MTFCA Forum

I have a rebuilt generator - refurbished armature, new bearlings, new fieldcoils, refurbished brush holder and new brushes. On the car it turned out not to work (well).
The other day I bought a basket of T-parts with a straight exhaust manifold, 7 nice nickelplated hubcaps and a generator with a pulley and the gear for the generator.
Today I testet them both setting 12 V to them with minus to the body of the generator and plus to the terminal and discovered that their direction of rotation was opposite of each other.
I presume the generator I bought the other day is assembled correct and that it actually works. The rebuilt is wrong.
What can I have done wrong rebuilding the generator? Have I connected the field coils incorrect? I am aware of that the wires have to cross over and believe I've done that right. Are there field coils out there made so the wires should not cross over? Should I just swap the wires?

Motoring a T generator can spin either way if the brush plate has not been set to the null point, best to read up on how to set in the workshop manual.

I have found & read that others have also found, setting the null point per the T-1 manual doesnt work well.

One recent rebuild gave me serious grief to adjust. So much that I did a phone a friend.

I was referred to a third method. (Ron Patterson, i believe)

Set as follows.
1) Set the 3rd brush to its minimum. (Away from the motor)
2) Loosen the 4 brush holder screws 1/2 turn
3) Run the motor. Shift the brush holder untill you are reading 2 amps.
4) Shut off & lock the 4 brush holder screws.
5) restart & reset the 3rd brush setting to desired output 4-6 amps is plenty.
6) Lock the 3rd brush down & confirm running output.

Speedytinc.... With your suggested method, is the third brush contacting the armature?..... Would armature rotation be clockwise or counterclockwise during motoring ? ..... The initial 2 amp setting during motoring , would armature rotation be slow, medium, or fast ?

Moxie26 wrote: ↑

Fri Jul 21, 2023 7:40 pm

Speedytinc.... With your suggested method, is the third brush contacting the armature?..... Would armature rotation be clockwise or counterclockwise during motoring ? ..... The initial 2 amp setting during motoring , would armature rotation be slow, medium, or fast ?

This method is with the 3rd brush down, in car running.
Motoring doesnt come into play @ this point.

During initial set up finding null point gets close to the brush holder setting.( 3rd brush up)
After dropping the third brush & providing power, the armature rotates CW as looking straight on @ the gear.

Its speed is moderate depending on voltage. 12V spins it faster.
I cant say I have seen a generator motor backwards, but I have the brushes set reasonably close initially.
I suppose its possible if the brush ring was set way off from null.

Standard Model T 3 gear set up, looking from the front, crankshaft gear goes clockwise, timing gear goes counter-clockwise and generator gear goes clockwise. Jim Patrick

speedytinc wrote: ↑

Fri Jul 21, 2023 8:12 pm

I cant say I have seen a generator motor backwards, but I have the brushes set reasonably close initially.
I suppose its possible if the brush ring was set way off from null.

I'll add to this with some context.
Generators definitely spin backwards with power applied if the brush plate is set incorrectly. I have also seen old rewrapped generator field windings wired incorrectly that can cause this.

When I set up the brush plate on a newly rebuilt generator, I first apply 6v, lift the 3rd brush and rotate the brush plate in both directions to test that the armature spins both forwards (clockwise) and backwards. That gives me a (very) rough indication that the armature is ok and field coils are functioning properly. If I can't get it to spin in both directions (or at all), something is wrong and it will never work. Since I always use new field coils, it's invariably a bad armature, most likely due to an open wire since I test armatures on a growler for shorts. Very rarely I've found the open wire and been able to fix it. Generator armatures fail A LOT. I'd say that 30-50% of the armatures I test are bad, mostly with shorted windings. I have a huge box full of them. There's really nothing you can do if that's the case other than rewinding it or replacing it. As time marches on it will become increasingly hard to find suitable armatures for reuse due to the lacquer insulation on the windings breaking down causing shorts, and most will need to be rewound.

Jeff

Kerry wrote: ↑

Fri Jul 21, 2023 6:21 pm

Motoring a T generator can spin either way if the brush plate has not been set to the null point, best to read up on how to set in the workshop manual.

Kerry, the refurbished generator is of course adjusted by the book and both was actually checked that with the 3 brush lifted, the hum but do not turn either way.

speedytinc wrote: ↑

Fri Jul 21, 2023 8:12 pm

During initial set up finding null point gets close to the brush holder setting.( 3rd brush up)
After dropping the third brush & providing power, the armature rotates CW as looking straight on @ the gear.

I appriciate all you thoughts and input, but actually I asked a straight question and speedytinc gave me the answer. When all is done right it is motoring clockwise when you look on the generator from the gearside.

Thanks!