Nordic Track 120" Belt Sander

[Me Tarzan]

I have been lusting over, learning about and considering buying a lathe off and on for years now. Decided instead to try and put what I have to good use in the meantime. Many of my favorite pipe artists are Danish and I have always marveled at the things they can accomplish with a flexible belt sander. So... I have a nice 2 HP treadmill in the garage with a bad board. In the upright position the similarities to a flexible belt sander are uncanny. I began to strip the treadmill of all unneeded components. Will keep the step-up transformer, motor, part of the frame, a pulley or two and add a variable control. Pipe dream? Maybe. Any advice or discouragement appreciated.
Stay tuned, Ron

[WCannoy]

Please, please, pleeeeeeaaase keep the updates and pic coming! I gotta see how this plays out!

[d.huber]

I cannot wait to see this!

[Me Tarzan]

Well I will try to stick with it and make it happen. Been hitting this forum for years, joined up recently but never felt like I had anything to contribute, so here I go... Considered using the incline motor as a tension adjustment but scrapped the idea because I hope to run 2-3 belts at the same time and each belt would probably do best with it's own tension adjustment. The roller at the bottom will have a quick release pin on one side for changing belts and the top will probably be 2-3 wooden rollers sprung for tension. Of course everything is subject to change.

[The Smoking Yeti]

This could be legit... I'm excited to see it!

[oklahoma red]

Interesting project.
Don't forget that somehow the pulleys will have to have a slight crown or the belt(s) will try to run all over the place.
Chas.

[caskwith]

Treadmill motors are quote commonly use to power lathes and milling machines. Search on some of the engineering forums and you will details of fitting speed controllers etc.

[Me Tarzan]

Interesting project.
Don't forget that somehow the pulleys will have to have a slight crown or the belt(s) will try to run all over the place.
Chas.

I was hoping to get away with just a groove in the top pulleys. To be safe and avoid having to go back and modify later I will groove out the bottom roller in 2 or 3 spots as well.
Thanks, Ron

[Me Tarzan]

Treadmill motors are quote commonly use to power lathes and milling machines. Search on some of the engineering forums and you will details of fitting speed controllers etc.

That is great to hear I had no idea. I first planned to just use the motor, but after contemplating how to mount and rig the motor/belt assembly, I figured the engineers at Nordic Track had put more thought into it than I ever could so I decided to use what was there.

[oklahoma red]

Interesting project.
Don't forget that somehow the pulleys will have to have a slight crown or the belt(s) will try to run all over the place.
Chas.

I was hoping to get away with just a groove in the top pulleys. To be safe and avoid having to go back and modify later I will groove out the bottom roller in 2 or 3 spots as well.
Thanks, Ron

You might be able to get away with grooving but if things are not in perfect alignment the belts will still try to wander and you'll wind up fraying their edges when the belts run up against the edges of the grooves. The act of using the belts in a sanding operation will most likely be enough to upset the tracking without crowned pulleys. If you have the capability, put a crown in the rollers when you cut the grooves. If you cannot do it yourself I'd for sure farm it out to a shop that can. Do it to both the upper and lower rollers. What are they made of?
Chas.

[caskwith]

Depending on the material the pulley is made of you may be able to file the crown in, you don't need too much.

[Me Tarzan]

Interesting project.
Don't forget that somehow the pulleys will have to have a slight crown or the belt(s) will try to run all over the place.
Chas.

I was hoping to get away with just a groove in the top pulleys. To be safe and avoid having to go back and modify later I will groove out the bottom roller in 2 or 3 spots as well.
Thanks, Ron

You might be able to get away with grooving but if things are not in perfect alignment the belts will still try to wander and you'll wind up fraying their edges when the belts run up against the edges of the grooves. The act of using the belts in a sanding operation will most likely be enough to upset the tracking without crowned pulleys. If you have the capability, put a crown in the rollers when you cut the grooves. If you cannot do it yourself I'd for sure farm it out to a shop that can. Do it to both the upper and lower rollers. What are they made of?
Chas.

