Servicing Seabee pitch trim system This is a discussion of the Seabee pitch trim system cables, how to service and maintain them.
The fundamental problem is that the cables are routed inside a metal bowden sheath, and the failure mode is going to be internal.
At some point in time, one of the wires of the 1/16 cable is going to wear enough to the point that it will break. During the normal operation of the trim system, that broken wire is going to unwind, double back on itself, and jam the trim system.
You have to keep in mind that this is inevitable. It is only a question of when.
So, what do you do?
The first thing is to get those cables out of your airframe and clean and service them. After they are pristine, you can examine them for wear.
The easiest way to clean the trim cables is the kerosene routine as outlined in the instructions for servicing push-pull controls.( __here__ ) Once the cables are cleaned up and free of all foreign material, you should carefully examine the individual strands of wire. This really has to be done with a 5X loop. Closely examine the wire where it exits the sheath. The only visible signs of wear will appear here.
If you see wires that are worn to the point that the flat is as wide as the strand, that means the wire is now 1/2 it's thickness. The internal cable must be replaced.
What you have to keep in mind is you are looking at the only portion of the wire rope where damage is visible. Just think about the strands inside the sheath, where it has been rubbing against the inside of the metal sheath. If what you can see on the outside is poor, the inside is worse.
Lets suppose there is no visible wear. Now what?
You have to get these parts absolutely clean internally, and lubricated internally. The fact that you have removed the cables, and the roller chains, and moved everything about, means you have repositioned the wires internally with respect to the sheath. This will serve to redistribute the wear points, and the cables should last a lot longer.
The disassembled cable should move freely inside the sheath with no rough spots or binding whatsoever. If you feel any snags, the wire rope has to be replaced.
What about the sheath? It will be rusted, and some of the coils might be somewhat open. As long as the sheath is still elastic enough that it can be reinstalled, it can probably be reused. It only serves as a guide for the wire rope. But if it is so rusted that bending the sheath breaks it, it will have to be replaced.
This may seem like a lot of effort to attend to something that works now, but it really has to be done. The downside risk is just too great.



Link back to Servicing Push-Pull Controls

Beechhurst Home