Singer Junior Generator

[david.bryant]

Hi
I am in the final stages of combining two generators to make one work.

Generator Singer Junior.JPG (145.2 KiB) Viewed 2721 times

The generator I have is a Rotax AT131 6V 10 A
Serial No 9784.

One had been sitting in water and one had a broken mounting plate. Both looked quite sad. On disassembly it is looking promising. I have not delt with a three brush generator before and a search led me to http://www.themagnetoguys.co.uk/three-brush-dynamos
and https://www.yesterdaystractors.com/articles/artint4.htm
So I have taken the armature to an auto electrician and it passed a growler test.
Once the field winding was removed the short to ground was found and the rest of the field winding looks ok with a dc vs ac 0.8A test current. The brushes look like they are able to be restored. All the insulation from the brushes to the field wires had broken down and new insulation bushes will be made for the studs then ready to assemble.

Three questions
the new bearings are like the original and are non sealed. Do I just pack them in grease?
What does the cover for the top smaller bearing look like? I have none just two small holes from where it would have attached.
What does the reverse current relay / charge controller look like for this three brush generator?


Regards
David

[ColinB]

Here is the top of my dynamo during testing and before repainting David. Hopefully you can see the cap. You unscrew the slotted fixing and it rotates so you can add grease. I'll take a picture of my cut out and post it later.

[ColinB]

This shows the cut out in a 1932 Junior with distributor ignition. Hope you can read the pictures.

[david.bryant]

Thanks Colin
That helps a lot.
So am I seeing it correctly it's a Negative earth system system and the field and armature are being disconnected when they are discharging the battery?

I can make a cap that sort of looks like yours to protect the bearing. I assume the lower bearing does not get greased as a regular service item.

This cap explains why there is a lot of discoloration on the field winding and top of the armature from excess grease over the years.
Regards
David

[ColinB]

Yes David - as I understand it the cut out connects the dynamo to the battery when it is producing sufficient current to close the connection. It has to overcome the current from the battery, which is always seeking to open it, so when the dynamo stops working the battery opens the cut out and avoids driving the dynamo as an electric motor! On the magneto cars you can switch the dynamo on and off from the switchboard but obviously on yours it will work all the time to power the ignition.

A skilled friend of mine rebuilt my dynamo with modern bearings. No greasing is required so I haven't really thought about the bottom bearing and the owner's manual doesn't cover it.

[david.bryant]

Thanks Colin
That helps so I will push on with the assembly.
Regards
David