The rollers are made out of iron. What I plan on doing for the bottom pulleys is drilling 3 blocks of wood to fit over the roller, epoxying them in place, and then "crowning" them to shape. I might do the same for the top roller/pulleys but think it would be best to have them separate to allow for individual tension adjustment.

[oklahoma red]

That would probably work. I would agree that individual adjustment would be best as the belts will surely vary a bit in length. As Chris said, you don't need a lot of crown to do the job. Check the web for belt grinders used in knife making. Some of them sell individual pulleys and you can see how much crown they have applied.
You might think about another method of attaching the blocks to the roller. You want to leave yourself some adjustment laterally to get everything in proper alignment.
Chas.

[Me Tarzan]

Found something very similar to what I had in mind over at pipedia. Strange but it looks to me like the pulleys are slightly convex instead of concave?
http://pipedia.org/index.php?title=Belt_Sander

[WCannoy]

Found something very similar to what I had in mind over at pipedia. Strange but it looks to me like the pulleys are slightly convex instead of concave?
http://pipedia.org/index.php?title=Belt_Sander

Having worked maintenance in plants with many conveyor belts, yes, the rollers are "crowned"...
http://woodgears.ca/bandsaw/crowned_pulleys.html
Usually not as extreme as shown on the linked page, but yes, convex...

[Me Tarzan]

Wow. Glad that got cleared up. I would have done the exact opposite. Terminology makes sense though, crowned.

Would a 2" belt be the width most desirable to use? I would think no wider but possibly down to 1", I don't know. Will probably go with a 180 and a 320 grit to start. Maybe 120, 220, 320.

[Me Tarzan]

Made some progress after work. Removed the running bed frame, spun it around 180 degrees and bolted it to the cross-member on the upper part of the frame. Everything is sturdy and not going anywhere. Also hung the other roller at the top. It can be adjusted on either side for tension but will probably end up securing it firmly to the top. From roller to roller there is about a 5 degree lean to the back. This should work out perfect as I intend to mount wooden rollers from the cross-member near the top. With a little adjustment this should allow me to get the tension I need and get the belts at a comfortable angle. I may end up using a wooden rolling pin to make the tension rollers. Also need to order a variable speed controller or possibly a kit but I just want to make sure the planets align before I spend any cash on this project.

[Me Tarzan]

It's funny. The more I research slack sanders the more I think I should just scrap this project. I think I would get better results by bolting the motor to the ground, using pulleys to reach the best speed and just having an on/off switch. Mount a tension wheel to the wall, order up a couple rolls of 2" J-weight welts and call it done. I plan on powering up the motor later to get an idea of how many FPM the belt will be turning as it stands.

[wmolaw]

It's funny. The more I research slack sanders the more I think I should just scrap this project. I think I would get better results by bolting the motor to the ground, using pulleys to reach the best speed and just having an on/off switch. Mount a tension wheel to the wall, order up a couple rolls of 2" J-weight welts and call it done. I plan on powering up the motor later to get an idea of how many FPM the belt will be turning as it stands.

I have never used a slack sander, and not sure what benefits you would get from it as opposed to a good wheel sander attached to a motor/lathe.

[Alan L]

What I'd do is use the motor and speed control off the treadmill to power a drive wheel (say, a 6" laminated wood pulley) at the bottom and a 2" backstand idler at the top. You can set that up to use a standard belt size like 2x72 or 2x132. Forget making your own belts from shop rolls, many have tried and not one has succeeded. You can easily split belts as narrow as you like to get into tight corners.

If you're not a machinist or good friends with one, you can buy the backstand idler assembly for not a lot of money. http://www.texasknife.com/vcom/product_ ... cts_id=694 is a decent one. THis will provide tension and tracking adjustment, but they're not that hard to make if you just have the pulley to begin with. Google is your friend here.

Oh, and the degree of crown is about 1 degree. A couple wraps of masking tape on the center of a flat pulley is enough.

As for the advantages of a slack belt sander over a disc sander, since I've never used a disk I can't help. A slack belt makes it very easy to get smooth radiused parts. It also makes it very easy to round over something you don't want rounded over.