Does any one know what the standard method is of making the drive shaft handle the change in distance in a RWD IRS set up between the diff and the wheel hub/stub axle.

Clearly the distance is smallest when the diff and hub are level and greatest when the suspension is in full bump or droop.

How is this change in length accommodated? Does the centre of the CV joint move in and out in relation to the body of the joint? Should the drive shaft slide through the centre of the joint? Or is some other form of joint used, such as a tripod, and if so how does that allow the length to change?

Clive.

I thought it stays the same length as the distance doesnt change during suspension travel?

does the axle not compress when you tighten the hub,??

GeorgeM

It is the CV joint that does the adjusting.

If you can imagine the end of the drive shaft as having a sphere-type gear on the end of it,this sphere can slide inside the tube that is the outer end or hub-end. As the hub moves up and down it's distance from the inner pivot on driveshaft changes. The change in distance is allowed by the sphere-type end of shaft sliding in and out of hub-end. Now to engage these two components so that they don't rotate independently there are effective teeth, much like a gear on both sphere and inside of hub-tube. These are in constant mesh.

This is not an accurate description of the components but an overly simplified one in order to explain the principles. In actual fact on most, if not all, CV joints there are ball bearings instead of gear teeth set into the driveshaft end. These ball bearings are trapped by large channels in the hub-end. Thus allowing the length adjustment.

I hope this is understandable!

Terry

I have also seen some shafts with slide on splines.

with the "bolt on" / Lobro type shafts the joints slide on splines (with copper circlips each side of each joint to limit the movement)

here's a diagram:


"push in" / Tripode joints are a bit different but do the same job:


[Edited on 12/6/08 by mcerd1]

The inner tripod joints accept the plunge movement.

Terry, your a star.

To confirm; I fix the "spheres" to each end of the driveshaft and they slide in the outer "tubes" of the CVs? All that remains is to fix the "spheres" on the drive shaft splines such that they take up the variation in length without over extending the joints?

The reason for the confusion is that the splines on the inboard ends of my drive shafts are longer than the splines in the centre of the "spheres". As the splines have no circlip groves it appeared that they were intended to slide in the "spheres". But that seemed completely wrong to me. I'm pretty sure the intention was to allow the user to set up their suspension and determine the exact position required for the inboard "sphere" before machining circlip grooves to locate it in the correct position on the shaft.

Does that sound about right to you?

Yours, Clive.

quote:

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Originally posted by mcerd1
with the "bolt on" / Lobro type shafts the joints slide on splines (with copper circlips each side of each joint to limit the movement)

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quote:

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Originally posted by Liam
For the Sierra shafts the joints are not supposed to slide on the shaft splines. The circlips locate the inner part of the joint and prevent it from moving at all. Plunge in the joint is accommodated by the ball bearings moving along channels in the inner and outer part of the joint.

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Hi Liam,

Yes, they are custom shafts designed to take Ford Fiesta or GKN f3 inner joints and Sierra outer joints. I think they were originally developed by Muffett for Fisher Fury's but are also used on the MNR VortX.

The final length of driveshaft required can vary with the amount of camber applied to the rear wheels so it is advantageous to have some flexibility in the final position of the inner joint "sphere".

I was pretty sure I was right that the shaft splines should not be left free to slide in the "sphere" but could not find anything definitive to say CV joints were designed to move with the driveshaft.