Is there any cascading slide rail system (similar to the rev linear motion kit for FRC) that can support the weight of a robot (likely using bearings)? I think it would be very cool to have something like this to use for climb as it doesn’t take up much space.
The prior 2 years, we’ve used an extrusion based elevator to tackle the climbing challenge effectively. No bearings, just a slide material inserted between the channels in the extrusion. If you’ve got a elevator with bearings it should be even smoother/lower friction.
Here’s a hand drawn diagram of our system:
The climbing wheel was a rollerskate wheel that stopped us from damaging the platform, and the outer stage string has an additional pulley for mechanical advantage. Attached is a drawing of a similar slide to what we used, this connected 2 extrusions and was made of a low friction material. drawing of slider for McMaster 2020 alu extrusion.pdf (55.4 KB). Here’s photo of the real version, slightly blocked by bumpers .
Here are a few photos from 2018, when climbing was more like this year’s bar:
https://i.imgur.com/152Kout.jpg
https://i.imgur.com/xB8IOF5.jpg
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We have a cascading arm system mostly modeled in our public CAD. It’s still missing the pulleys, spacers, and lines, but that’s mostly trivial if you know how they are routed.
Whether we are going to use this or not is still very much up in the air, but I’m confident a system like this, with the pivot point close to in-line with the COM, would work.
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To tack onto this, 1073 is looking at doing a similar arm using constant force springs to passively outtake, which reduces the complexity of the rigging by quite a bit. A good example is 2056’s 2016 climber, or 233’s 2011 arm. Using the springs to outtake means you only need a single spool attached to the highest point in order to retract the whole mechanism.
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Ours is currently set up to do both. We can attach CF springs (and pick them up on my way to the shop) to the two sections to extend them, or we can do cascading rigging by adding some rollers/pulleys. Again, haven’t gone far enough in the decision making process, so we’re not going to spend too many CAD resources until we figure out the details.
Design looks nice and simple
Where did you source the Flanged 1/2" OD bearings?
I pulled this bearing from MKCAD and it has a WCP product number, but it looks like they don’t sell them any more. That’s not too much of a concern though:
https://www.servocity.com/0-250-id-x-0-500-od-flanged-ball-bearing
Edit: Apparently WCP does have these bearings.
https://www.wcproducts.com/wcp-0072
/Edit
There is also these that make this packaging even smaller:
https://www.servocity.com/0-250-id-x-0-375-od-flanged-ball-bearing
I really don’t think that’s necessary though, it’s already small enough.
Again, this design is far from finalized, didn’t even consider sourcing of materials or anything yet. I just wanted to get it modeled so we could get an idea of how it might package into our robot.
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