polycord and yellow belt

[mlantry]

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.

[dodar]

I'd say ours is the cords walking around on the rollers.

[DonRotolo]

The worst thing that happened to our orange urethane belting is that students got this idea to cut and re-join it after almost every match "just in case". sheesh.

[mlantry]

Oh Don i never told u we only did it at the most twice a day

[quinxorin]

We've been using polycord since 2010, and honestly, no problems. As long as we follow the instructions and cut it 11% shorter than measured, it works beautifully. It doesn't just work for applications like collecting balls; if you want to prevent a motor from stalling, use polycord on a pully designed for a toothed belt, and the polycord will start to slip before the motor stalls. You can change its tension to adjust how much force it takes to make it slip.

The belts on our grabber in 2011 would fall off every once in a while, but that was more a symptom of the design of the rollers than anything else. It wasn't a problem, either; there were 4 belts on each side, and it only took 1 for the grabber to work. It was also the only part of the robot that worked at all that year, but at least it gave us something to be proud of, dog toys and all!

[470-RBTX]

The poly belting is some of the most durable stuff I've ever seen and used. 470 used belting from our Lunacy bot (which has endured 3 FIM competitions and countless demonstrations) on this years robot, and have had no problems with it. We just cut it to dimension and and rejoin it and it keeps holding strong, in the 3 years of us using that robot it's never snapped.

[Billfred]

Originally Posted by dodar

I'd say ours is the cords walking around on the rollers.

This is the problem we've had this year; we've tried to fix it by limiting the cord's ability to walk.

[MrForbes]

We first used it this year, it's been working fine for us, no problems. It did take us a little while to figure out how to keep it in place, we figured this out on our prototype and it's been working fine on our robot.

We're using a "comb" to keep the cords in place, at one end. They run on very simple ABS rollers. We used the connectors and hollow cord, and only about 3% stretch.

[Billfred]

Originally Posted by squirrel

We're using a "comb" to keep the cords in place, at one end. They run on very simple ABS rollers. We used the connectors and hollow cord, and only about 3% stretch.

Do you have a photo of this comb? (We used 5% stretch, though our belts are welded.)

[MrForbes]

sure....I have pics of almost everything!

[Duke461]

Originally Posted by Billfred

Do you have a photo of this comb? (We used 5% stretch, though our belts are welded.)

Second the picture motion. Our polycord was coming off our pulleys/rollers as well, but decreasing the amount of ball compression helped a TON, and we still could increase the amount of stretch in the polycord.
Something we considered but haven't done was switching over to rapid prototyping instead of pulleys.

-Duke

[MattC9]

We love our poly cord, we don't have a problem with walking, maybe once or twice at max (were using custom rollers with grooves cut in them) and the welds are strong as can be. We did a test weld to test its strength (put it in a vice and pulled on it) and it was amazing, after 3 students and a mentor pulled on it, all it did was stretch.

[FrankJ]

We are using Squirrel's comb. Except we made it out of 1/16" plexi. Works great.

[mathking]

Here is a picture of our "comb" for the belting. It will walk a little if a ball goes through, but it then walks back.

[Jim Wilks]

We are using 3% stretch on solid "welded" polycord. All seems well. What do others see as the advantage of greater amounts of stretch?