Treadmill motor drill press problem

[Stainless]

I see that a few of you have converted your tools to use ye olde treadmill motor. Me too, but it's not working like I hoped.

No torque. I can grab the motor pulley (while wearing welding gloves) and stall it out immediately at any speed I'm willing to try. It just shudders, and I can easily hold it dead. Obviously, my new adjustable drill press doesn't work too well this way.

The treadmill was old -- a 1991 vintage. I've checked the motor's brushes, which still have plenty of meat, and the comm looks healthy enough.

The motor is a GE 5P80LY2A rated at 1.5 HP @ 120V DC. The controller is a GE 52A103470AAP1. Can't find much about either, probably due to the age.

The controller is seeing 122 V AC. At minimum speed, the motor is only seeing 5.25 V DC and at max, about 40 V. There's a MAX SPEED pot on the controller board that doesn't appear to do much at low RPMs (predictably, I guess).

I was a little surprised at the extremely low motor voltage, and perhaps it's not a huge shock that there's no torque down low. But, I can't even picture this thing running a treadmill effectively with the torque that it has. Both the controller and motor appear to work fine, though, which is kind of weird. Is the motor just old, degmagnetized, and worn out?

I have other treadmill motors, but they don't have the tach signal wires that this controller needs. When installed on the controller, they simply spin at top speed. I don't have another controller to test this motor.

Any ideas? Thanks for any help.

S

 

[Outlawmws]

Pics of what you have may help. I suspect you have bypassed something.

I cannot stop my motor when it is turning as slowly as it will go.

 

[DocsMachine]

Treadmill motors are generally rated, let's say "optimistically" in the first place. And second, generally speaking they only generate the rated HP at their top speeds, which in my experience has been anywhere from 4,500 to 7,000 rpm.

Is there a data plate on the motor? What's it's operating voltage? What's top speed RPM?

If it's a 90V motor (I have a Baldor treadmill motor rated at that) you're already seeing less than half the rated voltage, and thus half (or less) the HP. Actually, you're probably down to more like a sixth or even just an eighth the HP- the power curve on those lightweight, high speed motors falls off real fast as the RPM drops.

Doc.

 

[Big-Foot]

Treadmill motors are generally rated, let's say "optimistically" in the first place. And second, generally speaking they only generate the rated HP at their top speeds, which in my experience has been anywhere from 4,500 to 7,000 rpm.

Is there a data plate on the motor? What's it's operating voltage? What's top speed RPM?

If it's a 90V motor (I have a Baldor treadmill motor rated at that) you're already seeing less than half the rated voltage, and thus half (or less) the HP. Actually, you're probably down to more like a sixth or even just an eighth the HP- the power curve on those lightweight, high speed motors falls off real fast as the RPM drops.

Doc.

Odd... I have always known electric motors to make their best torque starting at ZERO RPM rather than increasing in value as RPM rises..

Remember that the controller unit itself will likely limit the amount of current on a scale of sorts..

I think it is possible that the OP may have a motor with a shorted field winding which will severely decrease the efficiency of the motor. Or the motor control itself has a problem.

 

[Packard V8]

Yes, you've got a problem if the controller is only giving 40V.

No, it's not inherent to treadmill motors. As stated above, you can't stall out a good one.

Maybe, there was a reason the treadmill was junked out. Did it come from a freebie?

Some treadmills have a speed maintenance sensor which increases voltage if the set speed drops. Sometimes if that circuit is bypassed, it confuses the controller.

jack vines

 

[DocsMachine]

Odd... I have always known electric motors to make their best torque starting at ZERO RPM rather than increasing in value as RPM rises..

-IF they're fed full power at startup, sure. Typical treadmill controllers (and other off-the-shelf basic DC controllers) vary the speed by simply varying the voltage (as opposed to, say, pulse width modulation) so clearly the motor is not going to develop peak torque at 1V.

Which, I suspect, in the case of a typical cheap treadmill motor, results in the HP falling by the square of the speed- as in, at half RPM, HP is a quarter rating, at a quarter speed it's a sixteenth, etc.

Doc.

 

[Stainless]

The motor's operating voltage is 120 VDC, and there is no maximum RPM stated on the information plate. Yes, this was a freebie and, as I mentioned, it's old as hell.

However, with a 3:1 belt reduction, I am seeing between 160 and 1600 RPMs at the chuck. So, the motor is operating between about 480 and 4800 RPMs. To me, that sounds about right, despite the seemingly low voltage numbers. At 80 volts, the motor speed would approach 10k RPMs, which sounds totally unreasonable for a large permanent magnet motor. As it is, the motor spins unnervingly fast when run flat-out and unloaded off this controller. So, although 40 V seems wrong, 80 or 90 V would turn this thing into a gigantic Dremel tool. In addition, most of the treadmill press conversions I've seen are using a moderate belt reduction similar to mine, and they don't seem to suffer from this same problem at very low motor RPMs.

I'm going to retest the output voltages at the same time as I take some pictures of the motor plate and controller.

In the treadmill, the pulley reduction looks like it produced about a 5:1 ratio, but I can't believe that this setup ran a treadmill effectively. The motor with pulley is easy to stall at up to probably 700 motor RPMs (I haven't tried anything faster), and the press chuck is easy to stall by hand at up to 500 chuck RPMs (1800 motor RPMs). Perhaps this is why it was ready for the dump.

S

 

[larry_g]

Originally Posted by DocsMachine
Treadmill motors are generally rated, let's say "optimistically" in the first place. And second, generally speaking they only generate the rated HP at their top speeds, which in my experience has been anywhere from 4,500 to 7,000 rpm.

Odd... I have always known electric motors to make their best torque starting at ZERO RPM rather than increasing in value as RPM rises..

.

Lets not confuse horse power and torque here guys. Max torque at zero RPM's is zero horsepower.

lg
no neat sig line

 

[Outlawmws]

-IF they're fed full power at startup, sure. Typical treadmill controllers (and other off-the-shelf basic DC controllers) vary the speed by simply varying the voltage (as opposed to, say, pulse width modulation) so clearly the motor is not going to develop peak torque at 1V.

Which, I suspect, in the case of a typical cheap treadmill motor, results in the HP falling by the square of the speed- as in, at half RPM, HP is a quarter rating, at a quarter speed it's a sixteenth, etc.

Doc.

That would be incorrect. Most tread mill motors DO use Pulse Width Modulation controllers, and that is why I asked for pic of the setup.

The one I have setup will actually "pickup the slack" When I load it down and try to maintain the set speed.