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Thread: Belt Drive

  1. #1
    So the procurement and design stage is going well and our new team has made a good start; however I am having a nightmare with sorting out the belt drive system - where can i find pulleys/sprockets?

    I am looking to get a 7:1 / 8:1 ratio using pulleys - preferably with a toothed belt. Building a bot with a strong pushing power; from viewing other bots i have learnt those with a belt drive are better when it comes to self preservation (allowing slip and less back emf issues with the motor).

    Currently have 10 inch wheels / 3300RPM motor and looking to get 15mph drive.

    Any direction in this area would be much appreciated!

  2. #2
    What weight class are you building for? I can't help you with supply sources but with toothed belts you are not going to get any slip unless you have one pulley with no teeth. In that case you are likely to get nothing but slip unless you design a fancy belt tensioning system; its usually better to have no belt slip and use motors and ESCs that can take the stress.

  3. #3
    Wheels will slip on the ground if properly geared. Let that be your clutch mechanism.

    As for belts and pulleys, look at 8mm HTD belts and pulleys. Can find them all over the place. RS components, HTD gears and various specialist places do them. I always just go to ebay though. Cheapest I've found.

  4. #4

  5. #5
    Again thank-you all for swift replies (yet again Gary!)

    So using the floor as slip - I will use the toothed belt system.

    The motors I've purchased are modern replacements for the GPA 750 - apparently their application is belt drive systems in wharehouse machinery (perfect suitor it sounds like).

    I have done some calculations (with a few pointers from some mech mates) and it looks like I can drive the wheels without a gear box - is this wise? I find the simpler the design the less can be damaged.

    Is there some magical formula regarding belt tooth count in relation to size and pulley teeth? Or am I hoping for the impossible?

    I am finding knowing the name/source/brand of items to buy far harder than the physical design!

  6. #6
    3/8 chain is all I us. Its light easy to buy you can buy plate wheels which reduce machining and bolt them straight to the wheel with m8 bolts and aluminium spacers.

    And gary is bag on gear ratio is key. Wheels should break traction well before breaking anything

  7. #7
    Are you going to the gadget show ? Plenty of use to talk to directly there

  8. #8
    Just a point... Timing belts and pulleys are expensive when compared to gears. I discovered this when designing my own HW. You can use then, I reccomend HTD 8, but just a warning about the cost.

    The PCD for gears is easy to calculate - Mod number X Tooth count = diameter (If the tooth count is 12 or greater)
    For pulleys I use HPC's PDF's - http://www.hpcgears.com/n/products/1...leys_belts.php - You want Heavy Duty Timing Belts & Pulleys

    And then plug the numbers into this calculator to get your centre distances - http://www.hpcgears.com/calc.htm
    Last edited by Eventorizon; 30th March 2016 at 21:27.

  9. #9
    You could work out a formula as the number of teeth x pitch will equal the circumference of the pulley however to be honest, you would be better dividing the teeth on the large pulley by the teeth on the small pulley and that's your ratio.

    You will almost certainly need a two stage reduction if you are using timing belts based on the available pulley sizes. Your other issue is that the pulleys are generally made from steel and the large ones weigh a hell of a lot.

    To be honest, I'd look towards a chain driven system. It will withstand a bit of misalignment, take up less space, the cogs are likely to be lighter and you can make a custom length of chain. Gearboxes can be wonderful but custom ones require access to a milling machine to get the required tolerances to allow the gears to mesh properly. Mind you if you know someone with a mill this can be a good route for a dependable system.

    Technobots would be my go to for chain / sprockets and gears http://www.technobotsonline.com/spro...and-chain.html

    Not sure if there's anywhere better these days. Check out the 0.375" chain. The 0.5" can be used and I have done in the past with a heavyweight but it's really overkill.

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