2nd Most Awaited Q and A Answer?

[JB987]

Just wondering how may teams out there are awaiting a "helpful" reply to this question relating to the legality of (what many consider) one appendage that has two parallel arms attached mechanically and structurally so that they act as a singular appendage as they pivot to extend outside the robot...


Game - The Game » Robot Actions » G21
Q. If two members of a mechanism crosses one edge of a robot in two locations but the two members are connected via one axle and are controlled by one motor is this still considered one appendage?
Answer is in pending state
FRC1221 2012-01-14

So do you go ahead and build this "appendage" knowing that sometime down the road you may or may not find out your time and effort was worth it?

[Aren Siekmeier]

Honestly I think this has more reason to be the most anticipated Q&A response.

It may even be considered allowable to have two separate mechanical extensions, but that are otherwise linked to always operate in tandem and in a repeatable fashion (via code), count as a single appendage. But it would be really nice to know for sure. I'm hoping for an answer in the update tomorrow, or at the very least soon in the Q&A.

As for what to do in the meantime: have contingency plans; come up with and test ideas that work in multiple scenarios. Since we are not in a rush to build anything final until about a week from now, we can wait a short while to know what's right, but we don't have all the time in the world. If you are running out of time, go with what's safe, an appendage which is undeniably a single appendage.

[EricH]

That's the one thing I don't understand. The Q&A has probably half a dozen questions on appendages alone, and a number of them are "does this scenario count as an appendage?" type questions. I would think that the GDC would see that this is an issue that needs answering. So why hasn't it been answered?

My guess is, whichever GDC member is the "appendage rules expert" hasn't seen the Q&A yet. (It seems that certain question types are answered in groups, both last year and this year; this leads one to speculate that various GDC members are experts in various parts of the Manual. I don't know if this is actually the case, however.) If that is the case, then hopefully another GDC member nudges him/her to answer... some of these questions have been kicking around for a week now.

[Tristan Lall]

I seriously hope they realize that defining an appendage based on its construction is a losing game.

Thought experiment: I have a plastic toy trident which can be installed on my robot in several possible orientations, and which can be actuated in several ways during a match. (Imagine the craziest possible positions for this thing, with varying degrees of overhang, flexibility, etc..) If I poll 5 trained, experienced referees about the legality of all of these configurations, can I expect to get 5 identical, correct sets of answers? What if I repeat the test with 5 GDC members?

Almost certainly, the answer is no. Nobody knows what an appendage is, or where it begins, because that definition is not in the rules, and does not obviously follow from an ordinary person's understanding of any given robot design.

Mechanisms can do all sorts of weird stuff, and can take all sorts of forms. You don't want to end up with a definition that makes something an appendage in some positions, and two or more appendages in others. It's also a bad idea because it's non-obvious, and will be full of nuanced interpretations. Good luck getting every referee to call that the same way every time.*

The real way forward is to fix the definitions of frame perimeter and side (so that they properly account for curvilinear figures, and elegantly handle projections into the corners adjacent to two sides), and then allow only one side to be overhung at a time. No mention of what's overhanging, or how many—just a clear test that be applied by a referee with no knowledge of how various mechanisms are actuated.

*That's most assuredly not a slight against referees. The fact is, all officials will struggle with complicated definitions applied to complicated robots. Referees have the additional problem that their struggle takes place in real time, in front of an audience. The stakes are high for them, and they'll be expected to get this right. That's not easy.

[MikeReilly]

They are probably just waiting on wording. Look at the simulator, they have the type of appendage you're talking about. The intent of the rule is not to spread out multiple sides like wings, etc., is my guess.

[LH Machinist]

We have answers...kind of

A. There is no explicit width limit for a Robot appendage. Per Rule [R21], "Robots may extend one appendage up to 14 in. beyond a single edge of their Frame Perimeter at any time."

A. There is no formal definition of appendage, however a colloquial definition is "a subordinate part attached to something; an auxiliary part; addition" (courtesy of disctionary.com). To elaborate, an Appendage is a contiguous assembly that may extend beyond the Frame Perimeter per Rule [G21].

Contiguous - From Websters
1: being in actual contact : touching along a boundary or at a point of angles
2: adjacent 2
3: next or near in time or sequence
4: touching or connected throughout in an unbroken sequence <contiguous row houses>

[Aren Siekmeier]

So it appears according to today's answers that a mechanical linkage, e.g. a mechanically contiguous assembly in any way, will be considered a single appendage. No mention of whether this connection is inside or outside the frame means that it doesn't matter. Good to know this is the way they are thinking, and beyond that I think we can safely use common sense.

