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Unread 03-13-2012, 04:35 PM
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Re: polycord and yellow belt

Quote:
Originally Posted by S.P.A.M.er 17 View Post
Our robot used the hollow polycord, joined with a barb at first. The barbs would snap out over repeated use, and finally we decided to weld them together. They have not broken since, and we have already gone through a regional. I would definitely suggest welding them for anyone considering to put polycord on their robot.
Same here. The barbs were good for prototyping, but are no where near as strong as a welded connection. We made some special tools to help weld it and remove the flash.

The only problem we had was with the balls wanting to push the cord off a pulley under significant compression. We had to greatly reduce the compression to make it work, but I think our pulleys were also not as well machined as they might be. Some pulleys never came off and some always did. We will need to examine them when we get the time and improve our design.
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Unread 03-13-2012, 05:39 PM
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Re: polycord and yellow belt

we used the hollow poly cord with a barb and it hasn't come apart yet, but we were having quite the problem with it slipping right off our rollers, even though it's 8% (i believe) short. what we did was added a zip tie across it that allowed for just the right amount of increased tension in the middle and it didn't interfere with functionality at all! I recommend adding some sort of tensioner in the middle of the two ends of the loop of poly cord to avoid slippage problems, but other than that i've loved the poly cord. apparently in 2006 we used a belt that had to be sewn together and it was absolutely awful, it kept wearing down and bunching up and they had a ton of problems with it, that's why we went with poly cord this year. it's a good choice!
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Unread 03-13-2012, 11:26 PM
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Re: polycord and yellow belt

We are using 3/16" solid polycord and it works great. Most teams use 1/4" or larger diameter but we are on a tight budget so we went with the 3/16". We are using 1.5" pvc pipe with endcaps for the 3 rollers and the aluminum rod that came in the KOP for shafts. We use a heat gun to join the ends and 5 % stretch. All this is driven by one window motors mounted directly to the pvc endcap. To guide the cords a volunteer sliced up some pvc connectors to make rings that fit over the pipe. To hold the rings we glued the strips of clear vinyl tubing (with PVC cement). I'm pretty sure we don't need the rings and could just glue on the tubing strips. The system is student built and none of the rollers are parallel with each other. The saying around the workshop now is.."polycord is VERY forgiving".
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Unread 03-14-2012, 11:43 AM
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Re: polycord and yellow belt

Quote:
Originally Posted by mlantry View Post
From what I've seen most teams (including ours) are either using yellow belt or polycord for an elevator from the ground to the shooter/ launching device. What is the worst thing that has happened with your teams cord whether its snapping or something else. I just curious if teams have problems with these things.
worst that has happened is that when our holder/lifter fills up, the polycord derails... so our secondary driver has to keep a close eye on it. other than that, no problems
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