Belt tracking problems

[Gavj75]

My name is Gavin and this is the first forum I've ever joined so if I'm writing the wrong thing in the wrong place it's because it's all new to me.

This is my attempt at building a 2x72 belt sander and I'm really pleased with how it's coming, however it doesn't track properly and I think it's because my tracking wheel is not crowned.

Any thoughts anyone? 

[Frosty]

Welcome aboard, glad to have you. If you'll put your general location in the header you might be surprised how many of the gang live within visiting distance.

1 hour ago, Nivsknives said:

I think it's because my tracking wheel is not crowned.

I'm calling BINGO! 

Well, I THINK that's the most obvious probable tracking issue. It's the one that jumps out at me right away, could be wrong. I'm well practiced at being wrong you know. 

Pretty nice looking grinder you put together. What HP motor are you running in it?

Frosty The Lucky.

[ThomasPowers]

Ditto on the Crowning!!!!!

[Gavj75]

Not sure how to put my location in the header as I'm not very good with technology. I live in Marske, near Middlesbrough, north east UK.

The motor I'm using is from a 8" bench grinder. Not sure of the h/p but it's 540 watt which I think is about 3/4 h/p and it runs at 2950rpm. 

My grinder is built on a budget 

Admin did it for you

[Stew1803]

itll almost certainly be the tracking wheel needing crowned, as long as you've aligned the other wheels using a straight edge to each other.

[lyuv]

With no crown, there is no way/reason that the belt will stay centered, no matter how aligned and square everything is. If your driving a straight road, and hold your steering wheel fixed straight, the car WILL eventualy stray.

You can makeshift a crown by wraping tape on the middle of the driving or tracking wheels (or both!). 1-2mm will do.

A VERY nice machine you have there. Kudos.

[Gavj75]

Thankyou so much for your advice. I'm at work now but will give the makeshift idea ago as so as I finish 

[HP500]

I had a tracking problem with the 2x72 I just finished building. It ran fine when not under load, but as soon as I put pressure on the belt, the belt would move off to the side. A stronger spring in the tensioning tower fixed that.

[Gavj75]

Cheers to everyone for the feedback 

[Gavj75]

So I've just spent nearly 3 hours in the garage trying to rectify my belt tracking problems with absolutely no success at all. I tried the old making a crown with tape technique, starting with it being half a mil high, then a mil, then 1 and a half mil and finally 2 millimetres high. It never seemed to help at all.

I then tried realignment of my motor with again no improvement. 

I'm generally quite good at this sort of thing so as you can imagine I'm feeling pretty bummed. 

I find myself asking: "could it be the belt?"

I've only bought 2 belts so far and they seem to be very stiff,nothing like the 'KLINGSPOR' ones I used to use on my 1"x30 sander.

Could this be my problem? 

I'm starting to run out of ideas now so after work tomorrow I'm going to strip it all down to its component parts and then do a rebuild. Maybe this mite show me an obvious problem. 

It's really baffling me as it's not out a little bit, it's more like 'no-where near, never eva-eva' out, if you know what I mean? 

On a lighter note though here's a picture of my homemade forge and anvil 

(my forge needs it's chimney attaching)

[Frosty]

No, it's not the belts and starting over won't help. Take the tracking idler off and replace it with a crowned one. Unless you have a lathe to cut a proper crown on it?

I understand budgets but ask yourself. Is one roller worth the money and time I've invested in this already or should I just toss it ALL as a waste of time?  I don't know about you but it'd have to be a darned expensive roller for me to trash can that much of MY time.

There's a point when saving a buck costs more than just spending it. Ever hear the old saw, "Penny wise, dollar foolish." Hmmmm?

Frosty The Lucky.

[Gavj75]

Sounds like a plan, cheers Frosty

[Gavj75]

 So I've found someone who has a lathe and is willing to crown my tracking wheel for me however not to sure how big the height of it should be. Can someone please let me know 

[Smoggy]

Well hello and welcome Nivsknies, you're so close I can alsmost hear your grinder purring!

