Dynamo's

[Nick W]

After road testing my cooper s , it quickly developed a strange noise at high revs, when I got back the dynamo was RED HOT!...so looks like it cooked it's self ....
I've ordered a new one, but wondered if a bigger pulley was used on the S. I've seen the cast Works ones from time to time, but is there an off the shelf larger pulley?

[finchy533]

What state are the brushes in, and how old are they?

If they're not that new and are now worn out, there might not be any inherent problem - I think regular replacement of the brushes would be par for the course back in the day when subject to high revs/high load.

[Nick W]

It had new brushes ..but think the bearings might have gone

[Nick W]

I rang mini spares and was told they didn't do them ...but just found them on there website

[woodypup59]

Sounds like it was working very hard.

Perhaps your control box is u/s.

[Spider]

It's been a good many years since I've had one apart (over 35 !), but if memory serves, the Bearing at the front end is electrically insulated, though, it maybe the bush at the back end, regardless one is Insulated. If that Insulator cracks or is shorted to the frame of the Dynamo, it will do just this.

The Insulator here stops a circulating current flowing in a loop through the Armature back through the Frame of it. The current that circulates is of the order of around 80+ Amps. It has nothing to do with the windings, but it the magnetism between the stationary and rotating parts.

[floormanager]

I've refurbed a couple. Not hard. The worst part is field coils are usually filled with grease and the cotton wrapping has degraded. You can get new field coils and the Egyptian cotton. You need to re-fit the coils, which means opening them up. Best tool is an exhaust pipe expanders. Good fun refurbing them and probably better than "modern" copies.
Paul

[kit of bits]

Try these people
D

[Fanfaniracing]

Where is the best Adress to get good new brushes?

[kit of bits]

As above
Classic and vintage dynamos..
D

[mk1]

The Works cars certainly DID have a larger dynamo pulley. I have one on my Blue 850. These are the same diameter as the crank pulley. I am sure that MS have these available.