For those very slow speeds a DC servo motor is the choice, along with the feedback system and the drive electronics. Those are quite expensive new, but quite reasonably priced surplus, and even cheaper not working. Sometimes repairs are obvious, sometimes not. Generally, the more commutator segments the slower a motor can be run at. An old elevator motor makes a good slow speed drive, but don't ask it to go very fast, not over 1200RPM.
And as for one motor for every application, that is like those "One Size Fits All" jeans: When one size fits all, it does not fit any of them very well.

 

Have a look at some old washing machine, like the Fisher and Paykel Smart Drive ones. They are a fairly meaty BLDC.

 

And as for one motor for every application, that is like those "One Size Fits All" jeans: When one size fits all, it does not fit any of them very well.

He might get along with one well chosen motor and a selection of gear boxes and gears, but then you might as well choose a selection of motors.

If he wants to reuse, I’d suggest the treadmill motor and various gearing, with it’s driver, and the F&P type BLDC motor mentioned with its driver. We’ve got an F&P washer and that thing can get agitate the drum and still spin it up to 1K+ RPM.

But however you look at it, there’s no universal motor.

 

Have a look at some old washing machine, like the Fisher and Paykel Smart Drive ones..

Not really 'Old' they are used in current machines replacing the old induction ones!
Max.

 

Think you guys are missing that he wants a motor that turns at between 1(one) and 6(six) RPM. Other than a stepper or servo I know of no motor that will go that slow.

 

Other than a stepper or servo I know of no motor that will go that slow.

Or rather, I know of no motor that will reliably go that slow... I've been able to run 90 VDC motors at around 4 rpm, albeit in a "jumpy" or unstable manner. That's why the required torque for this application is an important piece of information.

 

@shortbus:

Basically I'm looking for help picking out a motor and a speed controller that I can use for various projects and experiments not just a ball mill hence the reason for it going up to 1800 rpm BUT I'm not worried about it being capable of attaining even higher speeds just as long as I can control the speed. By control the speed I mean very fine speed control so I could essentially run the motor at 1 rpm or maybe 6 rpm... Also if the size of the gear is smaller than the gear on the contraption the rpms are reduced and I think torque is increased.

He's basically asking for the ability to control a motor all the way down to just a few RPM. Whether he achieves that via gear reduction or not - that's part of the design and engineering work he has to do. He also wants to be able to run the snot out of the motor as well. So he's asking for a large range of RPM control. Obviously with gear reduction attaining high RMP with a seriously geared down output shaft is going to present major problems.

For instance (@A.C. Alden) running a motor at 10 RPM with an output of 1 RPM will mean that if you want an output as high as 1800 RPM the motor will have to spin at 18,000 RPM. I'd expect a motor to self destruct at those high RPM's. And it gets worse. Running a motor at 10 RPM with gear reduction means running a motor VERY slowly. Such low RPM would require extremely low amperage. Low amperage would mean a significant loss of torque and the motor can easily be stalled when asked to do some work.

Assume you want a 6 RPM output. Suppose you use a motor spinning at 600 RPM. That's reasonable, albeit rather low. With the gear reduction you DO gain torque, but the weight of the transmission (gear reduction) you're sacrificing some of the torque just to achieve the low RPM. But in this example we're using a 100:1 gear reduction. To achieve the 1800 RPM you mentioned, that motor under this example will have to spin at 180,000 RPM. An INSANE speed for ANY motor. Even small turbines struggle to get that high.

To achieve your goal you're probably going to need to narrow your parameters or accept the fact that you're going to need multiple machines designed for specific purposes. Personally, I believe you should abandon this idea of 6 to 1800 RPM output from ANY kind of machine. But that's my "personal" opinion.

 

Afterthought: I have a drill press. Depending on the belt / pulley configuration I can spin the drill chuck fairly slower than the motor RPM or fairly higher than the motor RPM. The motor itself is 120 VAC induction, meaning I don't control its speed. To attain different RPM's I have to swap the belt position on the stacked pulley sets. With extremely low RPM I get extremely high torque. Useful for drilling through hard surfaces. OR I can go the other way, extremely high RPM with extremely low torque (using "extremely" as an exaggeration for emphasis). High RPM may be good for grinding or sanding work. Or other such work as polishing metals. But you're not going to find a "One Size Fits All" solution. Especially for the ranges you're asking this machine to operate in. Mechanical is the way to go, not electronic control. You COULD do a hybrid mix of both, but again, it's going to be partly mechanical.

