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Universal joints

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pontiacjack

pontiacjack

Electrical
Apr 16, 2007
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I need a "primer" on u-joints. I don't even know the nomenclature for a typical cross-type automotive u-joint (steel cross with four needle bearings)? And I've never seen (or tried to derive) the math (output angular position vs. input as a function of running-angles, etc.). For a two-joint drive (typical front & rear of a driveshaft), what orientation of the joints provides maximum cancellation of angular velocity disturbances? Is it true that equal-but-opposite run-angles of the two joints is most desirable?
 
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You used a panhard or Watts link together with a leaf-sprung axle? That's an additional axle control device that can fight with the lateral location given by the leaf springs ...
 
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You used a panhard or Watts link together with a leaf-sprung axle? That's an additional axle control device that can fight with the lateral location given by the leaf springs ...
Click to expand...

I think the trick is setting the PHB or WL at the proper height.


Norm
 
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Brian, in our current Lotus Cortina vintage racer the PHB works out well enough. If care is not taken in the location (with limited adjustability) some adverse axle movement can be expected. In roadracing, suspension movement is rather limited and lateral movement is also quite small. Yes, I have several competitors that think the way you do (some professional teams also agree with you). All I can say is that my way works for us. I have had quite a few drivers in the seat over the years and, so far, NO complaints about the handling and drivability of the suspension setup. PHB aside, the big bugaboo with the leaf spring/live axle was "roll oversteer" which was more difficult to overcome.

Tmoose, I've competed against Bud Moore cars in vintage racing, including one Palm Springs Grand Prix in the late 80's where they were driven by Parnelli Jones and George Follmer. PJ broke and at the checker I could see Follmer's Mustang coming up to lap me. Good stuff!

Rod
 
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Well... thanks for the help understanding Cardan joints. I trust that my truck will work out just fine.

Internet searches let me down, however, on a description of ball-and-trunnion style joints, such as used in my '55 Plymouth (and I'm too lazy to work out the math myself). Anybody know (or direct me to) the expression for output velocity vs. run-angle for such a joint (at constant input velocity)?
 
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Thanks, Greg. Is that "strong" component in the same ballpark as a Cardan joint? The output rotational velocity of a Cardan joint at a run-angle of five degrees has a maximum second-order variation from .996 to 1.003 of the constant input velocity. Is a ball-and-trunnion variation even "stronger" than this at five degrees?
 
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Fex- thanks for the link. I won't pretend to having understood the whole paper. But unless I got it completely wrong, it appears that all those horrible instabilities occur at U-joint operating angles greater than fourteen degrees. My U-joints (as do most automotive applications) don't run at more than about five degrees.
 
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You're welcome.
Yes you should have no problem. It's more of something to look out for, and to gain some technical knowledge of the subject.



[peace]
Fe
 
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