Repair of roller cam-followers

[CPR]

On my 1935 250 o.h.v. JAP engine, the roller cam followers are worn. There is play between the roller pins and the rollers.

Phil Irving in Tuning For Speed sugests using silver steel, hardened and tempered to a straw colour in the centre but blued at the ends to enable them to be riveted over after assembly. Seeing that the pins are about 1/2 " long, this proceedure would be some what tricky to achieve. Has any one ever had to do this repair and how did you achieve it?  

Thanks

Chris R

[cottonjo]

Hi Chris,
I have some worn ones too. Interesting to know the outcome. Ewan Cameron in Malvern remanufactures but the are very costly.
Good luck
Paul

[nickg]

Hi Chris

Not done this but can you flare one end before hardening like making a rivet? Then harden and quench and temper in an oven. Finally wrap in something wet or push into a potato with other end protruding a few mm. Blast with a small hot flame to temper. Presumably not critical. Centre drilling the end a bit might make it easier to flare with a punch plus will heat up quicker at end.

Or grip with some soft ally strip (acting as heat sink) and mole grips with end protruding and press hard onto grinding wheel to adjust length as if sharpening a tool badly!

With short lengths would at least be possible to practice a bit!

( I’m always annoyed when people try and help by suggesting things they have not tried themselves!!)

Cheers

[CPR]

Hello Paul.
I think Ewan Cameron will be the last resort.
I do wonder with the milage I’m likely to do, am I being a bit fussy. Although, I don’t like replacing parts I know to be worn. But. If I start to replace the pin i’m committed to finishing it.

Chris R

[CPR]

Hello Nickg.
Thanks for your thoughts. You have given me some ideas to think about.
My idea at the moment is to harden the pin. Then press on a large diameter of metal over the centre part to act as a heat sink, and then soften the ends of the pin. One problem would be, will the heat sink be large enough to absorb the heat given its thickness will be small.
I like your idea of centre drilling the ends of the pin to aid riveting. I shall have to have a trial run on a test piece before the real thing.

Chris R

[nickg]

Chris, I'd try strips of soft ally bent round and Mole grips for the heat sink as is good conductor and easy to do. You will see if it works from the distance of the oxide colour. I was thinking one thick strip annealed but could use a stack of thin sheet if easier. Good luck, post a photo!

[CPR]

Hello. Nick
I’ve moved on a little regarding the roller cam problem.
I knocked the pins out and I was pleasantly surprised.
The pin/roller runs in a bush. Presumable made of bronze or phosphor bronze.
What was surprising was that the pins were worn and not the bushes.
Providing I can rivet the silver steel pins I don’t think I will heat treat them, as they are running in a bush.
For the record the pin diameter is 7/32” (0.2187”), the O.D. of the roller is 11/32” (0.3437”)

Chris R