Belt grinder build - tracking issues

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Jan 5, 2020
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69
I make knives, but I also build grinders, so this is not my first build. I have made 5 grinders before, but all in the same, basic design, somewhat similar to a KMG. This time I decided to upgrade my personal grinder - I wanted a VFD, more speed, small wheels and the ability to tilt.

All of the above was successful - I managed to wire my own VFD and controller (so the VFD can sit in a drawer below the grinder, out of harms way). The tilting and attachments are great, but the tracking is entirely wrong. Is is backwards in most of the adjustment range - the belt goes left when It should be going right, and the other way around. That would not be an issue, but I have no idea what is causing, and making the belt track over the edge is difficult if not impossible, at least consistently. I also need to tilt the wheel pretty much to max adjustment to get any movement.

I have a few ideas as to what might be causing the issue:
- the tension could be too low (first time using a gas strut, but nothing changes when I apply pressure with my hand, and as far as I know, tension only changes tracking under load)
- all of the wheels are crowned (the guy making the wheels misunderstood on the platen wheels, but I figured it should be no big deal. I have tried replacing platen/tracking wheels for flat ones, but with no results)
- misalignment on the wheels (the motor mounts have a fair bit of adjustment in/out, and side to side, but I was not able to find a position better than parallel with the base. I measured and remeasured the wheels for alignment, but even changing it significantly makes zero difference)
- wheel bolts being crooked (I tried replacing the entire platen with a known square one, no difference, the tracking wheel checks out as square, the drive wheels runs with no vibratons or runout)

I have tried every combination of the above, but I just can not get this grinder to track well. Today I also tried removing some crown from the drive/tracking wheels with tape, with no success. I researched online quite a bit, and found a post about crowned wheels interfering if they are too close together, possibly making tracking adjustments work backwards.

This grinder has been a dream come true, but the tracking really has me lost. I would really appreciate and advice, experiences ... I added a few pictures of the setup below. Sorry about the long post, and thanks for any help!

Mark

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Get new wheels.

If they are all crowned they will all fight whatever tracking adjustments you make.
 
That's a really nice grinder!

One issue with the tracking might be that the tracking arm is not horizontal. Hard to tell what the angle might be when the belt is on, but it looks like it would still be a good bit off the horizontal axis. I built a grinder with two-axis adjustment, and the second axis (yaw) behaves similar to what you describe when the first one (roll) is out of adjustment. I remember reading a few posts where people reported tracking problems with DIY grinders where the tracking hinge was angled.

I'm sure you'll figure it out, it just takes a little while to get everything adjusted right.
 
That's a really nice grinder!

One issue with the tracking might be that the tracking arm is not horizontal. Hard to tell what the angle might be when the belt is on, but it looks like it would still be a good bit off the horizontal axis. I built a grinder with two-axis adjustment, and the second axis (yaw) behaves similar to what you describe when the first one (roll) is out of adjustment. I remember reading a few posts where people reported tracking problems with DIY grinders where the tracking hinge was angled.

I'm sure you'll figure it out, it just takes a little while to get everything adjusted right.
The arm itself is angled when the belt is on, but my other grinders have all had this same construction for tracking. Could this be an issue? If you are referring to the pivot point in the tracking arm and the wheel itself, they are square and parallel with the main body of the grinder.
 
I have flat wheels from my old grinder - replacing the platen and/or tracking wheels with uncrowned ones makes no difference, sadly.
It is always misalignment on the wheels my friend and belt tension ......You should have only one crowned wheel . I would try with contact wheel and see what will happen ??
 
The arm itself is angled when the belt is on, but my other grinders have all had this same construction for tracking. Could this be an issue? If you are referring to the pivot point in the tracking arm and the wheel itself, they are square and parallel with the main body of the grinder.
I was referring to the angle of the hinge. That is normally close to horizontal when the belt is tensioned. There are some grinders (e.g., Reeder) that have both a horizontal and a vertical tracking adjustment. When researching DIY grinders, I saw a few posts where people had tracking issues with an arrangement similar to yours. It is impossible to tell whether the angle was actually the problem, or if there was some other misalignment.

Natlek has a point, misalignment and belt tension play a big role. However, having a crowned drive wheel and a crowned tracking wheel should not really be an issue. There are lots of grinders out there with that arrangement that work without problems. If you have a contact wheel, use that for testing instead of the platen with the crowned wheels.

Are the center lines of your drive wheel, tracking wheel and platen aligned? One thing that might help is to try and get the belt to run centered without the tracking wheel. I did that on my grinder with a contact wheel to get the contact wheel aligned with the drive wheel.
 
