Making continuous rubber belt

I need to make a continuous rubber belt to join two home made pulleys. I used large O rings at first, but I had to make one of the pulleys larger to reduce the speed, so the largest O rings at the HW store no longer fit. I then tried surgical tubing, shoving a short section of cut off O ring into the hollow ends. That had some promise, but they eventually slipped out. A standard V belt is too stiff and needs a pulley profile that is too hard for me to make with my lathe skills. I need something round and stretchy. Anyone have any suggestions?

Depends. What is the necessary diameter of the belt? Would it be possible to use a cross-section of an innertube (bike, motorcycle, car, truck, big freakin’ truck)? If you were truly looking at O-rings, i think you should be able to find an innertube that suits.

Head over to for the electronic version of what used to be the Thomas Industrial Buying Guide and Register. You should be able to locate an industrial supplier for the specific O-ring size you need. The problem may be dealing with them, unless you have a business entity-many shops are trade only. Good luck

I need something about 8" in diameter. I was able to find a 5" O-ring at my HW store. The inner tube idea is interesting.

A good office supply store should have heavy duty rubber bands in the size you’re looking for.

Not sure what kind of load you are putting on the o-ring, but there are splicing kits that you can make your own o-ring.

Loctite 495 is a cyanoacrylate-type adhesive that will bond most rubber materials together very will. I doubt you can buy it in a store but you should be able to order it online.

Loctite 495 and cyanoacrylate, Superglue, will make good bonds. But the Loctite has a rubberizing agent in it for flexibility. A small bottle the size of a Superglue bottle will run you $20.

Any idea what diameter of cross-section you need?

About 3/16"

A good place to look for stuff like this is McMaster-Carr. They happen to stock continuous lengths of hollow-core urethane belting, with connectors, in sizes down to 3/16". Or try the rubber belting. Or the coiled spring. All pretty much exactly what you need.

That looks like just what I want. Can’t find the couplers on their site however, even though they mention them on the description of the hollow-core urethane belting.

I suggest using flat leather belting. This can be joined nicely with sinew lacing. You will need crowned, (convex) not grooved pulleys. It will not stay on a flanged or grooved pully. The crowned profile should not be too hard to cut freehand, as it is not terribly critical.

When they mention the connectors, you should be able to click on the part number and get the conenctor information. They’re on page 994 of the online catalog, right next to the belts themselves. This link should go directly to the catalog page.

Edit: and, of course, you can search for other types of belting to see if they sell something that would be even better for what you’re looking for. McMaster’s got all sorts of oddball hardware stuff.

Those will need crowned, rather than grooved pullys too. In fact, because they stretch so much, and have such good traction, they will climb out of a groove much more readilly than flat leather belting.

Have you gone to your vacuum cleaner repair man? He might have what you are looking for.

Thanks for all the pointers. Mrs Blather’s motorized, industrial strength yarn winder is going to be great.

Swimming pool stores often have good sized ones in stock, too.

Why not a car parts store? They have all sorts of belts in multiple sizes.

I order from these guys "precision associates almost daily. Just about any size o-ring you want in any material you want.