On Mon, 6 Oct 2003 12:26:35 -0500, Rick Chamberlain
wrote:

In article ,
says...

"Loren Coe" wrote in message
news:R0ggb.507655$Oz4.359060@rwcrnsc54...
In article , Rick
Chamberlain wrote:
I've been looking at 14" abrasive chop saws and really don't like whats
out there. So, I turned my attention to 14" dry saws. Great idea, but
a little out of my price range.

I got to thinking, why couldn't I fab something? I have all the steel
tubing, nice 1" pillow blocks, and a 1725rpm motor. My only concern is
how big should the motor be?

Is there any difference in true HP for an induction motor vs. a
universal motor? If the universal motor on the PC Dry saw is 15A (about
1.5 hp), would I still need a 1.5hp induction motor for the same
performance? TIA for any advice.

not a technical response, they surely will follow, but the comparison is
sorta like two stroke vs four stroke engines. cc for cc, amp for amp
the 2-stroke, universal will be more powerful. there is a difference
in this anology, the univeral motor will have much more torque at
low rpms. --Loren

Actually a very good response, Loren. You are "right on" re. torque at low
RPM - that is probably the main reason that universal motors are used as
much as they are. Basically they are DC-type motors running on AC, and as
such they exhibit the "high torque at stall" characteristic of a DC motor.
Although I haven't tried it myself, I would be quite leery of powering a dry
saw with an induction motor. Certainly, a motor of sufficient HP to drive
the disc would be required (at least the same or larger than the universal
motor) Learning to saw all loads with a blade running at a single RPM might
be hard to do. I think it would work but it would work "best" when sawing
the same (optimum) size material every time. The old "chatter remedy" of
decreasing speed or increasing feed would not be at your disposal.

Bob (opinions are my own - feel free to disagree) Swinney

Thanks Bob. Makes sense. I also have access to DC treadmill motors
with speed controls. Sound like a better alternative?
No.
Unless they are wound feild DC motors.
Then built with laminated silicon steel armature and feild poles they
are a universal motor - and you do NOT need speed control. Just more
to burn out when you croud it a bit.
Ideal motor is an undercompounded? motor - a series motor with a shunt
winding to limit top speed (no load) and a series winding to provide
more torque under load (lower speed and heavier load means more
current, and more torque)