how area teams making these beautiful and perfectly tension’d pully belts (like for turret shooters)
is there a way to couple belt ends together to make a perfect length belt?
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Uhh our team had one long belt for our shooter and we ironed it together
like, cloth ironed?
Most of the belts you see in FRC are the result of using a center-to-center calculator, some form of tensioner, or both! Custom assembly and sewing or combination of belts (toothed, not like, polycord roller belt) is very uncommon given how variable the sizes you can buy from VEXpro and other suppliers are, and to make your life easier WCP (unsure about other vendors) has a calculator for belt C-C.
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Yeah the iron you use on clothes lol
We took a kitbot drive belt that was too long and cut it long enough for 3 overlapping teeth, cut the teeth off and contact cemented it and that held through our event.
+1 to what people have said here - it’s a almost definitely a really bad idea to try to make custom timing belts. For urethane/polyurethane belting, welding the ends together with an iron or heat knife (there are many threads here for good techniques) is fine, but with timing belts you should use a calculator to space the holes according to COTS belt lengths and pulley sizes. My default is the WCP calculator linked above.
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There are lots of belt center-to-center distance calculators available for FRC, including one in my design spreadsheet. They all do more or less the same thing: you say what size pulleys you’re using and the approximate distance you want between the pulley centers and it will tell you the exact distance apart they should be for the belt to be properly tensioned. If you can hold that distance to within a few thousandths of an inch of the value the calculator says, you should get a well tensioned belt without needing a tensioner.
If you aren’t able to hold those tolerances, you need some part of the belt system to be adjustable so you can tension the belt once everything is installed. This mobile part is called a tensioner. Depending on the design, sometimes one of the main pulleys will be adjustable, other times you can add an adjustable bearing or smooth surface to push on the back of the belt so it stays properly tensioned.
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https://practical-parts.com/ is an affordable tool to align round neoprene belting. You can do it with a soldering iron or other improvised heating solutions and make your own alignment tool.
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awesome solution for urethane belting! do you have anything for timing belts?
If your design requires multiple cycles of the belt like a drive train, design to the belt lengths available. Use a center distance calculator like this one from VEXPro . If you are using belts on an elevator you can terminate the belt on a stage of the elevator and use cut lengths.
If for some reason you cannot design around an existing continuous length (this should almost never happen), you could by a welded-to-length timing belt from BRECOflex, however keep in mind that a welded timing belt is roughly half the strength of a continuous belt.
I have to emphasize again in any application for FRC where you have to have a continuous belt, you should be able to design to a standard length. As the post above mentions you can use an open-ended belt to drive linear motion mechanisms like elevators that don’t have to travel a full loop.
I would advise you to reread some of the posts in this thread again. Welding timing belt is not a good idea. Properly designing your belt runs is how you get those “perfect” timing belt runs. There is no welding involved.
Remember that generally a good chunk of the strength of the belts we use in FRC comes from fiber backing (kevlar, fiberglass) which is strong because it is unbroken. If you cut and reattach that you are sacrificing that strength and creating a very clear weak point.
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If you really need a belt that is not continuous there is a product made for bicycles called split belt, I think its made by veer and assembles using rivet style things. The caveat is they look to be very expensive only come in specific sizes (though it looks like they can do custom lengths) and don’t seem to be any standard profile that I can find so your stuck with the very limited range of pulleys they offer.
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Even though we can machine to a ten-thousandth (if needed), we almost always use slots and cams to fine-tune the geometry of our belts and chains. (1) these parts aren’t always made to those tolerances and (2) they can stretch.
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As others have posted in other threads on belts throughout the season, vbeltguys.com carries a wide selection of belts. This is a source that was recommended by 3847 - Spectrum in their build blog this year. Once you get the hang of their numbering system, you can find belts in a large variety of lengths typically down to 1 tooth increments for shorter and medium length belts and 5 tooth increments for longer belts. We have used them extensively this season. There selection and prices are excellent.
Before you cut metal, you should be sure that you have a belt that is going to work with the C-C distance and pulleys that you have designed for (using one of the calculators that others have posted). We make sure that the belt we want to use is available / ordered before sending the parts to the machine shop. But we have not had an issue with the belts fitting when the calculations are done correctly.
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First it depends, are you speaking of timing belts? Those have cogs on them to prevent slippage and are specific distances and there are several sizes out there.
If you mean poly belting like many of the teams here are talking about(ie melting them together)
Team 931 developed a way that required a student and a mentor.
Tools:
1 heat gun
belt cut to length + 3 inches to join it.
heat the belt to a little past the midway melting point, BUT NOT melting,
while still hot:
complete the loop,
overlap the other end
smash the ends together ( we did it with two scrap aluminum extrusions)
let cool
This allowed us to create a relatively strong belt with a close fit for indexing purposes and it did transfer loads as well, cant say how it would have fared driving a flywheel however.
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