Running belts backwards? Tracking issues?

Drew Riley

Drew Riley

Joined
Oct 17, 2007
Messages
4,302
I built myself a pretty nice grinder a while back, and the only real complaint that I have with it thus far ,s that belts won't track in reverse.

I've tried pivoting the tracking wheel a number of ways, as well as moving the drive wheel back and forth on the shaft. I've also made sure that all of the center lines in the wheels are lined up as close as possible, but it still tends to track about 1/4" to the drive side (right side of the platen, away from the motor) every time I reverse the belt, and the tracking wheel does almost nothing to move it one way or the other at both extremes of its travel.

Forward, tracking is perfect, and rock solid.

I've made some pretty pain staking efforts to make sure everything in the machine as straigh, square, parrelel, etc... as it can be.

I also recently made a flat drive wheel (with no crown) thinking that maybe the crowns in both the drive and tracking wheel could be fighting eachother, but that seemed to make things worse in reverse.

Just wondering if there's something I'm missing, or haven't thought of? Those of you who can successfully run belts in reverse, is there something you did?

Curious what everybody thinks.
 
The TW-90 tracks with the drive wheel, and this improves the problem greatly.

If the belt tracks OK with a contact wheel but not your platen, then scrutinize the platen wheels.

The way I solved this on my KMG clone was to rotate the tracking wheel on the one axis that it is not made to rotate on. Viewing a KMG from the front, the wheel rolls on the 'pitch' axis. The tracking knob makes the wheel rotate on the 'roll' axis. I loosened the bolt and inserted an 0.005" shim on one side of the bolt to get it to rotate on the 'yaw' axis. If you can build a secondary tracking mechanism, that would obviously be slicker than a shim. I believe there was a recent post with a new belt grinder that could track in two axes as I describe here.
 
I got lucky and my KMG tracked in both directions out-of-the-box, meaning I can revers it in the middle of a grind and the belt stays centered and stable, and I just assumed that everybody's worked that way. But, I screwed this up once when I took the platen wheels off and reinstalled them in the opposite positions. None of that stuff is straight and square, it's just a tapped hole and the precision inherent in a nut and bolt, and errors can accumulate or cancel out. There are a number of places something could be out-of-wack including the platen attachment to the tool arm, the tracking wheel and the drive wheel. If it were me, I'd start loosening bolts and fiddling with stuff.
 
I have two KMG's and run both this way with no tracking issues.
Scott
 
Gossman Knives said:
I have two KMG's and run both this way with no tracking issues.
Scott
Click to expand...

I have two KMG with almost 10 years age difference between them. The old one works flawless, the new one kicks the belt off a 1/4" in reverse which can be adjusted in use pretty easy and could probably be tweaked in if I felt like fiddling with it.
 
I got the first KMG in 2004 and the second in 2008. The only tracking issue I should point out is with the rotary platen. The problem with this tool is when the grooved rollers become beveled from heat, they with mess with tracking causing the belt to track right or left. The rollers need to be replaced when they become beveled. That's why I wish Rob would make steel rollers. They would last longer then aluminum. I grind my convex bevels on the rotary platen. Never had any problems with tracking on the flat platen. I grind at 45 degree angles that's why I rotate the belt away from me.
Scott
 
Interesting comments, my TW 90 does not have a reverse, is that something you guys use a lot? I could probably add it if it is that useful.
 
golfer1 said:
Interesting comments, my TW 90 does not have a reverse, is that something you guys use a lot? I could probably add it if it is that useful.
Click to expand...

It's all I do. It works for me. Although I don't follow the norm with the way I make knives.
Scott
 
golfer1 said:
Interesting comments, my TW 90 does not have a reverse, is that something you guys use a lot? I could probably add it if it is that useful.
Click to expand...

It can be useful. I have a DPDT switch sitting around that I need to wire into my VFD to select forward or reverse I just haven't gotten around to it.
 
golfer1 said:
Interesting comments, my TW 90 does not have a reverse, is that something you guys use a lot? I could probably add it if it is that useful.
Click to expand...

I wouldn't say it's "necessary", but it is nice to have options and try different setups from time to time.
Personally, I typically sharpen edge up, and it would be nice to reverse it on the final polishes, as I tend to snag the edge of the belt from time to time and cut them in half. :D This is something that can be avoided if I'm careful, or if I'd just learn to sharpen edge down, but again, it's nice to have options for either/or.

