# Q&A response - new interpretation of R16

The rule states that the Robot may not have any two points more than 80 inches apart when measured horizontally. The parenthetical phrase is intended as a clarifying example, but it does not convey the same authority as the rule. It is recognized that a small set of configurations exist (with an equilateral triangle with 80 inch sides as the degenerate case) that are in compliance with the letter of the rule, but may violate the example. In all such cases the rule, and not the example, will be enforced.

Yes! No cylinder! (They have effectively declared a square, but your robot must fit in it in every orientation.)

(And Dave–if you read the edit–I did use the word “must” in the original.)

Even though I planned for the previous interpretation, I kinda thought they might go this way. It can be verified/enforced with a tape measure rather than an 80 inch diameter fixture. I’m OK with it since the ruling was made early enough in the season (although a week ago would have saved alot of headaches.)

No. They said, “the Robot may not have any two points more than 80 inches apart when measured horizontally.” An 80" square will have a horizontal dimension greater than 80" (its diagonal).

Take the rule for what it says. No more, no less.

The rule is exactly the same as it was when it was written. An 80-inch square would have a diagonal measurement of 113.14 inches, which is a clear violation of the rule.

-dave

Out of curiosity; who’s maniacal idea was it to have the 80" rule?

Dave, read Eric’s post again. He’s saying that the bounding box is a square, but your robot must fit in it in ANY orientation. If you can fit such a square regardless of your orientation, then you are within <R16>. If there is some orientation such that you don’t fit, then you are violating <R16>. As such, Eric’s definition is precisely <R16>.

I’m still confused…does that mean we can have an arm that reaches out to 80 inches, as measured from the back of the bumber, and still be ok? That’s the way I read it and then I see the Cylinder thing which contradicts it. Is there a definitive answer?

There is a definitive answer, but it’s a bit hard to understand, apparently

If your measure from the end of your robot arm to either end of the back bumper, and it is more than 80", then you violate the rule.

In the case if the end of the arm is just under 80" from the center of the rear bumper, and the arm extends straight forward from the center of the robot, it would voilate the rule when measured from the ends of the bumper.

Make a sketch…post it…we’re very good at arguing about stuff we can see.

For reasons of irony and superstition, I would like to keep tape measures away from this rule*.:ahh: Maybe FIRST should construct giant 80" pairs of outside calipers. It would be entertaining to watch the Refs/RIs use them (I certainly want to use one). Then in the offseason, we can bronze them and make them into statues! I’m sure a giant caliper statue would fit right in at Dean’s House.

But seriously, I think this affords everyone a little more room to make their mechanisms work and clears up the rule early enough in the season. Good Job!

*For those of you who were not around FIRST in 2002, see one of the many tape measure rule threads

Definition of ANY is “one or more”. Using Eric’s definition, if your 'bot fits corner to corner diagonally, your good. Properly it would have to fit into the box in EVERY orientation.

It’s called a “tram gage”, and you can buy them

http://www.chassisliner.com/Product_Measuring_All.shtml

Nope, I still don’t agree. Eric’s definition is much too permissive. If the explanation had been “must fit in an 80-inch square in every orientation” then I might buy it. But not as written.

Yeah, that is exactly the point.

-dave

Yea! We get a couple more inches to work with, even if bumpers stay included (I talked earlier in ohter threads about not including the bumpers in the 80 inches). I for one am a happy camper.

Re: <R16> Interpretation

The rule states that the Robot may not have any two points more than 80 inches apart when measured horizontally. The parenthetical phrase is intended as a clarifying example, but it does not convey the same authority as the rule. It is recognized that a small set of configurations exist (with an equilateral triangle with 80 inch sides as the degenerate case) that are in compliance with the letter of the rule, but may violate the example. In all such cases the rule, and not the example, will be enforced

EDIT: Wait a minute, no we don’t, now I “R” confused. In my head I saw a small window expanding in front of the robot, that is until I drew a picture. It all went away in a hurry. Two vertical poles, 80 inches apart, robot with bumpers on must past between the poles with any and all manipulators going through a full range of motion no matter what the orientation is.
Can we please exclude the bumpers? I know, if we excluded the bumpers then I would still want 83 inches. My head is finally starting to hurt! Thanxs Dave!

The maximum 80-inch dimension interpretation is very different than the you must fit within an 80-inch diameter cylinder interpretation if you have manipulators that articulate or open up to grab the ball. See this PDF.

I wasn’t going for practicality, I was kidding about building giant Motor Trend Car of the Year style outside calipers. Sort of a Geek Chic thing :] like MIT’s Giant Slide Rule, but enough threadjacking for me. I just couldn’t get the image of a team of Robot Inspectors wielding giant calipers out of my head.

Mea culpa. Your definition is unambiguous. Thank you, Dave.

I just wanted to point this out: the equilateral triangle isn’t really the limiting case for a 3-sided figure. It’s actually the curvilinear triangle with a width of 80 in. It has more area, for a given width.

Also, the triangle isn’t the only figure for which this works: see here for an applet that demonstrates the principle for odd numbers of sides, from 3 to 21.

So, who’s going to build a robot that fits a curvilinear pentagon, just to annoy the officials?

You may have been kidding, but it might be helpful to make your own giant outside calipers, set at 80", from whatever is handy…say an 8 foot long by 4" wide strip of plywood and two shorter strips screwed onto the ends at right angles, with exactly 80" open space between them. Then you can check yourself to see if there is any place around your robot that you can’t fit within the 80" limit.

I just wanted to point this out: the equilateral triangle isn’t really the limiting case for a 3-sided figure. It’s actually the curvilinear triangle with a width of 80 in. It has more area, for a given width.

I realized that after about 24 hours of thrashing around thinking about this problem. I’m still trying to figure out how much a difference this makes, and how to shape the robot so as to get the maximum useful area. Thanks, FIRST, for providing sleepless nights even when I don’t meet with the team.