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C40 dynamo rebuild queries

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Hi guys. I stripped my c40 after fitting a c40l. (thanks Roger)

I found a corrugated washer between the fan and pulley. Unusual and not in the book but wth!

I pulled the end bracket off and the brushes were fine, however there was no sign of the felt ring or alloy sealing disc...???. I then pulled the armature and found substantial play in the drive end ball bearing, as expected. After removing the bearing I found no corrugated washer or felt washer but there was a washer of sorts, a very flat 'w' shape.???

So......on reassembly, I fitted a felt washer under the 'w' washer, not realising the PO may have done some 'jiggling' :(

I then found that on fitting the fan, it went past the woodruff key and span freely!!!!! That is why the corrugated washer had been put there, to grip the pulley!!!

Rollocks! I just realised where the corrugated washer should have been and the bearing locating ring was too short??? or something else was amiss??

Well its all back together now. Spins freely and feels good.

The rivets were a nightmare to replace. Should I strip it down again and why does the fan not locate on the woodruff key? :(


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Cheers Dave, I'm more bothered about the felt washer and end play. It just seemed odd that the PO had used the washer from the bearing as a 'grip' on the fan !!  and used a weird one to replace it.

Not to worry. I'll swap it back on to the car and see how it runs.

Thanks for that info.

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Thanks Pete, must be in the right place then. I was thinking the whole shaft may be to far forward, what with me putting felt washers at both ends, as per the book.

I'd love to know what that aluminium retaining washer at the back end looks like! The books show a triangular shape !

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my dyno fan has a slot in it to locate on the same key as the pulley. As I explained in the other thread the key was destroyed when trying to remove it so I pinned the pulley and was going to just rely on the shaft nut to clamp the fan in place. However I changed my mind when I started to think about the dynamo being accelerating with the fan free to slip under inertia and made up a little bar to sit in the pulley and fan key ways so transmitting the drive... 

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Yes Johny, would not want that flying off!

Here is a picture of the corrugated washer. I guess this is meant to be under the bearing,  on top of the felt washer at the drive end?


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Hello Jeff

I do not think Lucas would have fitted one of those.

That is a shakeproof type!

They normally fitted the wavy washer that acts like a spring if you google wavy washer you will see what I mean


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Ahh, thank you both. The wsm and Haynes describe the washer under the bearing as 'corrugated' and that was what I thought that was.

The flat u u washer must be correct then. That's good. No need to re-strip my old one then

One more item for the spares box :)

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