Since I’m not actually building a robot this year, I’ve been spending hours behind the wheel (I do much of my best creative thinking driving or walking) and relaxing coming up with crazy climb ideas using only two degrees of freedom that can be implemented with COTS parts, a cold saw or horizontal band saw or even a hacksaw, a drill or drill press, and common hand tools. I’ve had quite a few, but most of them involve [as the GDC probably intended] getting first to the mid rung, then the high rung, and finally the traverse rung, meaning either three hooks or a really careful reuse strategy, and quite a bit of time. This one skips the high rung (saving time), might actually work, would be reasonably safe unlike this one, and doesn’t appear to hinge on getting a favorable ruling on Q&A like this one. It may require a third degree of freedom, but if so, it’ll be really simple. In fact, all of them will be in any case.
What to buy online (i.e. not available at the hardware store or home center): any one of the COTS climbers, along with an extra hook and one (or maybe two) extra winch kits, and a few extra inches of 1" tubing. And enough cord for all the winches, of course! If your teams manufacturing skills are better than I’m specifying, you can of course take some alternate routes.
The simple one (which probably won’t quite work without the third degree of freedom at the end)
Build and install the arm kit so that it can reach just short of legal height (66") and can contract to 48" or less, but leaves a few inches of the narrow tube above the top spring/bearing module of the next tube. I would start by mounting this near the CoG of the robot, but moving it fore or aft or at a bit of an angle may help. That’s what prototyping’s for, right?
Build the second hook (I will refer to this as the free hook) with a short piece of tubing (the same amount extending down as exposed on the arm). Mount the second winch kit somewhere low on the robot such that if you were to hang the robot from its axle (which we will), the robot will end up about 58° (tan^{-1}(24/{15 \frac{3}{8}} )) or a few degrees less from vertical, with the arm hook pointing down.
Install dual lock or hook-and-loop fasteners on the exposed faces of tubes below both hooks, on the side opposite of the hooks’ points.
That’s the build. Here’s the climb:
In starting configuration (hooks down), drive into the hangar with the arm hook pointing forward.
Once forward of the shadow line, raise the arm.
Back up until the free hook’s tube meets the mid rung.
Lower the arm to engage the hook tube on the mid rung.
Tension the free hook’s winch if you haven’t already.
Drive “forward” to disengage the dual lock or hook and loop fastener.
Lower the arm hook.
To minimize swinging, back up a bit so the pivot point for the free hook’s winch is below the mid rung.
Winch up on the free hook until the arm is positioned to go above the traverse rung.
Extend the arm so the hook is beyond the traverse rung
lower on the free hook until the traverse rung contacts the arm.
Retract the arm to engage the traverse arm.
Somehow disengage the free hook.
Optionally, winch up the arm to make room for alliance partners.
Yes, there’s the rub, in step 13. Here comes the third degree of freedom: install a third winch, with the cable also running up the tube (It may be mounted to a longer outer tube!). But in those empty inches of tubing, turn on a pulley or bolt and exit through a hole in the tubing facing towards the free hook (probably right down the middle of the dual lock). That cable is then tied onto the free hook somewhere near its peak, or even farther towards the hook’s point so you can pull it off. All through the climb, keep minimal tension on this cable (e.g. set the motor voltage at 10%). When you get to somewhere above, engage that motor and pull the hook off the rung. and continue.
This morning I realized that the third winch is critical, because without some additional constraint the free hook will go significantly further than 16" beyond the frame perimeter.
I’ve also determined that a single stage arm won’t get this unless the CoG of the robot is impossibly placed. My current design has a hook arm sloped 30° from vertical and a 32" combined extension. Made with the AM Climber in a box, this appears to fit inside the starting configuration height. Serendipitously, it also makes driving under the low bar a breeze.
I think I have it, though the high rung turned out to be a challenge I hadn’t anticipated. So I turned it into an opportunity. But it will still require some interesting parts to get the bearings past the high rung. I have 9 pictures spread across five power point slides. And OBTW, with the CoG being at the center of the robot front-to-back.
OK, here’s the animation, followed by the separate images. The dotted lines show initial configuration and maximum extension while in the hangar zone.:
The biggest problems I see so far, from worst to least worst:
On the lift, at least one top bearing kit is going to encounter the high rung in an unfavorable manner between images 5 and 6. Something will need to be done to make this work.
On retraction, it seems that one of the bearing kits is going to pass the high rung. This will actually be in a direction where this might not require any additional parts, but then again it might.
That sneaking between the high and traverse rungs is right up against a lot of limits.
This design involves one 2-stage arm, an extra hook, and three winches. One winch retracts the arm hook, a second one pulls the free hook towards the base of the robot near the CoG, and a third pulls the free hook towards the arm hook to disengage it from the mid rung. If I understand your question correctly, it is the second winch which does the heavy lifting from images 4 to 7.
OBTW, the actual attachment point is not changing; it’s consistently 6" above the base as defined by the BUMPER ZONE rules, centered on the 32" long frame.
No doubt! I would definitely want to put some rubber tubing, cargo bed lining, or other friction surface on the arm hook.
the reason I ask is: as drawn, that rope under tension might be in the way of the robot getting the arm up to the traversal rung at the correct angle if it is indeed supposed to be attached up by the arm hook
The upper rope is going to be under minimal tension (a pound or two to keep it straight) except in disengaging the free hook. At one point, I thought it might be necessary to use it to keep the free hook inside the 16" limit, but with the slanted arm and winch #2 being near the CoG, that isn’t necessary.
Yes, upon closer inspection, looking at the images and where the COG should be the tension on the upper rope should be relatively minimal until the end. I could see it working given enough playing around with the fine details of the geometry.
Like you said, there are some slim margins here in the deployment.
Yes, it moved a fraction of an inch. That doesn’t seem to change anything critical to this climb.
Added: That is the high rung, not a a part of the robot.
We came up with a couple of options like this to skip the High Rung and go straight for the T-Rung. I think yours will work with tuning. The biggest issue is you have to lift very high on the Mid Rung to pull it off - so much so that you are cutting off a lot of usable volume in your robot. But if you do pull this off it will be great. Good luck!
With the rungs being 1.66" in diameter, it appears that the rungs will roll over the AM climbers bearing on retraction. Perhaps some mitigation will be needed, but it looks OK from the drawings. The lift between images 5 and 6 as the upper bearing assembly passes the high rung will probably require some sort of fender on the middle stage that reaches around the upper bearing - but maybe it will work itself out.
Understood - giving up a bunch of volume on the back side. Honestly, I have been thinking of a low goal robot for cargo, so that wasn’t giving up very much. I was thinking of a CARGO manipulator similar to 3946’s 2018 off season robot - able to intake or shoot at fairly low velocity from the floor, terminal, or lower hub, but really simple with intake rollers and something to raise them up high enough to score low goal. This might be coupled with a wide ,possibly vectored, dedicated horizontal floor intake. This year, I expect RPs to mean more than MPs during selection, at least as far as CARGO is concerned…
We looked at this exact concept and mentioned some things about it in Open Alliance, it is possible but would take up considerable amount of space on our machine for the travel of it (and the fact the bars would also block other mechanisms) and we decided that some team out there might do it but it would be very tough.
I would definitely want to put some rubber tubing, cargo bed lining, or other friction surface on the arm hook.