Classic cars forum & vehicle restoration.

[colwyn500]

I rebuilt the generator using new brushes without electrical testing it. The car is just at the end of restoration so had never been run previously. When fitted to the car it didn't give more than a very negligible output even when tested by connecting together the terminals to directly energise the field coils.
I have removed the end plate to check the brushes and compared with the half worn originals. It appears that only the very tip of the brushes has been in contact with the commutator even though they are made with a reasonable attempt at the angle they will eventually wear to.
The question is, would this be likely to seriously affect the voltage output so is it worth me sculpting them to match the curvature of the commutator?

[ukdave2002]

What's it like with the original brushes in?

[DM]

If you want to improve the contact are of the brushes wrap some fine wet and dry paper around the commutator and turn it by hand to shape them.

If the dynamo has been unused for a long period of time flash (re polarise) it to strengthen the residual magnetism of the field coils.

[colwyn500]

Good points and appreciated.
I "flashed" the field coils already.
I may try the originals and will also try bedding the new ones.
The problem with this dynamo is it's very tricky to replace the brushes the way I plan, as they dont go in theough the side like a Lucas.
I am trying to avoid a complex dismantling job so need to increase my chances of success so I only need to do it once.

[kevin2306]

How do you flash the coils?
(genuine question, no smutty answers please..lol)
Kev

[peter scott]

Just connect the field terminal directly to the battery for a second or two.

Peter
_________________
http://www.nostalgiatech.co.uk
1939 SS Jaguar 2 1/2 litre saloon

[colwyn500]

Thanks for all the advice.
Bedded the brushes with Abranet 320 grit as it has no carborandum particles or dust of its own.
When refitted, the dynamo had a wee think for 30 seconds or so whilst it kicked in the coils and then away we went....charging light off

[Old Wrench]

It was usual, in days of yore before alternators were common, to skim the dynamo commutator in a lathe: carefully! Good idea after skimming to linish with say, 400 grit Wet and Dry, whilst the armature is still in the lathe.

Afterwards, it is usually necessary to trim off the mica separators; and then fit new brushes. The separators should properly lie slightly beneath the copper commutator sections.

Remembering to thoroughly clean out the brush housings to ensure easy sliding movement.

If in doubt, test the continuity of each segment winding, between common and the commutator segment: all windings should show an almost identical resistance.

Testing the field coils is the next step.