I am in the process of sorting thru a bunch of generator parts and am trying to determine if severial armatures are good or bad. I do not have a growler so would like to know if it is possible to check these with just a ohmmeter.?

Jim
Unfortunately not completely.
You can check for shorts between the commutator and armature shaft with the ohmmeter buy placing the probes on the copper commutator and the shaft. There should be no resistance reading.
The problem is you cannot check for inter & intra winding shorts with the ohmmeter. To do this you must have a growler and ideally one with a set of probes with an ammeter in series so you can check each winding individually.
You sometimes see growlers for sale on eBay pretty cheap.
Hope this helps.
Ron the Coilman

You can check for continuity by putting one ohmmeter lead on a commutator plate and with the other lead, check for continuity with each of the other plates. Also, check from the commutator to ground, (the armature shaft), for shorts.

I believe the rebuilders rewind them all anyway, regardless. So, if you're saving for cores, I'm not sure it matters.

Ron,

You beat me! Should have known.

Jim
If your intention is to send the armatures to the re-winder forget the original windings, it will all be replaced.
Carefully check the bearing surfaces and the shaft for straightness. The commutator should be as close to 1.75 inches in diameter as possible. The Model T generator was a high failure rate item and the commutators have usually been turned and undercut many times over the last 80 years.
Having done that, when I send armatures for rewinding, I do not get a one for one back as the commutators sometimes have inter segment bar shorts that disqualify the for reuse.
I try to keep a float of used armatures in the hands of my armature re-winder so I always have rebuilt units on hand.
One last thing, never never use a rebuilt armature until you have carefully checked the commutator undercutting and finish. Armature re-winders are great at rewinding, but notoriously poor at undercutting and finishing commutators. Poor armature undercutting will result in quick generator non-generation.
Hope this helps.
Ron the Coilman

Thank's for the information, I'll wait untill I have access to a growler to check these.

I should elaborate.
I stated "commutators sometimes have inter segment bar shorts that disqualify the for reuse"
I have high voltage test equipment that can be used to test commutators but it makes no sense to spend the time removing the windings and test them when a competent armature re-winder should conduct a commutator inter segment high voltage test prior to reuse.
Ron the Coilman

Ron: Speaking of rewinding. What's the status of the Map? I put mine aside for the holidays and never got back to it.

"You can check for continuity by putting one ohmmeter lead on a commutator plate and with the other lead, check for continuity with each of the other plates."

This doesn't work Jerry. You could have a burned or shorted coil and you would still read continuity. All the coils are connected in parallel. In other words, all the coils are connected to all the other coils in one way or the other. Except for a massive burnout, you will always have continuity.

Ken
I think you, me and Chris in England have it straight. The winding has a span of five lamination slots and is offset both right and left to commutator bars by five. This means each winding has a span of 10 bars.
If anyone disagrees please speak up?
Ron the Coilamn

Ken
You are correct.
As you know all the armature windings are interconnected and open circuit. This is why the growler test is best. Any closed circuit short inter of intra windings will show up on the growler.
Ron the Coilman

Ken,

I know that doesn't work but he wanted to know what could be done with a VOM only and what I suggested is just that. I should probably have stated that the VOM test is only of value for showing an open circuit.

Thanks.

http://cgi.ebay.com/ebaymotors/Parts-Accessories___SNAP-ON-MT-323-MT323-GROWLER- TESTER-ARMATURE-CAR-TRUCK_W0QQitemZ220335774042QQddnZPartsQ20Q26Q20AccessoriesQQ ddiZ2811QQcmdZViewItemQQptZMotors_Automotive_Tools?hash=item220335774042&_trksid =p4506.c0.m245&_trkparms=65%3A1%7C39%3A1%7C240%3A1318
I wonder if you could re charge magnets with this too!

Someone posted a diagram once showing how to modify the circuitry so you could use a growler for doing magnets, so yes, with a bit of work it could be done.

I did the first proof of concept on the growler magnet charger and someone from down under (sorry I can't remember who) did a very nice refinement of the idea. There have been many growlers on eBay for less then $10 (including Snap-On & Blue Point) that have gone unsold. Try to find one close to home as the shipping can be significant.

Here is the link to the thread :

http://www.mtfca.com/discus/messages/29/38427.html

Be_Zero_Be