Cut out

[Beauford]

I noticed a spark came off where the cut out attaches under the screw on generator. What is causing that?

[Tom Wesenberg]

Make sure the mounting screws aren't too long and touching the field coils of the generator.
Also make sure the mounting screws and cutout case are clean and tight.

[Mitch]

is it charging?

[Mike V. Florida]

Be sure you are on top of the insulator on the generator. You should be on top of #66 in the diagram from Brattons.

[Beauford]

It's charging...it did it before and I tightened up things and noticed the other day a spark jump. It weird as I had it rebuilt but when I got the car someone had a ground cable from water pump to gen.

[Beauford]

Mike, yes I have my wire on gen on top of rubber insulator.

[Tom Wesenberg]

You mentioned rubber insulator. The post Model A generators were made with two wires coming through a rubber grommet in the case, and one wire was fastened to the cutout mounting screw for it's ground connection.
The Model A generator shouldn't have any rubber.

[Beauford]

I have one (rubber) on new cutout. I'll take a pic

[Beauford]

This is what I have...

[Tom Wesenberg]

This is what I have...

Wow, that's the most rust pitted generator I've seen, but if it works, just keep running it. Your insulators should be plastic or Bakelite, and the thin one should go on the generator post side of the cutout. Also check the insulator on the output side. It needs to be turned so the curved part fits the curve of the case.

With that much pitting, I hope the rough pulley doesn't chew up your V belt.

[Beauford]

Pulley is good...if you remember when I started this journey it had been out in the elements for 60 some years in the woods. And yes, after a rebuild it works. Reads 10 on plus side when running.

[Mitch]

def make your adjustments with an external meter so you know its accurate.. many digitalis give false readings due to rf interference. my digital fluke has a smooth button which eliminates that interference. most just use an analog meter because of this

[Tom Wesenberg]

Running a constant 10 will boil the water out of the battery. If I wasn't using an electronic voltage regulator, I'd set the amps for 2 or 3 on the plus side with the lights off.

[Beauford]

Tom, no lights...just running chassis. How do you set the amps??

[Mitch]

sounds like another tech article is coming

[Beauford]

Guess I got more than I paid for with the rebuild on the Gen. Winning!!! Of course I'm reading that repo gauges are all hit and miss on accuracy...

[Mitch]

This is another great write up i had saved from Tom W...

. i think it would make a good addition to the tech forum

"QUOTE"


Generator Brushes and Adjustment and How It Works

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I'm asked quite often about brush adjustment and how they work, so hopefully these pictures will help.
The first picture is a cutaway taken at the Model A museum at Gilmore Auto Museum in Hickory Corners, Michigan. The second picture shows the 3 brushes. This happens to be the style with a ball bearing in the rear, as used until about March 1930. At that time the bearing was changed to a bushing and the output stud was moved from the front of the case to the rear.

The brush on the left is the output ground brush and has no insulators on the brush holder.
The top brush is the adjustable brush (third brush) and it sets the generator output amperage.
The brush on the right is the output brush and connects to the output stud in the generator case.
Notice all 3 brushes have a long and short side, and the short side is always closest to the brush holder pivot post.
Also notice the adjustable field brush is thinner than the 2 output brushes.

The adjustable brush connects to the field windings, and the other end of the windings is connected to ground. So, consider the ground brush as 0 potential and the output brush as 6 volts potential. Now you can see that as you move the adjustable brush (field brush) closer to the output brush, you will increase the voltage feeding the field coils. This will increase the magnetism of the field poles, which increases the generator output.

So, you can see this also becomes a runaway situation. As the field gets stronger, the output increases, and this also increases the output to the adjustable brush, and it becomes a vicious circle. However since the output is connected to the 6 volt battery, this keeps the output under control. If you have a poor connection in the charging circuit, then the battery is no longer connected and the voltage can rise to as high a 40 volts. This can smoke the field windings and cook the armature. If the lights are on they will also burn out.

With the generator on the car, as you face it from the front of the car, the adjustable brush will be about in the 2 o'clock position. Moving the brush UP lowers the output, and of course moving the brush DOWN will increase the output. For most daytime driving a couple amps should work fine. The more amps, the more the water is evaporated from the battery. If you do a lot of starts and short drives, or night drives, then you will need to move the brush down for more output.

This picture shows too much grease for the rear bearing, and I removed about half of it before the final assembly. I also put a thin coat of grease on the adjustable brush ring and 2 tension holders, and a drop of oil on each of the 3 brush pivot posts.