Monday, October 26, 2009

S7 Dynamo MC450 (early rather than late MC45L)

Well, thanks to Steve Benson's pix of his dynamo, I took a closer look at mine.  It is likely a forest for the trees type of thing.  The dynamo fitted to my bike only has two brushes instead of four.  I had never seen a picture of one with the cover off.  And I apparently missed this diagram.  (thanks to Phil)

Lucas Model 450 fitted to KYL95.

Apparently there's supposed to be a later Lucas model MC45L.  It must be an improvement.

So the question is ... what to do about it?  Fashion brush holders for the bottom to increase output and balance the load on the armature, or try to get a different dynamo plate or different dynamo / alternator altogether?  Shame I just spent the cash on a solid state regulator, if I would have known that I'd have so much trouble with it, I'd have been more inclined to covert to 12 volts.

First step will be new brushes.  I'll bodge a set if I have to just to see I can get less voltage drop across the brushes and charge better.


  1. Would it be easy to get a used upper plate and attach it? You know, I may have enough old motor/generators laying around that we could steel a couple brush holders and then mount on a phenolic or fiberglass PC board.

    I can see why they added the other brushes on, but what were they thinking initially. Perhaps the copper impregnated brushes allowed it to work. But even then, why weren't the brushes 180 degrees apart. Weird, weird. Can't even rationalize their logic. TT

  2. The problem is that if I wanted to add another pair of brushes to help carry the load, the cover holes are right where the lower brushes would have to be.
    Not sure why they mounted the brushes 90 degrees apart. Lucas specials department...