Michael Cochran

Belt grinder build driving me crazy

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I started building a 2x72" belt grinder several months ago and set it aside for more important things but decided to try to finish it this weekend. I'm not satisfied at all with my construction and I'm thinking it's time to tear it apart and start from scratch. The motor turns and the belt runs but it isn't even close to right. When you turn it on the belt wanders to the left of the tracking wheel (if the tension arm wasn't there it would come off) and it goes to the right on the drive and platen wheels to differing degrees. My first thought was the wheels were too far out of alignment but the platen wheels and the drive wheel are correct (unless I have a warp in my frame I don't see). The tracking wheel is not lined up as well but seeing as it can adjust 1/8" or so I thought it would be fine. I have included two pictures to better explain myself. If anyone can help me save this build I'd love to hear from you. If not, I might just take it apart and start over in the next couple weeks.

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It looks like you have the essentials. But could you show us a closer picture of the tracking wheel and how it adjusts (without the belt on the machine).  My guess is that you just need to make the tracking wheel have a larger degree of adjustment. Also, the second picture makes it look like the drive pulley is not aligned with the platen pulley.  If that is indeed the case fix that first.

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The tracking assembly is the basic style I've seen most everywhere. The arm has a hinge welded to it with a bolt coming through from the outside pushing the wheel side of the hinge. If you're correct I'll have to find a bigger hinge. 

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That looks like plenty of adjustment. Please check the three fixed pulleys for alignment with a large framing square and straight edges. A straight edge laid across the flat side of any two of the three pulleys (if they are the same thickness) should any misalignment.

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The old motor just died on me :(  

I will recheck alignment and everything just not today. I'll wait till I get the originally planned motor mounted and see what's what.

 

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In the second picture of your first post it's quite obvious that your drive wheel is way out of alignment with the bottom wheel of your platen.  You can get by with a small variance, but not that much.  As already mentioned you can check the alignment with a straight edge and adjust the motor location to get it right. The further out of alignment you are, the more friction created and therefore the hotter your wheels will get too.  With my grinder the closer the tracking wheel is to the same height as the top platen wheel the better it tracks as well, but that could just be my build and not a generalization.

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43 minutes ago, Buzzkill said:

In the second picture of your first post it's quite obvious that your drive wheel is way out of alignment with the bottom wheel of your platen.

I thought that too when looking at that picture which prompted me pulling a tape from the frame to the wheel and double checking. The picture is at a bad angle as there is less than 1/16" difference between them. 

I did take the time to put a framing square (and a speed square) on it, even after saying I wouldn't today, and it shows that my top platen wheel is cocked up a little on the right side. The bottom is also a little out but I think the problem lies more with the top one. I'm going to have to redrill and tap the holes for those two wheels or figure out a way to weld much more squarely next time. I think I'm going to rebuild even after finding what looks to be the main problem. I found other issues I don't like including too much sloppy welding (I was using a flux core wire welded on this and results look hideous) and adjustments that just aren't right.

Before I build the next one can someone tell me just how much tension should be on the slack of the belt? I feel like I shouldn't have as much play in there as I do. This is one finger pushing on my off hand (can't take a picture with my off hand cause I'm not that gifted).

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22 hours ago, WayneCoeArtistBlacksmith said:

Check out the Grinders and DVD pages on xxxxxxxxxxxxxxxxxxxxxxxxxx.  You will probably find some valuable information there.

Let me know if I can help you

Wayne

When I get around to starting over I might take you up on that offer.

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The pivot is also a wear point on the swing arm and will wear, eventually screwing things up.

We went with a telescoping tension arm and it's working nicely. Pic follows. It's two tweaks ago. The lever on links hooked to the top of the tension member is to compress the tension spring for easy belt changes. This 1/2 hp. motor is off my old Rockwell 2" x 48" belt grinder and is okay though could be stronger. As is it doesn't cut fast enough I screw things up permanently so quickly. The club built 13 in a 2 day work shop, 9 are running and making sparks to date for about $350.00 + belts. 

Frosty The Lucky.

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I have taken the grinder apart and started rebuilding from the ground up. I will take some time before I actually get building on it again but will be making the one like Frosty made. I have more pressing things to deal with for the next couple months but will post progress whenever it happens. 

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On 9/4/2017 at 3:57 PM, Frosty said:

Useless quote removed

Frosty, my build is the same design as yours. What type of spring did you use for the tension spring?

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I did a partial write up on tracking belts a long time ago here  

Reading back, it's a bit rambling but might give you some things to look for.  Remember that those pulleys have to be squared in ALL 3 dimensions, not just one.  

My initial comment from the photos is that your structure is too light and slightly flexible in many places---which will make tracking quite difficult, especially as you increase belt tensions.   I'd also replace that lightweight hinge you are using for tracking adjustment with a proper weld-on version that is much heavier--like the weld-on bullet hinges (adding your own thicker plate for the adjusting face).  

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2 hours ago, HP500 said:

Frosty, my build is the same design as yours. What type of spring did you use for the tension spring?

I can't give you a name off the top, one of the guys bought 20 for the quantity discount. It's a 30 lb. compression spring approx. 1 1/4" OD and 12" long. I could be off on the length and I'd have to take the grinder apart to measure it. 

Were I building another, I'd buy square tubing that telescoped more tightly. To get mine to track properly I had to shim the tensioner component with a strip of UHMW plastic cut from a cheap'O cutting board. The horizontal adjustment components, platen and rest, are held in alignment by the lock bolts.

Were we going to do this again I'd like to set it up like a production line, there are just too many club members with little or no shop skills. The last build was a frighteningly chaotic do stuff fest. I spent most of my time keeping people from hurting themselves, almost none on the builds.

A large flat table to tack jigs to. One for the roller frame another for the base plate and motor mount and lastly one to cut the steel. Having 15 guys taking turns at each station means precision is virtually impossible. Sure this isn't rocket science but +/- 1/32" isn't an unreasonable tolerance spec. and guys were eyeballing measurements. <sigh>

Stock is carried in on one side of the shop and cut using a <gasp> CUT PATTERN. Cut pieces are then stacked in order of use. TWO guys at the table are stacking and tacking in the jig. Two others are clamping and welding components together in another jig. The base is drilled or punched and stacked. It's the last part needed and takes up room so it's not on the table till everything else is finished. Final assembly is the last thing done, hopefully using the motor as a final gauge  to align the roller assembly with the base and a jig to keep everything square and plumb.  and the guys in the club wouldn't be trouble shooting all the tracking issues. Like mine has. 

From my upbringing using production tech is a no brainer, this wasn't a difficult build. I'd do it the same way for a one off in my shop.

Frosty The Lucky.

 

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No I haven’t. I’ve had too many other things come up that needed my attention. I haven’t been able to make it out to the shop in a couple months now and it’s killing me. As soon as things settle down I’ll see if I can’t get back on this project and others 

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