What size inner tube will produce rubber bands with 8" diameter?

Prof Wonmug wrote in news: snipped-for-privacy@4ax.com:

Call a truck/tractor/farm-equipment place. They'll know what you need right away.

I generally dislike duct tape and its many wayward applications, but I think a few turns of it may do it in this case.

Harbor freight has a wide assortment of cheap wheels/tires that should work well...

I called 2-3 tire dealers. None of them could tell me how to determine the cross section of the air chamber from the numbers on the tube box. I guess they don't work that way.

I bought a tube labeled 700/750 R15/16. I thought it might fit because the tires on my car are about 8" wide and 6" thick (rim to tread). It was way too tight. The bands had a diameter of just under 5", which meant I had to stretch it to double it's resting size. I couldn't do it. Apparently the tubes are designed to be about 30-50% smaller than the inside of the tire.

Then I realized that the width (W) of the air chamber when the deflated tube is laid flat is just half of the circumference (C), which means I can calculate the diameter (D):

D = C/pi = 2*W/pi

The width of the tube I bought was about 7.75", so

D = 2 * 7.75 / pi = 4.93

Which is about right.

Based on how hard it was to stretch the car tube from a 5" diameter to a 10" diameter, I figure I need a tube that will yield bands with a diameter between 8" and 9". But I don't know how to calculate the band sized from the numbers on the tube. So I made a little spreadsheet to calculate the diameters from the widths planning to go to a tire store and measure. Here's the table

width (C/2) diameter 6.28 4.00 7.75 4.93 The auto tube (700/750 R15/16) 7.85 5.00 9.42 6.00 11.00 7.00 12.50 7.96 A R20-1400 tube at one tire dealer 12.57 8.00 13.35 8.50 14.14 9.00 Upper limit on size 14.92 9.50 15.71 10.00 17.00 10.82 A R24 tube at one tire dealer

I found an R20 and an R24 tube at one dealer. The R24 is too big. The R20 might be too small. I have one more place to try for an R22./

I don't care much for duct tape, either, and I think it would not be a good choice here, but your suggestion got me thinking and I came up with a couple of alternatives.

1. Rescue Tape. I'd never heard of this before. If it has any thickness at all, it could be just the ticket.

1. Rubber Bands. Several companies make custom rubber bands. Here are a couple:

I looked into new tires. There are a couple of problems. If they are inflated, then they will eventually lose air. They there is size. The one you show for $4.99 looks too wide. It gives every other dimension. The wheels of the cart are very narrow -- about 1.5" and very little clearance. Then there's the axle size.

I paid about $15 for the tube, but I'll get 15-20 bands from one tube, which works out to about $1 each. ;-)

why not just cut strips from the tube you already have and glue them onto the wheels? make 'em too long, overlap the ends, then make one slice with a razor blade and remove the little pieces. et voila. Doesn't cost you a thing, unless you need to buy glue. I'd probably try either contact cement, or automotive trim cement (the 3M yellow snot stuff,) whichever you have handy.

nate

I was a little reluctant to use glue in case I ever needed to remove/replace them, but maybe you have a point. I've never used the trim cement. Is this it?

No, what I think I'm remembering I believe is the 08001. It's yellow, comes in a tube, and is about the consistency of mucus from a really bad head cold. It's like contact cement's evil cousin.

nate

Great trim adhesive:

We usually just refer to it as 3M Yellow Weather Strip Adhesive. It is, imo, far superior to the black adhesive. Has a lot of uses

String a piece of rope.Lift up the container and hook it on the rope and pull the container to where you want it. cuhulin

You mean like a dog runline??

Yep, like a dog run line.You can use rope, or wire, or cable.Rig a little grooved pully wheel on the trash bin. cuhulin