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jbowman

Grizzley contact wheel- contact wheel care

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I have a Grizzly 2x72 that I bought around the begining of the year. I know they aren't a top quality machine, but it got me grinding  out of the box. I have most of the parts for 3 KMG clones but havent found the time to start building. I bought the Grizzley knowing it would be a while to get them put together.  I sprung for the 10" wheel with the grinder and have to say, it was a better tool than I expected. I ground nearly a dozen blades, and while shaping a handle out of Corian, it developed a serious vibration. The machine is fine. The 8" wheel is smooth sailing, but that ten shakes the house apart! There is no really apparent damage to the 10 inch wheel. I contacted Grizzley, and they sent me a new wheel. I cant fault them at all in this. The new wheel runs smooth. The old wheel did too when new though. What I am wondering is 1- what did I do to screw up my wheel, and 2- can it be fixed? I recall someone in here mentioning refacing a Grizzley wheel, though I couldnt find the post. From the start the wheels seem softer than I expected. I know wheels are available with different durometers of  tire, are soft wheels more particular? I dont want to have to replace contact wheels regularly, the bastards are expensive, and I need to save up for a Bader....

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It sounds like the contact wheel bearing failed, but perhaps those with a Grizzly can give you better insight on possible issues & what sort of lifetime is reasonable for a contact wheel.

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I agree, sounds like bad bearings.  I am not familiar with the Grizzly, but don't they use the contact wheel as the drive wheel?  If so, that rules out wheel bearings.  Hmmm...

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Yep thats what I got. I use the standard eight inch wheel. The Grizzly doesn't have bearings in the contact wheel, and yes its the drive wheel. If the eight is running fine, then it sounds like the ten is out of round or balance. Take a nail or screw and put it in a vertical surface, hang the wheel on it and rotate it, if it doesn't show a tendency for one part to always rotate towards the bottom, then its still balanced. I would then use a pair of calipers and measure from the inside hub to the edge of the wheel all the way around. See if there is a high spot. You might also want to check the inside surface of the hub as well, see if its still perfectly round.

Edited by Brian Myers

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It would have to be the inside. The outer edge looks ok to the indicator, though it shows a little wear. The new wheel runs as smooth as the first one did when new. I am a bit worried that I did something to it that put it out of balance. Have you found that the Grizzly wheels wear very fast or are too soft? I pushed it kind of hard and chewed through a lot of pretty hard steel in the time before it got out of shape.

 

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It seems very unlikely to me that you could have done anything to the arbor hole to put it out of round.  

I would suspect an issue with the rubber.  If you have a dial indicator, put the old wheel on the arbor and turn it slowly by hand to measure the total run-out.  If you don't have an indicator, there are some simple ways to do this, but that would be better explained with a Google search.

My hypothesis is that the rubber got very hot when you were aggressively grinding, and then was allowed to cool with the belt tension on it and changed shape.  It would only take a few thousandths of an inch difference at the rim of the wheel to setup some strong vibration.

Edited by Brian Dougherty

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I hadnt considered the belt tension throwing the rubber off center. I havent measured the rim thickness, that might be the issue, or a rim seperation that I can detect with the belt off...My TIR on the wheel is .0002 which is why this baffles me so much. It seems really out of balance. When turned slow it is fine, but at running speed it acts like it is a half inch off center. There are some wear streaks in the tire , but for the most part it looks pretty consistant. The way the wheel was acting was as if a big chunk was missing.It seems plausable that it may have picked up grit in the face of the wheel , though if it did I shure cant see it. The wheels feel soft to me when grinding.  I have seen replacing the rubber mentioned in David Boye's book and Wayne Goddard's $50 Knife Shop. Perhaps it is worth just peeling it down and starting over with some harder rubber. I will try to be easier with the new wheel.

 

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Check those bearing I had a set go bad after very little time! If that is not it check for out of balance. I store mine when not in use in a special box I made for it. So nothing can touch against the wheel and the rubber is not compressed against anything!

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Great, now I am going to be worried about that too....   At the moment the bearings seem to pass all checks, but I will be keeping an eye on them

 

 

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C Craft the grizzly doesn't use bearings in the wheels. It's a lot like a dual buffer setup, a motor with the shaft coming out of each side. It's sealed up and the wheel is tightly attached to one spindle and is used as both contact and drive wheel. More and more it sounds like the wheel itself is out of round. Even a few millimeters of difference would be magnified at the high speeds. 

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Boy, if your TIR is was good as that, it's got me beat.  Delamination of the rubber is the only thought I have left.

I modified a grizzly wheel to accept bearings, and use it on my OBM grinder.  I'll be curious to see what you find out.

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9 hours ago, Brian Myers said:

C Craft the grizzly doesn't use bearings in the wheels. It's a lot like a dual buffer setup, a motor with the shaft coming out of each side. It's sealed up and the wheel is tightly attached to one spindle and is used as both contact and drive wheel. More and more it sounds like the wheel itself is out of round. Even a few millimeters of difference would be magnified at the high speeds. 

It does if you take it too a machine shop and have them cut and press in the bearing!! ;) That is what I use on my KMG clone.

I did not think about that he was using the wheel as original equipment! Here is my suggestion check the bearings on the grinder itself. If they are going bad you should have play in the shaft! If that is not it check the bearing on the tensioner at the top. In this pic!

If you think it may be the rubber has been distorted out of shape set you work rest so it is positioned as close to to horizontal center of the 10" wheel.

Using a set of digital calipers and the ID measurement side of the calipers measure the distance between the rest as you slowly rotate the 10" wheel. Mark your starting point and as you rotate if that measurement increase or decreases then the wheel itself is out of round and therefore out of balance! 

If the wheel is out of round you may be able to dress the outside of the wheel. A machine shop should be able to re-balance the wheel!

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Edited by C Craft

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I also have one more suggestion. Grizzly's grinders are notorious for having poor tracking lol. The solution is to wrap one or two layers of electricians tape around the center of the drive wheel to stabilize it. Give that a try on your ten inch wheel. It may stabilize the belt and reduce vibration. Just a thought, and most likely its not what is wrong with it. But every little trick helps with these finicky beasts!. 

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Has part of the tire become unglued? At high speeds the tire could lift off the wheel due to inertia. I know R/C car tires can stretch at high speeds, maybe other tires do the same? 

Well, most pneumatic tires have a wire or fabric mesh woven inside the rubber that keeps them from expanding when aired up, but a contact wheel certainly doesn't so it could stretch if spinning fast enough.

 

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Pardon me if this has already been asked, but how does it run with no belt?

If it runs rough without a belt, you've narrowed it down to the wheel.

If you are careful, you can feel the rubber with your fingers while its running. You might detect a high or low spot.

Have you taken the wheel off and remounted it?

I use a Grizzly with a 10" as well but have never encountered this problem.

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I think Brian D. may be on to something- at this point I'd suspect possibly delamination of a section of rubber.

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I hear a lot of good info but, nothing else from jbowman! You got to talk back and let us know where you are at. There is a lot of talent on this forum but, without some feedback from you,.....it's hard to help!!

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