I was referring to the angle of the hinge. That is normally close to horizontal when the belt is tensioned. There are some grinders (e.g., Reeder) that have both a horizontal and a vertical tracking adjustment. When researching DIY grinders, I saw a few posts where people had tracking issues with an arrangement similar to yours. It is impossible to tell whether the angle was actually the problem, or if there was some other misalignment.

Natlek has a point, misalignment and belt tension play a big role. However, having a crowned drive wheel and a crowned tracking wheel should not really be an issue. There are lots of grinders out there with that arrangement that work without problems. If you have a contact wheel, use that for testing instead of the platen with the crowned wheels.

Are the center lines of your drive wheel, tracking wheel and platen aligned? One thing that might help is to try and get the belt to run centered without the tracking wheel. I did that on my grinder with a contact wheel to get the contact wheel aligned with the drive wheel.
None of my grinders so far have had the arm horizontal, and it hasn't seemed to be an issue, I could, however, be wrong. I was wondering if the reduced distance between the drive and tracking wheels could be the main difference, or at least the one causing issues.

I have a contact wheels and platens (with straight wheels) that work well - none of them seem to change the problem at all, which honestly has me quite worried. The centre lines are aligned, I also just measured the drive wheel and it is straight. The belt runs well on just the platen and drive wheel, regardless of wheels (crowned or not) and speed.

Thanks for all of the advice so far!
 
Don't worry too much, at worst you have to make another tracking arm. Could the axle bolt for the tracking wheel be slightly off perpendicular? Can you post a close-up of the tracking hinge? Also, how strong is the strut?
 
Don't worry too much, at worst you have to make another tracking arm. Could the axle bolt for the tracking wheel be slightly off perpendicular? Can you post a close-up of the tracking hinge? Also, how strong is the strut?
The bolt is straight to the tolerance I can measure. I tried drilling out the thread and putting a bolt through the other way, but the issue remains the same. I also made a sacrificial tracking plate (the part the wheel itself is bolted to) with an oversize hole, so I can manually adjust the assembly, but that did not seem to help either. I will try making another hanger for the tracking plate today, and measuring the tracking arm hinge for parallel (it was welded with a bolt in, but welding does cause a fair bit of distortion.

Thanks, Mark
 
All of the above was successful - I managed to wire my own VFD and controller (so the VFD can sit in a drawer below the grinder, out of harms way). The tilting and attachments are great, but the tracking is entirely wrong. Is is backwards in most of the adjustment range - the belt goes left when It should be going right, and the other way around. That would not be an issue, but I have no idea what is causing, and making the belt track over the edge is difficult if not impossible, at least consistently. I also need to tilt the wheel pretty much to max adjustment to get any movement.
Silly question , but..........are you sure that belt run in right direction ?
 
Yes, it runs as it should. I can reverse it on the controller and the issue is the same both ways
Mark it is misalignment on the wheels .Only thing that affect tracking are WHEELS . Are you sure that drive wheel /crowned/ and tracking wheel /crowned/ are in same line ? I mean on center line ...............MUST be right in middle of both wheels , out of that they will have big FIGHT ............look in picture , red line is RIGHT one and blue one is misalignment between drive wheel and tracking wheel .
Again , only thing that affect tracking are WHEELS and tension/we assume the belt is good/ you just need to find which one it is or two ,or maybe three of them ....no mystique, you have to find problem .Change the way you check alignment of wheels , maybe ?

View from above............
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I checked all of the wheels again, tweaked the motor position by about a degree and added a thin washer to offset the platen and the grinder is perfectly functional now. The tracking is still backwards, but I guess I'm going to have to live with that.

Thanks for the help everyone! If there is any interest, I can post finished pics with the attachments and work rests.
 
The motor is 380V, 2800/min, with a VFD (in the drawer below) which can overdrive it to 4200/min. I run it with a simple forward/reverse and speed controller. Right now, I have a platen and a small wheel attachment. The entire grinder can tilt to horizontal, and I have 3 different adjustable work rests for everything I can imagine doing - a notched table for profiling and chamfering, a small wheel table and a simple flat plate for horizontal grinding flat/straight parts. All of these are adjustable in angle and height, and everything can be adjusted and locked using a combination of 3 keys/wrenches, which I keep just below, drilled into the right side of the cabinet. I have everything stored right above/behind the grinder on 2 shelves, with plenty more space in the cabinet below the grinder. Belts are stored to the left - along with a VFD and horizontal ability, I wanted to have everything in one place, so work can be as efficient as possible. I hate losing time because of bad design and shop layout, so I really did my best to keep it as simple yet versatile as possible.

I would love to build a SGA and get some proper contact wheels in the future, but I have no immediate need for them right now (I will have changed my mind by the time I do my next folder, at least on the SGA).

Overall, I absolutely love it!

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