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Unread 09-01-2015, 13:43
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Re: COTS Elevator in Action

Quote:
Originally Posted by lynca View Post
Thanks for the feedback.

There are definitely tradeoffs between a chain-lift and cable-lift. Let me see if we can summarize the differences.

Chain-lift:
handles more torque but heavier
needs more structure and pieces to implement

Cable-lift:
lighter but has the potential to slip or snap the cable with too much torque
easy to implement but more prone to failures


Teams can see some of the differences between the robots in Ri3D.
Team Indiana is a Chain Lift
Most of the other Ri3D teams are cord-lift

What do you base the thought that the cable lift is more prone to failure. I've seen chain lifts fail too and when they do it can be difficult to fix them quickly.

Properly designed they will not slip. Again I've seen chain lifts slip if the design is not done properly and tension not properly maintained.


As far as strength goes, chain does have a slightly higher ultimate strength that is for certain but don't discount the strength of paracord, the 1/8" stuff we choose from Home Depot has a 160lb working limit or ~3x what we determined we needed and most have a break strength of between 3 and 4 times their working limit. The chain I found on Amazon is rated for a 900lb break strength.

I'd rather have a cord fail than cause damage to the mechanisms and replacing the cord can be done very quickly. Replace it every few matches if you are afraid it will fail or you see signs of abrasion.


Now granted our machine had a very short life but when we discussed what we had done differently none of us even mentioned that a chain would be a better choice. A way to power it down would be a possibility of an addition.

Again my regular team has done chain lifts in the past and the fact that they are doing one for this season just makes me cringe. I would never choose to to a chain lift again after my Ri3D experience with a lift using paracord.
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