Just had a quick look at the construction, the obvious place to me, given that I can see little fine detail in the pics, if there is anyother issue to be found would be how the head arm is locked in place. Is it one screw on the top at the back? If so that proides a potential for it to become out of alignment after each adjustment. I would have opted for two screws, front and back on the side the belt is mounted firmly locating the tube againts the back wall each time in the plane that matters, it only takes the slightest degree of slogger to run a belt off.

The wheel will still need crowning either way.

That is a very nice looking grinder.

[lyuv]

4 hours ago, Nivsknives said:

 So I've found someone who has a lathe and is willing to crown my tracking wheel for me however not to sure how big the height of it should be. Can someone please let me know 

Check this out: http://www.visusa.com/belt_tracking_m01.htm#pt crown height table_mm

[Kozzy]

56 minutes ago, lyuv said:

Check this out: http://www.visusa.com/belt_tracking_m01.htm#pt crown height table_mm

This actually gets into a bit of voodoo.  Those figures are for belts with slight elasticity so might be a bit much for an inelastic sanding belt.  Additionally, too much crown can cause what is called an "approach bulge", where the belt bulges as it nears the pulley face--causing some of it's own problems.

If this was being done for tracking only without any of the odd uneven loading on the belt of grinding work, the crown should actually be only about 1/5 of the belt thickness--which is too small when you add in the uneven tension issues.  A crown of about the belt thickness is where you normally want to be because more than that on an inelastic belt means the edges are not normally touching the pulley face unless tension is distorting the belting.

But...belt grinders get hammered by users putting a lot of pressures and tensions on--And since it's basically a one-shot deal to have a pulley crowned, I'd probably go for about twice the belt thickness.  If you need more than that, it's likely that something else is out of whack and instead of trying to force the pulley to compensate, that problem needs to be chased down and corrected.

But as I said, it's a bit of voodoo---many will disagree with my figures above and I have seen pulleys with a LOT of crown work just fine.  Be sure to chase the other stuff first, no matter what else happens:  Even slight skew of the flat pulleys can cause an effect that emulates a reverse crown when 2 flat skewed pulleys are interacting (the closer together they are, the more they act this way when skewed). 3 dimensions, not just one here.  An effective reverse crown caused by slightly skewed flat pulleys will also reverse tracking control--kind of an anti-tracking pulley.

Also look for flex in the structure on which the pulleys are mounted as this can be a common problem when the belt is under tension:  They don't build the expensive versions with heavy structure just for looks.

[Gavj75]

2 hours ago, Smoggy said:

Well hello and welcome Nivsknies, you're so close I can alsmost hear your grinder purring!

Just had a quick look at the construction, the obvious place to me, given that I can see little fine detail in the pics, if there is anyother issue to be found would be how the head arm is locked in place. Is it one screw on the top at the back? If so that proides a potential for it to become out of alignment after each adjustment. I would have opted for two screws, front and back on the side the belt is mounted firmly locating the tube againts the back wall each time in the plane that matters, it only takes the slightest degree of slogger to run a belt off.

The wheel will still need crowning either way.

That is a very nice looking grinder.

Thanks for your help and advice with my tracking troubles. 

I've made my own hinge and adjustment screw to track my belts and it may be completely in-effective, i just don't know. My only reference has been what I've seen on u-tube and in pictures. 

Hopefully you'll be able to see my design better in these pics. 

I'm a novice in every sense of the word.I just hope with a bit more effort and advice from you chaps, it'll come good.

[BIGGUNDOCTOR]

The wheels on the horizontal band bun slicer at work are crowned from the center 1 degree each way.

[Gavj75]

Nice one Doc, you're a star. So if I'm right, the inclusive angle across the crown will be 178 degrees.

That gives me an accurate specification to pass on to my "lathe-man".

[Gavj75]

3 hours ago, Kozzy said:

This actually gets into a bit of voodoo.  Those figures are for belts with slight elasticity so might be a bit much for an inelastic sanding belt.  Additionally, too much crown can cause what is called an "approach bulge", where the belt bulges as it nears the pulley face--causing some of it's own problems.

 

After reading your advice over a few times and taking it in I'm beginning to think I may have some other 'gremlin' lurking around my troubles. 

I think that once I've sorted a crown out on my tracking wheel, I mite need to sort a new drive wheel out which is also crowned.

