What about constant-force-spring hooks BENEATH the robot?

I’ve come up with a climber that isn’t ultra simple (three hooks, but maybe only two need to be actuated). It depends on a weakness in the definition of robot height, and more particularly the base for purposes of the BUMPER zone. In particular, if something (e.g. a hook) extends below the plane where a robot is “normally supported by a flat floor”, but is incapable of supporting the robot were that hook ON the floor (e.g. it’s extended by a constant force spring of way less than the ROBOT weight), does that change the bottom plane for maximum height purposes? I think not.

OK, here’s the climber. You have two upward facing hooks, both open towards the rear of the robot. The rear upward hook is fixed a bit above the low rung, the forward upward hook can be raised above the mid rung; it normally reaches directly upward, but is on a fairly light duty spring so that it can rotate to the front, but has some polycord or similar to keep it inside the frame perimeter. Mid hook down, drive into the HANGAR from the side, and orient so your rear is facing the low bar. Raise the mid hook above the mid rung. Back up until the hook shafts engage the low and mid rungs. Pull the forward hook down until the robot is essentially horizontal, perhaps even a bit upside down. Now, release the lower hook so that it goes a bit above the traverse bar. (Who cares that the lower and traverse hook are more than 6’ apart, because all of that extension below the frame perimeter isn’t part of the robot height?!). Let the mid hook out a bit and pull in the lower hook so that it catches. Then pull up on the lower hook and disengage from the low and middle rungs. Swing like crazy (though a bit of rubber on that bottom hook should work wonders). OBTW, your robot is hanging upside down, but there’s nothing in the rules against that.

Actual dimensions are left as an exercise…

That would be a good Q&A. I would tend to agree with you, but just by appearance you’ll have plenty of people who want to call foul on it immediately.


I am honestly not following you here. R402 talks about “virtually transposing” your robot, which doesn’t imply physically placing it on a solid floor. If your extensions project into the virtual floor, you have redefined the “bottom” of your robot. It seems that you are relying on a clever parsing of the rule that would never stand up at competition.

Under the same concept, if my robot tips on its side during a match, can it legally extend a set of flimsy whiskers out its bottom and reach any distance across the field? The whiskers are weak enough that they would never support the robot’s weight…

Just be sure your BUMPERS stay below the HIGH bar.


I think this was addressed in the Q&A if I’m reading it correctly. Q29 and Q43 make me think that extending below your robot would push the bottom of your robot “standing normally on a flat floor” downward and thus your bumpers move upward and out of the bumper zone.


This is clearly against the intent of the rules.


Both Q29 and especially Q43 make it clear that the mechanism would be capable of lifting the robot or that the robot would be “standing” on the support provided by that mechanism (Q43 specifically talks about pneumatic pistons that would push against the floor to raise the robot.).

@GeeTwo specifically stated that his extend mechanism (light load CF springs) would not be capable of lifting the robot. So, therefore, neither Q29 nor Q43 address this situation directly.

I agree with him that per the letter of the rules, the bumpers are measured relative to anything that can support the robot. If a mechanism extends below the robot that cannot support the robot, then per the letter of the rule, it would not cause a change to the height of the bumpers.

While I also agree that this, on the face of it, appears to violate the spirit of the rules, to some degree, the rules were set up to create design challenges and puzzles that encourage out of the box thinking to solve. So, I think I am OK with this idea.

@GeeTwo, how do you “unhook” the two upper facing hooks. If they are open toward the back of the robot, then as you rotate the robot upward using the articulating second hook, the open side of these two hooks will facing downward (which is good to keep the robot supported). When the 3rd (downward extending) hook engages with the Trav Rung, how do you lift those first two hooks off of the other 2 rungs?

Where does it say that?

Blue box in R402 says “This measurement is intended to be made as if the ROBOT is resting on a flat floor (without changing the ROBOT configuration)…”

The robot configuration includes the pose of all extensions. Assuming that they would reconfigure under the weight of the robot is a complete red herring.

Interpreting the rule the way you are trying to would be extremely game-breaking. I’d bet a pair of Falcon 500’s that this idea violates the actual letter of the rule.

Rule in question

R402 *BUMPERS must stay low. BUMPERS must be located entirely within the BUMPER ZONE, which is the volume contained between the floor and a virtual horizontal plane 7½ in. (~19 cm) above the floor in reference to the ROBOT standing normally on a flat floor. BUMPERS do not have to be parallel to the floor.

‘Standing’ implies supported.

Blue Box:

This measurement is intended to be made as if the ROBOT is resting on a flat floor (without changing the ROBOT configuration), not relative to the height of the ROBOT from the FIELD carpet. Examples include:

Example 1: A ROBOT that is at an angle while navigating the FIELD has its BUMPERS outside the BUMPER ZONE. If this ROBOT were virtually transposed onto a flat floor, and its BUMPERS are in the BUMPER ZONE, it meets the requirements of this rule.

Example 2: A ROBOT deploys a MECHANISM which lifts the BUMPERS outside the BUMPER ZONE (when virtually transposed onto a flat floor). This violates this rule.

