Quote:
Originally Posted by magnets
Our second question deals with the drum itself. Is winding up the cable in a nice way something to be concerned about, or will it be okay to just let it wind up any way it wants?
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I'll bite on this one. I think my brother put it best when he described cable as the solution that you go to when all other solutions won't work. I would work very hard to avoid cable. It may seem cool, but you have to pay attention to a lot of stuff when designing a cable system.
When you spool the cable on and off the 2 spools, how are you going to design it so that the cable length doesn't grow or shrink? I have some not very fond memories of dealing with cable tension on 254's 2011 robot, and all the controls headaches that the solution caused. If you naively spool cable onto a spool without proper cable management, the cable can wrap over it's self, and take up more length when spooling than unspooling, which is bad. If the cable doesn't wrap over it's self, it will walk horizontally across the spool, causing the cable length to also either grow or shrink. If you then decide to ignore this problem and brute-force a solution, you need to either leave slack in the cable and prevent it from falling off of all the pulleys or tangling on the spool and/or add a spring tensioner in the system.
In 2011, 971 used timing belt the same way that 254 did in 2013. The really nice part about the system was that there was no spool and the belt run was designed so that it didn't change length at all while the elevator moved. You can do the same thing with 25 chain if you don't like timing belt. The end result was very compact and clean, and I would highly suggest looking at doing something similar.