The other day we were finishing somethings on our robot, 3750, and we’re using a winch to pull up our arm. For this we of course are using rope, we’re currently using some 1/8" nylon rope but originally we had some 1/8" twine we were using and it kept braking. I work up at a boyscout camp and teach things like knots and rope making so I took the 1/8" twine and made it into 3/8" rope. Would this be legal to use? In my opinion yes because it is something we manufactured with allowed materials, but we wanted to be safe and use the nylon. So what do you guys think?
I think it would be legal, I have wanted to make something that uses something like braided rope or string whatever we were allowed to use but, so far we haven’t had the need for string on any competition bots.
If you have 1/8" (3mm) cord around, why are you messing with twine? We’ve used the 3mm cord from REI on robots (when legal) for years and it has always been more than strong enough. Just wondering…
Another interesting use of the allowed rope is to make a net.
So long as the individual purchased strand of rope material meets the materials specifications for diameter and length, there is no issue with using that material to make your desired mechanism (in this case, a thicker rope).
The caveat to this is that it will be up to YOU to PROVE to the inspector that the individual strand was purchased as such (i.e. you can’t purchase a thick rope and say its individual strands meet the requirements…) as well as PROVE that the individual strands meet the size requirements. A very strict inspector may require you to unthread your rope if you go to inspections unprepared.
I’d also post this on the FTC Q&A just to be sure.
If you’re looking for strength, something you might want to look into is using the “plastic-coated wire rope with a bare wire diameter of 0.03125” or smaller” as they call it in the rules. We bought a short length and it was very strong, but surprisingly flexible; you should be able to use it in a wench. But if the rope works for your purposes, stick with it.