GraphicH

2x72 Alignment Issues

Recommended Posts

Built a 2x72 Grinder based on some designs found here . Right now I'm having a lot of issues with tracking that I think are due to alignment problems. A lot of stuff I'm reading mentions using straight edges to fix alignment issues, wondering if there are any other tips, or even better, possibly designs that are easier to build for those who are less experience with welding and overall precision.  I've attached some images below with what Im working with.  So I've had this running and have used it but in the first image you can clearly see the belt is riding all the way over to the tracking hinge and rubbing there, clearly no good.  It definitely has to be my alignment is awful just not sure how to adjust it.  Another question I had is how "tight" should the belt be, right now I try to get a pretty good amount of tension, but the sticky post in this forum seems to say that's not great.  I wish the image links on that post weren't missing.

IMG_20191212_165647.jpg

IMG_20191212_165655.jpg

IMG_20191212_165712.jpg

IMG_20191212_165734.jpg

IMG_20191212_165805.jpg

IMG_20191129_195409.jpg

Share this post


Link to post
Share on other sites

Ok, I have to ask this:  "Did you ask on that website about dealing with your alignment issues?"   Always the first step when working with something from someone else's plans!

Share this post


Link to post
Share on other sites
1 hour ago, ThomasPowers said:

 

No actually, I'll probably hit them up too. I think this is a pretty popular design and figured there are tips for general alignment issues. Just putting out feelers everywhere.

Share this post


Link to post
Share on other sites

Is the upper wheel in the rear adjustable? It looks fixed from what I can see. That is the wheel I would want to use to adjust the tracking. Looking again, it does look adjustable. Have you ran thru the available adjusting range?

Steve

Share this post


Link to post
Share on other sites

Um...your tracking wheel is crowned.  That means when you adjust the skew, it tries to use the crown to re-center the belt to where the crown wants it rather than to where you adjusted it.  That means you only get eventual tracking forces when you make large adjustments...and that in turn puts the belt into areas where things are far less stable.  Imagine your car steering wheel not really turning the car until you hit the gravel shoulders....then suddenly grabbing.

That should really be either a flat pulley or just barely crowned.  Flat might be a little too "touchy" to adjustment..in that small tweaks cause lots of belt movement.  Because of that, something called a "narrow bodied roll" is often preferred.  A narrow bodied roll is a bit of a hybrid:  The center 60% is flat and there is only a very slight taper or crown at the outer 20% of the face on each side.  That way, the flat does it's job but it doesn't act quite as strongly if the belt happens to wander toward the sides..those sides exert a very slight re-centering force to the belting sort of like a mild shock absorber.

As to correct tension...there is no single answer.  You need enough to not slip but if you go too high, you can start causing the belt edges to have more effect on belt tracking.  The center of any belt is the area you want to do most of the tracking with--centers of belts are pretty darned uniform.  Variations in belting tend to be mostly at the outer edges so when those start seeing a lot of pressure due to high tension, they can throw things off a little.

 

 

Share this post


Link to post
Share on other sites
14 hours ago, Kozzy said:

Um...your tracking wheel is crowned.

Aren't most crowned? All the DIYs for this kind of grinder recommend a crowned tracking wheel, including the one I linked. Seems to be a common enough recommendation. Considering I "eyeballed" the alignment of the pulleys, that's probably where I should start. going to do alignments with the straight edge. 

Share this post


Link to post
Share on other sites

I didn't want to get into a long tirade on the issue but when you have multiple self-tracking features in a belt string  they can basically battle each other...the closer they are together, the more they influence each other and do battle.  No, you do not want your tracking rolls to be crowned when close to a crowned drive roll.  And in fact, that can cause belt dither as they battle.  When far farm the drive, a bit of crown is ok but in most cases of belt grinders, crowns are waaaaay more severe than they really should be.

The fact that it doesn't fail in some cases does not make it good practice.

Part of my job involves designing and tracking high speed belt systems...

 

Share this post


Link to post
Share on other sites

I mean that makes sense I'd just never heard it before and lots of these things look like they have crowning on both.  I've actually got the thing running smooth on 3 rollers:

But you can see its still hanging off the drive and idlers by a good half inch.  That's what makes me think the biggest issue right now is the alignment, and specifically that of the tracking wheel, its like it needs to move back towards the motor a bit.  For getting an uncrowned tracking wheel do you have any suggestions on where to buy? I can't fabricate one / modify the one I have, I don't have a lathe. 

Share this post


Link to post
Share on other sites

When I built my grinder I had to play around with similar issues. My grinder has a crowned tracking wheel - all other wheels are flat. If you have more than one wheel that is crowned, they will fight each other if there is any miss-alignment. From your video I see several things going on - the belt seems to be tracking on the tracking wheel ok,  but there is misalignment in the other wheels. Here's the real issue in my opinion - and you already said it --> your tracking wheel only allows for adjustment in one plane - not two planes. The easiest way to fix this is to move the pivot pin for your tracking arm hinge farther outward - like at least 1/4" minimum - so that the hinge can pivot downwards or upwards. If the hinge has the ability to swing downwards this will lower the tracking wheel, and thus pull the belt towards the grinder frame on the wheel's crown. Note though - if you move the pivot for the hinge - you will have to move all the wheels farther outward or use washer shims to get good alignment. Hope this helps.

I also watched your video again and have one more suggestion. You only have one jacking/locking bolt on the frame tubes for the platten arm and the tracking wheel arm. I'd add another jack screw to each one on the frame to ensure the moving inner tubing is tightened down and secured on each end to prevent possible miss-alignment.

Share this post


Link to post
Share on other sites
21 hours ago, John in Oly, WA said:

Also, your D-backing plate is too thin. Way too much potential for flexing. Should be minimum 1/4" thick. 3/8" thick would be even better.

Yeah I'm definitely going to change that since I have thicker plate laying around, and its not helping with the alignment issues.

Share this post


Link to post
Share on other sites

Alright update video.  I think I'm good now, first off @ThomasPowers your advice was the best! I contacted Dan C. he was super helpful gave me a lot of things to try.  @Kozzy I think you're right, having the two crowned wheels (tracking and drive) do make things more complicated, it took me a while to get things situated so that the tracking wasn't "touchy" and I'm pretty sure it has to due with both the drive wheel and the tracking wheel being crowned.  @John in Oly, WA Your advice on the D-Plate was spot on: the thinner plate was definitely flexing, and on top of that the thinner plate made it that much harder to get the idlers aligned with the tracking wheel.  Besides taking some of the suggestions here and the ones Dan gave I also welded 1/8th inch bar to the top of the tool arm and the "front" of the tracking arm, then ground these down for a tight fit in the frame.  One problem with using this tube steel is there's a lot of "play" in the arms that reeks havoc on getting things well aligned, if I were to do this over I think I'd use tube steel for the arms but figure out a different way to build the frame so that the arms fit with 0 play into it.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.