[Brandon Holley]

Originally Posted by compwiztobe

So it appears according to today's answers that a mechanical linkage, e.g. a mechanically contiguous assembly in any way, will be considered a single appendage. No mention of whether this connection is inside or outside the frame means that it doesn't matter. Good to know this is the way they are thinking, and beyond that I think we can safely use common sense.

This now opens up the question that if its two mechanically independent systems operating in unison (and assumedly being used for the same/similar task), does this still satisfy the requirement?

-Brando

[Aren Siekmeier]

Originally Posted by Brandon Holley

This now opens up the question that if its two mechanically independent systems operating in unison (and assumedly being used for the same/similar task), does this still satisfy the requirement?

-Brando

I would think not, and probably call it out as ref/inspector, because of how they appeal to a colloquial definition of appendage, regardless of function. I would want to see a mechanical connection.

Then of course you could tie a string between them to make them "contiguous," but I think that's why they don't want us lawyering the rules.

[Brandon Holley]

Originally Posted by compwiztobe

Then of course you could tie a string between them to make them "contiguous," but I think that's why they don't want us lawyering the rules.

I agree, thats why the rule seems kind worded kind of silly to me.

[JB987]

I suspect the given answer is a relief for many teams who have spent many days developing flip out, push out linked arm appendages... the GDC got this one conceptually right.

[LinuxArchitect]

Originally Posted by MikeReilly

They are probably just waiting on wording. Look at the simulator, they have the type of appendage you're talking about. The intent of the rule is not to spread out multiple sides like wings, etc., is my guess.

I asked several of these questions and similar others. Some were rejected as being questions of if a certain design breaks a rule. They don't answer that. They answer questions about the rule itself.

I asked the question about wings, width etc.

My current interpretation is that they probably made a mistake in the rules and are trying to figure a way out. But the width is constrained within the perimeter frame until the appendage crosses one edge. Once outside the edge it can not go "beyond" that edge by more than 14 inches but beyond implies (in my mind) the direction in which the appendage is moving as it crosses the edge. Once out there, I see nothing to prohibit wings from extending out parallel to the edge that was crossed. These wings won't be crossing a second perimeter edge; perimeter edges surround the robot frame "like a piece of string", they do not extend virtually to the edges of the playing field.

What do YOU think?

[Akash Rastogi]

Originally Posted by JB987

Just wondering how may teams out there are awaiting a "helpful" reply to this question relating to the legality of (what many consider) one appendage that has two parallel arms attached mechanically and structurally so that they act as a singular appendage as they pivot to extend outside the robot...


Game - The Game » Robot Actions » G21
Q. If two members of a mechanism crosses one edge of a robot in two locations but the two members are connected via one axle and are controlled by one motor is this still considered one appendage?
Answer is in pending state
FRC1221 2012-01-14

So do you go ahead and build this "appendage" knowing that sometime down the road you may or may not find out your time and effort was worth it?

We were wondering this same thing, but in the end decided that we can just bend some tubing to avoid trouble.

[johnr]

Wow, i read that completely differently. The answer says ," the appendage". I took that to mean the appendage as a whole and once outside frame it must be one unit.

[Bob Steele]

i think that perhaps we are actually seeing a response to "don't lawyer the rules"

The rules committee was pushed into a corner...had to make a decision and now (after 3 + weeks) we have that decision.

I doubt seriously if they were going to tell the inspectors that this was the interpretation at the beginning of the season, it was going to be a loose definition of appendage probably.. If they did have that idea at the beginning and never told the teams it would have been a disaster at regionals so I doubt that this was their intention.

By asking all of our questions we have forced them into a narrow interpretation of this rule and now we have to live with it.

I think, now that we have created this narrow definition, it is incumbent on all of us to make sure that ALL teams know about it. (It would seem that this should be done through an update but) Update or not we HAVE to tell all of those other teams that don't follow the Q and A. (Or even sometimes the updates...)

As a community we could easily say that it is all of their responsibility to do this themselves but this would not be gracious. Many teams (especially newer teams) don't look at CD and some don't even know about the Q and A. I don't even think that team contacts are sent an email when an Update comes out any more...

Young teams are struggling just to build something. We need to help them understand the rules so we can all compete together.

I know as an inspector last year I had teams struggle with the bumper rules.
I mentioned the Q and A and they stated they didn't have time to watch it... it was difficult to pour through... this year it is substantially improved but still many teams won't use it..

Let's get the word out...