Making a Triple Helix style climbing rope

Technical Technical Discussion
#1

During the quarter-finals of our last competition our Pilot looked out over the field and noted that 3 of the teams of the field were using our climbing ropes, one of which was on the opposing alliance. After seeing so many posts about ropes failing in competition, 2363 has decided to share our method for making ropes with the FRC community.

Materials:
Solid braided rope from West Marine, 5/8" diameter.
3mm Spectra Speargun line
Plain backed loop side velcro
Upholstery thread
tape

Tools:
Scissors
long, pointy stick
sewing machine

Instructions:
Watch the instructional video we put together last night.

The length of the spectra rope will be specific to each team’s robot and climber. We use three knots in our rope: the figure 8 knot in the spectra, that keeps the core from pulling through the big knot; the big figure 8 knot, that rests on the davit fingers; and a slip knot just above the velcro patches, that allows a couple wraps around the climber shaft before starting to climb. Each of these knots consumes a surprising amount of rope length. You can figure out how much for yourselves, experimentally. If you are using some other type of loop knot at the bottom of your rope, be sure to use a version that’s suitable for spectra rope. Spectra is very slippery, and knots that work with other types of rope will pull out of spectra rope. As noted in the video, the only failure of our rope was one match where the spectra rope pulled through the big figure 8 knot. After that we added the stopper knot to the spectra above the big knot.

#2

Looks like you guys got it figured out. Luckily, we’ve avoided any issues with our rope failing; our robot has a semi-active rope catching mechanism, you can see it in action in detail here: https://youtu.be/MA3WYanS0Q8?t=31s and in-match here: https://www.facebook.com/Biohazard4050/videos/1363280017079884/

#3

I was unsure about whipping partway down the rope, but the Q&A does say that any cut end can be whipped, so good there.

I think the only improvement would be if you could thread the spectra through the core as well instead of beside the core through the cover. Then you’d have that much more material the davit would have to bite through to get your load carrying line.

#4

Interesting. This is only the 2nd of its kind that I’ve seen (the first being ours). I like the simplicity of the 1x1 + bow tie cone.

#5

Todd,
125 used a similar rope construction with a different method in last weekend’s Greater Boston district event (MABOS)

This rope from McMaster is ~1/8" spectra core with protective braided jacket (~1/4" OD)

  • 36965T15

We tied our knot up top (bowline), cut to length per robot hang drum height, then measured down ~1’ from the knot and remove all braided jacket below, to be left with something similar to your additive construction.
To finish, we frayed the bottom ~3-6" of exposed 1/8" Spectra to engage with our velcro hanging drum (no velcro on rope required!)

It worked great for us and we’ll continue this method going forward; however, we’ll probably be using a fresh rope for each new competition to be overly safe.

#6

Very interesting. Got any photos? Interested in seeing how you attach up top.

I wonder why there is such a dramatic difference in load ratings of the rope. I’d expect yours to be WAY stronger than ours. (Wait. Just saw the 5:1 safety factor. It IS way stronger.)

#7

Given there’s a bowline at the top, they’re doing a lark’s head knot over the davit fingers. Perfectly legal as long as the two standing lines of the loop pass over the top of the knot so there’s no way it could slip over the pin.

#8

Very cool!

In much the same way you ‘cored’ bigger ropes with the spectra line, we ‘cored’ our rope with a bit of elastic. This serves the same function as a slip knot, but no one has to remember to tie it to the proper length every match. I’m not sure if this can be integrated into the spectra rope easily (perhaps elastically retract the spectra inside the ‘sheathing’ rope?), but it might be worth considering to eliminate the reliance on human preparation/skill to get a climb.

http://i.imgur.com/QzaW9ec.jpg

#9

All the taped “wipped with tape” was tagged illegal at our regional and had to be removed. Cited as adhesive.

#10

Emphasis mine

This is the way I read it: The whipping material in the last 4 inches is exempted from the requirement to be entirely “flexible, non-metallic fibers”. Instead, it must be “flexible and non-metallic”. Therefore there is no rule that the whipping material must be fibrous. Adhesive tape, though it is an adhesive non-fibrous material, is generally both flexible and non-metallic. There is no rule outright allowing adhesive materials on the rope. I don’t see why this would have been ruled illegal. Maybe someone who was there or the LRI who made the ruling can explain otherwise.

#11

We didn’t buck the ruling as it didn’t end our day. Our rope was some material that when heated -melted. Removed the tape and moved on.

#12

This thread completely slipped my mind with the grind of competitions, better late than never I guess?

Please forgive the zip-tie that was constraining yet-to-be handled frayed outer casing ends.

Ended up using this rope through 3 competitions. We’ll have a new one for worlds.

Imgur

//can’t imgur don’t care to figure it out.

http://imgur.com/hZjdBCh