Trim aft copper fairlead

[jmvolpp]

We decided to cycle the trim through its entire range of motion, and jammed the cable in the aft fairlead.

Inspection with a flexible borescope-like camera from Harbor Freight Aviation revealed what looked like chewed up (copper) fairlead obstructing passage of the cable. A bit of somewhat controlled tugging moved it out of the way and returned the trim system to its usual recalcitrant ways.

That fairlead, and probably its forward companion, will rate replacement when recover time comes, but for the present I wonder if a bit of lube might be in order. I’m aware that we don’t want to lube the cable near the pulleys, but I can easily rig a borescope-guided syringe for a precision lube application. What does the tribe think?

Mike V.

[M Towsley]

Trim aft copper fairlead

I found any lube seems to somehow migrate onto the pulleys, either front or back. When that happens, the fun begins. I only lube the small hole on the left elevator for the jackscrew shaft, the jackscrew with a lube straw, (because someone way back when probably used heavy grease which slows things up in winter), the rear pulley 'shaft' and the front pulley shaft only, (along with the trim tab hinge and linkage).

[jmvolpp]

Trim aft copper fairlead

The feel of the cable through the fairlead compels me to try to improve its passage. The lube I have in mind is Boeshield T-9, which dries leaving a slick film - hopefully less prone to migrating 34" back to the pulley. I will substitute a saturated Q-tip for the syringe method of delivery, which should ensure less zeal of application. Down the line some I'll report the result, hoping it's not a "told you so" moment!

Mike V.

[Robert Lees]

Re: Trim aft copper fairlead

Hopefully this has started a new thread.
Rob

[jdoran]

Re: Trim aft copper fairlead

I like to lubricate the threads on the jack screw inside the fabric. I glued a seaplane grommet on the bottom of the stabilizer with the opening facing aft just behind the threads. I can squirt aeresol chain lube thru the straw directly onto the threads. If a friend is cranking the trim while you do this, it works the lube into the threads. I only need to do it about 2x a year. Also make sure the spring tension on the trim cable is adequate enough to not let the cable climb up out of the v in the rear pulley. It loses grip when it does.

[Guest]

Re: Trim aft copper fairlead

I like to lubricate the threads on the jack screw inside the fabric. I glued a seaplane grommet on the bottom of the stabilizer with the opening facing aft just behind the threads. I can squirt aeresol chain lube thru the straw directly onto the threads. If a friend is cranking the trim while you do this, it works the lube into the threads. I only need to do it about 2x a year. Also make sure the spring tension on the trim cable is adequate enough to not let the cable climb up out of the v in the rear pulley. It loses grip when it does.

Excellent idea John thanks for the tip.

Dave

[jmvolpp]

Re: Trim aft copper fairlead

Add cotter pin to the list of reasons the trim may hang up. If the head of it isn't flush in one of the spaces of the jackscrew nut, it'll interfere with the backside of the elevator leading edge tube as it (jackscrew) turns. Just when you think you're done...

Mike V.

[jmvolpp]

Re: Trim aft copper fairlead

Last Friday’s post annual test flight proved to be uneventful, returning with the same number of parts I took off with. The trim worked better than ever, even in a slightly below freezing temperature, making all the preceding frustration worthwhile. In retrospect, the cotter pin interference may have been at least as big a contributor as anything else, further evidenced by the roughed up fabric on the aforementioned tube just forward of the jackscrew nut. One might conclude that, in addition to the lift strut fittings on the fuselage, fabric shouldn’t be there in the first place.
Mike V.