What sort of motor is best for continous high torque applications?

Probably a basic question but one I don't really know the answer to. If I wanted to drive a belt at various speeds all however slow speeds. What is the best type of motor to use that provides the most power. I have a 3.1Nm Nema23 439oz that I would quite like to use, would that be any good?

When I think "High Torque" I think of a diesel engine in a semi-truck. So, I think a Caterpillar 1000hp engine should do.

Seriously, the only way to know if a motor is good enough for your application is to determine how much weight is being moved and how fast you need to move it.

Tough to say, but this is exactly what I'm wanting to replicate:

http://www.axminster.co.uk/jet-jet-22-44-osc-oscillating-drum-sander-prod801421/

They are showing that the unit takes 2.2Kw. 746 watts per Horse Power so... It would seem that the main motor is probably around 3HP although it looks too small to be 3HP. I am guessing because, I don't know how many motors the unit has.

Listening to the video, it seems the drive motor is running through a reduction gear box to lower speed and increase torque.

That's the motor that drives the sanding drum, it doesn't specify the motor that drives the belt that drives the workpiece through the machine. That's the one I was referring too, I should have made that clearer. It looks like a fairly beefy little motor.

You may be able to tell me what it is from the info from the manual for that motor:

Motor (TEFC) .................................................................................................. 1-3/4HP, 1Ph, 115V only

It does a max of 10 feet per minute so its not turning really fast.

TEFC = totally enclosed fan cooled

1ph = single phase = household 115 volt plug-in "USA"

My guess would be it is a 1200 rpm motor.

1200rpm motors have about 3 x torque over a 3600rpm motor.

The motor shown in the video is a "universal motor". That type of motor has brushes and are normally used in hand drills and vacuum cleaners. They operate in a similar manner to DC motors. They produce good torque and work well with adjustable voltage controls such as found in a hand drill with variable speed.

Thus far that is all I can tell you with the information given.

Perhaps, try to find replacement parts for the sanding machine and maybe you will find the specifications that way.

Thanks CG, I may just give it a try with the stepper I have and if it doesn't do the job look at getting something else now I know what I'm looking for.

cyclegadget:
The motor shown in the video is a "universal motor". That type of motor has brushes and are normally used in hand drills and vacuum cleaners. They operate in a similar manner to DC motors. They produce good torque and work well with adjustable voltage controls such as found in a hand drill with variable speed.

I'm going to counter-guess with a permanent magnet DC motor. PM motors tend to be lower RPM than universal and more appropriate in a gear-reduction situation. If it were a universal motor it would also be much louder.

To Chems, you should calculate how much torque your motor will need by pushing (or pulling) a board through using a weigh scale.

I think you might be right, I saw a mention of a permanent magnet DC motor somewhere in relation to the belt drive.

If its quoting 1.75hp then thats about 1.3kW. So I’d be looking for a 1.3kW motor that I can hook up to a speed controller. Hmmmmm

Chems:
If its quoting 1.75hp then thats about 1.3kW. So I'd be looking for a 1.3kW motor that I can hook up to a speed controller. Hmmmmm

For the belt drive?! No way it's that strong. It would be closer to 1/4HP (~200W).

I would suggest looking for a large worm drive (right angle) motor. A larger windshield wiper motor would probably work. Something to look at would be the diameter of the motor's output shaft as it is a good indicator to the motor's strength; you should be looking for something with about a 1/2" (13mm) shaft.

I read this from the manual "1-3/4HP" as 1.75hp. Not what it means am I reading that wrong?

That's referring to the sanding drum. If you drop to the bottom of the manual you'll find the parts list; the first part (coincidentally) is the belt drive motor and is listed as a "Gear Motor ... 90 Volt DC".

As an aside 90V DC motors are a common voltage for motors driven from residential circuits (as opposed to a battery) and similarly you'll find that there is a great availability of 90V DC motor speed controllers.

What sort of motor is best for continous high torque applications?

High torque - BLDC probably. Good for continuous as no commutator to wear.
Commercial BLDC + controller = expensive though - perhaps you don't mean "best"?

If very large motor needed and large budget, then superconducting motor will be
hard to beat for torque: 36.5 Megawatt superconducting motor Successfully Tested at Full Power | NextBigFuture.com 8)

Just a final question you may or may not be able to answer, given that we know its a 90v DC motor. What would a comparable stepper motor be of the same power?

Your stepper motor could possibly drive your feed belt but it's very difficult to say without knowing the torque and speed required. A better choice would be a DC gearhead motor (they are more efficient and easier to drive than a stepper). Robot Marketplace has a good selection of gearmotors http://www.robotmarketplace.com/products/motors_main.html although you could probably find a used motor for less on Ebay.
I would strongly suggest that you determine the torque and speed requirements before you select a motor. The manual for the machine in the video gives a spec of 150 W for the motor with a belt feed speed of 0-6 m/min.
If you use this information with the diameter of the feed belt roller you will be able to calculate the RPM's required and choose a motor based on this and the wattage of the motor.
As to the equivalence of your stepper to a PMDC motor, you would have to look at the torque curve chart for the motor in question as steppers develop the most torque at low rpm's and PMDC motors at high speeds.

Thanks for that Yankee, I'll do that when the time comes and be able to know for sure what I need.