Two extensions under 14" boundaries
 

Hi everybody,

We'd like to know if it is legal to have two independent extensions (appendages) that stretch less than 14" beyond the robot's frame permitier?

Thanks!

Team 2230.

Re: Two extensions under 14" boundaries
 

Per [G21] (Section 3.1.4):
So you can have multiple extensions, but you can't have more than one deployed at a time.

Re: Two extensions under 14" boundaries
 

There are several questions at the Q&A awaiting response that pertain to this. Namely, what constitutes a single appendage? Used, functionally, together at all times (separate powering mechanisms, but coded such that they are always in tandem)? Mechanically linked anywhere? Mechanically linked outside the frame perimeter? We don't know yet, and only the Q&A will tell.

https://frc-qa.usfirst.org/Questions.php, under The Game-Robot Actions-G21.

Re: Two extensions under 14" boundaries
 

For an official answer, ask in the official FRC Q&A forum.

For my opinion, keep reading.

I don't see any rules that limit the number of independent extensions/appendages that may be part of a robot, as long as no more than one of them extends beyond the frame perimeter at one time.

Re: Two extensions under 14" boundaries
 

Yes there is absolutely nothing preventing you from having more than one appendage, as long as only one extends beyond frame perimeter at a time. After all, that is precisely how G21 is worded. However, if you need an "appendage" to consist of two more or less separate extensions leaving the frame perimeter at the same time, but that are always powered and used together, with code or mechanically, where is the line drawn for determining if that is 1 or 2 (or more) "appendages" per G21? Waiting on something from the Q&A for that one.

Re: Two extensions under 14" boundaries
 

I think we are all assuming that they are indicating a 14" appendage measured perpendicular to the frame at the point it extends...at least I hope that is what they mean...

For example if we had an arm that was L-shaped and extended out from the frame perimeter with the base of the L at the frame and the L perpendicular to it ...(14" out and 14" over) the actual measured distance from the frame perimeter to the tip of the arm would be 19.8". The perpendicular distance would be 14"

I would think that the rule should read" No part of any appendage may extend more than 14 in. beyond a 14" parallel extension of the frame perimeter.

Not a big deal but nonetheless..

Re: Two extensions under 14" boundaries
 

Even as is, for every point on the appendage you described you would be able to find a point on the frame perimeter that is within 14". However it is leaving room for a goofy interpretation saying that since you can find a point on that edge that is more than 14 inches away from somewhere on the appendage, it would be illegal. But this is kind of ludicrous anyway because you could just pick the back side of the robot... So I think we all know what they're talking about. Normal distance to the frame perimeter.

Re: Two extensions under 14" boundaries
 

Is anyone concerned that we are almost to the end of week two about to start week three and there is still no answer to this from the GDC. It seems like this is a pretty big question by many teams. I hope the GDC will answer this in some fashion before Saturday so we can get on with our design. Sitting around waiting to see if any of our ideas are valid is kind of wasting a lot of time.

Re: Two extensions under 14" boundaries
 

Arizona,
The GDC is discussing items when they can and with everything else going on, it sometimes takes a while to come to a consensus. Please be patient.

Re: Two extensions under 14" boundaries
 

All,

Forget about 2 appendages below. We can barely put 1 below. Here is the Q&A response that clears it up:


Translation: If you have your bumper at the bottom of the bumper zone you get a maximum 3" to drop something below. If you have your bumper at the top of the bumper zone, then you get to extend 0" below your robot. This is a pretty big blow to some very good balancing strategies. First it was the no suction cups .. now this. FIRST 2 - Innovative Teams 0.

Re: Two extensions under 14" boundaries
 

So if i wanted an ramp to extend below [almost touching the floor] the robot but not outside of the frame perimeter and my bumpers are at the max hight. It would be illegal?

Re: Two extensions under 14" boundaries
 

It's a bit worse than that. FIRST has been terrible with defining the circumstances under which the bumper rules apply, given various field obstacles.

Their test of "plac[ing it] flat on the floor" doesn't even guarantee a unique result for every situation. You can have a robot that sits stably on the ground in two (or more) positions. Which of them is the right one? (And for that matter, does "flat" necessarily imply stability?)

Perhaps a reasonable officiating practice would be to choose from the set of stable positions the one that is most lenient toward the team. (You can't enforce all possible positions simultaneously, because then every robot would be illegal.) But that leads to perverse possibilities as well. What if the most lenient position is upside-down (wheels in the air)? There's nothing in the rules/Q&A that would indicate that this position could be disregarded.

I hope we'll see robots with flat roofs about 2 in above the bumpers being allowed, because when they're flat on the floor (in the wheels-up inverted position), their bumpers are in the correct zone. (Actually, what I really hope is that FIRST realizes that they've messed up a question of geometry again, and suspends the relevant parts of the bumper requirements for robots in contact with the barrier and ramps. There's simply no value in enforcing this given the current state of the rules.)

Re: Two extensions under 14" boundaries
 

Here's a question that will bring accusations of "lawyering the rules":

What if your appendage droops below the level of your wheels due to gravity while on the bridge (if it were hanging over the bridge)? If you take the robot off the bridge and place it flat on the floor, the appendage easily becomes level with the wheels since it is floppy in nature. This satisfies the "if the Robot were to be placed flat on the floor, Bumper Zone requirements must be met." I don't see "imaginary plane of the wheels" anywhere. So, is a floppy mechanism that can go below the wheels illegal based on the bumper rules?

The above may sound like I'm trying to be facetious with the rule, but I'm really not. This scenario might impact us, and I'm sure others.

