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Thread: O rings as drive belts?
01-26-2006, 11:03 AM #1
What is the ideal o ring material for use in low torque drive belt applications? The belts which came with the motorized spin grinding fixture are just about used up. I have tried regular buna rubber and viton in the past. Neither one lasted very long as a belt. Any suggestions would be appreciated.
01-26-2006, 11:21 AM #2
Look at Ebay item number 5079769423. I have used this type of material with good success on some of the machines that I have made. There are several people that sell it. It comes in several different sizes. Making the splice is easy if you take your time.
01-26-2006, 11:56 AM #3
Try www.habasitusa.com. They make a round urethane belting material that has a very finely textured surface finish. Just figure the actual length you need minus a certain percentage of stretch allowance(depending on diameter and length), cut to length and heat weld. Real easy and lasts for thousands of hours.
01-31-2006, 04:40 PM #4
Thanks for the advise. I bought a piece of the material from ebay and it welded up nicely. Only problem was that it lasts less than an hour with the small motor pulley (less than 1") I'm using.
The first crack appears on the outside of the weld after only a few minutes and grows steadily.
I'll try to get myself a molded belt in the necessary size.
01-31-2006, 05:02 PM #5
01-31-2006, 05:15 PM #6
always used O rings and never had any problems.
01-31-2006, 05:23 PM #7
Try McMasterCarr under urethane round belting. I work on convayors and this stuff is tough. you can melt it together with a lighter with excelent results.
01-31-2006, 06:08 PM #8
The Urethane belts are common in conveyor applications, as has been mentioned. I am not sure what a spin grinding fixture is, ie is this a high speed belt drive for a grinding spindle?
It is available in quite a few grades, the harder grades transmit more torque, but are stiffer (ie won't go round small pulleys) and the real strong grades have a non-stretch core.
But you would be looking at the softest grade probably.
Check your pulley diameters and compare them with the belting minimum diameter specs.
The joins are done with a welding kit. This is like a special set of pliers that holds the two ends square, and a teflon covered heating element (like a flattened soldering iron). When the ends are nicely melted, you squeeze the pliers together and lock them, leaving it to cool down. Carefully linish off the excess.
Can you weld them with a hot cardboard cutter knife, gas flame, cigarette lighter etc? Yes, but they will almost inevitably break soon after.
In fact, we don't even weld our own despite having the correct gear - there are still failures, we order them made to length - much the best option!
Generally the tension on the installed belt will be around 5-10%. Simple way is to wrap a long length to the setup, with just enough tension to remove the sag, mark the length with a felt pen, then deduct 5-10% of this length to give you the correct pre-tension.
Jim has mentioned Habasit - this should be top quality (Swiss!), there are several others too. Fenner is another brand.
I think the real secret is in ordering the belt pre-made.
Actually, urethane belting can be a frustrating product - generally because too much is expected of it. If you overload it, it will break, wear, jump off....
It seems very forgiving stuff, but even mis-aligned pulleys will wear it, because it is so 'grippy'. Having said that, you can use it for crossed drives, but don't let the belts touch where they cross.
Another thought, if this is a high speed grinding application, then you really will need a perfect join.
01-31-2006, 06:25 PM #9
Check out your local vacuum & sewing machine repair shop. Many of these units use o-ring type belts. They usually have a variety of different sizes on hand. I have one running the chuck on my valve grinder.
01-31-2006, 07:13 PM #10
I make these out of 3/16 diameter polyurethane if you can use that diameter. It's what I use with my spin fixtures, and they last a long time. Much longer than O rings.
01-31-2006, 08:59 PM #11
I need 3/16 or 5mm belts approximately 6"dia. or 18" long. My setup is adjustable for tension.
RJ, do you make your own? I have used your fixtures in the past (nothing better than a new Newbould indexer) and the original belts seemed to last forever. What material and hardness do you use?
I got some fairly hard polyurethane belting on ebay and welded it up with a shop made fixture. The welds looked good to the eye, but like I stated above they came apart inside of an hour.
01-31-2006, 09:09 PM #12
Norb... Glad you like my Newbould Indexer. I have started a forum just for folks who have used, or are using my tools.
Newbould user forum
I do make my own. You need a teflon heat blade to weld the ends together. If you give me an exact length, I can put one together for you.
01-31-2006, 09:19 PM #13
Norb, Reweld it and try it again. Make sure that you don't move it while it cools, if you do the joint won't hold. The ones I use are also on a pulley less than 1" diameter.
01-31-2006, 09:29 PM #14
02-01-2006, 01:42 AM #15
The heading "O rings as drive belts" makes me think of the Swamp Rat that Don Garlits broke 200mph(?) in. In an effort to reduce drag on the dragster he used Kevlar vee-belts as front tires, I think only 10" in dia. I think they were good for one or two 1/4 mile passes.
02-01-2006, 05:12 AM #16
I use belts of urethane (green color) and I never have problems. I weld them with an electronic iron, first I cut off to square, then joint to the iron both sides and when they fuse I press until solidifies the union. Then clean the joint. No problem
02-01-2006, 09:26 AM #17
you may want to check at a conveyor dealer, live roll comveyors use pu round belts in large numbers, those look molded with no noticeable seam and they certainly need to last a long time
02-01-2006, 12:03 PM #18
I got Urethane belting from my local belt distributor - it is inexpensive and comes in lots of diameters.
I was taught how to make a belt with it in a watchmaking class (these belts are used on watchmaker's lathes).
You need a piece of spring steel and an alcohol lamp or candle. It is best if you hold the spring steel in a clamp. You heat the spring steel with the alcohol lamp until it is quite hot. You then press the two ends of the belt onto the steel until they mushroom. You can then slip them off the spring steel and bring them together - do this carefully so that the are lined up accurately. Hold them together until the joint cools and then use a bench grinder to remove the burr. There are fancy fixtures for doing this but this technique works well and if you do it a few times you will get the hang of it.