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MMD > Archives > November 1999 > 1999.11.12 > 08Prev  Next

Repairing Ampico B Electric Spool Drive Motor
By A. B. Bonds

Harvey Roehl wrote:

> Help!  I'm looking for either (a) a complete roll electric roll motor
> for my Ampico 'B' or (b) referral of a good motor shop that can rewind
> one.  I burned mine, and the armature has to be rewound and the field
> probably should be.

I have the following comments on the Ampico B motor which I'm sure
echo concerns many have previously considered, but may be news to some.

This is a very well-built motor and given care should last
indefinitely.  However, age can take its toll in two ways:

(1)  The compound used to imbed the commutator segments on the armature
does seem not to be a permanently setting compound.  Over the years,
if the armature is left in one position, the stuff can "sag" or ooze
out between the segments.  This disrupts the smooth operation of the
brushes.  One solution is to chuck the armature in a lathe and with a
_very_ sharp tool take a small cut across the commutator segments.
This re-centers the commutator and gets rid of any high spots the
bedding compound may form.  Do _not_ cut into the ends of the segments
that are soldered.  This is unnecessary and can disconnect windings.

(2)  I was having a terrible time with the interrupter (governor)
contacts arcing and getting dirty.  After some consulting with our
electrical machinery guy (it helps to be in an Electrical Engineering
department) we concluded that this arose from sticky brushes.  Works
this way:

The brushes are meant to provide a smooth transfer of current to
successive segments of the armature.  If the brushes are sticky in
their holders, they do not bed firmly to the commutator segments and
arcing results.  The motor will run, but not efficiently.  The arcing
signifies frequent disconnection of the armature.

This is a highly inductive load.  The consequence is that whenever the
arcing occurs, it throws high (flyback) voltages into the remainder of
the motor circuit, which aggravates arcing at the governor contacts.
This eats up the contacts.  The cure is to make sure that the brushes
don't stick.  The holders are made of pot metal, which can swell as it
corrodes.  You can use a jeweler's file to loosen the holders (don't
file the brushes).  Alternatively, new brush holders (of brass) are

A. B. Bonds

(Message sent Sat 13 Nov 1999, 00:07:41 GMT, from time zone GMT-0600.)

Key Words in Subject:  Ampico, B, Drive, Electric, Motor, Repairing, Spool

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