Another Treadmill Powered Belt Grinder Build - Speed Control Questions

E

Enzo McGavin

Joined
Dec 26, 2021
Messages
12
Hello all,

I've been an amateur metal artist using welding and forging for a couple of years now. I have made a couple of RR spike knives and now I have the itch to try and make some respectable blades for myself.

I homebuilt the Frankengrinder Mk1 last year - a 2" x 48" driven by a 3/4hp bench buffer.

20211220_154308-01.jpg


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For the available power it worked fairly well. Then I found out about treadmill motors...

Last week I retrofitted a 2.5hp version using the original speed/treadmill controller. Wow, what a difference, but running at 3000rpm I managed to fry the board. (Yes, the controller box was sealed up at the time - no metal intrusion but no ventilation either)

20220108-141026-01.jpg


Instead of trying another board, I'm going to try the Amazon AC speed control / rectifier route.

Does anyone have any experience or advice doing this? There are plenty of YT videos to guide me, but I like to pick the brains of those that have been down a similar road.

Thx!
 
Take a good look at the motor plate. Chances are it is a DC motor. Take a close-up photo and post it.

As far as an AC controller running a motor, it won't work on most motors. It may seem to work for a short while and then it quits, or the smoke pours out of the motor.
 
Yes, it's a DC motor. The rectifier will switch the AC output to DC - it's a cheap and easy way to power a motor like this and have variable speed control.

61SxZLGB1hL._AC_SL1500_.jpg


The AC enters this motor controller, then the AC output is hooked to the rectifier:

91n+aDEn+ML._SL1500_.jpg


And DC power comes out the other side and to the motor. $25 in parts is less than $100 for an actual DC 130V motor control board meant for a treadmill.

My questions come as in the longevity of this type of control, possible long-term damage to the motor, the necessity of a choke - stuff like that. The interwebs are divided on these questions - hoping someone here may have been down this path already.
 
Enzo McGavin said:
Yes, it's a DC motor. The rectifier will switch the AC output to DC - it's a cheap and easy way to power a motor like this and have variable speed control.

61SxZLGB1hL._AC_SL1500_.jpg


The AC enters this motor controller, then the AC output is hooked to the rectifier:

91n+aDEn+ML._SL1500_.jpg


And DC power comes out the other side and to the motor. $25 in parts is less than $100 for an actual DC 130V motor control board meant for a treadmill.

My questions come as in the longevity of this type of control, possible long-term damage to the motor, the necessity of a choke - stuff like that. The interwebs are divided on these questions - hoping someone here may have been down this path already.
Click to expand...
My setup has run like this for a couple years. For the price, order a second controller and bridge rectifier and you'll have a spare if it fries. As noted my last one has lasted about 2 years
 
200V / 25A AC, so I believe that is 3000W or so? The motor is 1850W/130V DC, I do not know how that relates to the AC ratings. DC = Approx. 15A at 130V at 1850W?
 
That should be sufficient to power the motor if it is a PM motor. If it needs field power, then it needs a different power source.
 
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