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Looking to drive a series of belts for lateral translation using a series of pallet bands (92" rubber bands about 1" wide). Approximately 16 bands would be driven by a singular band as illustrated (roughly) below. I am hoping to use a geared up stepper motor with planetary gearbox that will respond to sound levels to effect the speed of translation. I am wondering if anyone has any advice about using rubber bands as belts in a pulley driven system, ideal arrangements for transfer of power, pulley types etc.

upper zig zaging band for power distribution from stepper motor, lower bands only need to slowly tanslate

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I would seriously consider using separate motors for each element. A drive train as long as that has a very high chance of causing a lot of practical problems with friction, slip and backlash as well as the difficulties of keeping everything aligned.

The chances are that a single motor would need to be significantly more powerful than the sum of individual ones due to the additional resistance of the shared drive system and the additional complexity is likely to wipe out any cost savings of one large over several small motors.

I would also be concerned about hanging the mounting point directly on a rubber belt of such a large span, even a modest load is going to cause significant sag of the belt which will further exacerbate problems with friction and alignment. This should be resolvable by using rails to support the weight of the moving elements.

If having a common drive is essential then I suggest that using a horizontal shaft driving each belt with bevel gears or a similar right angle drive system is likely to be less trouble.

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  • $\begingroup$ Thanks Chris. I am in agreement with you. The issue is that the budget for the project is fairly small (10k). The current scheme involves about 300 of these catenary ball chains in series through a long former subway tunnel. This means that each of the 300 has two belts from which two points hang (3 catenary loops rather than two as in the drawing above). $\endgroup$
    – user15921
    Feb 23 '16 at 4:35
  • $\begingroup$ The movement can be very slow and subtle, I was thinking of using stepper motors with some serious gearing 100:1 to gain torque from a lower cost motor. Also, what would you think about using 1/8 or 1/16 inch steel cable and v groove pulleys to prevent more sagging? Basically I am trying to find the cheapest dumbest system for a very slow gentle translation of the hanging points. Many Thanks. $\endgroup$
    – user15921
    Feb 23 '16 at 4:42
  • $\begingroup$ I was assuming that the mounting points would go all the way round the pulleys but from what you have said it sounds like they will just go back and forth between two points ie the motor will periodically swap between forward and reverse, is this correct ? $\endgroup$ Feb 24 '16 at 14:52
  • $\begingroup$ Chris, Thanks for the Help. You are absolutely right about the need to carry support the hanging load somehow. I was thinking that if I were to extend the bolt for the pulley and then run a tension cable between those points. The issue here becomes about how to transverse with out getting stuck at the anchor points. If I were to use a long fishing leader with swivel joints I think I could get around this. I uploaded a quick drawing here. Thanks again. <imgur.com/8tefxmy> $\endgroup$
    – user15921
    Feb 25 '16 at 14:27
  • $\begingroup$ Sorry, this links should work. <i.imgur.com/8tefxmy.jpg> $\endgroup$
    – user15921
    Feb 25 '16 at 14:51

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