Treadmill Motor on Belt Grinder Build

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RW Creations

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Jan 8, 2019
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I wanted to build a 2"x72" belt grinder to use to make a few knives. I viewed many videos on YouTube how a treadmill motor was used and how it was wired with a speed control purchased off Ebay. I got the unit all put together and started grinding a bevel on a knife blank. It lasted about 3 minutes and the grinder quit. The control that was recommended for the build, that I used, has a small fuse in it that blew. I replaced it and tried again and the same thing happened. Has anyone built one of these belt grinders and used these controls? (4000W 220V AC SCR Motor Speed Controller Module Voltage Regulator Dimmer) In the videos where they are used they appear to work. I'm not sure what is causing my problem.
 
Did you replace the fuse with a larger fuse? At 66 yrs old you should remember putting a penny behind a screw in fuse?

What size (how many amps?) fuse blew? They might have put an undersize fuse in.
 
What size/length is your power cord? What size motor?
 
Yes I remember the penny trick.:) The little fuse was a 10amp I think. Hard to see the marking. The power cord I used is about 4 ft. long. The DC treadmill motor is 2.5hp. I ordered a larger control unit and maybe that would work. ?? I bought the motor on Ebay and it was just the motor. I get disgusted when my projects hit a wall and I'm not experienced or knowledgeable about where to look. That's when I hit the forums and hope somebody has suggestions on what to do.
 
interesting. I have a 3hp treadmill motor and have been using these.

https://www.ebay.ca/itm/AC110-220V-...h=item2ab87de474:g:ndMAAOSwKQFbwVTv:rk:7:pf:0

Ive burned out two in the last year but only when laying into the flat platen with a bar. I just switched to the one you got (110v version) and did about 4 hrs today wide open but on the slack belt with no platen without issues.

just curious, is your rectifier wired before or after the scr controller?

My wiring goes into my toggle switch, then the scr controller than the rectifier.
 
Scott, I have mine wired the same way. I also burned them grinding the piece against the platen. What gets me is I wired mine the same as the videos are showing and they are grinding against the platen with no issues. Confusing
 
Grinding against the platen puts more load on the motor and controller. The answer is a larger controller?
 
not sure if it makes a difference but the link you posted is for a 220V SCR. Mine is 110V. Is your grinder wired for 220v? Do you have a clamp tester to check current draw? 220v would reduce the amperage by half. Is your motor reversible and if not, is it running the wrong direction? Is the motor new or used? I don't know a whole lot about electronics, just what I learn from you tube university.

I bought two SCR's in case it burned out again. I'll try putting the platen on and see if she burns out as I have a spare. They've been pretty good until I i get silly at full speed. Even then they haven't burned out, they just loose the regulator and only run at full speed but the old ones didn't have a fuse. My old SCR's were 10,000 watt and these new ones are 4000 but they had the cooling fan which I liked and I wanted to try something different. I was going to wire in a fuse but I didn't realize that these have a fuse in them.

I just looked at the surplus center website and their 2.5HP motors are rated at 12.5 to 14.5 amps. This could be why your 10 amp fuse is blowing. You could try a 15 amp fuse or tinfoil but you run the risk of burning up the SCR. Maybe try without the flat platen and see if it still blows.
 
Hey guys, I had a AC motor Speed Control from another project. I totally forgot I had it. It's much heavier duty. I wired it in and I may have fixed my problem. This is one like it on Ebay. For Router Fan Variable Speed Controller Electric Motor Rheostat AC 120V Newest. I have to get longer bolts for the motor mount and get that alignment set, then I'll give her a go.
 
I finally had a chance to try the new scr against the glass platen. 8 hours of grinding without issue. Curious how the new one you have works out
 
Fellas, I spoke to quickly as I was hoping wouldn't happen. I wired the new speed control that I earlier post and it worked. I run it for a time to see if it would quit and it didn't. Well,,, I got set to start on a blade and turned the grinder on and it tripped the breaker. I reset the breaker and tried again and it burned the fuse. This is just turning it on like I did when I first tested it. I started and run nicely then next start is a no go. I am wondering not if I have an issue with the motor I bought off Ebay. This is getting frustrating. I'm starting to think maybe I should go with an AC motor. How much HP does one need to run a 2"x72" grinder? The treadmill motor just seems to be a great choice but with limited budget I can't be doing much trial and error.
 
Update: I just bought a 1/2hp wash machine motor off Ebay. I'll give this a whirl. No speed control either. We'll see.
 
RW Creations said:
Update: I just bought a 1/2hp wash machine motor off Ebay. I'll give this a whirl. No speed control either. We'll see.
Click to expand...
Is it a 3 phase washingmachine motor ? Those are fun to play with.
Either way, keep it clear of metallic dust...
 
If I were you, I’d just buy a Chinese vfd and a 3 phase TEFC motor and call it a day.
Not sure how much you’ve spent thus far, but VFDs are cheaper than ever (you do have to keep the dust out of course), and I’ve seen good 3 phase motors for as low as $50, with brand new motors under $200. For anywhere from $150 to $300 you could have a variable speed set up that will work much better that piecing together old treadmills and washing machines.
 
Even if that 1/2 hp motor is 3 ph that's not really enough for a 2X72 grinder. I think the general consensus is 1 hp, with better a 1-1/2 hp, and best of all is a 2hp. If purchasing new there just isn't much difference in cost of a 1-1/2 hp vs 2 hp motor. Looks like about $11 difference for Ironhorse motor on this site: https://goo.gl/GcqUPa $147 (1-1/2hp) vs $158 (2hp) in 3600 rpm.
 
Watch Craigslist if you are in or close to a large metro area. I recently picked up a 2 hp 3 phase Baldor TEFC for $50, in the past I purchased a 10 hp 3 phase freshly back from a rebuild for $100 to build our 3 phase convertor. It seems that some 3 phase motors have value a little greater than scrap.

I just ordered a 1.5 kW VFD off of ebay for about $60 to give that a whirl to power my 2 x 72 for home use.
 
1/2HP won't run a grinder well at all. If it isn't TEFC ( which most washer motors are not), it won't last long anyway.

Get at least 1Hp, TEFC, and preferably 3Ph with a VFD. The money you spend now will give you many years of enjoyment in return. The plans you have so far are set to end in frustration.
 
RW Creations said:
Update: I just bought a 1/2hp wash machine motor off Ebay. I'll give this a whirl. No speed control either. We'll see.
Click to expand...
Do yourself a favor and use that motor for this......because it is too weak for grinder and more important dust will kill that motor in hour........:)
sgdtAoo.jpg
 
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