3-brush dynamos

[rustinpeace]

Recently acquired a Jowett 10 (also have a Javelin) with a faulty dynamo (armiture segment dropped out). Contacted Jowett Spares for a replacement, only had in stock a 12 volt, 3 brush. This was a slightly smaller construction and only had single chain sprocket as opposed to a duplex chain drive on the original dynamo. I have had the drive sprocket modified to a duplex and it fits onto the engine ok. The difference being it has four pole pieces as opposed to the two pole pieces in the old unit. What is confusing me - it has three wires rather than 2 wires which was the case on the old one. In the old dynamo I understand the 3rd brush goes through the field windings and ends up as one of the wires coming out of the dynamo. The other wire is the main dynamo brush wire. With this new dynamo I am unsure of what to connect the wires to. Has anyone got any information for me, or where, or who I can get it from? John

[Tony Fearn]

Hello John,

I don't now any technical details, but these diagrams in the Gallery might be of help, if you can understand them.

TOPIC

[rustinpeace]

Thanks for the info Tony. Unfortunately it is not very clear what the 3 wires coming out of the dynamo are connected to. Will have to keep on searching.
John

[k. rogers]

John, why don't you just fit a Subaru engine in it? Only joking, but I'm pleased to hear about your latest purchase and your upholding the flat-four tradition! I seem to remember when I was sorting out my timing chain at Wakefield, Ian Thompson was replacing his dynamo and had the same problem. He must have sorted it out quickly because his car was running by the end of that day - it might be worth giving him a call!