Another thing I'd like to try is Travis Wuertz latest method of hollow grinding but running the blade on a table UNDER a reversed running wheel. I think this is something that I could easily set my grinder up for, if only it would track center.
 
Just a few more details: I've actually tried bypassing the tracking wheel, and just pulling the platen or a contact wheel straight off of the drive, and the machine still tracks dead center, So I'm not sure my issue is anything being out of square or center. I'd run the machine this way, but you really can't get enough tension to maintain tracking.

I think the order of drive, track, platen/contact wheel is the main issue here, as well as perhaps my tracking wheel relative to my drive wheel. I'm wondering if I lengthen my tracking arm so that it's closer to the platen, if that would change anything? I hesitate to do this, however, because then that puts the tracing wheel out farther from my gas strut and rear tracking arm pivot, and if I'm not mistaken, this will decrease my belt tension, no? Maybe not noticeably though. I may fab up a longer tracking arm and see.

I'm also intrigued by the idea of an additional tracking "tilt axis".

I have thought a little bit in the past about an auxiliary tracking wheel on the bottom of the machine, but I'm not sure if it will work on my frame or not... POSSIBLY though.

Definitely something I'll be playing around with.
 
knife; wish I could help you with your tracking problem. It would seem if it tracks one direction, it would track the other. Dumb question, but have you attempted to make a more sever movement to the adjustment wheel since you are reversing the direction.
Do you have any more info on Travis idea as I had not heard of it?
Best wishes.
 
golfer1 said:
knife; wish I could help you with your tracking problem. It would seem if it tracks one direction, it would track the other. Dumb question, but have you attempted to make a more sever movement to the adjustment wheel since you are reversing the direction.
Do you have any more info on Travis idea as I had not heard of it?
Best wishes.
Click to expand...

I've tried both extremes (all the way in, all the way out) and there's really little to no change in reverse, at least until the outer corner of the tracking wheel raises past the level of the crown, then the belt wants to track even farther off the machine.

The issue as I see it is the tracking wheel relative to the drive wheel. Forward, the tracking wheel is the first thing the belt touches after the drive wheel, so it's relatively easy to adjust. Reverse, the belt now goes over two fixed platen wheels that want to steer it one way or the other, BEFORE it hits the tracking wheel. What's odd though, is that it seems to track dead center WITHOUT the tracking wheel, so that would lead me to believe that the drive and platen wheels are lined up accurately. This is definitely something I'm going to play with more.

As for the TW grinding method, it's on Jim Skelton's youtube channel. I think the video is titled "In the shop with Travis Wuertz" or something to that effect. If I'm not mistaken, the video was taken in Jerry Moen's shop, and he's got a couple of neat ideas that he shows a little bit too.
 
knife to a gunfight said:
Another thing I'd like to try is Travis Wuertz latest method of hollow grinding but running the blade on a table UNDER a reversed running wheel. I think this is something that I could easily set my grinder up for, if only it would track center.
Click to expand...

This is how I ground thousands of throwing knives in previous years. You need the wheel to run backwards, otherwise the knife (and maybe your fingers) is pulled into the wheel. The method is very effective, but miserable to operate at lower grits because you are showered with hot sparks. Pic of my old setup: https://www.flickr.com/photos/110785734@N05/22231857551
 
Just wanted to report a bit of a success this evening... well, now morning:
I got to looking a little harder at my machine, and noticed that the pivot block for the tracking wheel was about 1/32" out of square from front to back. I pivoted the block that much, and was able to adjust tracking in reverse for once, and just barely get it centered.

So I re-made the pivot block to be much more precise, and things were improved. Finally, I noticed that if I pulled my tool arm out a little farther, before engaging my gas spring (100lbs), I could get a little bit more tension and this gave me a little more control in reverse as well.

It seems like it was a combination of a couple things, and I can probably still tweek the wheel alignment just a little bit more, but now I am able to track centered in reverse, even if it is on the far inside of my drive and tracking wheel.

Now, I do notice that j-flex belts, which stretch a little, are a little bit harder to still center up, but the heavier weight, or less "stretchy" belts can track just fine. I CAN still track with a j-flex, but I've really got to put some tension on it via the tool arm location. Also, I'm wondering now if the radius on my 2" platen wheel corners isn't perhaps working against me as well. I think I may invest in some non-radiused idlers and see if that's any better, but right now, I'm pretty happy.

So two major things: How square the tracking wheel is in line with the frame (front to back, not side to side tilt), and then belt tension. The more, the better.
 
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