2x72 belt wobble?

R

Rickoo

Joined
Feb 23, 2017
Messages
68
Just began using a Reeder products grinder. I'm pretty happy with the quality of the machine the and service from Don and Greg Reeder. I picked up 20 +/- various belts from Trugrit to try out. I'm noticing about half of the belts don't track consitently. I'm getting a left/right variation (wobble) as they turn. Not sure how much movement would be considered normal, but it would seem in order to keep a plunge line straight, the belt would need to run true. I've wondered if one of the wheels were off somehow, but the fact that some of the belts run pretty straight, I'm leaning toward either normal variation for these belts or just plain bad belts? The worse ones are AO, but even the scotchbrite are pretty bad.

Opinions welcome!

I have a short video I took with my phone. Is there a way to upload it? Have no clue how to put it on Youtube.

Thanks!
 
Are the belts tensioned enough? That's a pretty common culprit to belt wobble on my KMG. Try compressing the spring more before tightening the tooling arm. The scotchbrite belts always seem to wobble a bit.
 
when you have the tracking arm down with the little lock on adjust the tooling arm out just enough to allow a belt swap with the slack available. if this works put a scribe line on the tool arm so it's easy to get back in the same distance every time. sometimes belts can be junk though.
 
Thanks. I pulled the tooling arm out hard and as far as possible, locked it and the released the upper arm lock and it definitely helped. Can't swap belts like this tho. Would have to release the clamp on the tooling arm. Not really a big deal. Don't think I'd buy these belts again. I'd be curious if anyone had a similar experience with Trugrit.
 
Belt wobble (In my opinion) is related to 3 things, in order of most often to least often: 1- Belt tension too low. Some guys here are using 100lb gas springs. I use 60. Most extension or coil spring setups I've seen are only generating about 30lb. 2- Wheel run out. If your contact wheel or platen wheel axis are not perpendicular to your drive wheel axis, the belt is trying to run around a wobbly circle like a slow spinning top, chasing the next tracking axis constantly. 3- The belt itself. I've never had a new belt, whether it was $1 or $12 not track straight once I resolved #1 and #2. I have had old, used belts that stretched unevenly begin to wobble, but they usually straighten back out after running on the grinder again for a short period of time.

I think percentage wise #1 is 45%, #2 is 40% and #3 is maybe 5% of tracking issues.

#1 and #2 maybe are even more equal. Because I run scotchbrite belts with only the tension I put on them by pulling the tool arm out, to keep them from stretching, and they don't wobble at all. They're loose enough I can make them slip on the drive wheel if I press against the platen too hard.
 
Thanks Kuraki, your principles make sense.

I ran the same belts on a platen, a four inch and a ten inch contact wheel with pretty much the same results. That makes me think if it's an offset wheel axis, it would likely be on the tracking or drive wheel? Being that the tracking wheel is movable as you adjust it (at least in one plane) would that maybe make you suspect the drive wheel? Any thoughts on ways to measure or confirm that?

Weird that it only happens on some of the belts though.
 
Like you said the tracking wheel will always be off, that's why it's crowned. It's entirely possible the drive wheel is off even if it's a cface direct drive, I had to shim my motor because of a warp in the plate it mounted to on the first one I built, so it was square with the tooling arms.
 
Does it happen with a specific brand belt weight grit size? Ie it happens with every regalite 707 120 grit? Or one of these, one of those..?
 
do you have reverse capability? your grinder has an extra tracking adjustment that could solve your problem. you should be able to get it to track centered both directions without adjusting the main tracking knob. another thing to check would be wheel alignment. the belt should be in the center of the drive, tracking, and contact wheels while running. because the drive and tracking are both crowned they can end up fighting eachother. on a 1/2'' thick frame you only get about an inch of wheel on the motor shaft. did reeder send you instructions about the gap between the wheel and frame? you can also mount the tracking wheel backwards on that grinder.
 
I'm sure the tracking wheel is correct. (Concave side inward). I noticed the motor mount bolts weren't all that tight. Thought that might have been it, tightened them good and no change. I also tried adjusting the forward/aft adjustments on the tracking wheel mount with no change. No matter where they are, the wobble is the same.

Forward/reverse, the same result.

Didn't get anything from Reeder regarding the position of the drive wheel. I just installed it where it looked centered with the tracking wheel. I'll have another look at that. When installing the motor, I noticed the motor shaft only reaches about half way through the drive wheel. Called and talked to Don. He said it was normal and should be fine. Do you have a Reeder? What should the gap be between the drive wheel and frame?

The thing that's making me think it's the belts is that some of them track perfectly. J-flex run true as can be. Some of the AO run ok. Most wobble. I bought two scotchbrite. One wobbles badly. The other one a little less.

Scratching my head on this.
 
no, i dont own one. when the grinder is running with a platen is the belt centered on all 4 wheels? are you using a face mount motor? i've seen folks use a non-face-mount motor bolted to blocks by the feet is why i ask. that throws a whole other level of tuning into the bag. i really dont think you have got that many bad belts considering theyre different makes and types.
 
Face mount motor. Belt is not perfectly centered on the tracking wheel. Not sure that's the issue tho. After all, isn't the tracking adjustment in place to move the belt to keep it aligned on the contact wheel or platen? I've moved the drive wheel to better line up with the tracking wheel. No change is belt wobble. I sent some videos to the folks at Reader. Will update when I figure out what the source is.
 
Rickoo said:
Face mount motor. Belt is not perfectly centered on the tracking wheel. Not sure that's the issue tho. After all, isn't the tracking adjustment in place to move the belt to keep it aligned on the contact wheel or platen? I've moved the drive wheel to better line up with the tracking wheel. No change is belt wobble. I sent some videos to the folks at Reader. Will update when I figure out what the source is.
Click to expand...

Did you find a solution?
 
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