Drive flange / CV joint face flatness and design

[tmvolumex]

I need to add a spacer in between a CV joint and a transaxle output shaft drive flange and I am wondering what the best face design of the spacer is, flat or cupped. I noticed that the "flat" surface on a factory CV joint appears to be slightly cupped or dished. It is this surface that mates with the " flat" (also dished) face of the output shaft. Since the CV joint / output shaft is designed so that faces carry the load (not the bolts that pass through the bolted assembly) I was wondering if this cupped face was intentional or just a manufacturing variation. IE is the cupped design used so that when the assembly is bolted together the OD of the assembly mates first and has the highest interface pressure, in order to carry the highest load. Also should my spacer be harder or softer than the CV joint and output shaft hardness for the best torque capability. I was thinking of making the spacer out of an old CV joint and leaving the CV joint heat treatment as is. The CV is locally induction heat treated on the inside where the CV joint ball carrier features are located.
Thanks

 

[GregLocock]

Your description sounds a bit odd. Can you post a photo of the relevant end of each part?

Cheers

Greg Locock

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[patprimmer]

Yes, it has me beat also.

Every CV I have seen has a flat bearing area on the flange that contains the bolt holes. It would be VERY important that the surface I envisage should match perfectly so as to minimise load on the bolts. The concave on the final drive output flange is normally between the mounting flange with the bolt holes and the spline. That concave is normally a clearance area.

Regards
Pat
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[tmvolumex]

I put both the CV joints and the output shaft flanges on a surface plate with a sheet of 600 grit sandpaper and gave piece a couple of swipes. The mating face of each is cupped, not flat. I was surprised that they were not flat also, thus my post. The output shaft flanges are new so distortion from being used is not the answer. The CV joint is 1.5 inches thick so I really dont think it will flatten out with the clamping bolt load. 6 ea, 8mm bolts. I found another CV joint that actually has a step around the mating face of .030". Thus only the outer portion of the CV joint contacts the output flange. The step starts ar the center of the bolt holes.
Tom

 

[GregLocock]

Your first post claims the convex/concave surfaces mate to transfer torque. They don't, the torque is transferred by shear across the joint in the outer sections with the bolts through them.


Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.