"Michael Koblic" fired this volley in
news
1) Is such degree of heating abnormal? I have never encountered a
motor that heats up this much so I assume the answer is yes.

It doesn't sound terribly out of line. Decently-made motors typically
are rated for an _internal_ temperature rise of up to 40C.

2) What is the likely cause? My first thoughts was "bearings" but
why
would the housing be hotter than the shaft? Superficially there is
nothing to suggest that the bearings are at fault.

If it's one of those light-housing open-frame motors, there can be
some eddy losses in the frame as well as the stator. Plus, the stator
is usually in intimate contact with the frame, and conducts copper
loss heat as well as stator excitation losses into the frame.

LLoyd