How durable does this need to be? Super temporary...or like, every night for a few months?
Hello Chicago Dave.
It can't exceed 300$-350$.
The mechanism should be kept for ten shows this fall maybe more next year. So it is not supposed to be super temporary. We will only ajust its length to the stages we will visit in the future
What's the diameter of the pulley? Pi * d will give you the amount of linear movement for one revolution of the pulley, assuming no slippage. From that you can work out how fast the cable will move (RPM * Pi * d).
Speed of a walking man = 3 to 4MPH..say 3.5MPH. 3.5 * 5280 /3600 = ~5.1 feet per second.
Assuming a 4" diameter pulley and taking Pi as 3 for ease of calculation, one revolution of your pulley will move the cable ~1 foot. You need ~5 ft per second for walking speed, so 5 revs/second = 300 RPM. You'll have to experiment with the RPM to match the walking speed of your actors. 300 RPM seems a bit fast. I'd start with 150 RPM and increase it, if it's too slow.
Torque will depend more on the amount of friction in the system and the weight of the moving parts than the speed.
Thanks for your explanations.
3 light coat hangers will be moved, their overall weight won't exceed 1kg.
Pulleys will be machined in aluminum by a friend and bearings will decrease friction as much as possible.
Until now I have only used cheap steppers with small stall torque and low speed.
So, I wish I could find a strong stepper, even with specs beyond my needs, and not to worry about its capabilities.
would you have an idea of the stepper I could pick to use with the big easy driver?
Do you think 3 Nm cnc machine steppers will do the job?