crank hardness

[David Kemp]

From memory Jowett cranks have a special hardening done to them, If a crank is ground , does it destroy this process? Do the cranks need to be rehardened?

[Drummond Black]

David, I take it that you are referring to the Oval Web Crankshaft retro fitted to Javelin and Jupiter's. If not then the following is NOT relevant.

The Oval Web Crankshafts were manufactured from EN19 steel and were hardened using the nitriding process. The surface hardness for a new shaft was 600 VPN ( Vickers Pyramid Number ) or approx. 54 on the Rockwell scale. The Nitride process only goes a few thousands of an inch deep so when you have the Crankshaft reground then the hardened surface is removed. So it has then to go through the nitriding process again. Now this process does very slightly swell the steel so after the regrind and the re-nitriding the Crankshaft requires to be polished to the final dimension and to obtain the correct surface finish to allow it to run in the Lead Indium Bearings.

If you ignore the nitriding and polishing step then, from experience, the crankpins will wear a lot quicker.

Trust the above is of assistance. If you require more in-depth advice just PM me.

Regards Drummond

[robert lintott]

In view of the hardening applied would it be unusual to have to regrind an oval web crankshaft . I would have thought the bearing shells woud wear preferentially? What is the experience ? Bob

[Forumadmin]

Most regrinds are due to failure rather than wear. I would expect at least 20000 miles before a regrind and how many of you have done that in a Jowett?
Premature failure is caused by poor fitting or bad oil delivery. It is not just about plonking new shells in. The fit of all the shells should be accurate both in the housing and on the shaft. Rods must be checked for twist. Case must be line bored. Everything must be clean.
Anti scuff paste and sympathetic running in will prevent early failure (perhaps).

[robert lintott]

Do you mean 200,000 ? Bob

[Nick Webster]

I can't find the article I want at the moment, not can I lay my hands on the various oval web cranks I have stored away. So from memory - it is worth saying there are two types of oval cranks. The first ones were made of a different material and cannot be hardened. The later ones do have EN19 identified somewhere on them.

Nick

[Forumadmin]

https://jowettnet/forum/download/file.p ... &mode=view

[David Kemp]

So when did Jowett change to nitride cranks? & if an engine rebuild was necessary would it be worth hunting for a nitride crank?

[johnairey]

Oval cranks before mid 1959 can not be nitrided.

[Forumadmin]

Worth reading the article referenced.

[David Kemp]

Ihave long given up trying to use the Jowett gallery, been locked out ,kicked out …….it is a piece of doo doo...

[Drummond Black]

I agree

[Jack]

Ihave long given up trying to use the Jowett gallery, been locked out ,kicked out …….it is a piece of doo doo...

Have you tried e-mailing Keith?

I got locked out once, just sent Keith an e-mail and it was fixed in 5 minutes, he just reset the password for me which fixed the problem. I think I had used a different password for the Gallery to the main forum, which created the problem my end but it was fairly straightforward to fix.

Jack.