[Arm-netbook] physics analysis needed of belt-driven pulley system

Luke Kenneth Casson Leighton lkcl at lkcl.net
Sat Aug 19 11:52:42 BST 2017

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On Sat, Aug 19, 2017 at 11:38 AM, Hrvoje Lasic <lasich at gmail.com> wrote:
> Ok, so correct me if I am wrong but you are asking some mechanical
> questions.

 mechanical / physics, yes.

> so, I speak in general now and if you have question ask deeper.
> Force needed to drive whatever you want to drive will be exactly the same
> at the end part of system.

 on the print-head yes.  but because of the doubled speed, the DRIVE
end *NO*, the force is NOT the same.

> But efficiency of belt system could be slightly
> different then efficiency of `non` pulley system (whatever it is). But
> again, efficiency could be neglected for sake of easy of calculation or you
> can put around some value that (guess) could be 80-90%.

 i'm assuming that there are no significant losses around pulley bearings.

> What you will be looking is gear ratio on pulley that could alter
> force/speed ratio and same thing on other system.

 the gear ratio on a single pulley system is 2:1.

> also, you will be looking on backlash.

 *thinks*... backlash should be reduced (halved) due to the better
effectiveness of the pulleys - assuming that there is no "play" in the
bearings (we can assume decent bearings / idlers).


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