing.
 
I too ran into this problem. My rudder is already as close as it can be to the HS (within one turn of the bottom rod end bearing). I so far have only 32 degrees of travel left and right (with acceptable range being 30-35 degrees), so I'm not trying to get too much travel. But despite all this, my rudder cable clevises still hang up slightly on the first grommet on both sides. Why Van's couldn't make these cables even just 1/4" longer, entirely eliminating this problem, I have no idea. (OK, venting off.)

But perhaps I'm missing something? Any other RV7/9 folks have any suggestions or confirmation that the sheathing is the way I need to go? I'm reluctant to go this way as I must then find some way to make sure it doesn't slide back and forth on the cable and create a new potential for jamming the rudder.

Thanks.

EDIT: I used different key words and came up with better search results. Yes, this is VERY common and sheathing it seems to be the predominant consensus.
 
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Read your plans, and make sure that you have the proper cable for your installation. Measure and compare.
 
I cut a slot and built a guide block for the cable. It lets the end of the clevis go thru without touching.
 
The barrel of the clevis is too long for this application. If 30% of the tail of the clevis was cut off before swaging it on to the cable, this 20+ year old problem would be solved.

You are not capable of failing the cut down swaged clevis with leg pressure no matter what the other end of the cable is connected to.

I installed a clevis on the end of a 1/16" cable with a standard wire crimper and tested it to failure. The chart had failure at 500# and on my test, first strand release was at 550#. The clevis never moved!
 
I had the same problem

and vans suggested tapering the cable (aft) end of the swaged eyelet to allow it to pass through the grommet easier. Being as careful as I could (cables in place), I still nicked one of the cables with my dremel tool:mad:. After a new cable $$ tapered outside the plane, I'm happy with the results. Van's should just make the cables 1/2" longer IMHO.
 
Based on a tip in a different thread, I just reversed the orientation of the grommet (pushed it in from the aft side of the bulkhead). As counter-intuitive as that seems, the profile of the "tail" of the grommet is such that the clevis enters the grommet more smoothly. Also, Joe Blank noted in a different thread that, especially for taildraggers, that last tiny bit of rudder throw isn't really that important since ground steering in the taildragger doesn't require as much rudder travel as the nosewheel versions. I still wonder why Van's doesn't make that slightly longer, given the LONG history of people reporting problems with it, but I'm happy with my solution for right now.
 
same problem here, despite having the proper rudder travel etc... the clevis would "catch" the bushing on the last mm of travel or so.

we took a 1/4" outside diameter thin wall flex line (like used on pitot/static system, made a slit along the full length and put it on the clevis and cable, long enough that it is still in then snap bushing when the cable is fully forward.
this smoothes the surface and keeps the cable gliding nicely.
only potential issue to look for in the long run would be trapping of moisture but this shouldn't really matter in that location.

rgds, bernie
 
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