One thing at a time tho' eh

[Frosty]

ONE crowned wheel or the minor imperfections will get the belt tracking back and forth in a high speed wobble.

Is your "lathe-man" a machinist or someone who owns a lathe? There is a big difference and as it stands this wheel will serve as a spare if another one fails. Buying one will  have the CORRECT crown, rather than what you measure.

It's fun building our own tools and equipment but there is a point when it's  just not worth it. I had a book when I was a kid that had directions for winding both DC and AC motors among other things electrical. Getting the contacts and brushes right was a little touchy but nothing a 10 yr. old couldn't handle. I'll have my Sister mail them to me if you'd like to give it a try. Induction motors are a little different but what the hey.

FedEx would've had it to you while you were still asking us about it. 

Just saying, Frosty The Lucky.

[Gavj75]

4 hours ago, Kozzy said:

This actually gets into a bit of voodoo.  Those figures are for belts with slight elasticity so might be a bit much for an inelastic sanding belt.  Additionally, too much crown can cause what is called an "approach bulge", where the belt bulges as it nears the pulley face--causing some of it's own problems.

If this was being done for tracking only without any of the odd uneven loading on the belt of grinding work, the crown should actually be only about 1/5 of the belt thickness--which is too small when you add in the uneven tension issues.  A crown of about the belt thickness is where you normally want to be because more than that on an inelastic belt means the edges are not normally touching the pulley face unless tension is distorting the belting.

But...belt grinders get hammered by users putting a lot of pressures and tensions on--And since it's basically a one-shot deal to have a pulley crowned, I'd probably go for about twice the belt thickness.  If you need more than that, it's likely that something else is out of whack and instead of trying to force the pulley to compensate, that problem needs to be chased down and corrected.

But as I said, it's a bit of voodoo---many will disagree with my figures above and I have seen pulleys with a LOT of crown work just fine.  Be sure to chase the other stuff first, no matter what else happens:  Even slight skew of the flat pulleys can cause an effect that emulates a reverse crown when 2 flat skewed pulleys are interacting (the closer together they are, the more they act this way when skewed). 3 dimensions, not just one here.  An effective reverse crown caused by slightly skewed flat pulleys will also reverse tracking control--kind of an anti-tracking pulley.

Also look for flex in the structure on which the pulleys are mounted as this can be a common problem when the belt is under tension:  They don't build the expensive versions with heavy structure just for looks.

After reading your advice over a few times and taking it in I'm beginning to think I may have some other 'gremlin' lurking around my troubles. 

I think that once I've sorted a crown out on my tracking wheel, I mite need to sort a new drive wheel out which is also crowned.

One thing at a time tho' eh

30 minutes ago, Frosty said:

ONE crowned wheel or the minor imperfections will get the belt tracking back and forth in a high speed wobble.

Is your "lathe-man" a machinist or someone who owns a lathe? There is a big difference and as it stands this wheel will serve as a spare if another one fails. Buying one will  have the CORRECT crown, rather than what you measure.

It's fun building our own tools and equipment but there is a point when it's  just not worth it. I had a book when I was a kid that had directions for winding both DC and AC motors among other things electrical. Getting the contacts and brushes right was a little touchy but nothing a 10 yr. old couldn't handle. I'll have my Sister mail them to me if you'd like to give it a try. Induction motors are a little different but what the hey.

FedEx would've had it to you while you were still asking us about it. 

Just saying, Frosty The Lucky.

I hear you Frosty

[Gavj75]

Is It's taken me quite a bit of head scratching but I've finally identified the cause of my tracking troubles. From the way the belt was being thrown off I new it had to be more than the lack of crowns. The problem was at some point I must of banged the tracking arm what the tracking wheel bolts onto, and it was slightly twisted. Using an adjustable to get a bit of leverage, I gave it a tweek and what do you know?,  the belt stays on. It's not perfect and has a bit of a wobble however, I'm sure that with a crown or two in the right place everything will be hunky-dory.

So thanks to all who've assisted and advised me and I'll catch y'z next time

Edited April 25, 2018 by Nivsknives
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[Smoggy]

Good to know you've got it sorted, it is all too easy to overlook one small detail and embark on an endless cirumnavigtion of head scratching, dropping the problem on the table for others to peruse can often be help in itself.