This is my first year doing this, and I have seen some robot using a elevator with chains, I am not sure how it works, does the moving parts clamp onto the chain to move up and down?
Pretty much, yes.
As for HOW they clamp… there’s custom connection clamp plates, but some teams will stick bolts through their chain (there’s a particular size pairing that works well, but I can’t recall what it is offhand).
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Thanks! Is there some kind of pictures you can show for me to get an better idea of it?
4-40 for #25, you’ll want to use a few.
We intentionally tuned the number (I think settling on 4 eventually?) because it’s much easier to replace some sheared 4-40s than a snapped chain. Make sure there’s some exposed threads you can grab onto with pliers if necessary. Only had to do that at Beach Blitz 2018, and a few times during testing when the zeroing sensor went wonky. We replaced them for every comp anyways to stave off cyclic fatigue iirc.
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Some ideas are in this topic:
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There is a chain block or attachment to that moving stage. We have used this a couple of times and we based the original concepts we make off of this video here which is quite popular for FRC designs
Also recommend taking a look at our blog if you want close ups of an actual application as we have used this for a climber and an actual pick and place elevator from 2019.
That chain component that we bolt through can be purchased through WCP:
Roller Chain – WestCoast Products (0052)
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Andymark released this recently. I have no experience with it (I try pretty hard to avoid chain and use belts instead). Seems like it would be a good solution to an elevator though.
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I would be very careful using this in any elevator setup as the single point load for chain attachment. Great for FTC elevators but FRC loads would make quick work of that linkage if you were doing a full tower setup only using that.
To distribute the load using that WCP chain block I will add that we ran a 1/4-20 bolt through a 1/2 Dia. piece of round stock and our attachment point knock on wood has never failed on any of our robots.
Keep in mind tensile load of #25 roller chain I think is like 80 pounds and #35 is around 150 pounds. So in 2019 for instance we had two runs of #25 chain which was more than one run of #35 for strength. I don’t think that is true for that clip in tensile loading.
I’ve used the McMaster equivalent before. They work well, especially if the application requires the connection point to roll around a sprocket (a typical elevator won’t need to do this, but there are some conveyor mechanisms can utilize it). For anything else though, the bolt through the chain probably works just as well.
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True. This does allow you to move from 4-40 hardware to 6-32, which may be easier to deal with in some situations.
Fair Point. I assume that you could use more than 1?
Using them in series would help if you master link them together for sure. A bit tougher to assemble but more robust!
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We ran a chain drive on our 2018 elevator. We installed a Spartan Chain Tensioner in our chain run (to attach the two ends of the chain and tension the run). We installed the chain tensioner with longer bolts and oriented it with the bolts coming up from the bottom. We then then installed an angle bracket (made from thick wall aluminum angle, 1" x 1" x 0.125" if I recall) to our main stage with two holes in the bracket that the two bolts of the chain tensioner would pass through. We added a set of nuts on the chain tensioner bolts to clamp the lower block of the chain tensioner to the bracket. The bolts were long enough that we could then install the upper block and use a second set of nuts to tension the chain. We used the main stage as our climber so the high load case was pulling down on the elevator, so that is why we clamped the bracket rigidly to the lower half of the chain tensioner.
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3946 did something much like this in both 2015 and 2018. Of course, the chain tensioners weren’t commercially available yet, so we cut, hammered, and drilled some 1/4-20 bolts.
On mobile so I don’t have pictures handy, but 148 has two 2D aluminum plate parts on their 2018 elevator to engage with the chain and provide a mounting solution to the first stage of the elevator. 1885 just straight copied it in 2019 with great success. CAD should be available on 148s website.
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For double or triple stage elevators, does that robot need more than one chain to work?
For continuous elevators, no. The rigging will passively control all subsequent stages as long as the first one is being actively driven.
Thanks!
Chain can be used for either continuous or cascade designs. We used chain for cascade designs where each succcessive stage was driven by a separate chain loop. It works well because it is easy to tension the loop for a single stage. Dyneema rope seems like the more obvious choice for continuous elevators. But there may be cases where a chain is the right choice.
We did an elevator system for 3 years it was all based on how a forklift works. The downside is it can get quite heavy as we used extruded aluminum with slides
If you aren’t trying to design in a failure mode, and you want to avoid the cyclic fatigue, you can use 1/8" roll pins to take the shear load and just use the 4-40s for compression / holding the attachment assembly together. It’s entirely possible to make it strong enough to lift the robot this way with a little forethought.
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