[ironmonger]

http://picasaweb.google.com/11411279123 ... 4985078226

I finished, well finished for now, this grinder this past year. It is a KMG clone, all the rolly parts came from Beaumont Tool, hard to make them for what he gets for them. Most of the grinder chassis is bolted together to eliminate weld stress and warping in the long tunnel for the tool shanks. If I built another one I would most likely TIG weld a lot more of the grinders framework.
The belt tensioner is pneumatic and there is also a quick connect for an air hose to blow off parts. There is also a small pneumatic knife valve that vents the air cylinder for belt changes
The motor is a 3 hp 3 phase driven by a Motortronics VFD. I have three drive speeds available via the three step pulleys but have pretty much used the VFD exclusively.
Lotsa holes to drill and tap, but the whole project was well worth the time.

[Rugar]

Very cool! Thanks for posting.

[Vernon]

Thats cool. Does the air cyl. tighting the belt and how does that work for you. Is it better than a spring. Well great job anyways, thanks for showing. Here is my sander that I'm still working on!

http://s795.photobucket.com/albums/yy23 ... %20Sander/

[ironmonger]

Actually, seeing your grinder inspired me to get off my butt and post my pics.

The air cylinder is indeed a tensioning device. It is fed by a small regulator and in my case it is set to about 20 psi. The idea for the original grinder was discussed on another forum a few years ago. I freely admit to lifting the idea for the belt tensioner from another builder. I most likely would never even thought about it much, but the other builder caught a ration of poop from a flamer on that forum for using the air spring... why it even needed air to operate! lol

The flamer was concerned that the grinder need compressed air to operate... ya, well it also needs 240 volts of 3 phase power, so the air didn't seem like much of a stretch. Not to many shops that would use the grinder would be without compressed air, I suspect.

It seems a little frivolous, but it does present a constant pressure on the belt idler without any adjustment. I have found after using it for a year or so that all belts are not the same length and swapping out a belt means that I don't' have to re-adjust the tension, not that it's hard, but this was more fun.

I also have a small air switch that vents the cylinder if you turnoff the air. That drops the idler and allow the belt to slip on quickly. Some thing else that I added after using the grinder for a while was a debris 'scraper' that intercepts the small pieces of swarf that follow the belt around and pelt you in the face. I suspect that they are dragged around by a boundary layer of air flowing with the belt, but physics aside, they are a pain. The 'scrapper is a small piece of sheet metal located like a grinder rest that seems to block the swarf pretty well.

Have fun, build more.