MTFCA Forum

Spins, but has no torque. What can I expect? Bad field winding, brushes...?

You get the same symptoms when the potmetal bush is swelling and grabbing the armature shaft, or has grabbed it and is spinning in the housing.

Allan from down under.

Check the terminal stud to be sure it’s not lose.
They are prone to breaking lose at the solder joint and creating a poor connection resulting in increased resistance and poor operation.
The old Babbitt bushing could also be the culprit as mentioned above.

What are you working on? Bad bendix? (Starter drive)

Steve Jelf wrote: ↑

Mon Nov 22, 2021 11:29 pm

How's your battery?

Brand new battery. Even had a 'booster' hooked to it.

It could be any of the items mentioned, and/or a dirty commutator, sticky brushes, oil in starter case, armature dragging on field shoes due to bent shaft or bad bushings, poor internal connections. Did this situation develop suddenly? If so, look very carefully for problems in all connections, including ground connections, the cable connection post the starter, and the starter switch. A starter that has mechanical issues such as bad bushings will draw a lot of current but perform poorly.

TXGOAT2 wrote: ↑

Tue Nov 23, 2021 12:46 pm

It could be any of the items mentioned, and/or a dirty commutator, sticky brushes, oil in starter case, armature dragging on field shoes due to bent shaft or bad bushings, poor internal connections. Did this situation develop suddenly? If so, look very carefully for problems in all connections, including ground connections, the cable connection post the starter, and the starter switch. A starter that has mechanical issues such as bad bushings will draw a lot of current but perform poorly.

This car has been sitting for near 20 years. It pulled the starter and had it on the bench. It spins fine, just no torque. I have rebuilt a few old tractor 6v starters back in the day, it's just been close to 40 years ago.

The cables might be corroded. Some of the connections an cables are pressed on and could have corroded over a 20 year period. Also was the former battery 6 volts or 12 volts? Some starters have been rewound for 12 volt use.
Norm

I found my starter commuttater be be very oily when the starter wasn't working. After cleaning it, the starter worked very well.

The oil problem was probably a result of over filling the crankcase.

Art Mirtes

The small spaces between commutator segments can become packed with material from the brushes which can allow current to "leak" from one segment to another instead of passing through the armature windings and energizing the motor. Old oil and gum can interfere with brush function too. The narrow spaces between the commutator segments can be cleaned with a suitable tool. Use care to avoid damaging the copper segments. A good starter can jump off a bench due to torque reaction when battery voltage is applied unless it is restrained.