Belt Wander

C

CJQ

Joined
Sep 23, 2010
Messages
5
Hello, just finished making a 2X72 grinder, purchased pulleys ,tread mill motor, and welded up the framing. Mounted the first belt and fired it up. I aligned the tension-er pulley, and the two head pulleys. The belt will center and not walk off, my problem is the belt hunt's or wanders about 1/4 inches. No matter what I adjust it won't eliminate the problem. Any suggestions to correct the issue?
Thanks

CJQ
 
Did you try increasing the belt tension?
Is your tracking wheel crowned?
Did you try a different belt?
 
can you be more specific ? you said the belt will center and not walk off, then you said the belt wanders 1/4". if the belt stays centered while running with out grinding anything, but when you try to grind something the belt moves to one side it means there is not enough tension or the spring is too weak.
 
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Pics would help. What's your tensioning method? How heavy is your spring? Try compressing your tension arm all the way down, while pulling your tool arm as far out as it will go (with the belt on, of course). This should increase your tension and improve your tracking. If there's still wander/wobble, then you've got an alignment issue.
 
Hi, thanks for the suggestions and comments, The belt wanders left to right about 1/4 in total at the work surface and upper and lower pulleys. Those pulleys are flat. Only the motor pulley and idler /tensioner are crowned. , the belt won't walk off the pulleys even when heavy grinding it stays centered. The wandering bothers me as I want it steady. I did increase the idler tensioner and that reduced the problem a tiny bit. As mentioned this is a home made grinder. The idler pulley has a 1/2 inch bolt with the head welded to a 4 1/2 inch hinge, I saw that design on a utube video and thought it was a neat way to build in adjustment. I'm now thinking maybe this isn't the hot setup. I can flex the 1/2 inch bolt / hinge and it causes the belt to start walking off. I might have to go back and remake that assembly with something more sturdy. But getting back to the wander I'm surprised that the belt stays centered. .
I did make a big mistake and bought plastic pulleys, the 4" motor pulley was not smooth. The plastic is not a solid block, it has
ribs , between the ribs there was a slight hollow on the pulley surface. That cupping made a flapping noise especially at higher belt speeds. I put the pulley in a lathe and resurfaced the pulley with the same crown as original. Runs smooth now. I should have bought aluminum. (next time) .
I'll keep you informed with my progress,
Thanks guy's

CJQ
 
Being "homemade" doesn't affect the quality at all, provided you did a good job of keeping everything lined up. Two things standout.

1; you mention the idler wheel (tracking wheel) has flex - that's bad, very bad. The tracking hinge assembly and the tracking/tension arm all need to be solid with NO flex. Those will cause the belt to wander for sure.

2; You mention both the tracking wheel (idler?) and the motor drive wheel are both crowned. Normally speaking you want only one of those to be crowned. Doesn't really matter which. If both are crowned it will sometimes cause the exact wandering problem you mention. The crown in one wheel pulls belt, then crown in other wheel fights that pull and pulls belt back.

As mentioned a photo of your grinder would surely help. Oh, you mentioned you wanted aluminum wheels - aluminum is good for the tracking and drive wheel. Personally I prefer something a tad softer for the platen wheels. Aluminum just doesn't grind that good. I use longboard wheels for the platen wheel - they're about 3" diameter and 2" wide. Been using them for over 5 yrs in hobby use, grinding a few times each week.

Ken H>
 
I’ll add that while having both your drive and tracking wheels crowned can cause tracking issues as Ken described, if all your wheels lie on a common plane and are properly square to that plane it can be a non issue. I built my grinder with a 5” crowned drive wheel and a 4” crowned tracking wheel and it runs perfectly true. That being said, I took a lot of care to make sure that all the wheels were perfectly aligned to each other and I have a relatively rigid tracking system.

Edit: One more thought, usually the drive and tracking wheels are wider than 2” so you have to take that into consideration when defining their common plane. If the outside edge of each wheel forms a common plane then the center of the wheels (where the belt wants to run) won’t form a plane and will create an unstable belt path.
 
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Hi guy's, went back to the drawing board,,:>) I followed advise and machined smooth (no crown) my tensioner wheel. That made a huge difference,,, I eliminated the play in the tensioner hinge , and ensured the wheels were on or close to the same plane. I made the unit on two separate sub assembly's The one assy. is the motor on a platform and the second is the wheel assy. I had them clamped together before welding,,,,glad I did, now I'm set for final welding. Now I want to make a dedicated table for the whole unit. I need to determine a comfortable height for the platen/table.
I want to thank everybody for sharing your suggestions,,I was lost and frustrated.

CLIFF
 
Take a look at the Reeder Grinder site and see his mobile base table. It would be pretty easy to weld up something similar.


I prefer the tracking wheel crowned and the drive wheel flat.
 
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