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You are a gentleman indeed. I will sort out the beer fund donation.

Thanks,

Steve

Hmm now I can't rest until I have the correct one on my S. 15/16" is the same size as a sump nut isn't it?

floormanager wrote: ↑Sat Jun 15, 2024 6:58 pm Hmm now I can't rest until I have the correct one on my S. 15/16" is the same size as a sump nut isn't it?

Rest easy, but yes, same size as the sump drain bolt.

Might try modifying one

All very interesting however, if my S is typical and has remained unaltered the tensioner arm is on the outside which aligns it perfectly with the clamping mount on the front of the block block

I originally tried mine with the tensioner arm bracket on the dynamo, fixed to the side nearer the radiator, as you say yours is. It would get in the way of the very edges of the fan blades. Also, it seems that Cooper S cars were fitted with two of the tensioner arms, one on top of the other. So definitly would connect with the fan blades.

However, what year is your Cooper S Allen? I'm guessing that you have an earlier dynamo that doesn't have such a thick threaded dynamo mounting. I can only imagine that the threads were failing so they made the aluminium casting thicker there. So the problem with the tensioner getting in the way of the fan then became an issue, especially if they then decided to go for two tensioner arms. So easy fix, fit the tensioners on the other side, which then meant a different spacer had to be made on the engine plate end. When all that would have happened, who knows.

Steve

I know it's been a couple of months since I got this post rolling but just to finish up, this is how it all worked out in the end, in case anyone else ever needs to know about the oddities of dynamo fitting on a Cooper S.

I sent off the tension arm spacer, which Peter Laidler kindly sent to me, to a mate who has a very acurate lathe. He turned down the hex to the exact size as outlined ealier in this thread then sent it back to me. I then cut the thread a little further towards the hex, otherwise the nut would have bottomed out before gripping properly. I then painted the hex part to match the green of the engine and dynamo.

Then I fitted it all to the car as per the pictures and descriptions earlier in this thread using two new tension arms together. It seems this is how a Cooper S should be. I have used the all metal lock nuts and washers Peter sent with the spacer.

It's now all assembled and the fan belt is tensioned correctly and all is working well. Thanks for your help with this everyone.

Steve