improving bearing 'Fit' in a U-Joint

racasey · May 13, 2014

I need to replace the cross in a u-joint on a circa 1984 Moto Guzzi drive shaft. The cross is 20x44 mm and is retained in the yokes by Seeger snap rings. This shaft is not readily available as a new part; I have had a drive shaft on back order for almost 1 year.

My existing used shaft shows very slight movement where the needle cups press into the yokes. Suggested methods of restoring an interference fit suggest copper plating of the yokes.

I'm hoping some of the rather insightful folks here might have an idea or two. Any takers?

Ciao,
Dick C

JRIowa · May 13, 2014

Loctite 640
JR

Tony Quiring · May 13, 2014

Assuming hp is not real high then swedge in a beer can.

Press the cup into the yoke with a cup of beer can and it may deform and fill the gap.

Or other liquid that cures hard enough.

matt_isserstedt · May 13, 2014

Along the lines of Tony, wondering if speedi-sleeving the OD of the cup would give enough thickness, and not be sheared off going into a press fit. I think you'd have to control the interference by some machining of the assembled sleeve or a very light cut on the ID of the yokes.

Plating would be nice as then you don't need anything custom in the future. I'm very very far from even being an amateur on plating, but it would seem directionally better if you could get a harder surface like nickel or chromium, as soft copper would tend to be the weakest link again.

adama · May 13, 2014

Im in the high strength loctite camp if you want it fixed. Its very very reliable if used with care. That said, grease it and i think you will find they last a lot longer being able to slowly rotate if its only just a non interference fit, if actual slop then loctite is your friend. Electric motor end bearings do much the same, it spreads the wear from 2 points over the eniter outer race.

adama · May 13, 2014

With plating you need to watch for hydrogen embrittle, a forged and hardened yoke is more than good enough steel in all likely hood for it to be a risk.

Oldwrench · May 13, 2014

Loctite 680 (green). Makes a slip fit into a press fit. Stake the yoke after installation for stability in curing. Cure overnight.

Limy Sami · May 13, 2014

Oldwrench said:
Loctite 680 (green). Makes a slip fit into a press fit. Stake the yoke after installation for stability in curing. Cure overnight.

Loctite for me too, my neighbours do a lot of propshaft work - due to their reputation for getting it right, first time and lasting**, the same reputation often hangs on Loctite!

They ''know'' from certain customers their work will not be pussied either.

jlevie · May 13, 2014

There can be pretty large loads on those bearing seats as well as vibration. The fix that I'd prefer would hard chrome plating and honing to the correct ID.

tailstock · May 13, 2014

you say you have a new shaft on order, so this won't be a for ever fix. Prick punch the yoke that the cups set in Loctite and get to riding. Down time is lost time , and lost time you never get back. :codger:

Mud · May 13, 2014

I'd loctite them.

If you're a belt and suspenders kind of guy and want a press fit, plate up the cups' ODs and hone the yokes to fit, or make new oversize cups.

CalG · May 13, 2014

Before loc-tite, one might tin the bores with solder, scrape with a bearing scraper if needed, then press the cups home.

But, that was before loc-tite ;-)

Heavey Metal · May 13, 2014

635 is 1500psi stronger than 640

http://www.henkelna.com/us/content_...rialAssembly_RetainingCompounds_pg131_132.pdf

magneticanomaly · May 14, 2014

If you heat the thin part of the ear above the cross bore quickly with a torch to a red heat, after cooling the bore will have shrunk. Hone or line-ream to desired size. In my experience with auto and truck and tractor PTO drivelines, the yoke wil not fail from loss of heat-treatment, but YMMV.

reedeprintice · May 14, 2014

I was just getting ready to post what Magnetcamaly said .

Mud · May 15, 2014

reedeprintice said:
I was just getting ready to post what Magnetcamaly said .

Does this hold up in those huge power off road machines you build?

greggv · May 15, 2014

I'd use the locktite in a second! Be sure to use the primer spray, too. Cures a lot faster.

racasey · May 17, 2014

Thanks all. You have certainly given me some excellent options.

Ciao,
Dick C.

improving bearing 'Fit' in a U-Joint

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