On Tue, 07 Oct 2003 22:19:38 -0500, Don Foreman
wrote:

On Tue, 07 Oct 2003 12:12:57 GMT, Rick Chamberlain

My preliminary design is really quite simple - a pivoting box frame with
the blade arbor mounted using high grade pillow block bearings. I would
drive the arbor with a belt/idler combination to take up slack when
bringing the blade down. Or I could change the pivot mechanism so that
the idler is mounted on the pivot point and eliminate the slack problem.

In this application, what motor would you suggest? And, where could I
find one?

Of course, if there is an inexpensive source for 15A universal motors
with a 1" arbor running at 1300 rpm, I'd be all for it. :-)

Some of the treadmill motors are universal motors. The one I have
is. Just look for brushes: if the motor has brushes it's almost
certainly a universal motor.

Actually, that is not accurate. If it has brushes it will run on DC.
A universal motor is specially designed to reduce eddie current loss
in the iron. IF the motor has a laminated feild "core" and a laminated
armature it MAY be a universal motor.
Solid pole peices or armature most definitely is not, and permanent
magnet motors have brushes, but absolutely can NOT be run on AC.

Noload speed of nearly any universal motor will be considerably higher
than 1300 RPM but you can manage that with belt and pulleys. In
general, the larger the diameter of the motor the lower the running
speed. Small diameter motors rated at 10 to 15 amps, as used in
portable power tools, run at very high speeds with two-stage planetary
gear reduction. I seem to recall that the treadmill motors run at
about 5000 RPM no-load. You could "dial down" the speed with a
speed controller, but you'll want the torque multiplication that you'd
get with a gearbox or belt 'n pulley speed reducer.

A DC PM treadmill motor might also work OK here. They don' t have the
stall torque that a series-wound universal motor does, but are
considerably better than an induction motor. Again, you'll need
speed reduction. See, e.g.
http://www.sciplus.com/category.cfm?category=174

4800 RPM, 11.2 amps, 1.5 to 2.0 HP, $49.50 for a new one. A
suitable bridge rectifier will set you back another $2.