My team is working on out transverse bar climb. Do to the compactness of our robot, we are looking for ways to extend something from 12 inches in length to 60 inches in length, We have settled on nested drawer slides for the extending part of the climber as they provide the lateral strength we need to do this successfully. Our issue comes in the actuation of them. We originally considered using a tape measure system to extend and retract them but the extension just wasn’t quite strong enough to perform reliably.
The retraction part is pretty easy as it can be done with a winch, but I was wondering if anyone had any ideas for something to extend the mechanism.
Note: the reason it needs to go from 12 to 60 inches is because we want everything to be mounted below our shooter to minimize interference.
While a climber with that many stages is possible, it’ll be incredibly heavy and complex to pull off. I don’t think I’ve ever seen a climbing system with over 4 stages.
It’d really help you get better advice if you post a picture of your setup. This could be an example of the XY problem - there could be an easier solution than trying to package your climber in such a small space.
To extend, there are a couple of potential methods - a continuous elevator arrangement where your winch pulls up as well as down, through pulleys, or a spring hooked to a block & tackle arrangement, which allows a (relatively) short spring retraction to pull the system up. As Amicus1 said you will lose in overlap.
We used drawer slides in 2020 on our first iteration climber and they broke. A lot. We averaged one break per match, of the 4 slides on the robot. They really can’t take any kind of “side” load at all. Be brutal with your testing because your drivers will be. We had an updated design all ready to go - and then covid hit, and we never used it.
If you really need that kind of extension ratio I would look at an accordion arm, or something simliar that unfolds rather than telescopes.
We tried something like this with 8020 last season, but could not get the mechanics to work. We either had a great extension, or we had great retraction. We could not get both.
Where we ended was using a spring to pull us up and the rope to extend. While this is theoretically possible, it was more work than we had time for.
It is theoretically possible to do this with two winches (or one with rope wrapped in the opposite direction. However, in our testing, unless they give and take the exact same amount, you will need a tensioner to take up the slack.
I would question the initial assertion that you need to package the robot under 12". There’s no real benefit to being that short this year (that I see), and it’s going to compromise the rest of the design in a lot of ways.
Adam’s right. Get this done in two stages. A reliable climber is better than a tiny climber.
It would be my assumption (we all know what happens when you assume) that they are using a turrent shooter. They would not want any obstruction at any angle.
2767 had a beefy 4 stage (i think) telescoping climber for 2020. It didn’t package well with the robot architecture. Definitely worked, but it was a whole “thing”.
I would recommend looking into the 148 / 2056 / 330 style climbers from 2016 if a super low robot architecture is the priority.
118 fish tape climber was a crazy number of stages…
We are using a fish tape for push and pull… I built something like it in the working world that would push hundreds of pounds and pull 5,000 pounds on a 1/4" diameter wire made of unobtaium
I agree with others that so many stages is asking for issues.
That being said, check out some FTC telescope mechanisms. Multi-stage mechanisms are more common there than in FRC, and in a form factor closer to what you’re proposing.
If you want to reach really high, but retract really low, the method we used in 2020 (as well as 111 in 2020, 3847 in 2022, 1114 and 148 and probably a bunch more in 2016) is worth considering. Two arms and an elbow joint would be way lighter than a 5 stage telescoping thing. https://5406.ca/2020/gallery.html#&gid=1&pid=5
A “full extension” drawer slide is already two stages. Five twelve inch full extension drawer slides isn’t five stages, it’s ten. That’s crazy talk. I’d love to see it if you pull it off.
In 2020 we did that with a scissor lift. We had two X’s and then an upside down V on the top.
I will rotate that by 90 degrees to talk about it here. Use this diagram for reference below, but in reality it’s mounted pointing up: XX>
Scissor lifts are very tricky mechanically. If it’s folded up compactly you can’t extend it by “squeezing” the ends of the left-most two points together (like scissors) because you have no leverage. You can, however, push to the right on the first cross joint (middle of the first X) while holding the two left-most points fixed in a plane, and mechanically you just have to push 5 times harder than you would push the right-most point of the >.
High school physics: work = force times distance. You can do the same work by pushing the load up 60 inches as you would by pushing the first cross piece of the scissor up 12", but with 5 times the force.
However, once you know all that, building a scissor lift is no easy feat. There are a lot of forces when you’re trying to hold those left-most two points in a plane, but allow them to move together, for instance. The joints have to pivot very nicely. For stability you want it to be wide, but you may not have that much space in your robot. You also probably don’t want it to extend 100%, so it all has to be bigger than you think.
Example extension of the scissor lift here, just after the 2 minute mark: 2020 ONOSH Q45 - YouTube
