Q&A response - new interpretation of R16

[Gary Dillard]

From Q&A answers:

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.

[EricH]

From Q&A answers:

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.)

[Gary Dillard]

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.)

[George1902]

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

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.

[dlavery]

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

No they didn't. Read the Q&A answer again.

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

[AdamHeard]

No they didn't. Read the Q&A answer again.

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? :D

[jgannon]

No they didn't. Read the Q&A answer again.
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>.

[Lavapicker]

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?

[MrForbes]

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.

[The Lucas]

It can be verified/enforced with a tape measure rather than an 80 inch diameter fixture.
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. :D 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. :D

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 (http://www.chiefdelphi.com/forums/showthread.php?t=3868)

[MCahoon]

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.

[MrForbes]

Maybe FIRST should construct giant 80" pairs of outside calipers.

It's called a "tram gage", and you can buy them

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

[dlavery]

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>.

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.
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.
Yeah, that is exactly the point.

-dave

[ALIBI]

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

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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!

[JonA]

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 (http://team1675.org/forum/download.php?id=36).

[The Lucas]

It's called a "tram gage", and you can buy them

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

I wasn't going for practicality, I was kidding about building giant Motor Trend Car of the Year (http://en.wikipedia.org/wiki/Image:MT_Coty_calipers.jpg) style outside calipers. Sort of a Geek Chic thing :] like MIT's Giant Slide Rule (http://hacks.mit.edu/Hacks/by_year/1990/slide_rule/sr_close.html), 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.

[jgannon]

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

[Tristan Lall]

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 (http://www.cut-the-knot.org/do_you_know/cwidth.shtml) 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 (http://www.cut-the-knot.org/Curriculum/Geometry/CWStar.shtml) 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?

[MrForbes]

I wasn't going for practicality, I was kidding about building giant Motor Trend Car of the Year (http://en.wikipedia.org/wiki/Image:MT_Coty_calipers.jpg) style outside calipers.

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.

[StevenB]

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.

[Kims Robot]

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

I guarantee someone will need something other than an equilateral triangle or a circle to fit (heck my team may even try it to make our programmers lives easier - last year we made them take an 86" jointed arm and contstrain it to 72" at all times through feedback on our sensors!!).

But what I want to know is is this going to be in the referee training... keep your Q&A and rulebooks on hand if you really want to nitpick this rule!!

[Gdeaver]

This is a bad rule. Even with a Q and A response it's still gray to teams. On the field with a fast moving wide open game this year , refs will have a difficult time enforcing the rule. I predict many teams will violate it and get away with it. There is still time for the rule to be modified so that teams can more easily comply and make the refee's job easier.

[EricH]

This is a bad rule. Even with a Q and A response it's still gray to teams. On the field with a fast moving wide open game this year , refs will have a difficult time enforcing the rule. I predict many teams will violate it and get away with it. There is still time for the rule to be modified so that teams can more easily comply and make the refee's job easier.Remember the similar rule from last year? How do you determine whether a team is in the box? There were infractions last year that apparently weren't called, even on the diagonal part. This year at least means that the refs don't have to call on diagonals. They have one standard size. So some teams slide through. It's part of the game. I've seen soccer games where the ref saw a hand ball and didn't call it. As long as the rules are applied evenly to all teams at the event (and, ideally, all events), I don't really care.

[AdamC]

Checking that article about curvilinear triangles (please don't harangue me for steering away from the original topic), does anybody know of a company that sells a curvilinear drill bit? It would be useful for drilling holes and then mounting a square locking pin as opposed to cutting notches and then mounting the pieces together (which changes the size of the bar stock). I suppose if they don't exist, I'll try and make one myself.

[jgannon]

Checking that article about curvilinear triangles (please don't harangue me for steering away from the original topic), does anybody know of a company that sells a curvilinear drill bit? It would be useful for drilling holes and then mounting a square locking pin as opposed to cutting notches and then mounting the pieces together (which changes the size of the bar stock). I suppose if they don't exist, I'll try and make one myself.
I don't totally understand the geometry behind it, but the second sentence in the linked article was "No - you can't drill square holes", so I'm guessing there's some reason that doesn't work.

[MrForbes]

look at what happens when you start drilling a hole in a piece of metal, with a relatively large drill bit, like 1/2", using a handheld drill. Often the hole will start out with 3 curved sides, even though the bit has only two cutting sides. I think this is sort of what you're thinking of?

so try a 3 sided bit to make a square hole.

[ay2b]

This is a bad rule. Even with a Q and A response it's still gray to teams.

I think this is a GREAT rule. In the past the rule was that robots had to fit inside a certain box. There was all sorts of confusion about orientation of the robot inside the box, and how the box shifted, etc. It lead to lots of diagrams and complex measurements.

Now the rule is simple - if any two points on the robot, measured parallel to the ground, are more than 80" apart, the robot is too big.

[DPTeam270Driver]

if the rule says a CYLINDER, then why is there talk of squares and triangles
we cant do anything by complaining. its just one of the thing that we have to design around. its part of engineering.

but.......
the way my team figured it out was that if the up right arm is 5 ft, and another arm(52 in) to extend out and reach up w/ claws ( at least 20 in it grab ball) to clear the front of the bot and bumpers, it will extend past the 80 in. theres almost no way that any bot would be able to pick the ball up and put it on the rack.

this was just my team, and we put it 2gether this morning, and found out it was 31 in too long when we had to grab the ball.

-team 270

[jgannon]

if the rule says a CYLINDER, then why is there talk of squares and triangles
Please reread the Q&A response that this thread is about. The rule itself is not about a cylinder... that is provided only as an example. As it turns out, there are degenerate cases that satisfy the rule without fitting in the cylinder. One such case is an 80" equilateral triangle. The actual way the rule will be interpreted is that no two points on your robot can be more than 80" apart. If it's too confusing, forget about the cylinder entirely.

[Gdeaver]

The 80" rule is very restrictive. So far our team has worked out the bottom part of the arm geometry and extend out a maximum of 76". To get the top part to be with in is the hard part. If we get it right it should be about 79". To get to this point has given our team lots of problems. So much to do and so little time.

[dlavery]

I don't totally understand the geometry behind it, but the second sentence in the linked article was "No - you can't drill square holes", so I'm guessing there's some reason that doesn't work.
The article is pretty good, but actually the second sentence is incorrect. You CAN drill square holes! Although fairly rare, wobbling drill bits that describe Reuleaux Traiangles have been around for years. There is a great article about drilling square holes (http://upper.us.edu/faculty/smith/reuleaux.htm) from the October 1993 issue of The Mathematics Teacher. One of my friends used to have one of the Watts Brothers square hole bits (after we stumbled across the Mathematics Teacher article several years ago, his immediate reaction was "I've gotta have one of those!"), and it was fascinating to watch. As best as I can tell, the Watts Brothers Tool Works is still the only U.S. manufacturer of these drill bits, but you can still get them.

-dave



.

[purduephotog]

The 80" rule is very restrictive. So far our team has worked out the bottom part of the arm geometry and extend out a maximum of 76". To get the top part to be with in is the hard part. If we get it right it should be about 79". To get to this point has given our team lots of problems. So much to do and so little time.

Same here.

We're weak on mentors- very little mech Eng, very little programming... great machinists though! This year we were going to experiment with a 4 bar- team put it to a vote and it won- and then the design headaches started.

I guess (from today's build session) we've scrapped the 4 bar and now have a simple arm that just goes up.

Oh, and square holes are easy:http://www.hartvilletool.com/product/11429