Rear Hub Shafts

[Dave-M]

On my spare rear struts, One hub shaft is grooved at the outer bearing position. The groove is about 0.75mm deep (0.030 in). I have access to TIG, MIG and Metal Spraying to repair it. All come for Beer money so please don't say buy a new shaft. Which would be best?
Regards
Dave-M

[rgh0]

Dave

If I was going to attempt to repair the shaft (and I normally would not having had a shaft fail on the track) then I would do the following.

1. Find out why the groove was worn there in the first place and fix that problem.

2. If the worn groove has any sharp edges or roughness, grind to blend in smoothly the groove with the parent metal to avoid any stress raisers.

3. Crack test the shaft looking for any cracks especially in the area between the inside of the hub flange and the inside of the outer bearing paying special attention to the area where the groove has worn. If you find even the smallest crack indications junk the shaft. If their is any indication of overheating of the shaft and "blueing" of the metal in the area of the groove then you will probably find cracking, even if you dont you should consider junking the shaft if its been heat affected

4. I would use metal spray to build up the worn area and then grind the surface back to required dimensions ensuring I get it concentric with the taper and inner bearing mounting surface.

In the end the shaft will not be as strong as orginally and has the potential to fail as it is relatively highly stressed in the area you will be building up. Bad workmanship will guarrantee a failure good workmanship and it may be OK. Personally I dont think its worth the risk.

Rohan

[Hamish Coutts]

Dave,

I had similar problems to yourself and had similar access to metal spraying facilities (although they cost a bit more than beer money). I had a long discussion with the metal sprayer (who is also a very good engineer and used to race).
In the end our conclusion was pretty much the same as Rohan's. I didn't have any doubt about workman ship (the guy did a fab job of a crank regrind/polish and a rebore for me) but I ended up getting a new shaft from TTR. That has been fitted and I'm a happy pup.

Hamish.

[elanman3]

Dave,

Being an ex-welder I know that welding special steels like hardened drive shafts will be a specialised job including a full Post Weld Heat Treatment process, so I don't recommend that you tig weld it. I don't know too much about metal spraying so I'm guessing that there is less of a direct heat input but the metal sprayed/lapped on instead of fused. The grove may be full of metal, but technically it's still there. Therefore in my opinion the weak point in the axel is still there.
Having recently had a rear hub and wheel come off, which is what will happen if your's fails, I recommend you dig deep and fit new shafts. You won't have to buy new underwear either then.

Colin

[david.g.chapman]

I had a similar problem with a rear axle shaft, but the wear groove was only a couple of thou deep - caused by the rear wheel bearing spinning on the shaft.

I fixed the problem (those of you with a nervous disposition look away now) by gluing a feeler gauge around the groove and reducing the diameter again to give an interference fit with the bearing!

That was 10K miles ago and I am still smiling. I do NOT suggest this for a 30 thou groove - that's 60 thou off the diameter of the shaft. I think you will have to replace it.

Dave Chapman.

[Dave-M]

Thanks for the input from you all
Badly written by me, it's 0.030 in on diameter not 0.060.
David, Nice bit of innovation, you are not from australia or south africa are you? I always admire their approach to finding solutions to problems.
I don't think I will follow the feeler guage method and have decided to bite the bullet and buy new. Having said that I still think a repair would be OK. assuming the car is driven with respect.
Once again, thanks to you all.
Regards
Dave