Engineering: Lifting Robots

How do you lift a robot up on the ladder without any string/rope? Fascinating question, I think…

Simple, get Cody Smith’s hovering robot and just fly it right up to the top and sit there. :wink:

Well, if you wanted to use string/rope that badly, then I would recommending using PWM cables.

But you can use vertical lifts and junk. I think the more interesting part is when you get up, how do you keep yourself up there?

  • Sunny

Vex gears do a surprisingly good job of helping out with this. Because they’re a bit inefficient, when you remove power (as in turn off, not as in send a 127 PWM command) from any high spur gear reduction (25:1 or more) they tend to just stay up.

That exact technique is how I got my robot to hang from a vertical bar way back in FTC. Your mileage may vary, but I would recommend prototyping to determine of the “holding yourself up” problem is an actual problem before you spend the time on a solution.

Heh. In “Hangin’ Around” our second robot (“The Goat”) had a variety of heavy, complex latching mechanisms the students were using to get the robot to stay up when lifted. The final solution was to take off the latching mechanism and rely on the motors not back-driving when powered off. The latching mechanism itself added enough weight that the mechanism sagged, and once they stripped off the weight, the robot stayed up. This was all before aluminum was in use. (Aluminum might have been available, but we couldn’t afford it anyway. :slight_smile: )

The problem as I see it is neither how to get yourself up there nor how to stay up there. HS chain is certainly a viable alternative for string/rope, and can be reinforced if it’s not high-strength enough for you anyways. As was explained by others, the motors and the slope of the ladder itself do a pretty good job of keeping you up there.

The more significant issue is “how do you get up there fast enough to make it efficient in gameplay terms”? For a robot like ours, which can remove 7+ points’ worth from an opponent’s goal in less than ten seconds (assuming the tubes are on the opposite side of the field from the robot), unless a low hang can be achieved in less time than this it is not worthwhile. 20 point swings are still achievable in less than 20 seconds without hanging.

agree with the slop of the motors ect,
but i remembered once a pmw wire got caught in the teeth of two gears, that stopped it from going anywhere… :wink:
latex tubing is also a good way to keep things taught
you remember the power of the catapults at dallas last year?

but can your robot SCORE at least 7 points in that same seconds?
you are relying on your opponents to have scored quite a bit
and by worlds there will no doubt be FAST hangers and i mean 5 sec or less assuming you can get past the defense

If your opponents haven’t scored at least 20 points than you’ve won the match anyway. If you haven’t, you have a lot more to worry about than hanging, since you only need to score 3 single tubes on empty goals to get 20 points yourself.

One of the teams I’m coaching is taking advantage of the angle of the ladder as well as a worm gear which doesn’t have the same problems back-driving. If all goes well over the next couple weeks they hope to be able to high-hang within 10 seconds of hitting the ladder. We’ll see…


vamfun seems to have engineered a solution:

OK, John, there’s one way… :slight_smile: How many others are there?

Good thing that brainstorming…isn’t my job anymore! :smiley:

Though from some tests we ran, there really aren’t that many ways to high-hang quickly without messing up a lot of parts.

In about 15 seconds our bot can high hang using HS motors and conveyor belts, it stays in place after power is cut off. We have two HS motors and a gear ratio using HS gears w/ 12 spur on motor shaft and 60 spur on axle responsible for wrapping up conveyor belts. But we still need a better way to grab onto the top of the ladder(we plan to grab if from the side). Any suggestions?:slight_smile:
Team 2443M Maui High School Robotics

Without a picture of the current method, it’s pretty hard for anyone to reccomend a better method. Know what I mean? We aren’t psychic. :wink:

I swear to God, I’m buying you a cookie. Hilarious! Yes, PTD has mastered the art of hovering, sadly the technology only works in coordinate planes that we have complete control over (like the ones in 3ds max).

I agree! When I first started thinking about this my solution was a spring (tension) loaded grapple hook type thing that could been reeled in, thus lifting a robot. Big problem is that your robot’s base must be able to span at least two of the pegs or it will stick.

Another idea featured the Vex off-road tires. You know, those big black “X” looking wheels. Basically a chain of six of those should be able to climb. But you guys all know us, PTD’s gunna run a holonomic, guaranteed. Won’t do.

So… my last idea is well, quite elaborate. Which is probably a bad thing, but I would say that one could shimmy up the ladder with two clamps, kind of like climbing the trunk of a tree.

And then theres the combo, We had considered building one robot to basically carry the other up the ladder. The biggest problem is that the rules say both robots have to touch the ladder, I think that some clever thinking could make that doable.

In other news…
I"M TIRED, Physics sucks (stupid Russian professor)…

The rules say both have to touch the ladder for both to get points, but if you built a nice little ramp, then only the ramping robot has to for the ramped robot to get points. :smiley:

Our team has been discussing the concept of the “buddy lift”. Technically it’s easier than the self-lift, but from a strategic standpoint it’s significantly less viable.

Consider the following.
Given: your alliance is 1) you and 2) a robot that cannot lift others or hang itself. Both robots are capable of scoring fairly quickly.
Possibility A: Your robot cannot hang or lift others.
Possibility B: Your robot can lift others, but not hang itself.
Possibility C: Your robot can hang itself, but not lift others.
Possibility D: Your robot can lift others AND hang itself, but not simultaneously.
Possibility E: Your robot can lift others AND hang itself simultaneously.

Possibility A is the vacuous case, since neither robot in the alliance can hang.
Possibility E is pretty insane, and while I’d love to see it I doubt I ever will.

Accepting Possibility B: Your robot goes off and hangs.
Accepting Possibility C: Their robot drives over to your robot and you hang them.

Of course, the problem is that Possibility C leaves you with no robots playing defense or scoring for however long it takes you to hang, while Possibility B at least leaves you with one. On top of this, C is inevitably going to take longer to set up because both bots need to get into position (instead of just one).

Therefore, Accepting Possibility D: It will always be more viable to hang yourself.

Not to mention that if you go with C, and you drop just a single robot, no one’s going to trust you ever again :stuck_out_tongue:

well thats for HIGH SCHOOL
COLLEGE get to make their OWN alliance partners :wink:
and the other team will probably kill you for destroying their robot :stuck_out_tongue:

Hanging your other robot seems to me to be even more inferior in college, because if you can figure out how to hang one robot you can figure out how to copy the mechanism to the other robot. 2 robots hanging > 1 robot hanging and one holding it up, especially given that it probably takes less time.

I wouldn’t say so. It’s really, really easy to deploy a ramp and for one robot to drive up it, for example, but it’s a lot harder to figure out how to support yourself while interfacing with the tower, which a ramp team doesn’t have to figure out how to do. In fact, I think the only viable way to “ultra high hang” is with a lifter / ramp.