Part needed (Trim)

[Carl Ellis]

I need a new fairlead for the trim cable. It's piece of phenolic a couple of inches long with two brass fairleads in it that mounts vertically right inside the tail inspection plate. The cable has worn almost through the brass. From the looks of things, the trim cable must be disconnected and threaded through unless anyone has any alternate ideas.

As near as I can tell it's part number B12-A136. I'll post a picture later today after I take my camera out to the hangar.

Also, my IA is telling that the trim linkage is too loose. I countered that every Taylorcraft that I've seen has lots of wiggle in the trim linkage. He showed me that the play is in the bellcrank pivot and the pivot where the actuator arm attaches to the trim flipper. Presumably, the bolts have worn the holes larger. Should I do something about this or leave well enough alone?


- Carl -

[Carl Ellis]

Re: Part needed (Trim)

And here is an image of the trim fairlead.

[Robert Lees]

Re: Part needed (Trim)

Carl:

I need a new fairlead for the trim cable

I remanufacture the broken aft trim cable fairlead, using solid copper. The original was exemplary in its lightness, but made of fibreboard with copper inserts must have been very expensive to make, but bless CG for his attention to a light design. But I cannot afford the tooling or time, so I have ventured for 1/16 oz extra weight and gone for the easy option. I got the copper from an electrical supplier (it's a standard bus-bar section).


The above in italics is an extract from my website. Full text and photos at www.Taylorcraft.org.uk/Brey_rebuild1.htm

Photos of my installed fairlead at www.Taylorcraft.org.uk/fairlead-aft-trim.jpg
and

https://www.Taylorcraft.org.uk/fairlead-aft-trim1.jpg

Yes, to re-thread the cable, it does need to be disconnected.

Also, my IA is telling that the trim linkage is too loose

They all are. You are right, most Taylorcrafts with the elevator trim tab as part of the left elevator will not be without play, there is an awful lot of play in most systems.

Should I do something about this or leave well enough alone?

Leave it well alone unless
a) it becomes a problem (flutter)
b) you wish to correct it
c) your IA asks you to correct it.

Rob

[Carl Ellis]

Re: Part needed (Trim)

Rob -

Thanks for the feedback. Now you didn't happen to make two of those fairleads did you?

- Carl -

[Carl Ellis]

Re: Part needed (Trim)

Rob -

Is it important for the cable to actually rub on the bottom of the through hole? If the hole was bigger the cable would not rub.

- Carl -

[paulp]

Re: Part needed (Trim)

Hey Carl,

Could you just turn the phenolic over and have the worn portions on the top instead of the bottom? Just a thought.

[Howard Wilson]

Re: Part needed (Trim)

Another thought, Maybe cut a slit in the copper tube fairlead replacement (top side) and fit cable into it thru slit instead of disconbobulating end of cable. squeeze and solder ???

[lktiller]

Re: Part needed (Trim)

concerning the play in the trim tab: I had probably two inches of movement at the trailing edge of the tab. No flutter.
I cut the covering top & bottom, pulled everything apart. All holes were egg shaped, including the bellcrank center. Drilled and bushed all holes, even those for the pushrod.
Replaced the jackscrew, note there is a roll-pin holding the jackscrew pushrod on. Drilled it and pressed in a larger roll-pin.
After doing all that there is still an inch of loose play.
At least the IA was satisfied.
Note: the biggest improvement came from replacing the jackscrew.

LKT

[Hank Jarrett]

Re: Part needed (Trim)

First thing is the cables are supposed to be a little loose. If they are tight all the time they will get REAL tight when you deflect the elevator to its limit (which will make them loose again, but not in a real good way). The jack screw in the elevator isolates the cable slack from the tab. Second, the Taylorcraft was originally tested with the trim link to the tab un-hooked to prove to the FAA (CAA then) that it WOULD NOT flutter. You don't need to sweat the play in the tab (you DO have to sweat the IA wanting it tight, he's the boss on your annual unless you can PROVE he is wrong). Third, the bow rosin trick on the pulleys was something I came up with years ago and put on the group (great for slipping fan belts on the car too, a musical background helps sometimes). You want the cable to not slip on the pulley but not be too tight. Last and MOST IMPORTANT is NEVER change the trim with the elevator hanging down. It should be in neutral (or close). If you have someone move the controls while you look at the fairlead you will see that the trim cable passes through the middle of the fairlead at neutral and hits the top with full up and bottom on full down. When you change trim with the wheel full forward you are sawing the fairlead with the cable. That's why they used copper. So the fairlead would wear and not the cable. My fairleads have been in since 1941 and they still look new. All of the past owners of my plane held the wheel neutral while changing trim. I think I will too.
Hank J

[Mark Julicher]

Re: Part needed (Trim)

Great discussion on trim! I finally understand that my trim cable is too tight.

It would not be terribly difficult to replace the copper guides inthe tail fairing.
Use a piece of copper tubing from the local hobby store. Anneal it. Cut the desired length. Carefully work it into an oval shape. Slide it into the phenolic and splay the ends with a round nosed tool such as a hardwood dowel.

After that, see if you can get a solid copper one from Robert : ).

And as a side note, my trim tab did once upon a time have a NASTY flutter problem. The fix was to use a larger diameter hinge-pin wire and pre-load the hinge by bending a curve into the hinge-pin wire. Somewhere along the way the trim tab hinge guides must have worn oversize. I have had no flutter since I repaired it.

Best Regards,
Mark Julicher

[lktiller]

Re: Part needed (Trim)

Mark, how did you identify the trim flutter? Sound, feel, visual, speed?
I hear a buzz at stall speeds but think it is the tail brace wires vibrating in the ripple from the wings.

Larry Tillery

[Mark Julicher]

Re: Part needed (Trim)

Ahhh A great question! Sorry I did not say earlier.

I felt a vibration in the yoke, and then got a (trusted) friend to fly beside me and have a look. The tab was flapping pretty hard.

[Robert Lees]

Re: Part needed (Trim)

After that, see if you can get a solid copper one from Robert

Well Mark, my fibre bit holding the two copper bits apart at the correct distance broke where the clamping bolt goes through. So I needed to do something.

Sorry Carl, I only made one. Go get some copper, create an "Owner-produced part". Lordy, even I know the American regs, how sad is that?

I have also had trim tab flutter. Reworking the linkage worked to recify it.

(I guess exceeding Vne didn't help

[Carl Ellis]

Re: Part needed (Trim)

After many trials and tribulations, the new trim fairlead is complete, sans paint.

This was constructed from the original Taylorcraft drawings and was made available in 1992 as a replacement for Part# BC12-1064.

I had it milled from 1/2" x 1/2 1018 steel.

[Carl Ellis]

Re: Part needed (Trim)

Here is the completed part.