How to Test Swap Meet Generator

[56servi]

I bought a generator at the swap meet to replace my alternator that came with the car. Don't like the looks of alternator on a Model A engine. The seller said it was a rebuilt gen. I looked at the commutator and it was shinny so I bought it. I also picked up a cutout from a friend.

I want to check the generator before installing it on the car. I have a 20 amp bench power supply to use. I checked the cutout by connecting the neg to the gen post & the pos to the cover. I turned up the power supply up until I heard the points close. They closed around 6.3 volts.

I put the cutout on the gen & tried to test it to see if it would motor. Pos to cutout mounting screw. Set supply to 6.3 volts and touched neg to gen output term on cutout. Nothing happened & overload light on supply went on.

I have read the posts on generators but would like to know if there is a step by step checklist for checking a generator that doesn't work.

[Tom Wesenberg]

You can use a 6 volt battery with + to the case and - to the output stud. The generator should motor rather slow in the same direction it normally spins.

There was a recent thread about a "rebuilt" generator that had the 2 wires mixed up inside the generator. You must make sure the field wire is connected to the adjustable brush, or you will fry the generator in a couple minutes.

[Purdy Swoft]

If the ground wire from the field coils is reversed, as in connected to the third brush, the generator will motor backwards but won't charge.

[56servi]

I got it to motor using my 6v battery. The leads on my supply weren't big enough to supply the current needed.
I am mounting it in my Smithy lathe so I can spin it & check the output. I will connect it thru an amp meter & to my battery.

[Fred K-OR]

I know nothing about this sort of thing, but could you not install it in your A easer that doing this type of testing and then test it in the car? Like I said I know nothing about testing generators but it would seem like installing a generator is not that big of a job.

[Purdy Swoft]

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I agree with Fred K. I would install the generator on the car to test it.. If it motors in the direction that the engine turns when its running , that is a good sign that it will charge. With the generator mounted on the car you can watch the ammeter. The next test would be to see if moving the third brush regulates the rate of charge.Rotating the third brush downward increases the rate of charge. Rotating the third brush assy. upward decreases the rate of charge.

[chopo]

send me the alternator

[Willie Krash]

Be sure you have it polarized positive ground or you'll have 12v across the cut out. That would be a bad thing.

[56servi]

I ran the gen on the lathe for about 15 seconds & there is output. Didn't run it too fast because I didn't have a good holding fixture. Will mount it on the engine for final testing. My car is apart for painting & cleaning so I can't run the engine now.

The pulley doesn't fit on the shaft well. It has a lot of wobble. Don't think I have the correct pulley. I don't understand the 1/2" taper & how to measure it. I did measure the pulley ID & the shaft OD.
Pulley Small end ID=.490
Pulley large end ID=.640
Pulley length of taper .600

Shaft Small end OD=.525
Shaft large end OD=.665
Shaft length of taper .490

[Tom Wesenberg]

About March 1930 the shaft taper was shortened to 1/2" long and the pulley hub was also made shorter to match. If your pulley has a wobble almost for sure someone hammered on the tapered end and smashed it some. I've had to straighten them in my lathe by filing the high part caused by hammering. You may be able to see the high spots on the end of the taper, and file it without taking it all apart.

[56servi]

I think the wobble is from the pulley taper not matching the shaft taper. The shaft runs true when turning. The pulley doesn't go all the way on the shaft. It stops about 1/8" from the end.
Is it possible that it has an early pulley that was put on the late shaft. Only about 2 threads on the nut go into the shaft?

[Joe K]

There are some aftermarket pulleys out there. And some "field expedient" pulleys as well. It pays to be aware of the differences and get the right one.

I recently had an accident with a type three pulley and had to replace it. (This holding up my testing of the new type 3 powerhouse we talked about earlier, Tom.)

Joe K

[Tom Wesenberg]

Originally Posted by 56servi

I think the wobble is from the pulley taper not matching the shaft taper. The shaft runs true when turning. The pulley doesn't go all the way on the shaft. It stops about 1/8" from the end.
Is it possible that it has an early pulley that was put on the late shaft. Only about 2 threads on the nut go into the shaft?

The pulley hub should extend about 1/8" beyond the shaft taper, so the bolt will hold it tight. Sounds like you might have a bolt that's too short though.

[Purdy Swoft]

The early tube type generators used, Oct 1928 thru april 1930 had a 7/8 taper on the pulley end of the armature. The armatures with the 7/8 taper used a bearing on the brush end. The later tube type generators used a 1/2 inch taper on the pulley end and a bushing on the brush end. The last tube type generator made in early 30 had the 7/8 taper and a bushing on the brush end. There is an adapter for using the 1/2 inch taper pulley on the 7/8 tapered shaft.This adapter is listed on page A-141 of the new Snyders catalog. The part number is A-10144-R and lists for $1.75