Dynamo woes

[britab1967]

Hi all

Last year I had the dynamo on Sky fail on the way to work which, with a poor battery, left us having to temporeraly repair the wire connection to one of the brushes. I latter replaced the brushes but on the next drive the dynamo made an awfull noise and when I got back and stripped it down again the soldered connections between the winding and commutator had been ground down with solder splattered onto the inside of the housing.
I rreplaced the dynamo with another spare which worked fine until this week when exactly the same happened, even down to the grinding of the soldreed joint.

I'm obviously doing something wrong when re-assembling the end plate onto the dynamo, but I can't see what can be causing the damage unless theer is eccessive lateral movement on the brushes or the windings which allows the brushes to sit on the soldered area of the commutator.

Any ideas where I've gone wrong?

The first dynamo gave a charge when the brushes were changed, and still did even with the damage. The second one didn't charge even with new brushes giving 3v output, just enoughto keep the pump working for the journey home but no lights or indicators.

Brian

[bmcecosse]

Can only suggest another dynamo - the others may just have been too badly worn to last. As I remember - there really isn't much you CAN do wrong when fitting new brushes! I suppose it's possible a fault in the regulator has been forcing the dynamo to run flat out - were there any other signs of that - very bright lights/bulbs blowing/battery hot/battery losing water ? I have to say - I much prefer the simplicity and reliability of my alternator! Which as regulars well know - I pick up for £1 at autojumbles

[britab1967]

Thanks for the reply BMC.
I fitted another dynamo, which was in visibly good condition. Went out for a drive on Sunday, between spraying the bonnet for Molly, and all went well.
James took Sky out yesterday without problems.
I came to work today and, probably as I drive faster than James, smelt things starting to get warm and before I could pull over I heard the noise which I have become familiar with - the dynamo failing.
I can only conclude that it is a problem with the regulator.

So, I either get another dynamo and regulator, or I go for the alternator conversion.

So at this point and jnowing that it's difficult to get dynamo's from the scrap yards today, is it worth looking at something more popular or is there a cheap source availble?

Brian

[bmcecosse]

Oh dear -well as I said - alternators can be cheap enough when you don't need them, but of course when you do - they become like rocking horse poo. I would definitely grab an alternator from a scrappy - or ebay.

[britab1967]

If only there were some in the local scrap yards!

What I don't understand is, why have the soldered joints only melted with the new brushes, which I also fitted to the third dynamo.
I ensured that the brushes were well bedded in, and there were no problems until the run this morning.

Brian

[bmcecosse]

They must be passing a huge current to melt soldered joints. I used to have by-pass switch which I used to push full battery volts into the field of my dynamo - to maximise power for the lights on my rally car - and that never melted anything!