Ok, I Wat To Play Dc Motor Swap On My Lathe!

John, I was wondering if you can use a standard PW or SCR controller on those series wond treadmill motors. Do you know? Also what are you using for a feedback on the close loop system? I haven't had any experience with PW units but I hear they are good. Right now I am using an SCR on the jig borer. Maybe I need to start a new thread.
 
ARKnack said:
John, I was wondering if you can use a standard PW or SCR controller on those series wond treadmill motors. Do you know? Also what are you using for a feedback on the close loop system? I haven't had any experience with PW units but I hear they are good. Right now I am using an SCR on the jig borer. Maybe I need to start a new thread.
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A closed-loop controller for a series motor must be designed (or at least tuned) for it. The series motor I'm using on my lathe has a built-in tachometer generator. I'm using the triac controller that came with it (slighly modified).
 
Hp in DC as in all electric motors are rated at max rpm. With an AC motor when you slow it down with belts or gearing you are multiplying the delivered torque by the % of speed change. Most of us confuse torque with HP. HP equals torque multiplied by RPM. When we reduce the RPM on a DC motor the delivered torque per rpm remains close to the same but the delivered HP goes way down as well. This is compensated by raising the amperage delivered as the rpm is reduced which increases the Torque per Revolution. The limiting factor is the motor windings ability to dissipate the heat generated by the additional amperage.

The reason for RPM change is partially to deliver a higher torque to the material so that you can make a larger cut per revolution. The size cut you can make at 30 rpm is a whole lot larger than you can make at 2000 with the motor at full load. I have the torque setting easily acceptable on my tread mill controllers so that I can turn down the torque for power threading, the tap will stop instead of breaking off, it is quite handy when doing a lot of taping.

I have found that the rated rpm on the tread mill motors can be as high as 5500 on the small diameter motors one i have is rated at 2.65 hp but in fine print it says 1.5 HP Cont. but that is fan cooled at 5500 Rpm the motor that came on your lathe was probably 1 hp at 1725 this motor would be lucky to put out 1/3 to 1/2 at 1725 even with controller compensation.
The small motor I'm putting on a craftsman 109 lathe that I'm working over to sell and it will be about right.
I use a a 2 hp 4800 rpm on my Mill/drill, and a 3 hp 3000 rpm on my atlas 12 by 36 lathe. on the lathe i run the torque setting at max most of the time. I use the small pulley size on the motor which seems to bring the delivered torque into the right range even when making .100 to .150 cuts on something that is 8 inch in diameter.

I hope this helps some

Art B
 
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I think it's well worth using the flywheel and matching poly-V pulley that came off the treadmill. The motor pulley diameter on mine is about an inch, which is at least 1/2 the size of the V-pulley I had on there before, plus the countershaft pulley is larger, so the motor is geared down a lot more. I couldn't go any smaller with the V-pulley and even then I was having slippage issues. Mine will bog down at less than 1/4 motor speed (~1000rpm at the motor), but with the new pulleys and back gears I can get down to ~25rpm for turning and less than 10rpm for tapping.

Beware though, some of those treadmill motors+flywheels may not be very well balanced - I'm going to pull mine off and balance it this week as the flywheel is well out of round.
 
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