# 2x72 belt sander/grinder (diy) : heat and belt wobble



## bbaley (Nov 20, 2018)

Hi,
I am trying to finish my 2x72 belt sander  project, but still fighting a few issues.

I have just about got all the belt wobble out of the system, which varies a bit between belts - I suppose part of it is the junk belts I have bought so far, not sure yet entirely.
At any rate there is still some side-side belt wobble you can see in this video;





Along with that, I have noticed running it at high speed for a while (> 2 minutes) the wheel shafts/axles (1/2" grade 8 bolts) get pretty warm to the touch. not so hot you can't touch them, but it makes me suspect the wobble has something to do with it ? 

The rollers/wheels spin freely by hand and do not seems to be loose either - meaning no obvious excessive play.
The fit of the bearings to the shaft/bolts is fairly good? not a press fit and not loose/wobbly.
I bought the wheels and D-backing plate from OregonBladeMaker. they are the nylon ones.
Also, the bearings are on the smooth shaft of the bolts, not riding on any threaded portion.

I only have smaller woodworking belt sanders aside from this one which are very different - so I am not sure how "normal" this is.
But the heat to me means friction, and friction means wear, so I am assuming something "ain't right"

Any shared experience much appreciated !


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## bhigdog (Nov 20, 2018)

bbaley said:


> Hi,
> I am trying to finish my 2x72 belt sander  project, but still fighting a few issues.
> 
> I have just about got all the belt wobble out of the system, which varies a bit between belts - I suppose part of it is the junk belts I have bought so far, not sure yet entirely.
> ...



My only reference is my Bader commercial grade 2" grinder. Id say the wobble is negligible. Id also say the hot bearings are not normal. My Bader drive wheel is about half the diameter of the idlers. Im thinking you may be exceeding the design rpm limits of the bearings or the design load. Over greased bearings will also over heat. Just my 2 cents worth and maybe worth about that.........bob


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## ttabbal (Nov 20, 2018)

I have the same wheel/bearing set. They do get warm and I've seen other people mention it. It doesn't seem to be causing any problems though. The belt looks about the same as mine when running. I think you're good to go. Every belt will run a little different. I usually have to adjust the tracking wheel a bit per belt change. Looks good!


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## bbaley (Nov 20, 2018)

bhigdog said:


> . Im thinking you may be exceeding the design rpm limits of the bearings or the design load. Over greased bearings will also over heat.



Hey Bob - not sure on the exceeding limits. I guess that's why I chose to start with a known "kit" of wheels, etc. and pretty standard fare 2x72 design. As for the RPM it's running on a VFD and the motor is 3450 rpm max, but the things I mentioned happen at lower speeds as well, just "differnt" (harmonics, friction, etc). As for the bearings they are 2RS precision sealed, so no clue whats inside for lube....


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## bbaley (Nov 20, 2018)

ttabbal said:


> I have the same wheel/bearing set. They do get warm and I've seen other people mention it. It doesn't seem to be causing any problems though. The belt looks about the same as mine when running. I think you're good to go. Every belt will run a little different. I usually have to adjust the tracking wheel a bit per belt change. Looks good!



Thanks! good to know. maybe I'm just paranoid or nit-picking then.


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## bhigdog (Nov 20, 2018)

Just mentioning my thoughts. I figured the bearings were sealed but ive seen folks "lmprove" them by injecting grease.
Sounds like you should be OK. Proof will be in the use........bob


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## bbaley (Nov 20, 2018)

Nit-picking aside, there is some vibration running the motor alone with just the drive wheel... not a huge amount but you can feel it quite a bit with your hand on the motor or the "chassis". by not a huge amount I mean the grinder doesn't "walk" around...but then it weighs about 1/2 ton.

I suppose I am thinking it should be like my bench grinders... little to no vibration and when I turn them off they spin down for a good couple minutes (i realize the belt won't allow that, just thinking of the lack of vibration in that assembly with motor, shaft and grinding wheels ). maybe I am already in the market for a good set of aluminum wheels before having used these 

Wondering maybe I should throw it on the lathe and true up the sides and diameter... . The drive wheel is crowned (as is the idler), so if I did that I'd need to determine the crown to follow or a good target. Just holding a screwdriver tip on it lightly while it is spinning at high speed I can feel it isn't perfectly round (or the bushing isn't centered in relation to the outside circumference? it is a pressed in bushing, so i am now realizing the wheel was not turned on that center like it would have been with a solid aluminum wheel !)


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## bbaley (Nov 20, 2018)

bhigdog said:


> Just mentioning my thoughts. I figured the bearings were sealed but ive seen folks "lmprove" them by injecting grease.
> Sounds like you should be OK. Proof will be in the use........bob



I appreciate it! not argumentative, just responding to your points with what I thought was relevant.


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## P. Waller (Nov 20, 2018)

I do not know squat about abrasive belt grinders, however I do work in a machine shop where there are several scattered about for deburring.
All of the abrasives are VSM which seem to run well and have a good MMR.


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## ttabbal (Nov 20, 2018)

Mine has near zero vibration. I credit that mostly to the motor running very smooth. 

For spin up/down, the VFD likely has long ramp times set by default. You can likely turn them way down. I've got mine set to 5 seconds. I think the default was 30 seconds. If you go too fast, it will throw errors on the VFD.


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## bbaley (Nov 21, 2018)

ttabbal said:


> Mine has near zero vibration. I credit that mostly to the motor running very smooth.
> 
> For spin up/down, the VFD likely has long ramp times set by default. You can likely turn them way down. I've got mine set to 5 seconds. I think the default was 30 seconds. If you go too fast, it will throw errors on the VFD.



I do have the ramp set about that -  5+ seconds, don't remember exactly.

I alos found some settings for this particular VFD that were the cause of significant "wobble" early in the project, for which the MFG had specific settings.


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