On Mon, 9 Sep 2013 15:59:04 +0000 (UTC), Larry Blanchard
wrote:

On Sun, 08 Sep 2013 18:10:21 -0400, krw wrote:

A new one might not have the weight of an old one and may not be as
efficient (or more) but HP is HP. (HP == torque*RPM - RPM is constant).

Offhand I don't recall what the HP rating is, but I bet it's for real and
not "peak developed HP" :-).

The point being that, for motors, HP is defined as torque*RPM (times
some constant - 5550 if torque is in ft-lbs). SO for a given HP,
(real) torque will be the same for all motors of the same RPM (which
60Hz induction motors used in saws will be).

Who knows what "peak developed HP" is? I think it's also called
"Sears HP". ;-) I really like their 3.5HP shop vacs. Those things
really suck! ;-)

I wonder if the heavier motor has more inertia to keep it going through
momentary tough spots?

Not enough to mention. Most of the weight difference will be in the
stator and housing, anyway. Again, a heavier motor may be more
efficient because it may have more copper in the windings, something a
newer motor is certainly going to try to minimize. It's more likely
that the older ones are under-engineered[*], though.
[*] Any fool can build a bridge that stands. It takes a real engineer
to make a bridge that barely stands. ;-)