Hello Ian; I have a 60 watt dynamo that needs brushes, can you advise where I might be able to buy the correct grade brushes?? that are good quality Thanks Keith

email (option): keithatkinson@hotmail.com

Hi Kieth...Google 'Hawker Electrical'...you'll find the correct brushes there made of the right carbon grade....£8.50 a pair...Ian

email (option): ian@wright52.plus.com

Thanks for that Ian; I had forgotten about Hawker's.
I found an unknown brush in my junk box, and filed it to fit, but I thought it best to obtain the correct grade so it doesn't wear premature, or worse still carve away the commutator.
I am working on a 60 watt dynamo, and also a 40 watt. Both will motor with the D & F connected ect, but both will not output any voltage when driven by an electric drill. Not sure what's going on. I thought that if the armature coils are either shorted, or open, the dynamo would not motor.
I checked the connections of the field coils, and the brush leads against a known good unit, but still no joy. I guess I'll just keep playing around with them, and either get a result, or get fed up and send the dynamo's to an expert for overhaul.
Keith

email (option): keithatkinson@hotmail.com

Only a growler test is definitive. Did you try reversing field connections and polarizing.Does it motor in the right direction?

Is Sean Hawker still in business? Ron

email (option): ronpier@talk21.com

email (option): t.j.walker@btinternet.com

His website is still running with a 'shopping cart' facility...I know Sean has got a full time job doing something else...I think he got worn out by the struggle to earn a crust in this game...Ian

email (option): ian@wright52.plus.com

Well I spoke to him a couple of months ago and he said he was enjoying his new job on the railways. But his website looks up and running (But I didn't try to buy anything). Maybe he still sells stuff on line? I never see him at jumbles anymore. Ron

email (option): ronpier@talk21.com

Thanks for your reply. Yes That's correct. I originally had the 40 watt dynamo motor in the wrong direction, so I changed the polarity of the field coil, so that it motor's in the right direction. (clockwise from the driven end)
The 60 watt unit was OK. I flashed the field (only) with a positive
6 or 8 volt DC, with a negative to the frame. Gave it a couple of swiping motions, like striking a match, as Ian kindly suggested. I did noticed brush powder sediment/contamination between the commutator segments that I thought might be contributing to a low resistance between the commutator bars. I cleaned away until fresh "mica"
Final clean up with a petrol rag, and compressed air, placed an upturned peice of 2000 grit wet and dry under the spring pressure of the brush, and rotated away until shiny.
For now, I would like to find out how an armature is wound. I have a growler I can use to test the armature, but I don't know what I'm looking for??
I would imagine (while the armature is rotating, for example) the two commutator bars/segments that are about to come around into contact with the brushes (ie 180 degees apart) would be an individual and separate coil, and there would be a resistance in that coil. Therefore all the other coils would be the same resistance. From www research, I recall some-one saying, all of the coils are series wound with respect to each other.
I can test for low ohms, or shorts (zero ohms)or inject a higher voltage to check for insulation breakdown.
Any thoughts on this.
Thanks Keith

email (option): keithatkinson@hotmail.com

Check for resistance on ajoining segments on the armature they will be well under 1 ohm check also to the shaft for a short, although this will show up on your segment test. Check the field windings you need above 2.5 ohms.