DDoerschuk wrote:

Fellow RCMers,

I've been reading a book from the 50's that describes different kinds
of electrical motors and how to repair/rebuild them. In one part, it
very briefly recommends using a "growler" to test an armature.
Unfortunately, the reference was short and pretty obscure, and I was
left in the dark as to what the test would even accomplish. Does
anyone know the answers to any of these questions?:
1) What does a growler measure?
2) How to you correctly use one?
3) Can you build your own?
4) Has it been replaced by a newer device? I notice that neither HP
or Fluke offer one, so I suspect it may be antiquated.

It's a 2-part device. The first part is a U-shaped chunk
of iron with ends of the U in a vee shape so that an
armature can be set inside them. A coil is wound around
the U and AC is applied to it.

The second part is a set of probes and some kind of
indicator.

By putting the suspect armature in the crotch of the U
and applying power to the coil, you induce a voltage
into the windings of the armature. You can then probe
the segments of the commutator and test for shorts or
opens.

It's called a growler because of the obnoxious sound
the armature makes rattling against the U shaped pole.

Snapon still sells them:

www.associatedequip.com/associated/ pdf/manuals/mt326c.pdf