Lucas E3L Dynamo

[Superarnie]

Hi to all,

I am restoring a BSA A10 Spitfire Scrambler and have converted the dynamo from 6v to 12v, in the course of which it has had new bearings, field coil, brushes and armature. I have tried 'motoring' the dynamo to ensure my field coil connections are the right way round (ie; armature spinning the correct way). However when I connect the 'F' and 'D' wires together and then connect them to the live battery terminal (It's a positive earth system) and earth the other field coil wire and brush wire to battery earth pole, the dynamo slowly rolls over but within a few seconds comes to a stop. The outer metal casing gets quite hot.

When I reassembled the dynamo, with no power to it, the armature rotated easily and smoothly. It seems that when power is connected, the armature gets stiffer (I'm assuming the magnet is therefore in function due to the charge) and the power of the battery seems to be too weak to overcome it?

The two outer field coil shoe attachment screws are as tight as the will go.

Can anyone advise what I may need to do do.

Many thanks and kind regards

Gary

[Bsareg]

Sound like either the field or armature is not energising. Try earthing the body and powering up just the field. Armature should get tight, then with the field disconnected power the armature, normally a click is heard and you can feel the armature tighten a little. If both test ok, join f and d together and it should rotate in direction that it'll be turned by the engine. If reversed, change over either field or brush connections (not both).

[Superarnie]

Thanks Bsareg, I'll give that a try.
Regards
Gary

[CheeserBeezer]

There's a good test page here, with diagrams of how everything should be wired-up. Worth a look if you're still not having any joy.

https://sites.google.com/site/priorymagnetos/dynamos

[Superarnie]

Thanks Cheeserbeezer!

[Superarnie]

Hi to all, by way of an update, it seems the issue I had is now resolved. I have stripped the dynamo down again as I suspected the clearance between the armature and coil shoe may have been to close, despite the free rotation of the armature when no power connected. On closer examination the show had a few rough spots which I have smoothed out with a dremel and final smooth with fine wet and dry. Then reassembled the dynamo and followed the procedure outlined by Bsareg. Hey Presto! When connected to a 12v battery in motor mode, it spins away quite freely now.
Thanks again to everyone for your input.
Regards
Gary

[trevinoz]

It motors but does it generate?

[Superarnie]

No idea yet Trevinoz! I'll let you know in due course.