How to bundle up string for Horiz. Expansion

I’m just wondering what is the best way to bundle up the string on a catapult-like horizontal expansion system so that it doesn’t fall off during the match. I’m looking for ideas, and I’m curious what people have come up with.


I’ve seen a few different ways. Some robots use a spool of sorts, though that often makes it difficult for the string to fully unspool. Some have some kind of “box” made of c-channel or polycarbonate. Some just rest it in an upturned c-channel. There are a million ways, but the simpler is usually the better.


Our team spooled the string onto the projectile like a yo-yo. Doesn’t get as much air time but rolls across the field


You seen a fishing rod cast? Replicate that.

I think that I can figure out a way to use a U-Channel like the catapults “basket.” Thanks everyone for the ideas. :slight_smile:

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Another thing we experimented with today at our tournament was braiding it loosely with some kind of magical slip-braid that usually unravels nicely. It was kinda satisfying, but it didn’t actually unbraid all the way.

(This was last second expansion bit we built during the comp, unfortunately we ran out of time to make sure it was good enough to not DQ us).


Thats actually pretty smart!

We had to remove the string for the finals because it kept falling off or getting yoinked off of the robot by another bot as they went by.

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As a boater, sometimes you need to throw a line that is attached to a life ring / float to someone that is overboard. Or if you are a sailor on a sailboat sheet lines need to run clean while tacking. Smooth flow of the line is important.

The secret is a figure 8 “flake”

You would create a tray on your robot, flake the line, and then attach the weight to the end. When you toss / fling / drop the weight, it should flow smoothly off the tray.

(I’m assuming you are using some form of braided line)


Oh that makes sense. We’ll try that. Thanks!

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Who knew that sailors from the 1500’s could help roboteers in 2022?


lol. As a sailor myself, I knew some sort of coil/running knot would do the trick