Next project: Craftsman 101.07301 6" lathe

[LX Kid]

I have a couple of treadmill motors and have decided to use one of them, with a DC controller, for this lathe. It's 1.5 hp with an rpm of 4900. That way I can do away with the counter shaft assembly and be able to have a infinite chuck speed. (Rpm faster than the law/mfg allows. LoL) Converted the AC power supply to DC by adding in a bridge rectifier and changing out the potentiometer to a smaller 200k ohm.

 

[LX Kid]

Anyone have a work around for heavy power surge when starting motor? Here's a link over in the Electrical forum. Maybe some sort of resistor/capacitor network to ramp up power?

14amp DC motor surge work around?

I'm planning on using a treadmill 100v DC, 14amp, 2.5hp motor for my 6" swing lathe. I bought a cheap regulated AC power supply and converted it to DC by adding a bridge rectifier and a smaller 200k ohm potentiometer. It works fine "except" it really draws current when starting and shoots...

www.hobby-machinist.com

 

[LX Kid]

Guess I solved my surge problem. I added a coil choke to the neg side of the motor and no more dimming of my lights and sparks shooting out the back. Just has a smooth operation.

 

[wa5cab]

One thing that you need to keep in mind here is that you are putting a 1,5 HP motor onto a machine that is only rated for a 1/3 HP one. So you need to limit the input to the motor somehow. If you don't, sooner or later you are going to break something. The fact that the motor that you are using is a variable speed DC one instead of a single-phase or 3-phase AC one is immaterial.

 

[LX Kid]

One thing that you need to keep in mind here is that you are putting a 1,5 HP motor onto a machine that is only rated for a 1/3 HP one. So you need to limit the input to the motor somehow. If you don't, sooner or later you are going to break something. The fact that the motor that you are using is a variable speed DC one instead of a single-phase or 3-phase AC one is immaterial.

Yes that thought has already occurred to me. Got any suggestions how I might limit the speed to 1800 rpm? I've had these two DC motors awhile and just trying to find a use for them. Could just go ahead with the original 1/3hp motor and maybe a use will come at a late date for the DC motors.

Maybe using the original power supply form the treadmill might take care of this problem. I'm sure the treadmill wasn't spinning at 4900 rpm.

 

[DavidR8]

Yes that thought has already occurred to me. Got any suggestions how I might limit the speed to 1800 rpm? I've had these two DC motors awhile and just trying to find a use for them. Could just go ahead with the original 1/3hp motor and maybe a use will come at a late date for the DC motors.

Since you're selling it I wouldn't put the DC motor on it.

 

[LX Kid]

Since you're selling it I wouldn't put the DC motor on it.

That's true but it's nice to play around with "feasible" ideas to see if it works successfully. Boredom soon relieves a man from his money with his dumb ideas! LoL

Been toying around with making a belt sander and could use one for it. (As soon as I learn to weld a little better, being a beginner, that hasn't even started to learn to use my welder. "Tool junky!")

 

[wa5cab]

You don't need to limit the motor RPM to 1800. You merely pick what you want to be the maximum spindle RPM (which strangely enough for the 101.07301 and 618 could be anything up to 3225) by using the largest step on the spindle cone pulley and picking the motor pulley diameter to give that with the motor at its maximum rated RPM.

What you need to do if your variable voltage AC supply doesn't already is to add a current limiter circuit to your system. One HP mechanical is 746 Watts electrical. And Watts equals Volts times Amperes. So 1/3 HP equals 249 Watts and if the DC motor is a nominal 180 VDC one, then 1/3 HP @ 180 VDC is 1.38 Amperes DC. Ideally, the current limit should vary inversely with the upstream voltage. So with the voltage set to nominal 1/2 speed which we will assume would be 80 VDC, the current limit should rise to 2.76 A. If it isn't a 180 VDC machine, the adjust all of the figures accordingly.

However, the motor controller is fast becoming quite complex.

 

[LX Kid]

You don't need to limit the motor RPM to 1800. You merely pick what you want to be the maximum spindle RPM (which strangely enough for the 101.07301 and 618 could be anything up to 3225) by using the largest step on the spindle cone pulley and picking the motor pulley diameter to give that with the motor at its maximum rated RPM.

What you need to do if your variable voltage AC supply doesn't already is to add a current limiter circuit to your system. One HP mechanical is 746 Watts electrical. And Watts equals Volts times Amperes. So 1/3 HP equals 249 Watts and if the DC motor is a nominal 180 VDC one, then 1/3 HP @ 180 VDC is 1.38 Amperes DC. Ideally, the current limit should vary inversely with the upstream voltage. So with the voltage set to nominal 1/2 speed which we will assume would be 80 VDC, the current limit should rise to 2.76 A. If it isn't a 180 VDC machine, the adjust all of the figures accordingly.

However, the motor controller is fast becoming quite complex.

Yup it is getting a little complex. The motor is 100v 14 amp. I've been trying to make "chicken salad" out of "chicken s**t" and it's not working out so well for me. If I can find a 1/2" bore serpentine pulley somewhere I'll hook everything up and see how it holds when putting a load on the motor.

 

[wa5cab]

Well, from what I can see in the two photos, there are only two things keeping you from selling it as it was originally sold (sans motor). One is that it doesn't have the 2-step motor pulley and 2-step countershaft pulley. And two, the back gear lever belongs on the other end of the shaft. Where it is now, I think that if you try to mount the gear guard. it won't close fully.