CV Joints/Rzeppa joints

For many years, when I have heard you discussing constant velocity joints, I have thought about a particular type of power transmission joint that I was familiar with when I was in the coal mining industry. One brand of continuous miners had a cutter head with angled sections on both sides that required that the driving force be delivered around that angle. To do so, the machine employed a “Rzeppa” joint, which included very large ball bearings, around two inches in diameter, trapped in cages. In today’s show (2/04), while discussing a CV joint, it sounded like you said something about a “Zeppa” joint. Does that confirm my conjecture that a CV joint is the same thing as a Rzeppa joint, only much smaller?

It would seem that the “Zeppa” joint is the Rzeppa joint. All recent FWDs use the Rzeppa joint at the outer, wheel hub end of the drive shaft. The inner joints are tulip joints which allow the shaft to move in and out as needed when the angle changes. The only other constant velocity joint commonly used on automobiles is the double cardon joint which was once common on the front axles of 4 wheel drives.

The outer CV joints in cars are Rzeppa joints. The inners are not.

As you can see from page 2 of the attached drawing
the inside CV joints are of a different design.

Rzeppa joints transmit constant torque while allowing varyng angles, but the axle assembly as a whole has an additional need… If you follow the movement of the wheel hub throughout its suspension travel, you’ll find its distance from the transmission changes as the A-frames control the camber via their respective arcs (or the struts if they’re used). That requires the axle assembly to be able to change length as it transmits torque. The design of the inner joint allows

  1. constant torque to be transmitted through the axle
  2. the inner axle to change angles to accomodate suspension movement
  3. the length of the axle assembly as a whole to change length to acccomodate free movement of the wheel through its geometries.

EDIT: Rod, you beat me. I MUST learn to be more succinct!