 

Or rather, I know of no motor that will reliably go that slow... I've been able to run 90 VDC motors at around 4 rpm, albeit in a "jumpy" or unstable manner. That's why the required torque for this application is an important piece of information.

You also wouldn't be able to run them that slow for very long without burning one up. They are made to run at the listed RPM plus or minus a little. Not from zero to full speed.

 

As I mentioned in the Fuse post, All or most motor that a made to be variable speed, DC, BLDC etc usually come with a manuf declaration of maximum and continuous torque, Continuous is down to zero speed where the torque rating is at maximum.
With a Opto feedback the T.M. motor can be made to control down to a couple of rpm, as any fairly high pole count motor should do.
As long a the continuous torque(current) is not exceeded, then it is fine.
Max.

 

You also wouldn't be able to run them that slow for very long without burning one up. They are made to run at the listed RPM plus or minus a little. Not from zero to full speed.

Quite true ... if one of the motor's windings stays energized for too long it will warm up, which is what happens at very low RPM, not to mention the lack of air flow at normal RPM

 

The

Quite true ... if one of the motor's windings stays energized for too long it will warm up, which is what happens at very low RPM, not to mention the lack of air flow at normal RPM

The old Fanuc DC motors and the make that they copied ran all day in CNC in applications that controlled down to zero RPM.
They had no fan on them!
Max.

 

The


The old Fanuc DC motors and the make that they copied ran all day in CNC in applications that controlled down to zero RPM.
They had no fan on them!
Max.

I believe that, but at what motor size, and running torque?

 

The old Fanuc DC motors and the make that they copied ran all day in CNC in applications that controlled down to zero RPM.
They had no fan on them!

Weren't they heavily heat-sinked? And were they stepper motors, requiring significant computer control power? Can they achieve 1800 RPM? (I think that may be a dumb question, they probably can - I didn't think about CNC mills and lathes and such).

And again, we're working on this problem without knowing what "Size" means and without knowing what "Torque" requirements there may be.

 

The big motors that we used and that ran at lower speeds all had external blowers for cooling air. The motors were in in the ten to 50 Hp range and would have to run at various speeds for an entire shift. Cooling air does become an issue for motors that depend on their fans.
So probably the solution is a motor with a controller and probably a 5:1 speed control ratio and then an arrangement of belt reductions for the really slow speeds. And while a few brushless DC motors can be found in some discarded wash machines those are not very common yet because thew high price for those machines tends to get them fixed most of the time. AND creating an electronic driver for such is not a trivial task.

 

Plus, normally motors that are designed to run at low RPM have a higher number of windings (poles) in them. A few years ago I upgraded a piece of equipment by replacing a gearmotor with a single 5 HP, 8-pole, three phase motor. Worked like a charm.

 

@cmartinez What RPM range? What torque?

 

Weren't they heavily heat-sinked? And were they stepper motors, requiring significant computer control power? Can they achieve 1800 RPM? (I think that may be a dumb question, they probably can - I didn't think about CNC mills and lathes and such).

I have never seen a major commercial CNC manufacturer use steppers, and I have been retro-fitting them since the late 80's.
The old Getty's and Fanuc DC servo's could achieve 2000rpm at that time and controlled down to zero.
They had no Heatsink on them.
They were controlled at the manufactures constant torque.
There are VFD's out there that can position a 3phase motor induction motor, as in gantry crane lift motor and also they have been used on elevator control.
Max.

 

@cmartinez What RPM range? What torque?

900 RPM, can't recall the torque, but I do remember that it was working at 80% of its rated capacity.

From: http://wentec.com/unipower/calculators/power_torque.asp

Torque (lb-in) = 63,025 x Power (HP) / Speed (RPM) -> 350 lb-in x 0.80 = 280 lb-in​

 

@MaxHeadRoom
@cmartinez
OK. I now know better. Thank you.