Thread: An idea for a contact grinder.

Nice score on the dc motor!
Look forward to seeing the build.

Seems Cangooner built a grinder with a treadmill motor?

Maybe he can chime-in....

Originally Posted by sharptonn

Seems Cangooner built a grinder with a treadmill motor?

Maybe he can chime-in....

I found a couple of youtube videos of folks building contact grinders, and a bunch more of all sorts of other things.

My plan is a little different than most.

The downside of these DC motors for grinders is that they're completely open and force air through the body of the motor.

The motor I got is a little unusual for a treadmill motor in that it's got two spindles. One of them is short, keyed and has a pulley wheel, the other is threaded, keyed and had the flywheel with an integrated fanblade.

I'm not going to use the flywheel, but I am going to make a small fan blade to go on there. The motor is just the right size for drier ducting to slip over it, so I'm going to duct out the end with the fanblade and put the other in a small mostly sealed box. There should be no vents that dust can get into, then I can run the ducting to well away from my work area and put a filter on it. VOILA! Clean motor!

That I did!

Mine was sourced from a free treadmill, and was a 1.9hp DC motor. When it worked, it worked perfectly. I more or less followed this video to wire up a controller for it:



The problem was that it pretty quickly died. I had shielded the hell out of it to protect from metal dust, but it still let the smoke out. One of the brushes completely burned out, taking the plastic end cap of the motor with it. I managed to find some cheap replacement parts for it, and it worked just fine again for a shorter while then let the smoke out again. But I think that was due to a faulty motor, and not dust getting in. Both times it died I opened the motor up, checked it closely and found nothing that should not have been there other than bits of brush. I.e. no visible dust, and I'd expect if it had got into the motor, the magnets should have kept at least some.

Then I bought a 3-phase 1.5hp motor from Automation Direct and a kbac 27d vfd to control it. Haven't looked back since.

So long story short, *with my motor* I should have just gone the vfd/3-phase motor route from the get go. However, I'm pretty sure that there was a fault in the motor itself and that its demise wasn't due to grinding dust. Even though it crapped out, I still ended up with a bunch of steel from the treadmill frame (useful for fabricating stuff in the shop - like my hammer rack), a bunch of electronic doodads I do not yet understand, and some copper ingots after tearing the motor apart and melting down the good stuff.

But when it worked, the treadmill motor along with the SCR/bridge rectifier controller really did work well. So hopefully yours will too, and last much longer than mine! Any questions, please feel free to shoot me a PM.

Originally Posted by Cangooner

That I did!

Mine was sourced from a free treadmill, and was a 1.9hp DC motor. When it worked, it worked perfectly. I more or less followed this video to wire up a controller for it:



The problem was that it pretty quickly died. I had shielded the hell out of it to protect from metal dust, but it still let the smoke out. One of the brushes completely burned out, taking the plastic end cap of the motor with it. I managed to find some cheap replacement parts for it, and it worked just fine again for a shorter while then let the smoke out again. But I think that was due to a faulty motor, and not dust getting in. Both times it died I opened the motor up, checked it closely and found nothing that should not have been there other than bits of brush. I.e. no visible dust, and I'd expect if it had got into the motor, the magnets should have kept at least some.

Then I bought a 3-phase 1.5hp motor from Automation Direct and a kbac 27d vfd to control it. Haven't looked back since.

So long story short, *with my motor* I should have just gone the vfd/3-phase motor route from the get go. However, I'm pretty sure that there was a fault in the motor itself and that its demise wasn't due to grinding dust. Even though it crapped out, I still ended up with a bunch of steel from the treadmill frame (useful for fabricating stuff in the shop - like my hammer rack), a bunch of electronic doodads I do not yet understand, and some copper ingots after tearing the motor apart and melting down the good stuff.

But when it worked, the treadmill motor along with the SCR/bridge rectifier controller really did work well. So hopefully yours will too, and last much longer than mine! Any questions, please feel free to shoot me a PM.

I'm still pondering what to do with the linear actuator that this one used for raising & lowering the treadmill. I'm kinda pondering rigging it up to raise and lower the table on my drill press. It's otherwise a huge hassle!

I kept everything. The frame was pretty beefy steel tube, the tread belt looks potentially useful for... Something. The rollers have good bearings in them. There was even a little metal grab bar that'd be awful nice to have in a street brawl, should that ever come up. Heavy and rubber coated!

Originally Posted by Voidmonster

I'm still pondering what to do with the linear actuator that this one used for raising & lowering the treadmill. I'm kinda pondering rigging it up to raise and lower the table on my drill press. It's otherwise a huge hassle!

I kept everything. The frame was pretty beefy steel tube, the tread belt looks potentially useful for... Something. The rollers have good bearings in them. There was even a little metal grab bar that'd be awful nice to have in a street brawl, should that ever come up. Heavy and rubber coated!

Oh man, I LOVE the idea of using the actuator on the drill press. Mine's still sitting here looking for a new use too. I had the same thought about the tread belt too.

Watch out for label makers. Anyone with a smidge of OCD can disappear down that rabbit hole for days.

Originally Posted by Cangooner

Oh man, I LOVE the idea of using the actuator on the drill press. Mine's still sitting here looking for a new use too. I had the same thought about the tread belt too.

It's especially tempting on mine, which doesn't even have a crank to raise and lower it. It's just a cast iron plate that weighs about 30 pounds that has a brake to keep it in place when you position it on the mast of the drill press.

Then I added a 15 pound milling vise onto it. So it'd be really nice to be able to raise and lower that without all the weird crab dancing.

Originally Posted by DZEC

Watch out for label makers. Anyone with a smidge of OCD can disappear down that rabbit hole for days.

I've been living with my OCD long enough I can mostly keep it under control... It was just realizing I had two extremely similar looking jars of liquid and one of them I actively want to put very hot things into and the other one I should definitely never put very hot things into... It seemed like a good idea to make sure I knew which was which.

Honestly, the smell would probably have been enough. There's no mistaking the smell of solvent from canola oil that's quenched 3-4 red hot lumps of steel. Well. Except that the whole garage kind of smells like the quenching for a day or two.

OH MY!