Best tensioning systems for rope on a cascade elevator?

Our team used the Thriftybot clamp tensioning for the rope this year but found it quite frustrating and slow to use. If anyone could post a good alternative that would be great.

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1323 uses rachets for their elevators. There is a good view of it in their 2019 Behind the Bumpers and I believe they have a similar mechanism in their 2023 Behind the Bumpers. Behind the Bumpers FRC1323 Madtown Robotics 2019 Competition Season - YouTube
Behind the Bumpers | 1323 MadTown Robotics | World Champions - YouTube

We copied the rachet this season and it worked amazing. 10/10 would recommend:

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@R.C showed some samples of an FRC designed rachet that fits the standard hole pattern, both online and while at champs. I’m sure he can provide more details, let’s just hope we caught him in his sweater today.

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I know I’ve been hyping these up but they came in a few weeks ago. They’ll be up on the site starting next month as we start rolling out new products and cleaning up the site

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Me waiting for the rachet plates this season:

Happy to hear you got the issues sorted, they will be a such a cool product.

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Cast housing? Steel?

There are lots of clever splicing techniques for spectra cords online, but this looks like a better solution.

Splicing is pretty neat but a simple bowline knot is perfectly sufficient for FRC.

I’d love to see how y’all used them @GPGARY. A picture would be good just to see how they were implemented on your robot so I can help offer advice.

Sure thing! I’ll give some photos tomorrow when I’m in the shop

An eye splice doesn’t solve the issue of joining the ends. A loop splice doesn’t solve the problem of tensioning, as it is not adjustable. We initially considered using the same techniques as are used for UHMW standing rigging on sailboats (Making Dyneema Deadeyes — Rigging Doctor) but abandoned this after realizing that we had no room for the splice tails in the system. The bury distance for 1/8" UHMW is 7.5", so there’s a diameter increase at each end that causes a “bump” as it rolls over the sheave. Theoretically, you could increase the bury distance and make the entire line a double-braid, but that’s a lot of work when knots are strong enough. And when knots are strong enough…

While not pretty, off-the-shelf turnbuckles work for the job of tensioning. Jam nuts prevent the turnbuckles from coming loose.

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As an offseason project we decided to test out using timing belt for the “rigging” in our cascade elevator rather than rope. This took a little time in the design phase laying out the clamps based on the teeth, but eliminated the need to tension anything. It also made an extremely clean solution.

In the off season we actually drove the belts. In season though, we opted to drive the first stage with chain and the belt just did the “cascade” part.

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:point_up: This is a really slick way of doing cascade. I’ll have to remember that for the future. For our string-based continuous lift this year, my students ended up adding some stiff tension springs on the pull-down lines. Combined with good pully geometry, that reduced rope slack so it didn’t come unraveled.

Wow, what a cool elevator. Do you think you could send more images or the CAD file? Thanks.

Sure, No problem. This was a really cool feature on our robot. This season we worked to implement configurations in our parts and assembles. You can adjust the height of the elevator here, to get a feel on how it works:

image

The nifty thing was getting the wire chain to follow the elevator height. :grinning:

Here is the Elevator for the 2023 robot

Here is our preseason cascade elevator design

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Awesome. Thanks a ton.

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