What part in the trim mechanism results in the most wiggle in the trim tab?

[Guest]

I am going to make an attempt to take most of the wiggle and play out of my elevator trim tab.

For those of you that have fixed these before I would like to ask what part in the mechanism is responsible for the largest portion of the play?

Thanks, Dave R.

[PA1195]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

Never fixed but mine's in the bellcrank linkage inside the elevator. I'd like and may have my tech install an inspection cover under that crank so it can be inspected (typical ring and four prong flush cover that'll withstand a breeze). The oil hole for the treaded shaft has been lubed and the pulley is tight on the shaft. There might also be play in the piano hinge.

I'll measure my tab play up and down so we have some data.

Gary

[astjp2]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

Most of the ones that I have messed with have been the triangle plate and the link rods are just flat wore out.

[Nefj40]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

I spent some time working on mine a few months ago at annual. From what I could come up with, I'm in the same boat as Gary. The majority of the play I could find seemed to be inside the elevator.

[3Dreaming]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

Any play in the system from the pulley attached at the elevator horn to the attachment at the trim tab. Starting at where the pulley attaches to the jackscrew make sure that the jackscrew shaft doesn't slide back and forth in the bushing in the elevator. You may need to shim between the pulley and the bushing. Any wear in the jackscrew and barrel. Any of the connections between the jackscrew and the bell crank. The bell crank pivot point. The connection from the bell crank and the pushrod. The connection between the pushrod and trim tab. The trim tac hinges.
Any play at any of these points will be amplified at the trailing edge of the trim tab, and the smallest play at each has an accumulative effect.

[PA1195]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

Had another look at my trim ('41) today. It moves up and down the thickness of the adjacent elevator tubing...a spot on the edge of the tab moved the elevator's width. No tape with but that's about 3/8" O.D. tubing ???

I can now see the exposed trim pulley in the tail that drives the screw moves in and out about 1/16" when the tab is flexed up and down by hand. Can't see the internal bell crank stuff. I could shim the pulley or for a quick fix wrap a piece of safety wire along side of it to reduce free play.

The former owner was a good mechanic and told me he had done some rebuilding to the trim, and that left elevator fabric is a different weave that the rest of the tail so I believe he did.

Gary

[Guest]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

I played with mine today too. Very little movement of my pulley shaft but a lot of trailing edge movement.

I think the linkage and bellcrank may be the problem.

I have a spare set so I guess I need to prep it.

Thanks to all for the info!

Dave R

[Scott]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

Because the bellcrank is asymmetrical (the tab pushrod side is longer than the screw-jack side) a small amount of play in the shaft and associated pushrod,translates into a relatively larger amount of slop at the tab. I used a thin nylon washer to take out all the end play in the screw-jack. This made a big improvement.
http://4.bp.blogspot.com/-u08gTg_hw1...0/DSCN3156.JPG

I also found the holes in the pushrods and the tab horn were worn. The original material is quite thin (040 or less) so there is very little in the way of a bearing surface. The horn is easy to make, pushrod ends a little more involved as they need to be welded. I used 050 chromoly and suggest a sticky grease like EZ Turn to keep the pins from spinning/vibrating/wearing.

http://3.bp.blogspot.com/-x6cAPor_gn...0/DSCN3154.JPG

[Robert Lees]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

I found exactly the same play. This is what I did: http://www.taylorcraft.org.uk/Brey_r...-gear-legs.htm

(but most of the work requires either re-covering the elevator or cutting an access hole).

Rob

[astjp2]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

No to safety wire, use a shim washer...

Had another look at my trim ('41) today. It moves up and down the thickness of the adjacent elevator tubing...a spot on the edge of the tab moved the elevator's width. No tape with but that's about 3/8" O.D. tubing ???

I can now see the exposed trim pulley in the tail that drives the screw moves in and out about 1/16" when the tab is flexed up and down by hand. Can't see the internal bell crank stuff. I could shim the pulley or for a quick fix wrap a piece of safety wire along side of it to reduce free play.

The former owner was a good mechanic and told me he had done some rebuilding to the trim, and that left elevator fabric is a different weave that the rest of the tail so I believe he did.

Gary

[PA1195]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

No to safety wire, use a shim washer...

Hah! Caught again by someone who knows better. I never really looked at mine before. But from the fine pics offered above I guess I need to look again.

If that castle nut with key comes off then I should be able to washer it up. My inspection covers are new lexan so I can look and get right to it after I call my mechanic about my plan. I have or can get thin aircraft washers or maybe a nylon on but usually they are Ace Hardware stuff and thick.

Thanks for the tip.

The previous owner did mention replacing the parts and particularly the brass screw but I never saw one until now.

Anyway full nose up trim it flys 55. Rocker Sammy Hagar would not approve: https://www.youtube.com/watch?v=RvV3nn_de2k

Gary

[Bonanza91K]

Re: What part in the trim mechanism results in the most wiggle in the trim tab?

I looked at mine yesterday and found that most of my play comes from the hinges. Mainly the inboard hinge. When I pull it apart, I'll let you know how I fixed it.

Jim
F21