Team 118 2020 Seson Climb Mechanism

Hi guys,

I just wanted to ask if any of you guys figured out how the Team 118- Robonauts 2020 season climber works. I spent a good amount of time but couldn’t get how the climber elevates itself up. If any of you guys have good ideas about low (trenchbot) robot climber mechanisms, feel free to share :slight_smile: Thanks…

3 Likes

See above thread for an example of the underlying drive mechanism.

4 Likes

Thanks :slight_smile: @ThaddeusMaximus helped a lot…

So, there are a lot of trenchbots out there with excellent climbers. Some use multi-stage, telescoping fixed arms, like 118’s. Many of those telescoping arms use constant force springs to deploy them. 118’s solution is very clever and kudos to them for their execution. These type of multi-stage telescoping arms are tricky because the whole package needs to be short enough to fit under the trench which means that you end up with several short stages that need to nest. It is obviously not impossible, but it requires a lot of attention to detail to get it to fit.

Many other trenchbots use folding arm systems that “lay down” to clear the trench and then “flip up” to deploy the hook. Some of these are two stage telescoping systems. Others use arms with hinge joints between the arms. Still others use scissor mechanisms to deploy the hooks.

Obviously, there are a good number of reveal videos out there as well as the open alliance design and RI3D designs. A little bit of digging and you should be able to find several good examples of different types of mechanisms that you can study to evaluate what the best design is for your climber.

Good Luck!

1 Like

For me what’s crazy is my team tried to do that in 2016, using a collapsable fishing rod and a kind od steel cable ended up not working, but supercool to see this concept working

1 Like

image
This is an ftc thing but you could use something like this + a winch to climb
not sure I would trust it since if you jerk around you miss(and probably get a penalty) but its the simplest solution can think of

1 Like

Thanks for the reply. I’ve watched a lot of robot reveals this season lmao… Some of those were really compact and especially some telescoping arms were super compact with fitted 3-4 stages inside. However, I couldnt find any decent cad models or designs of those telescoping arms… The only point where I have some questions is the lifting the arm itself in to air. I think pulling the arm down is considerably easier compared to lifting it up since u could just attach a rope and pull it down with a motor…

Our robot uses a 4 stage telescoping arm. Each stage uses constant force springs to extend the stage. The installation of the constant force spring on each stage is pretty typical of similar systems from previous years. The only difference, at least with our design, is that you have several of these nested in series. There is a single rope that attaches to the base of the last stage. By reeling out that rope, the arm extends. By reeling the rope back in, the arm retracts (and the robot climbs if the hook in on the bar).

The winch spool is located to the side of the arm and there is a pulley at the bottom of the base stage that allows the rope to be fed out of the bottom of the assembly to the winch. It is important to realize that this pulley is carrying the full weight of the robot when hanging, so it needs to be well secured to the robot frame. By having this pulley at the base of the arm assembly, the bottom of the assembly can be lower which allows the length of each stage to be a little bit longer. Keep in mind that each inch you can add to the length of the assembly adds 4 inches to the overall reach of the arm (for a 4 stage system), so these details are important in being able to reach the hang bar with an arm that can fit under the trench.

One of the other tricks we used is that the constant force springs that are used for each stage gets progressively weaker as you get to the upper stages. So, as you reel out the rope, the second stage extends out of the base stage first, then the third stage extends out of the second stage next, then the 4th stage extends out of the 3rd stage last. Not really sure how important this is, but it definitely makes a very satisfying design when the arms deploy in an orderly fashion. By doing this trick, we were able to mount our Pat Sajak device on the second stage of one of the arms and we could raise it up to engage the WOF without violating the non-endgame height restriction.

You can see these details in the picture of our robot posted here. The one thing you will not be able to see is the winch system, but you should be able to see the constant force springs and how we nested each of the stages. One other thing you may not be able to tell from that picture is that the 4th stage is a C-channel that fits inside the 1x1 tube of the 3rd stage. The constant force spring fits in the open gap of the C-channel. We did improve the holder for the 4th stage constant force spring since that picture was taken.

1 Like

Really solid bot there :slight_smile: One more question though… Do you keep the system in place without the extension by wrapping the rope with the climber motor prior to the math start and when its go for climb you release the tension holding the constant force springs and when they are in the right height you pull back the rope? Is that the way how it stays closed/stuffed inside?
Again, you have an amazing bot… Also could you add any pics or CAD models if possible for the community :slight_smile:

Yes, you have it basically correct. The climb rope holds the telescoping arm in the compressed state. We use the climb winch itself to do that. So, extending the arm is accomplished by running the climb winch motors backward to unwind the winch. Once we extend the arm and hook on to the bar, we just run the climb winch forward to climb.

If you look closely in the picture I linked above, you can almost make out the winch at the base of the arm. Our rope is orange and you can see a bit of the orange rope and kinda make out the winch just behind the aft link of the 4 bar intake linkage system if you look carefully. you can see that the rope is wrapped around the winch.

We took that picture right before our first comp (just before packing up the trailer). And we shut down for COVID shortly after our comp. We have not met since then. :frowning_face: I know our CAD model is a little out of step with our bot as we ended up modifying some things during build to help make some things fit. But we have a goal to get the CAD model updated. I think the team would be willing to post it once they clean it up. When we do, I will post an update to our robot reveal thread. Stay tuned…

1 Like

How do you keep the arm from re-extending (and lowering you to the ground) when the power goes off at the end of the match?

Brake mode on the motor is sufficient if we are climbing alone. This is what we used at our first comp.

We have a locking system that will lock off the winch using pneumatic pistons to drive a pin through holes in the gear of each of the gearboxes. But we will only need to use that if we use the buddy lift. We built that system into the robot, but we have not used it… yet.

1 Like

Interesting! We found that brake mode was insufficient for us and we had to add a ratchet to our winch.

1 Like

What motors are you using? We have 2 NEOs (one on each arm) for our climb. I don’t know if brushless does a better job with brake mode than brushed motors…

Some other factors: We are not at max regulation weight. I think the team said we weighed in at 110 lbs, but I honestly can’t remember. I just remember that, for once, we had some weight margin for changes between events. We also have geared our winch a little more slowly because we planned to use buddy climb and geared it to lift 300 lbs with comfortable margins.

1 Like

We only have a single motor (a NEO IIRC) for the winch and we’re quite close to the weight limit.

1 Like