Nylon Sleeve in Rudder S-tube

Some time ago JJ had a good writeup on rudder pedals, S-tubes, rudder cables, etc. I'm in the process of replacing a rudder cable that has a bit of fraying. The nylon sleeves in both S-tubes are too far out the rear with no sleeve showing at the front. In addition, I suspect one nylon sleeve is damaged. Is there a simple, not too painful way to replace these sleeves?

Mike

On Friday, May 23, 2014 7:12:36 AM UTC-7, Mike J. wrote:
Is there a simple, not too painful way to replace these sleeves?



Mike

Mike,

I used Teflon tubing on a Stemme S10-VT that for whatever reason had *no* S-tube liner. Thin wall tubeing with the correct ID (1/8" IIRC) and an OD that will fit into ID of S-tube. Make a tubing splitter frpmtwo small blocks of wood, each with a corner sanded off to make a "V" when clamped together with the tip of a utility knife blade between them sticking up at an angle just enough to slice through one tubing wall. Tubing is then pulled through the V and splits tube nicely without any spiral.

To install, start the split tubing over cable and slide into S-tube as far a possible. Slide rudder adjustment forward while holding split tube in position. Clamp split tubing onto cable a suitable distance from S-tube and slide rudder adjustment back toward you while holding split tubing so it enters S-tube and doesn't "buckle off" cable - repeat.

There's probably better tubing choices available than nylon or teflon for this purpose. Teflon is very slick but not so mechanically strong. UHMW polyethylene tubing is both slippery and has excellent mechanical strength - often used for anti-chafe and rubbing or wear blocks. UHMW, like nylon, and to a lesser extent Teflon, is semi-rigid. UHMW also does not absorb moisture as does nylon.

bumper

On Friday, May 23, 2014 7:12:36 AM UTC-7, Mike J. wrote:
Some time ago JJ had a good writeup on rudder pedals, S-tubes, rudder cables, etc. I'm in the process of replacing a rudder cable that has a bit of fraying. The nylon sleeves in both S-tubes are too far out the rear with no sleeve showing at the front. In addition, I suspect one nylon sleeve is damaged. Is there a simple, not too painful way to replace these sleeves?



Mike

Applying heat to the S tube may make the old sleeve soft enough so it can be forced back into the correct location with some nylon exposed at each end.. A block of wood with a 1/8" slit cut half way through, could be placed over the cable, then hammer the block to try and force the nylon sleeve back in place. If you have to replace the sleeve, you might try applying heat at the point where it enters the S tube.
JJ

Recently did an ASK-21 where the nylon tubing in the S-tubes of the pedals
was so old, it had hardened out and would not budge. At all. Whatsoever.
Applied heat by putting it in hot water, hairdrier an even a paint stripper
gun. Combined those with a custom built pull-device (cable broke!). Tried
cutting the diameter, knifetip broke. Sometimes everything you throw at it
does not work... Ended up welding new S-tubes to the pedals and putting new
guides in. Major work, to be done by a professional welder with the correct
authorization.

Appreciate the input gentlemen. Since the IA and I are replacing the cables I just pulled the old sleeves out with pliers .... they were really stiff .... reason I couldn't push them back in through the second bend. I'm replacing them with the polyethylene sleeves Bumper mentioned. I'm also toying with the idea of putting cable ties around the sleeves at each end of the S-tube .... just tight enough to keep it in the tube without binding the rudder cable.

Mike J.

I think you'll find a lot of manufacturers recommend such a thing as
cable-ties to keep them from moving. I used crimped metal ties that
Schleicher recommends.