Treadmill motor on rong fu rf-30.

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Ktencza

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I own a good condition rf30 . Changing the speeds can be blah. Anyhow i came across a 2.25 hp treadmill motor. Has anyone successfully tried adapting one to this or other larger mills. I just dont wanna go through the trouble making the stock pulley work and such, can be a lot of work. But would it be worth it to have variable speed control? Does the motor have the power to cut and suck torque meaning. Where would i put the final belts on change pulleys? I do have a 3 phase motor sutting around needs a bearing and vfd. Just curious about the treadmill motor thing.
 
I also have a RF30 and have a supposed 3hp treadmill motor. Several problems with them. The hp rating is very dubious kinda like how they rate shop vacs. Personally I’d use the 3ph motor and VFD. Better low end torque and useable rpm range.
 
Thank you for replying. I was leaning torwards the 3 phase. Just wanted some insight.
 
FWIW I realized my post might have implied I had the treadmill motor or my RF30, I don’t. I have contemplated it but my original motor is working fine. But after many threads on H-M and much more knowledgeable people than me I have decided if I was going to use that motor because of its high rpm(3K) and DC I think it might be better suited for a belt sander.
 
Personally I find variable speed more useful on a lathe than a mill, and I don't mind changing belts. I kind of enjoy it. I feel like Tim (tool time)Taylor with MORE POWER when I do it
DC treadmill motors have good torque when paired with a good controller, but the permanent magnets can sometimes lose their spice
and get weaker with time on some cheaper units
 
I replaced a 1hp motor on my Grizzly G0602 lathe with a 2.5hp brushed treadmill motor. Without feedback, the low end torque suffers. I added an encoder and custom PWM drive circuit. I have a useful speed range of 100:1. Full throttle no load, the motor puts out close to 5,000 rpm but I limited max rpm to 1 little over 4,000. I run in the medium low belt configuration and this gives me about 800 rpm at the spindle. In that configuration, I can run at less than 10 rpm. The reason for the wide range of operation is the feedback circuit which can apply up to full pulse width if torque demands it.

The OEM drive system on the RF30 and clones provides for torque multiplication through the pulleys; something a variable speed drive cannot do.
On my RF30 clone, the lowest speed setting offers an 18:1 torque multiplication. A 2 hp motor has 6 lb-ft of torque at full speed. With the low speed belt setting, that works out to over 100 lb-ft. at 90 rpm at the spindle. I contrast, my Tormach mill with its VFD driven 1 hp 3Φ motor has trouble countersinking a hole for a #10 screw at 150 rpm.
 
RJSakowski said:
I replaced a 1hp motor on my Grizzly G0602 lathe with a 2.5hp brushed treadmill motor. Without feedback, the low end torque suffers. I added an encoder and custom PWM drive circuit.
Click to expand...

Would it be fair to rephrase what you wrote like this? "unless you know all about feedback, encoders, and you're capable of designing your own custom PWM drive circuit, then you should probably not try this"

I barely know a PWM from a BLT, I mean I know what the letters stand for but I'd have to take a few college courses before I'd be able to do what you did, and even then it'd be designed by a beginner, predictably sub-optimal. Yet I have easily converted four of my machines to 3-phase with VFD. Just a few tricks you need to learn, and youtube or helpful people here can quickly explain it all.

I know about the torque issues when turning the VFD way down, so I change the belts for anything that needs it, but for most tasks I can just dial in the speed I want, if I leave the belts in a middle-ish speed position. Or put another way, belt changing happens a lot less often, but it'll never go away completely. Still very much worth it, a big quality-of-life improvement

If you can afford it, it helps to put a more powerful motor on, so even when torque drops off you still have enough in reserve.

This is the experience of a decidedly non-expert hobbyist, so take it with the appropriate amount of salt.
 
Buying a KB controller is the easier way to go; Ebay usually has several for around 100$ or less
KBIC-125 is a good model for dc motors up to 1.5 HP
Dart controls is another good brand
 
Last edited:
RJSakowski said:
I replaced a 1hp motor on my Grizzly G0602 lathe with a 2.5hp brushed treadmill motor. Without feedback, the low end torque suffers. I added an encoder and custom PWM drive circuit. I have a useful speed range of 100:1. Full throttle no load, the motor puts out close to 5,000 rpm but I limited max rpm to 1 little over 4,000. I run in the medium low belt configuration and this gives me about 800 rpm at the spindle. In that configuration, I can run at less than 10 rpm. The reason for the wide range of operation is the feedback circuit which can apply up to full pulse width if torque demands it.

The OEM drive system on the RF30 and clones provides for torque multiplication through the pulleys; something a variable speed drive cannot do.
On my RF30 clone, the lowest speed setting offers an 18:1 torque multiplication. A 2 hp motor has 6 lb-ft of torque at full speed. With the low speed belt setting, that works out to over 100 lb-ft. at 90 rpm at the spindle. I contrast, my Tormach mill with its VFD driven 1 hp 3Φ motor has trouble countersinking a hole for a #10 screw at 150 rpm.
Click to expand...
I’m in the same boat as bulgie. I wish I had the skills to do what you did, but truth be told I’d probably have a challenge with the vfd manual if I tried the 3ph conversion.
 
bulgie said:
Would it be fair to rephrase what you wrote like this? "unless you know all about feedback, encoders, and you're capable of designing your own custom PWM drive circuit, then you should probably not try this"

I barely know a PWM from a BLT, I mean I know what the letters stand for but I'd have to take a few college courses before I'd be able to do what you did, and even then it'd be designed by a beginner, predictably sub-optimal. Yet I have easily converted four of my machines to 3-phase with VFD. Just a few tricks you need to learn, and youtube or helpful people here can quickly explain it all.

I know about the torque issues when turning the VFD way down, so I change the belts for anything that needs it, but for most tasks I can just dial in the speed I want, if I leave the belts in a middle-ish speed position. Or put another way, belt changing happens a lot less often, but it'll never go away completely. Still very much worth it, a big quality-of-life improvement

If you can afford it, it helps to put a more powerful motor on, so even when torque drops off you still have enough in reserve.

This is the experience of a decidedly non-expert hobbyist, so take it with the appropriate amount of salt.
Click to expand...
There are off the shelf controllers that employ feedback to improve torque characteristics. I am not familiar with them to be able to comment on their methodology.

I chose to roll my own because:
1. I have other sensitive electronics, namely Touch DRO and ELS, and I didn't want use an SCR controller because of possible interference.
2. I wanted a controller that used simple, low cost, and commonly available components that I was reasonably certain would be available in the distant future. I didn't want to use a specialized integrated circuit that would be a black box regarding trouble shooting.
3. I wanted simple construction that would facilitate ease of repair if necessary.
 
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