Dynamo Commutator Question

[Keith.owen]

Hi,
I have just taken delivery of a new armature for my dynamo which I am changing along with the field coil as part of a rebuild / desperate measure to get the charging system going after trying everything else; the manufacturer of the regulator says that it is ok and everything worked before. Wiring all checks out o.k as well and the dynamo did pass the basic tests!!

Anyway, the commutator contacts used, traditionally, to have a groove separating them from each other. The new commutator has no such groove and the insulating material on which the contacts are mounted fills gap between them (there is no groove). The surface seems perfectly smooth as though it had been intentionally finished off. The separation between the contacts is also minimal.

My question is, is this the 'new' way of doing things or should I scrape out the material between the contacts (which given the minimal separation between them will be a challenge)?

Comments and advice would be appreciated.

Thanks and BR,

Keith

[nevhunter]

The "old" way of undercutting them would still be the way I'd go. They've probably taken a short cut and not bothered to do the hand work. Get a fine 32 tooth hacksaw blade and grind the "set" off the side of a portion (end) the get the thickness correct and prevent making a mess of the side of the groove. You only need do it where the brushes run plus a bit on the end where you are up to the place where the wires are soldered into. Later ones may have no solder Some are welded. Welded is better. It's only a spot but they don't fling apart when hot like soldered ones can do if you work them too hard. Clean the copper with fine glasspaper, not wet and dry and blow off with air. Nev

[Keith.owen]

Hi Nev,
This I will do.

thanks and BR,
Keith

PS. Out of curiosity, what's the reason fro not using wet and dry?

[simon.holyfield]

The abrasive is electrically conductive.