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Dynamo overhaul!

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Dynamo overhaul!

Post by Locknut on Wed Mar 11 2015, 10:27

Hi All,



I have taken this dynamo apart to clean it up as the commutator(?)and the plates( in front of the coils) inside  were covered in rust - this I have now done as best I can.
My question is - should I now coat the steel part of the commutator and the plates with something to prevent rust developing again eg shellac,marine varnish? or just leave them as they are?
Also there does not appear to be any magnetism left in the unit - should there be any?
Electrics are a black art to me so any help or advice would be much appreciated.Thanks.
All the best,
Kev.

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Re: Dynamo overhaul!

Post by StewartH on Wed Mar 11 2015, 16:10

Hello Kev,

I'm doing the same with an old motor - I painted the areas between the contact areas with a electrical motor varish - of fleabay you'll see it for about £5... its just a precaution as with use it shouldnt get too rusty..

instead of me boring you here's a good link to a site explaining the basics -

http://electrical4u.com/working-or-operating-principle-of-dc-motor/

hope it helps!

best

hamish

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Re: Dynamo overhaul!

Post by Woodsman on Thu Mar 12 2015, 10:05

Hi Kev,
If you have cleaned up the commutator the chances are you may have left some fine metal particles in the gaps between each segment. Run along the insulation in each gap with a junior hacksaw blade then wash out with contact cleaning spray.

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Re: Dynamo overhaul!

Post by Locknut on Thu Mar 12 2015, 13:22

Thanks for getting back to me  Hamish and Paul with that useful information.
Hamish -My goodness - Flemming's left hand rule!I last came across that in a physics lesson many years ago!
Good tip there Paul - I will go and do that now.
I should have added that the dynamo is from a genset that I hope to rally,and given our weather I had thought that as I had it apart it would be a good idea,now that I have got the rust off, to treat the metal strips on the armature and the metal plates(4) in the stator with something to prevent/delay rust.It seems like the electric motor varnish could well be the stuff to use.
All the best,
Kev.

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Re: Dynamo overhaul!

Post by woody on Thu Mar 12 2015, 15:07

Old dynamos often loose the small amount of magnetism they need to get them working the next time they are used.  If they are used regularly, its not a problem.

When I fit a new (unknown) dynamo to my old cars, fit it as normal and connect to the regulator as normal.

Start the engine, set to run at a fast idle and briefly connect (flash) the D and F terminal of the dynamo together a few times.

This kicks the field coils into life and it will start generating.


Last edited by woody on Fri Mar 13 2015, 11:09; edited 1 time in total

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Re: Dynamo overhaul!

Post by Locknut on Fri Mar 13 2015, 10:15

Hi Woody,
Thanks for your reply.
I have 4 wires coming out of the dynamo - a red one (+ve?),a black one ( -ve?), and 2 black wires which appear to be painted white! Any idea how I find out which are the D and F ones please?
All the best,
Kev.

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Re: Dynamo overhaul!

Post by woody on Fri Mar 13 2015, 11:07

Check continuity between the brushes and the 4 wires you have.

I'd guess that black and red will be conected to the brushes (perhaps -ve or earth, and +ve or D).

If so, the two others are the field coils, so one will go to -ve or earth, and the other to the field terminal (F).


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Re: Dynamo overhaul!

Post by Locknut on Fri Mar 13 2015, 20:06

Hi Woody,
Thanks for that.I still have the dynamo in bits but will put your advice into practice when I have it back together again.Thanks again.
All the best,
Kev.

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Re: Dynamo overhaul!

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