Get me up to Speed on DC Motors

[Harold_V]

Or I could have two sanders. No law against it.

Are you sure?

Harold

[HDB]

Why not buy an old treadmill and use the parts?

[wlw-19958]

Hi There,

Why not buy an old treadmill and use the parts?

I've got an idea. Why not just use the treadmill as is except replace the
tread belt with a wide sanding belt. For heavy stock removal, you can
stand on the stock and go "surf sanding."

Good Luck!
-Blue Chips-
Webb

[HDB]

Hi There,

Why not buy an old treadmill and use the parts?

I've got an idea. Why not just use the treadmill as is except replace the
tread belt with a wide sanding belt. For heavy stock removal, you can
stand on the stock and go "surf sanding."

Good Luck!
-Blue Chips-
Webb

Or one hell of a callus remover

[Carm]

"I've got an idea. Why not just use the treadmill as is except replace the
tread belt with a wide sanding belt. Good Luck!"

As he looks at the wife's treadmill stored in upright position next to the computer.....
yeah I would need some luck from such a dangerous proposition

[rbertalotto]

I've gone the whole treadmill DC motor route a few times with various sucess. Yes they work, but nothing like the "real deal"

You can buy brand new DC motors on Amazon for quite inexpensive ($179-$229) and Surpus Center sells a fantastic controller for $80

Check out my web site for conversions I did on my 12 X 36 lathe and my 14" bandsaw. Absolutely the best modification I ever made to my tools.

www.rvbprecision.com

[SteveHGraham]

For that money I could get a VFD and 3-phase motor.

What's wrong with treadmill motors? I haven't seen anyone else say anything negative.

[rbertalotto]

In my experience, they simply didn't have the power I needed. But then again it might have been the type I was using. A bunch of us bought a whole slew of New Old Stock motors a few years ago. Lots of folks had issues with them burning out at the time. I didn't suffer that, but they didn't have the power I needed.

This is a picture of the motor I'm talking about:



It was replaced with this:



Best $179 I ever spent!

[SteveHGraham]

The tool I'm fooling with originally came with a 1/2 HP motor, and the motor I bought is rated 1 HP. If that turns out to be 50% more than the actual power it produces, I'll still be at 1/2 HP. Hope it works.

I have read that treadmill motors are not rated honestly, and that you need to go to a higher figure to get what you actually want.

[SteveHGraham]

Supposedly they are rated at peak power, which they can't sustain long.

[ken572]

"I've got an idea. Why not just use the treadmill as is except replace the
tread belt with a wide sanding belt. Good Luck!"

As he looks at the wife's treadmill stored in upright position next to the computer.....
yeah I would need some luck from such a dangerous proposition

HEY STEVE
"Carm" might have a pretty good idea.
I was doing one of my Good Will Store walk through's
looking for goodies, and I stopped to checkout this
tread mill that was there. Thinkin what ever size
sanding belt you want to buy you could narrow and shorten to
size with only the pieces that are already there. I think that
could make a pretty tuff and cool belt grinder/sander.
The only part you would have to make from scratch would be
the adjustable table/rest. You could make it adjust Verticle or
Horizontal.

Ken.

[atunguyd]

Steve, most DC speed controllers are PWM controllers.

A lot of DC speed controllers, especially for higher power motors, are actually SCR based rather than PWM. They are cheaper, but are simply rectifying the 60hz AC signal. Voltage is clipped to reduce the speed. Motors tend to run noisier with a typical AC hum and hotter. There is a significant loss of torque at low speeds since torque is proportional to voltage.

By contrast, PWM controllers supply a fixed voltage at high frequency (eg: 16,000 hz), in variable duration pulses. Pulse duration (and therefore current) is reduced to reduce speed. Low speed torque is still reduced somewhat, but remains considerably higher than with an SCR controller.

I swapped out the SCR controller that came with my 1.5hp Chinese machine with good quality PWM controllers and the difference is like night and day.

Agreed Torch, I was very much simplifying things and putting the SCR based controller in the same camp as the DC based PWM controller. Technically a SCR controller is a PWM controller since it does change the width of the pulse - sure the pulse may not be a square wave but from a purely electronic point of view a PWM controller does not have to have a square wave output, it can be sawtooth, triangular or even sinusoidal (rectified of course).

What I was trying to get across is that the PWM controller pretty much generates whatever voltage is put in, they typically do not contain any sort of voltage conversion whereas a VFD typically creates the 3 phase from an internally created DC signal, so the inverter is capable or creating an output voltage that is independant (in a limited way) of the input AC voltage.