Forward trim pulley

[Pearson]

Does anyone know what size the pulley is that is front and center overhead for the trim? Mine is slipping, but I haven't had a chance to take the headliner out.

[Mark Julicher]

Re: Phenolic pulleys

Richard,
The trim pulley is 3 inches in diameter but it is a special trim pulley with the V groove in it and splined onto the trim crank.

You can fix it by re-grooving the pulley with a sharp tool. If that does not work then I believe I still have a few of the ones I made.

Try re-grooving it first- that usually works.

[Robert Lees]

Re: Phenolic pulleys

Hi Richard,

OD 3 1/8 (as measured...I see a difference to Mark's).
Groove Dia 2 3/4" (keep the groove sharp)
Bore 3/8 (I assume grooved, so that it's a press-fit on the shaft)
Thickness = 5mm ...strange, but that's what it is (a smidge over 3/16)
Keyway 1/8 x 1/8

Mine was chipped so I made a new one out of phenolic.



Regards,
Rob

[Pearson]

Re: Phenolic pulleys

Robert,

Thanks for the quick reply. I have dug through my spare parts inventory, sometimes called my "project plane", but do not see a pulley with a keyway cut into it. Sooo....., I guess I need to find somewhere to buy one of these. It gets really frustrating trying to reach through the zipper in the headliner to help move the trim cable with your hand while turning the crank.

So does anyone know where to buy these pulleys?

[Robert Lees]

Re: Phenolic pulleys

I would doubt if they are readily available (unless Forrest has some NOS ones).

My new one took less than an hour labour for my friendly local lathe operator to make, using an off-cut of flat phenolic sheet from the local electricity supply company (who use it as electrical insulation).

After roughing out, he used a fine Junior Hacksaw blade in the toolstock to get the Vee in the groove, and I cut out the keyway by hand, which I'm sure would satisfy the requirements of the US Owner-produced parts regs.

But I think in the first instance you should try re-grooving, as Mark suggests.

[Pearson]

Re: Phenolic pulleys

Mark I didn't see your post when I logged on last. My apologies! I will follow your advice and regroove my old one. Thanks!

[Robert Lees]

Re: Phenolic pulleys

Another thing to look at, Richard, is the friction within the whole system (and hereonin I'm referring to the post-war trim system).

For example, the reason why most post-war trim systems slip is due to friction in the trim barrell inside the port elevator. Or there might be slip at the smaller aft pulley due to some well-meaning person lubricating the trim cable back there.

If I can remember how to do it, I'll split this trim pulley discussion from the OP's subject.
[edit: done...original post regarding phenolic pulleys with bearings is here]

[Pearson]

Re: Forward trim pulley

Robert,

That was the first thing I checked. I took the cable loose from the rear pulley and easily turned it with one finger. I am quite sure it is the forward pulley that is slipping. I will take it apart and figure out how to regroove it.

Thanks!

[Hank Jarrett]

Re: Forward trim pulley

After all of the suggestions so far, try a little violin bow rosin on the cable and pulley groove. Clean the cable and pulley well with a light solvent to get any oils off first.
There has GOT to be a kid learning violin near you. Kids ruin the rosin blocks fast.
Hank

[jdoran]

Re: Forward trim pulley

One other suggestion before you do anything:

Check to see that the spring tension is adequate. If the cable is too loose, the friction won't exist if the cable is allowed to ride up in the v-groove in either pulley.

[Robert Lees]

Re: Forward trim pulley

I have a few new stainless trim springs left.

[freightpilot27]

Re: Forward trim pulley

Robert-
Do you have any info on the springs? pull force, length, wire size ect.
would like to find one on locally on this side of the pond.

thanks

[Robert Lees]

Re: Forward trim pulley

No details, sorry...I had them replicated by a spring manufacturing company many moons ago. They did all the pull test, elongation / force etc, and made me a batch in shot-peened stainless.

$35 delivered, if you'd like one.

[freightpilot27]

Re: Forward trim pulley

robert
check your PM

[Robert Lees]

Re: Forward trim pulley

Received...and responded.

Rob