Re: Two extensions under 14" boundaries
 

If it doesn't lift the wheels off the floor, I'm expecting it to be irrelevant, Thus legal. If it does, then not legal. Just MO...

Re: Two extensions under 14" boundaries
 

u can only use one of them at a time but yes its legal

Re: Two extensions under 14" boundaries
 

Are Q&A's legal and binding or does it have to be in the rules to make it official?

It seems to me that this is a big deal because Update 4 talks about transitions to/from barriers and bridges being exceptional states.

If your robot is transitioning between one of these is it legal to have bits of the robot extend below the plane defined by the tires?

I would think that this rule should involve actual bumper zone violations not theoretical ones.

Violations occur if and only if you extend something (or somethings -- appendage rules do not apply) below your robot and it moves your robot such that your bumpers are outside the bumper zone (for the surface you are actually on not a theoretical surface you may be placed on).

The barrier/floor transition is a special case. While in contact with the barrier, tilts and such may move your bumpers outside the zone. I think that there is a modified bumper zone (in WORLD Coords, not robot coords) that can be defined near the bumper to make this work.

The bridge/floor should be a case where the bumper zone should be modified to be such that your bumpers must not leave a fixed zone defined by the floor and a bridge coords zone defined by the surface of the bridge.

Joe J.

Re: Two extensions under 14" boundaries
 

Yes. The Q&A is an extension set of the manual. Often the updates are issued to ensure the manual is up to date in regards to any rule changes that may come from the Q&A system.

I agree with your proposed definition of the bumper rules as well. I think they are trying to oversimplify this particular case, and therefore severely limiting teams.

I was expecting to see many mechanisms this year designed to cross the center barrier. Simple gurneys, or "skis" that would drop down and lift the front wheels over the barrier. As per that Q&A answer, and through Paul's analysis (which I agree with) this looks like an impossibility.

Chris brings up the same question I had. What if the extension coming down can collapse upon the weight of the robot. Or even better, what if upon realizing the robot was now sitting on a flat surface, it automatically retracted said extension? Meaning, as soon as the robot was lowered and made contact with a flat floor, it retracted its extension to be in compliance with the bumper rules? I agree this may be lawyering, but I'm really disappointed by that Q&A answer.

-Brando

Re: Two extensions under 14" boundaries
 

Joe,
The Q&A is only answered by the GDC and no one else. The answers reflect a consensus of the GDC. The Team Updates are in effect changes, additions or modifications of the manual(s) also coming from the GDC and sometimes prompted by input from others or from the Q&A. Team updates in effect will prompt revisions in the manual at some future date. Q&A are usually answers to directed questions that are answered in relation to the current rules as reflected in the manual/team updates. If team makes a design decision based on a Q&A, I expect them to have the documentation to show. Not every volunteer/ref/FTA/inspector will have access to or a hard copy of the Q&A.

In respect to the bumper in the last team update, please note that the bumper zone is referenced to the robot sitting on a flat surface when determining the bumper zone. Additionally, the bumper zone is not checked when a robot is traversing the barrier or the bridges per the latest team update.

Re: Two extensions under 14" boundaries
 

So, to be clear, the view of the Collected Wisdom is what?

Specifically, do we have to pretend that someone may freeze time and place our robot on a flat floor and if our bumper is outside the bumper zone wrt that flat floor, we are in violation of the rules at that moment in time?

OR...

Are we exempt from that rule when in transitions to/from the barrier?
Are we exempt from that rule when in transitions to/from a bridge?

AND...

For the record, I think that FIRST should go to the "bumpers must stay inside this zone" rule define the zone in real world (not robot) coords (perhaps with a relative to a moving field element if robots have to drive over it, e.g. a bridge) and the penalize teams for actual violations not potential violations.

Joe J.

Re: Two extensions under 14" boundaries
 

Joe,
The Update in question..."The carpet, the Bridge surfaces, and Keys are considered the flat floors – and thus are the reference planes for the Bumper Zone requirements. A Robot in a transitory state of crossing onto/off of a Bridge or Barrier is not considered to be on a flat floor."
When in a transitory state (only as listed) the robot by definition is not on a flat floor so the bumper zone cannot be determined, is what I believe the update is stating. During inspections we will be checking the bumper zone height when the robot is flat on the floor. As in the past, this will require teams to mount their bumpers during inspection. There may be robot designs that violate this rule.

Re: Two extensions under 14" boundaries
 

How does this interpretation jive with this other Q&A Quote?

It looks like I can drop something more than 0 to 3 inches as long as it is into the space below the plane of the floor that the robot is resting on at the time.

Re: Two extensions under 14" boundaries
 

if i have two appendages (powered by two seperate mechanism) that meet all the rules with a string tied between them does that count as one or two appendages? please post a response quickly thanks
:eek: :confused: :eek: :confused: :eek:

Re: Two extensions under 14" boundaries
 

According to a Q & A response I received:


Q. In a prior answer it was stated that an appendage can fork outside the frame perimeter yielding a Y shaped appendage. Can an appendage be attached to the frame at 2 points and terminate in 2 points as long as they are joined by a cross member, yielding a single H shaped appendage?

FRC0063

A. Yes, but the contiguous part of the appendage must be outside the Frame Perimeter.

So yes, you can have an appendage with multiple "points" as long as they are "mechanically connected" and that "mechanical connection" also extends outside of the frame. So....that roller with multiple pieces of surgical tubing on it would have to be inside the frame perimeter at the start of a match and then extended once the match starts.

Re: Two extensions under 14" boundaries
 

thanks i guess i missed that answer i couldnt find it but that helps a ton hope to have a great competition!
:D