O-Rings For Drive Belts - New Experiment For Old Projects

idbruce

Hello Everyone

It has been a while since I have started a thread, mostly because of disappointments and setbacks, so I have just been taking a break for quite some time. During this vacation, I have been pondering some of the problems that were confronting me and devising plans to overcome them. One of these plans involved making a few attachments for my wood lathe to turn it into a small metal turning lathe. I am currently at the point of just needing a drive system to turn the workpiece with sufficient speed and torque. I have a small surplus AC drill press motor laying around and have decided to use this for my project, however adapting this motor to my project has been a bit tricky.

To make a long story short, after many hours of considering a belt and pulley setup, I have decided to attempt the use of large O-Rings for my drive belts, and custom make my pulleys. With this thought in mind, I recently attempted a successful experiment. As many of you know, I frequently use a drill press and a milling vise for many machining operations. For my latest experiment, I ground the end of 1/4" drill bit to make the end square, I then chucked up a piece of round aluminum stock in the press, followed by turning the drill press on and advancing the bit end into the rotating stock. To my amazement, it actually worked quite well, creating a convex groove in the aluminum. I am now fairly certain that I can now make pulleys for O-Rings having a reasonably small cross sectional diameter. I am not certain that this will work for my current project, but it does have possibilities for other projects.

Anyhow, over the course of the next day or so, I will be attempting an O-Ring drive setup for my miniature metal turning lathe and I will keep you posted on the results. I suppose calling it a lathe it is a bit of an exaggeration, because it is basically just two bearings with a cutting tool attachment for metal, but close enough for me.

Here is a brief article that I found about using O-Rings for drive belts.
http://www.applerubber.com/seal-design-guide/special-elastomer-applications/drive-belt.cfm

Bruce

GordonMcComb

This is the outfit I used to buy my o-rings from, both as "tires" for small wheels, and as treads or other drive belts:

http://www.allorings.com/

They have a low minimum order, and if you need a package of them the price is quite reasonable.

idbruce

Gordon

Thanks for link, because I always love good links, especially those pertaining to parts.

I had forgotten about using o-rings for tires. If all goes well with the pulley making process, I should then be able to make a nice set of wheels for a robot that I have been contemplating. However the robot project is also on hold until I acquire a nice set of bevel gears for making a differential.

Bruce

W9GFO

Polycord (Urethane) is also nice to use for power transmission. It is very easy to cut and then melt the ends together to make any length belt you need.

http://www.mcmaster.com/#round-belts/=pwb0m3

Phil Pilgrim (PhiPi)

Avoid any power transmission media that stretch. Stiffness matters for metal working. That's why V-belts have cords.

-Phil

idbruce

Rich

I read that urethane is good for power transmission, but I don't know about melting my own belts together. However, I would like to learn how to cut and splice timing belts.

Back to your original post..... Don't the belts turn out lop-sided from the melting process?

Bruce

idbruce

Phil

Avoid any power transmission media that stretch. Stiffness matters for metal working. That's why V-belts have cords.

Stretching is most definitely a concern for me, however I have read about several watchmakers lathes successfully using o-rings, so I will at least give it a try. If it doesn't work out well, I suppose I will have to order a small v-belt and another set of pulleys. Even the v-belts take a beating, but like you said they are less prone to stretching.

W9GFO

It is real easy to do. I use a candle flame, hold each end above the flame - not in it - and rotate to evenly heat the ends. When they are melted squish them together and hold for about a minute to cool. The squishing together will make a ring all the way around the belt, you can either use flush cutters to trim it off or what I do is use a disc sander to smooth it out. They shouldn't be lopsided unless you squish them together off center.

idbruce

Rich

Thanks for the information. I am sure it comes in very handy for custom belting applications. By the way, what type of pulleys do you use and is there any noticable slippage? I would imagine, that only timing belts should used for high accuracy applications, such as for CNC operations, but I could be wrong.

W9GFO

We used it on the shooting mechanism for last years FRC robot and it worked flawlessly, quiet too. This year we are going to use it for the drive train as well. The trick is to cut the belt 10% short. We have had no noticeable slippage on either printed, machined aluminum or wooden pulleys. I would't use it for precise positioning, I am sure that the belt does at least creep, if not slip small amounts.

edit: tried to find a picture, this is the best I can do. I need to get some better photos of the drive. It's the bit right in the center. Two motors, either side of the shaft, each with one polycord belt.

electromanj

Reading this thread reminded me of the coolest transmission I have seen. Back in the 80's I was mowing a yard with the homeowner's Snapper mower. I was curious how it was shifting speeds, so I took a closer look. It was simply a V groove pulley on a vertical plane above a horizontal metal disc. The vertical pulley had a section of V belt glued into the groove to make a rubber outer surface. As the pulley was moved closer or further from the center of the metal disc, the speed would decrease or increase. Simple and awesome!

This is the only picture I could find, looks like they have made some improvements since then.

traVis.

idbruce

I am sure the oring belts and wheels have their uses, but I decided to take Phil's advice on this one and go for the v-belt. It has been a little tricky and time consuming making the modifications, but I am getting there.

W9GFO

electromanj wrote: »

Reading this thread reminded me of the coolest transmission I have seen. Back in the 80's I was mowing a yard with the homeowner's Snapper mower.

We had one of those mowers in the early 80's. Don't remember the brand. It had a rear 8hp engine vertically mounted that had a crank on it. You wound up the crank several turns then flipped a lever to release it to spin the engine for starting. It was steered with a tee handle and of course had the variable transmission with the disk. The metal disk was about a foot in diameter and about a half inch thick, connected directly to the engine. There was a hard rubber wheel about five inches in diameter that could slide back and forth for varying the speed, even reverse. It was way faster than modern riding mowers. I had a lot of fun on that thing.