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Michael Stuart

treadmill conversion to grinder?

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I got a broken-down exercise treadmill today with an eye toward using the still-working 2.5 hp variable-speed DC motor to power a grinder. On taking things apart a bit, it's got a lot of electronic stuff inside that I don't understand. Does anyone have good ideas about how to power and control such a motor if I take it out? Or should I stick with the existing treadmill controls, which seem to work OK? I'm not even really sure how it turns the 120V AC into 120VDC, the only thing inside that looks like a transformer doesn't seem big enough somehow to handle that much current. Yes, I am in over my head, but no, I don't have the money to buy a motor like this new, and this was free (the belt you walk on is torn up along one edge from where it didn't track well).

 

The setup as-is runs a 1 5/8" drive roller (approx. 5 1/8" circumference) between 1 and 10 mph. At 5,280 feet/mile that's about 88 to 880 feet per minute if I did the math right, so it looks like it will need a bigger drive wheel. 88 feet/min is just over 200 rpm on the current drive roller. To make the math easier, a 3.8" drive wheel would give 1 foot of belt movement per revolution.

 

So, what do you all think?

 

Michael

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It should have a transformer, diodes and capacitors to change from AC to DC and a rheostat or potentiometer to control power to the motor. Anything more is just display stuff for the treadmill. If you know a little about electronics you should be able to separate the needed from the un-needed. If not, as long as you can get it to work with the controls, go for it. It is all engineered to use that particular motor under load.

Edited by Tim Crocker

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are those enclosed motors...... if not you may have to make some kind of a housing for it .....to keep all that grinder dust out of the windings.... or it may not last...

 

should be easy enough

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There is no transformer needed to convert 110 AC to DC, A bridge rectifier is used and requires a heat sink because it gets hot when operating. If you use it just make sure you find the rectifier and the heat sink and have it mounted on something metallic with some mass to pull the heat away.

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Hi Michael,

 

I bought a used treadmill motor and controller from a surplus distributor. I currently use it for a 9" disc sander. Even through it claims it is a 2HP, it barely has enough power to function as a disc sander. I suspect you will be significantly under powered if you are going to use it for anything other than a very small grinder (30" or less).

 

Hope that helps.

 

Philip

Flat_Disc.jpg

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Thanks all. I'll keep an eye out for the rectifier. Greg, the motor does seem to be enclosed, and if I can leave it mostly as-is it also has a hard plastic cover that goes over the motor and electronics. The motor claims to be rated at 2 1/2 hp, so I'll just have to see how it holds up power-wise. But it almost has to be better than the 1/2 hp motor I used on my previous homemade grinder. With work the way it is, it will likely be a couple of months before I have the time to mess with it, but I'll let folks know how it goes.

 

Michael

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