2" X 42" Belt Grinder

A 6-inch pulley at 1725 should produce the same surface speed as 3-inch at 3450. 3/4HP should be more than enough...

But check my math!
 
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I think you are correct on both counts. I may run a 5" pulley on the motor and use a 2" tracking pulley. I guess I will make a tracking adjustment mechanism somehow.
Thinking about this:


I will start my own thread when I get going.
Robert
 
I thought about the math... you need a 6-inch to get the same surface speed as mine. Your tracking adjustment would work well but keep in mind only very small amount of adjustments will be needed. If I was making mine again I would make the tension arm a bit wider so that there was more room for a set screw below the pivot point. My arm is 1.25" but 1.5 or 1.75 would leave room for a single set screw. Look at this picture and you will see what I mean. I installed 2 screw but one would have worked just as well. Ultimately I found I needed nothing for tracking but I was probably lucky. Despite the fact that the pivot point it a bit tight (no slop) tightening the tracking screw even a small amount drastically effects tracking.

Something I just thought of... a 6-inch drive wheel or pulley would drastically increase belt contact area. I don't have any problems with slippage but with a 6-inch drive would probably eliminate this possibility completely.

tracking.jpg
 
3-inch drive pulley. The short motor shaft was 5/8" with a reduced threaded end. I had to bore fairly deep to leave enough thread exposure for the nut. On the other side the shaft is about 1-inch deep. I was very careful to get a perfect fit because of the limited depth. I'm fairly new to the hobby and was proud of the fit... same with the bearing fits on the upper pulley. My Logan 200 adjustments are 1:1. In other words, if you move the tool .001 it reduces the diameter by .002. It would be a lot better if it was made like new lathes... a movement of .001 is actually .0005 or .001 in diameter. I don't mind the math but small moves are hard to make.

drive.jpg
 
Maybe the tracking adjustment is overkill. Hmmm...what about using a a long bolt mounted along the side of the vertical support between two blocks. Tightening the bolt would cause minor flex in the vertical support and very slightly tilt the tracking wheel? Thoughts?
I'm going to use aluminum for the base and place a piece vertically outboard of the drive pulley. That piece will have a fitting for dust collection. The drive pulley will essentially be enclosed in a box that way.
I'm looking at 5" stock and its pretty pricey. Maybe I'll have to cast a pulley.
R

Edit: After doing some napkin math and playing with my 12" disc sander I believe a 1725 rpm motor with a 5" pulley will be too slow. I think I need a 3450 motor or I would have to use at least an 8" pulley to get good speeds for steel. I may try to find a 3450 motor and use the 5" pulley.

Robert
 
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RWM, I thought about doing exactly as you suggested but I used angle iron for the upright which won't flex as needed. If I had used 1.25" x 3/8" this method would work excellent.

A 6 inch pulley would be the same speed as my 3 inch pulley on a 1725 motor... which is fast enough. 3450 with a 5 inch pulley would be smoking! My biggest concern would be vibration but if you are careful it would be one mean machine :o) Be careful with things like setscrews and key ways. My motor has no key way and the pulley mounts with a nut on the end. When I got the motor I saw this as a bad thing but in hindsight it's probably a big plus.... the grinder is smooth as silk. I would suggest looking at commercial belt grinders and see what they use.

Here's a fairly fast one. Belt SFPM: 4400

Hmmm... My sander figures out to be 2700 FPM - Interesting. Your idea about using a 5 inch is about the same as the link. Go for it!

https://www.zoro.com/dayton-beltdis...ktHi3NMeV8u8FqZ72mzm0BoCgfjw_wcB&gclsrc=aw.ds

Dust collection would be nice but don't sand any wood. I heard they had a fire at work because somebody sanded a bunch of wood. Somebody else was grinding away on metal and saw smoke. Apparently there wasn't enough sawdust to create a big fire but they did have to replace the bag. Just a comical side note. Be careful vacuuming up ashes around a wood stove too. I had a vacuum turn into a jet engine!
 
Oops...I just bought a Marathon 3/4 HP TEFC washdown motor on Ebay for $70. Are Marathons' any good?
R
 
Ha... I have no idea. I'm sure if you are not in an industrial environment just about any motor is a good one. The only one I know to be good is Baldor. I can't even remember what my motor is... i think it's a Wagner. It has a noising bearing but unless it gets worse I'm not going to fool with it.
 
I also work in the print industry. And unless a belt in the press is sloppy loose or has a cut half way across it, theres no worry about it shooting off into the machine. Its very much like watching antique tractors run a belt to other equipment. You see it flip around, and jerk on that pulley, but because of the crown on it the belt hardly ever falls off.

I like your set up, mind if I copy it someday?
 
Copy? Go for it.

Harrisonburg??? Do you also work at RRD?
 
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