Groove worn into tracking wheel

[dwc34205]

I built my own grinder a while back. It's not as pretty as a KMG, Bador or any of the other big names. But I did spend the time on the drawings, dimensions and the machining of the parts. Its runs good and true but I noticed a few months ago that the tracking wheel has a slight groove worn into it on the right side. The tracking wheel was bought from one of the main grinder manufacturers and I expect that there was problem to begin with. Just that the belt has cut a groove. Needless to say, as I am sure all of you figured, this causes the belt to jump when tracking. Once it is set it is good, but not easy to set.

Question time...
1) Is this common and the wheel just has to be replaced on a semi-regular basis?
2) Does anyone know what the radius is on a tracking wheel so that I can run a clean-up pass on the lathe?

Thanks in advance...

[Kevster]

Can't you wrap some electrical tape around the tracking wheel, it would be a cheap fix if it works.

[Ray Rogers]

1. No, I don't think that is common at all. I've been using 2 grinders for 20 years and never replaced a wheel and see no damage on them. I don't recall anyone on these forums ever asking that question before either.

2. I don't know the radius but its slight and probably not overly critical because many of us have built grinders that had flat idler wheels with a couple of turns of electrical tape in the center to 'crown' it and they work fine...

[Reverend Greg]

At my day job we have just finished a lot of 100 idler rollers for a german company.They are 1" wide with a 250mm radius(9.8425").....if this helps.I plan on making my own 2" wide rollers on a similar radius,I will just have to see if that is too severe at that width.
(G)

[DanCom]

I am building my grinder now and accumulating parts.

dwc - Assuming the tracking wheel is aluminum: 2" or wider than 2? Is it possible that the outer edge of a belt has partly curled under? This seems plausible if the wheel is say 2 -3/16" wide and rides on the left of the crown most of the time. Crowned 2" and 4" idlers are typical for tracking.

I would think the larger diameter tracking wheel would mean the bearings would last longer as they are not going to be spinning a million miles per hour. The large tracking wheel diameter would need a more precise camber adjustment. Maybe NF bolt instead of NC? Curious to see what the final design looks like with a 10" tracking wheel. Please post pics. :-)

[Crex]

I'm with Ray on this. Interesting problem. Could the Idler bearing be wearing or "stiffening" up such that the belt is sliding over the wheel? Another words the wheel surface is moving slower than the belt.
Even with the edge of a belt turned under, if everything is moving at the same speed it should not produce a groove only a fine abraded scratch, maybe.

If the idler wheel is solid material. Take it off and reshape it smooth to same profile as before. Too much crown will make the belt tracking more sensitive to adjustments. Check the bearings while you have it off and make sure they are getting lubed properly before reinstalling.
Hope you get it resolved. Keep us posted.

[dwc34205]

DanCom and Crex,

Both theories are good and I will spend a little more time this weekend trying to figure it out. My theory was a bit of a combination of both of yours. The tracking wheel is wider than two inches, stiff belts, and wear in bearings and/or wheel has exaggerated the issue. The bearings seem to be good. I run 3M Blaze belts a lot and as I am sure you know they have a pretty stiff backing. I am starting to wonder if they are the culprit. I called the manufacturer of the tracking wheel (big name that we all know) and they didn?t seem to care that this happened or want to help me figure out why. One solution that I have considered and still lean heavily towards is to heat treat a piece of stainless (such as 17-4), throw on a lathe and make a new wheel that will never have that issue again. I know it is a pricier method but buying an aluminum one every two years will be too. Thoughts?

[DanCom]

A saw a great video of a guy that interference fit a piece of schedule 40 pipe over a wheel. (in his case an idler from a 4 cyl. engine's timing belt setup.) You could make it any width and being steel it would hold up better. He cut it to about 2-1/2", tidied up the inside and pressed it on to the wheel with his press. I guess you'd still have to spin it on the lathe to crown it a bit.

Good luck!

[Crex]

*** One solution that I have considered and still lean heavily towards is to heat treat a piece of stainless (such as 17-4), throw on a lathe and make a new wheel that will never have that issue again.***
While that will probably fix the issue of the existing groove, it does not resolve the problem of the cause of the grooving. Because this is a machine that requires all the parts to work in unison to operate correctly, you will only be moving the issue to the next "weakest" part. This will manifest itself at some point in the future and more grief, maybe more serious.
I agree with Ray on it is an odd duck, but a steel bandaide will not keep the feathers on long. You need to find the true cause and fix that. Then the aluminum wheel can do it's designed job correctly.

[Gary Mulkey]

I'm of the same opinion in that it sounds as if the tracking wheel isn't turning at the same speed as the belts. It sounds as if there is some friction going on there. Have you noticed if the tracking wheel gets hot from use? If so then that tells you where your problems lies.

Gary

[ckluftinger]

My two cents worth: my old Kalamazoo grinder doesn't have a tracking wheel as such - you swivel the top wheel in either direction to make the belt track. These are steel wheels with rubber facing and I also noticed that the top wheel has wear marks on one side. I considered all the possibilities listed here - belt dragging, bearing seizing, etc. but it's none of those. It's the belt tension. I found that if the belt has too much tension (especially j-weight) they tend to curl downward, away from the grit side. I can really notice this on the slack section of the grinder. My new grinder does the same thing. No issue there with any marks. Having built your own grinder, is it possible that the stationary wheels are so far out of alignment that the tracking wheel has to compensate so much that the belt runs at an angle across the trcking wheel to a point where it chafes across the surface instead of running straight - kind of like a car tire which is poorly aligned? That and the curling problem could cause a groove to wear into your tracking wheel I guess...