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Dynamo problem


Chris Launders

Well Known and Active Website User
VOC Member
Well I'm not sure this comes under industrial engines but here goes.
A friend had a Lucas E3L dynamo rebuilt "professionally" about three or four years ago but has only just got round to fitting it to a Norton ES2 with a magdyno and it won't work, we've tried all the usual tests and anything anyone has suggested, flashing the field coil etc it does "motor" quite happily but won't charge whatever we try, has anyone come across this before, what can we try other than building another one.
 

Len Matthews

Well Known and Active Website User
VOC Member
Is it rotating the correct way? Could be loss of residual magnetism. I can't remember how to restore it-step forward electrical wizard!
 

Chris Launders

Well Known and Active Website User
VOC Member
We try it both directions every time we do something, just in case, Flashing the field coil should restore the residual magnetism, I am familiar with dynamo's but this has me stumped.
 

Len Matthews

Well Known and Active Website User
VOC Member
We try it both directions every time we do something, just in case, Flashing the field coil should restore the residual magnetism, I am familiar with dynamo's but this has me stumped.
Another thought,is the air gap between armature and field pole piece too great?
 

Chris Launders

Well Known and Active Website User
VOC Member
Right an update, after comments off another forum I cleaned the commutator (oxidation though invisible after being stood for at least 3 years) no result but as soon as I applied extra pressure on the brushes it powered up, lit the bulb briefly and then continued with the same drag but slight arcing. Tested the bulb and it was open circuit (blown) tried another bulb, same thing had to use extra pressure on the brushes, bulb lit and went out again.
Two items here, first I wonder as it's running at the equivalent of full speed its generating too much power for the bulb to handle, and why does it need the extra pressure on the brushes to start. my idea now is to strip the dynamo and clean the commutator properly and check the brush spring tension. then run it at a more sedate speed.
 

roy the mechanic

Well Known and Active Website User
VOC Member
Try a strip of abrasive paper on the commutator,to bed in the brushes. They are square ended when new.-Put paper rough side out.
 

Marcus Bowden

Well Known and Active Website User
VOC Member
Roy's idea was my first thought, the other I use is a silicon brush end grain and it polishes up the commutator beautifully, then under cut segments of commutator.On big ships DC motors I use to put them in the lathe with a parting tool ground & mounted side ways then run saddle wheel to under cut the mica, some electricians I sailed with used a candle (wax) to & throw across the commutator as it was working and would prolong the brush life considerably. D & F connected together and put positive to D & F and negative to earth / body , this will polarise it to Negative earth connect and it should motor in direction to be driven, with a strong but slow RPM.
Kick mechanical regulators into touch as one gets an additional 10 to 20 watts out of them. With added reliability.
What I like about a dynamo is that it only produces what is required, with having Alton's on most of my bikes they produce maximum all the time with lighting on LED's my hand warmers are used nearly all the time, summer I ride with just the lightest touch on the handle bars otherwise my hands over heat, use what ever power you produce so that the regulators don't OVER heat and burn out, I've never had on go, but know several folf that have.
bananaman.
 

nkt267

Well Known and Active Website User
VOC Member
Right an update, after comments off another forum I cleaned the commutator (oxidation though invisible after being stood for at least 3 years) no result but as soon as I applied extra pressure on the brushes it powered up, lit the bulb briefly and then continued with the same drag but slight arcing. Tested the bulb and it was open circuit (blown) tried another bulb, same thing had to use extra pressure on the brushes, bulb lit and went out again.
Two items here, first I wonder as it's running at the equivalent of full speed its generating too much power for the bulb to handle, and why does it need the extra pressure on the brushes to start. my idea now is to strip the dynamo and clean the commutator properly and check the brush spring tension. then run it at a more sedate speed.
An unregulated Lucas dynamo can get to nearly 20 volts, don't run too fast and use a 12Volt bulb..There has been talk that some of the brushes are too hard(and too soft) for the use in these dynamos, could this be a problem? John
 

Bill Cannon

Well Known and Active Website User
VOC Member
After cleaning the commutator it is essential to carefully clean out the gaps between segments.
Bill
 

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