Re: [CAD_CAM_EDM_DRO] Re: Spindle motors

R/C hobby motors are designed for high output for short bursts and not many iterations. Run for 5 minutes, cool for 30. They are stripped down all out hot rods. It'd be like putting a 1/4 mile race engine in the family wagon. Wouldn't get far, but you'd get their in a hurry.

Ron

caudlet <thom@...> wrote:
--- In CAD_CAM_EDM_DRO@yahoogroups.com, "David G. LeVine"
<dlevine@...> wrote:

>
> At 10:22 PM 8/28/2007, you wrote:
> >By the way, what is the voltage rating on those motors? I didn't

see

> >one listed.
>
> Count the NiCad cells and multiply by 1.25 or the LiPo cells and

multiply by 4.

>
> They tend to run from 10 Volts to 40 Volts. And I was wrong,
> controllers now go to 300 Amps!
>
> Still, a 1 HP, 60K RPM engraving spindle is reasonably hefty. For
> slower speeds, more conventional motors and VFDs are probably a

better choice.

>
> Since the motors are optimized for props and ducted fans, I bet a
> smaller ducted fan would both cool the motor and remove the

engraving chips...

>
>
> David G. LeVine
> Nashua, NH 03060
>

This interesting but something in my engineer mind says to ask some
basic questions. Since 1 HP is 746 watts and the voltage is 30 to
40 volts to get the RPM the current has to be like 15 to 20 Amps at
that voltage! That is a sizable power supply.

I suspect those motors are not designed to run continuously given
their application of running off batteries. I would also question
the lifespan in hours. RC stuff is designed for a different duty
cycle than running 8 hours a day. As discussed I think heat
removal will be a problem. The controllers are pretty neat but not
real cheap considering you would need to front end them with a DC
supply of 40V at 20A (based on the specs). At that point it would
probably be cheaper to build in a voltage regulator on the supply
(even a simple phase control of the transformer primary).

I guess we won't know until someone can play with one and get some
test results. I'm not sure how they do the HP ratings (even on the
standard routers) unless it takes in to account RPM and inertia. If
you look at the ratings of a 2hP full sized router that runs on
120VAC it should pull more current running than it does....If you
try to ask the vendors how that rating is measured they give you
blank stares.

Not trying to be negative but just working through the physics!

Tom C






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