Started my 72" belt grinder build.

**officerdread** · 04-13-2013, 11:23 PM

Originally Posted by Bruno

That's an interesting idea

LOL, sorry my mistake. NO Bearings in drive wheel. It's keyed. Silly me....

**officerdread** · 04-13-2013, 11:28 PM

Originally Posted by 10Pups

I just want to toss some thoughts out here and see what happens. I love your design and I am wondering if you have thought about a few things.
1. If your drive shaft is spinning and your drive wheel has a bearing in it, what makes the belt go round ? I am picturing a bearing spinning inside a drive wheel that doesn't move. Doesn't the wheel have to be fastened to the shaft ?
Sorry Ment No bearings in drive wheel it's keyed.

2. Your tubing looks beefy enough for sure but if it's not a tight enough fit will the contact wheel vibrate or worse yet move under the pressure of grinding? I am sure the pressure of the locking bolt will hold it from moving side to side but what about up and down ?
Not done yet. Verticle bolt to be added

3. The gas shock sounds like a great idea however I am wondering how long a belt will last before it slaps you in the face at 35lbs. of pressure. I would think 5lbs would be more than enough. Some of which may be reduced or increased depending on where you mount the shock. (Think leverage here).
Have to do more research. Going by a guy that had a tracking problem and changed his spring out. He stated that kmg spring said between 30 and 40 lbs of pressure. Didnt order the strut yet.

And finally. It looks like your 3" grinder is hanging by the wheel pushed into a crack on your bench? I had one one those fly apart and stick in my chin bone once because it was cracked and I didn't know it. They crack real easy so be careful with that if what I am seeing is what I am seeing. If I drop one of those onto the work bench nowadays, I don't even risk it, it goes in the trash. (Yes, I was wearing a face shield but looking down and then up, raised it enough to expose my chin.)
Nope, it is actually hanging by a Y fork. the wheel just happened to be under the plywood

As for the belt tension this is what I was going by. Going to do more research.
http://www.youtube.com/watch?v=wsHMY4O7nGI

**10Pups** · 04-14-2013, 06:13 AM

your right, I looked around and the 30 to 35 pounds sounds like what they use. Seems high to me is all. On this particular vid it looked like this guys idler was moving even after start up. I am thinking that the start up torque and the loose set up may be fixed with more tension but is that best for the belt? I have to find my fish scale now and check my grinder. It has no problems tracking or pulling to the side. I just pulled on the handle and it feels like it's about 10lbs but it is a completely different set up. At the wheel, the tension may be a lot more. When I re purpose it to a 72" I will know how well I did if it still tracks right without problems. :<0)

**officerdread** · 04-14-2013, 01:49 PM

Originally Posted by 10Pups

your right, I looked around and the 30 to 35 pounds sounds like what they use. Seems high to me is all. On this particular vid it looked like this guys idler was moving even after start up. I am thinking that the start up torque and the loose set up may be fixed with more tension but is that best for the belt? I have to find my fish scale now and check my grinder. It has no problems tracking or pulling to the side. I just pulled on the handle and it feels like it's about 10lbs but it is a completely different set up. At the wheel, the tension may be a lot more. When I re purpose it to a 72" I will know how well I did if it still tracks right without problems. :<0)

So I guess it's safe to order that gas strut...

**officerdread** · 04-14-2013, 01:53 PM

A little more progress. the motor is up and running. tac welded the hinge on the base plate. Also changed my mind about using one flange bearing on the leg of the machine for the drive wheel. Going with two pillow blocks. Keep it simple. Also I think Im going to change the position on my bench. More room but close to the door. Don't have much of a choice in a tiny shop.

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**skipnord** · 04-14-2013, 03:09 PM

I'd agree that the setup in the video looked like flex in the idler pulley was causing the belt to "kick" when he started it up. The spring on my KMG seems to be no where near 30 lbs..When I change belts, I back off the adjusting screw on the bar that holds the contact wheel and slide the bar in to give me slack in the belt. I retension the new belt by pushing down on the spring, pulling out on the bar, and then retightening the locking screw. I'd suggest checking the tension on some of the factory belt grinders before I bought a 35# gas strut. Too much tension may be a factor in belt "explosions". I haven't had one yet.

**skipnord** · 04-14-2013, 10:46 PM

Ok, I was wrong. I checked the compression spring on my KMG. Wire is .15 inches, and uncompressed length is 3 inches. When I compress it to tension the belt, the length goes to 2 1/2 inches. The best I could do for weight to see how much it took to compress it was 20 lbs. compresses it 1/4 inch. I don't have any higher weights of a convenient size, so ---- it looks like 30-35 lbs. is just about right. If you try a 35# gas strut, be sure to let us know how it works.

**officerdread** · 04-15-2013, 10:13 PM

Will do. 30 to 35 lbs seems to be the popular consensus within specs...

**officerdread** · 04-17-2013, 11:14 PM

Ordered a 30 lb gas strut. Contact and drive wheels arriving tomorrow.

**officerdread** · 04-18-2013, 02:09 AM

Precision drill rod arrived, 5/8" 0.6250" and won't fit in my 5/8" pillow blocks or my step pulley... The rod on the motor fit the step pulley like a glove. Suggestions?

Thread: Started my 72" belt grinder build.

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