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Thread: custom length belts for pulleys question

  1. #1
    Join Date
    Mar 2018
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    Default custom length belts for pulleys question

    There are ton of videos on welding urethane belts together by heating tips, pressing them together then after cooling removing the excess with a knife.
    Now I'm no expert in belts so i don't know if this is a practical approach used outside of the field of hobbyists and can be a reliable solution for longer than a month or two of use.

    All I can see is my pulleys are going to be rotated with a 1000-2000 RPM motor, with a constant RPM controlled by a hall effect sensor, there is going to be almost no torque as one of the pulleys just has a 200 gram optical element attached to it and all the pulleys are on bearings.

    I would first like to know if urethane belts are the way to go here or if they are unreliable.

    If for custom length closed loop belt I need I should just go with welding the belt or whether it is unreliable. I can that that at least for reinforced belts welding probably doesnt weld the reinforcement wire.

    If for my described application I should use round belts or V belts.

    That's all and thanks again.

  2. #2
    Join Date
    Mar 2015
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    Cambridgeshire, England
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    Default

    That method works well for non-reinforced urethane belts and, done correctly, is as strong as a 1 piece belt. It is the way professionally made custom length round section belts are made, so it's not just a hobbyist method, although the tools the professionals use are a bit more sophisticated than a hobbyist will have at their disposal.

  3. #3
    Join Date
    Mar 2018
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    Thank you for the info.

    Any suggestions on choosing v belt or circular belt.
    Price is pretty similar and v seems to reduce risk of slipping and has better grip.
    Cant find a disadvantage of v belts.

  4. #4
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    Mar 2015
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    Cambridgeshire, England
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    V belts require very precisely shaped pulleys in order to work correctly, round belts are a lot more forgiving. As you've said there's almost no torque being transmitted, I'm not sure I understand why you're concerned about slippage. If you need to maintain accurate positional control, then you need to be looking at a different transmission method, e.g. toothed belts or gears.

  5. #5
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    Mar 2018
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    Thank you.
    Below comments are again just ideas from someone with limited engineering knowledge. Please correct me where I'm wrong.

    I just assumed slippage might become in issue at these RPMs if there isn't enough grip, no other reason.

    There can be some room for error, as long as dynamically adjusting the speed via say a magnet and a hall effect sensor to make it rotate at a given RPM will fix it.

    I'd imagine tooted belts wouldn't provide much advantage here besides any backlash or slippage when the system begins rotating but I don't see how it would be more precise after the speed is reached and the speed and load remain constant during operation.

    If anything I am more concerned whether ordinary BLDC motors themselves can provide reliable constant RPMs, not the belts and pulleys. One of the motors I ordered is used in car CD players and the other in small quadcopters.

    I've considered gears but that will require custom CNC parts with added wear and noise.
    Last edited by shoujin; 03-18-2018 at 10:32.

  6. #6
    Join Date
    Mar 2018
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    96

    Default

    In practice is it better to use round groove pulleys or v groove pulleys with round belts?

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