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Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

thread78-315976

Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

(OP)
Its long been my understanding that U-joints (and CV joints) were not that good at carrying large axial loads as might be found in the trust action produced by marine props transmitting their thrust forces to propel a vessel forward.

I ran across this Thompson Joint techonolgy and believe it is capabile of carrying much more 'prop thrust loading' than normal U-joints. Am I wrong??

http://www.thompsoncouplings.com/site/pages/product_videos.php

http://www.boatdesign.net/forums/propulsion/u-joint-cv-joint-thompson-coupling-16397.html

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

The Thompson website states that the coupling can "transfer thrust loads", but I couldn't find a rated value. The maximum rated speed I saw was 2,500 RPM. And I was surprised that constant running at less than two degrees will destroy the coupling!

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

(OP)
WOW, I didn't see such a notice about that constant running at less than 2 degrees. Can you direct me a little more to that area?

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

A minimum angulation is also required for survival of u-joints.  It has to do with making the needle's tracks overlap enough to keep the grease flowing.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

^ Frequently it will be found that on front-drive cars, the diff is slightly offset (usually forward) of the front wheel centerline, and on rear-drive cars, it's often seen that either the entire drivetrain is shifted to one side or the input shaft at the rear axle is shifted to one side a little, or the transmission tailshaft isn't aimed exactly at the diff at any plausible ride height.

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

You can find the confirmation you seek in the fine print in the back of a thick needle bearing catalog.
 

Mike Halloran
Pembroke Pines, FL, USA

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

beiland- Rather than using the link you posted, go to Thompson's main website, click on 'more info' of CV joints, then on 'more info' of one of the 2,500 RPM units. Near the bottom of the info list is the item about running at angles less than two degrees.

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

"A minimum angulation is also required for survival of u-joints.  It has to do with making the needle's tracks overlap enough to keep the grease flowing."

It also puts all of the load and wear on only one needle in the bearing.

ISZ

RE: Axial Load Capabilities of Thompson Coupling vs U-joint, Marine Shaft

You can get some idea of the axial capacity of the joint by looking at its torque capacity and the OD of the joint. I can't see any particular reason why a Thompson coupling would be much different to any cardan joint in this respect. The claims made for that coupling seem to overegg the pudding, in my opinion.

Cheers

Greg Locock


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