My KMG - M.G. edition pic heavy

I use the polar bear grinder.. he spec'd out the gas shock and its been wonderful. I got the 60# one for no real reason and I'm pretty happy with it. I can run the belts *tight* or loose depending on how much pre-load I put on the shock.

I didn't have a 56 motor so I fab'd up a belt/pulley system with an old 110v 1hp.. I can see a VFD/driect drive upgrade in my future
 
Here's my grinder with frequency doubler enabled. Goes from barely a crawl to... "spaceball one... they've gone to plaid!"

[video=youtube;EdtC2FIr_aA]https://www.youtube.com/watch?v=EdtC2FIr_aA[/video]
 
I not meaning to nitpick but a few things stand out in the 2 videos you posted. First video with vibration and wabble problems was a green belt and a flat platen. Then the direct drive video which had no vibration and wabble was a yellow belt and just a contact wheel. In my experience the belt seam running over the flat platten will great vibration and with wabble that's a belt thing at least for me. Some will track laser stright and others won't, And I'm not talking diffrent types of belts. I'm talking same belt brand and type. A box of 10 blaze belts and some might wabble and some won't. I think it has to do with how square and perfect the seam is. I took a video of my KMG clone going from 250-9000 SFPM to show its vibration and wabble. Once it's uploaded I will post it. I like the idea about direct drive but I need more speed then what it can give me. Maybe if I ditched this motor and went with a motor that started in the 3k rpm range then doubled it. But this set up works great for me.
 
That's a good point. I checked it again just now with the flat platen. There is still about 1/16th wobble with the belt although that belt may have been stretched somewhat with the old setup. There is no vibration though with the new setup, the wrench didn't move. I see your point about the need for pulleys with the speed you grind at. For now, I'm going to double my speed at the vfd and see how that goes. I'm not sure how to calculate sfm but I think I'll be in a good range for ceramic belts.

Another thing I haven't tried yet is to grind my stock flat
lengthwise with a magnet. Before I would get the belt to stop while the motor spun. I tried to use the belt it came with and a link belt, both with the same results.
 
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Up to this point I was using a link belt and it finly had it and kept busting. It has had a lot of use. So I grabbed a normal belt and because my motor has a hinge on the back to keep tension I used a screw at the front of the motor to pull it down an tension the belt. It really helped a lot with the stalling problem if your use using motor weight to tension the belt.
 
Well calculating SFPM is easy for the most part. On your system because your direct drive and using a 1740 rpm motor that's doubled in speed and a 5" wheel the math looks like this.
((1740x2)X(5"x3.1415))/12=4,555sfpm
 
JT, I agree with all of your assessments. The 'test' should have been done with all the same materials. I agree with Josh, however, that the differences in vibration are incomparable afterward.

I also want to point out that you have a KMG clone, which YOU made, making certain that tolerances were tight and things were properly aligned. Like a fool, I threw out the notes I kept when I was chasing the bullshit out of my own machine. Please take my word for it when I tell you that things weren't quite as dialed in as I suspect your one-off machine is. Both the bolt holes on my platen were drilled and tapped out of square, for example. The vibration of my pulleys alone would have brought the walls of your shop down had you tried to run it at 9000sfpm.

As I mentioned before, it seems that the machines that were right were right, but the ones that weren't...
 
Mine worked just perfectly, but I wanted to up the power from 2hp to 3hp, and I wanted to be able to add the ability to pivot it sideways, which required a direct drive =)

Next project for me is to fabricate a pair of pivot legs to go from vertical to horizontal.
 
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