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RoyJ RoyJ is offline
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Default Electric motor shafts

1) properly lubed sleeve bearing have a longer service life in certain
applications like furnace blowers. In the 'old' days, they were used in
the majority of motors since ball bearings had both shorter life and
were much more expensive.

2) Rotors have a steel shaft pressed through a stack of laminations made
from a high silcon steel. The stuff is extremely hard and brittle.
Easily bites into a normal steel shaft.

3) If you try pressing the shaft the way it was pressed on, you MIGHT
have a chance. Smashing it with a hammer won't do the job. Gear puller
is not even an option.

Michael Koblic wrote:
In an effort to educate myself and hopefully gain a 3/4" shaft in the
process I attacked an electric motor I bought for $1 in a garage sale. It
has seen better days. I suspect it powered some sort of woodworking machine
as the whole thing was coated liberally with sawdust inside and out. The
insulation was rotten and falling off the wires. I should mention that
physically it was a big beast but only 1/2hp (the label was barely
readable).

I managed to get the front off. I expected ball bearings supporting the
shaft but there were sleeve bearings at both ends - the front one quite
chewed up which surprised me as the shaft seemed to turn freely. The oiling
port was plugged with sawdust.

I got the fan off and tried to get the rotor off but could not even shift
it. I should say I have never attempted anything similar and use of Workmate
and sledge hammer is probably not the recommended method. I managed to
mushroom the end of the shaft nicely but the rotor would not shift.

The rotor sits on the central part of the shaft which is 1.25" as opposed to
the ends which are 0.75". There appears to be a small key in a slot but
trying to punch it out did not meet with success either.

Questions:

1) Are sleeve bearings usual in electric motors or is this some old, cheap
model?
2) Are shafts in such motor usually machined in one piece or is a 3/4" shaft
rammed into a mandrel to hold the rotor? In spite copious cleaning I cannot
tell for sure.
3) I am puzzled at the inability to shift the rotor. If the sledge hammer
did not do the job is a gear puller (or some other gizmo) likely to succeed
(as well as protect the shaft, of course)?
4) Am I missing some method by which the rotor is held onto the shaft
rendering the sledge hammer ineffective?

Books and Google have been no help. Neither was liberal application of
Liquid Wrench.

Thanks,