All of the description in the blue box refers to stances of the robot that imply that the mechanism needs to be able to support the weight of the robot in order for it to count against the bumper height. Example 2 specifically mentions a mechanism that can lift the robot.

To provide another example, suppose that there was a loose piece of rope dangling down below the robot while the robot was hanging, would that violate the bumper rule?

Yes, it would, and I’m pretty sure I’ve seen it called that way in past games.

What would stop my robot from tipping on its side and then extending a pair of Inspector Gadget arms out across the field? I could slap cargo around or perhaps entangle your robot at the far end of the field. As long as the tentacles break off or bend if I stand the robot up, that’s legal?

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Don’t get me wrong; I see your point about whether it should be legal or not. I was only pointing out that per the letter of the rule, it appears to me that it would be legal to do what GeeTwo is suggesting.

I’ve seen numerous examples of the years of things (rope, wire, loose bumper fabric) that, if you lifted the robot up, would still be touching the ground when the bumpers were well out of the bumper zone. Now, I am not sure that any of those were intentional mechanisms, but none of them were ruled illegal at the time. So, I guess your experience with how this has been ruled is different from my own experience. By the way, the implication in the rule that the item that extends below the robot be done intentionally is no more strongly stated than the the implication I pointed out that the device needs to be able to support the robot.

BTW, while I believe that this is within the letter of the rule, I think GeeTwo is on pretty thin ice unless he gets a clear ruling on this from the Q&A.

I may be thinking of frame extension fouls that I’ve seen called on a bot dragging a wire, but that wouldn’t be “intentional” either.

Correct me if I’m wrong, but a robot can pass inspection if it has a mechanism that is physically capable of over-extension. The foul is only called if the robot actually over-extends during competition. So a dangling rope would not be an illegal mechanism per se, but it could trigger a frame/bumper violation under the right circumstances.

I’ll eat my left shoe if Q&A rules this legal. And I will personally send a pair of Falcons to the first team to successfully deploy this strategy in an official 2022 event.

I’m reading the use of “as if standing” and “when virtually transposed” to indicate we’re not talking about the robot being physically supported by mechanisms touching the floor in this measurement state. Otherwise, those words are not necessary. I agree that this is a simple one to get clarified by Q&A if teams are questioning it and I’ll be interested to see the ruling on it.


Previous year rulings in Q&A are not necessarily binding precedent for ruling for this year, but Q4 in 2018 seems to be applicable for this scenario.

Q4 R24 clarification
Q: A robot includes a flexible material that extends below everything else on the robot. At some point during a
match, the bottom of the flexible material is more than 7 inches below the top of the robot’s bumpers. However, if
the robot were placed on a flat surface, the flexible material would bend and the lowest point of the robot would be
less than 7 inches below the top of the robot’s bumpers. Has this robot broken R24?
A: Provided the ROBOT’s BUMPERS are within the BUMPER ZONE when the ROBOT is placed normally on a
flat floor, then no, !R24 is not violated.
(Asked by 3504 at Jan 10th 18)


Thinking more on this situation, the parallels with flexible drivetrains in Stronghold come to mind. There were some robots that year that had drive modules that could tilt back and forth within their frame, in order to cross the defenses. There was one team in my division at champs that had a terrible time with the ref about that. Their wheel modules rotated passively, so if the robot accelerated quickly or stopped suddenly, the bumpers would tilt as it came to rest - but that tilt put one side or corner above the bumper zone. The ref on that field was penalizing them for that, even though taking them in that position, and placing them unmoving on a flat floor would result in the bumpers naturally lowering to be level inside the zone.

Obviously, this is not Stronghold, and understandings of these things may have changed since then… so anyone wanting to do something like this should definitely get clarity in the Q&A!


I’m fairly sure that I’ve seen at least 1 failed climb due to loose bumper cloth. Maybe in 2018 where a string was hanging below the climb line?


IMO, a robot still contacting the ground (and therefore failing the climb criteria) is different from violating the bumper rule.

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Very interesting.

Well bookmark my post. It’ll be worth a pair of falcons (and a pair of shoes) to see this play out.

I saw that as well in 2018, but I don’t think that was a bumper violation, just that the string was part of the robot and thus didn’t clear the climb line. I will say that the Q&A answer from 2018 seems to imply that this may not be a bumper violation if the question is answered the same way in 2022. But I’m still not convinced it wouldn’t run into inspection issues. “Without changing the robot configuration” - so we virtually move the robot from its moment of reach to transversal and set it on the ground. If this system is fully extended and you set it on the floor, at what moment do you take the measurement of frame perimeter extensions and bumper zone? Do we wait for the system to retract and come to rest inside the robot or measure those zones immediately? I’ll be watching for it in Q&A.


Ah you’re absolutely right, that was the reason they failed the climb. Doesn’t apply here.

The word “resting” implies that the system has come to rest. I can think of a whole lot of ways to exploit this if that’s what it really means.

If the bot is hanging upside down, does it need to be set on the floor in the same orientation (on its head?) when this determination is made?

I’d hate to be a ref.

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