Dynamo speed?

I have been working on my E3HM generator. I've checked the field coil, the armature and all tested good, I cleaned and checked the brushes as well.yet it produces only 4vlts at about 2000rpm.It does motor when D&F are connected.

I re polarized it and no difference.

I ended up ordering a new armature & field coil .

I had a similar problem. It turned out to be poor earthing between the dynamo body and the bike. Some things you shouldn't paint...

Previously ian_soady wrote:

I've rebuilt the Norton dynamo, but the brushes seemed fine so I reused them. The commutator was oily but has cleaned up nicely. When reassembled, I'm getting good continuity between the D terminal and the dynamo body - 4 ohms or so, and can see it fluctuating as I rotate the spindle. Again continuity between the F terminal and body of around 5 ohms (there are based on my memory so are approximate and may even be the wrong way round).

The dynamo motors well and in the correct direction with a small 6 volt battery.

However, when I join the F and D terminals and spin the dynamo with an electric drill, I see only a tiny voltage between the F and D and earth. Is it merely that I'm not spinning it fast enough to start generating?

I seem to remember I had a similar problem years ago with an A10 dynamo and took it to Tony Cooper who returned it to me working and charged a very small amount but I don't know what he did to it (if anything!)

Hi Ian,The dynamo needs to be turning at about 1000rpm for it to excite its self then the faster it turns the higher the voiltage.If it is still not working at 1000rpm you ether got it wired wrong or the armature has a problem and it will need to be tested on a growler and the field coil should have a resistance between 2.8 & 3.2 ohms.If you live near Bristol i will test your armature on a growler for free.Beat of luck Paul Wolf 07831446958