Non-level bumpers
 

When our team builds our bumpers do the tops of all the bumpers have to be at the same (or at least very similar) heights? To be more specific: Do the front and back bumpers have to be at the same height as the side bumpers?

Re: Non-level bumpers
 

Please see Q199 and R22's blue box.

Longer answer: If a bumper section happened to be lower than the rest of the bumper sections, but the bumper was still level and entirely within the bumper zone, I can't see anything that would rule it illegal. However, if the bumper was angled, it would be illegal per R22 (blue box), clarified by Q199.

Re: Non-level bumpers
 

The same blue box was present in 2013, yet angled bumpers were ok.

Re: Non-level bumpers
 

No blue box in the bumper section of the 2013 rules says anything about angle of bumpers. I checked the archived 2013 Manual just to be sure.

Re: Non-level bumpers
 

See question 42 from the 2013 question and answer. It has the exact words from the blue box.

http://www.usfirst.org/sites/default...13_Q_and_A.pdf

If it was good to have angled bumpers with that answer, what rule makes it illegal this year?

Re: Non-level bumpers
 

As follows:

Q&A is not the rules. Correct? However, Q&A does interpret the rules, and give guidance on following them.

The difference between last year and this year is that this year, the ruling is in the rules, not the Q&A. Admittedly, it is in a blue box, AKA "intent and clarification", but it is still in the Manual.

Note too that the word "overtly" is used. Slight variations from level with the ground would probably be OK, you made the effort, but going from 10" (at the top) down to 7" (at the top) over the span of an 8" bumper would raise flags.

Re: Non-level bumpers
 

I don't know how you're reading the "blue box". It specifically allows non-horizontal bumpers, as long as they stay in the 2"-10" range. Since the bumper is specified to be 5" high, that lets you slope it a massive 3". Even over an 8" run, I don't see that sloping it at atan(.375) =20 degrees is an "overt deviation", but then I'm not a judge. I think that they're trying to keep you from doing vertical pieces or something else silly, like putting a third row of pool noodle into that 3" of space.
That said, if you're design requires a bumper (or any other part) that you can't be sure fits the rules, change the design, or at least make a backup plan!

Re: Non-level bumpers
 

So, between 2013 and 2014, the definition of "overtly deviate" has changed.
This is horrible and extremely frustrating for me, as our team has designed our pickup off of an angled bumper. We figured that since this EXACT SENTENCE allowed angled bumpers in the past, it would again allow angled bumpers in the future.


Here's the rule which allowed them in 2013, and disallows them in 2014. If this can happen for this rule, who's to say that a all of a sudden roughtop tread is a traction material, and all roughtop wheels are illegal?

To begin with, this is just the GDC being lazy and copying a sentence from next year's manual and not giving an answer. This really doesn't answer the question at all.
The first part (there is no explicit requirement that BUMPERS be perfectly parallel to the floor) is fine. It means "nowhere does it say bumpers must be perfectly parallel to the floor".

The next part "however the
requirement that BUMPERS be constructed per Figure 4-4, the vertical cross-section, does implicitly
mean that a BUMPER should not overtly deviate from this orientation." A vertical cross section of an angled bumper would have the pool noodles be slightly oval shaped.

In 2013, an oval would not be considered "overtly deviated" from a circle, which makes sense, as a very slight oval could be mistaken, by everybody's favorite "reasonably astute observer" as a circle.

In 2014, an oval does "overtly deviate" from a circle.

If they're making changes like this, I'm begging for them to let us know before halfway through build season after we've wasted a lot of time and money building three sets of nice angled bumpers. But we'll be keeping our angled bumpers, because I'd be willing to bet that between now and the end of build, there's a chance that the definition of "overtly deviate" will change again.

In 2013, we made 4 competition bumpers (red/blue, angled/nonangled) and two practice bumpers (angled/nonangled) because of unclear rules

This year, we've made 3 angled ones, and again, because of THE SAME RULE, we're making 3 more. This sucks. Can the GDC get any more unclear?

Re: Non-level bumpers
 

The answer to q268 says that angled bumpers are not legal by referencing the blue box, which states they are legal, but don't forget, the blue boxes aren't really the rules like the rest of the manual...
EDIT: that's q199, not 268. oops.

Re: Non-level bumpers
 

If you're complaining about a Q&A answer (to a somewhat vague question to begin with) not being sufficient enough, then ask a Q&A yourself with a more specific question (ie. can a single bumper segment be at a 45 degree angle with the ground or something).

And if the rule you quoted allowed angled bumpers last year, maybe, it technically didn't, but there was no one who asked a Q&A to get an interpretation of that rule. Maybe the GDC's intent of not allowing traction devices DOES include roughtop tread. If someone asked the Q&A if roughtop tread is a traction device, then we'd know for sure their stance on that.

What I'm trying to get at is, if you're committing to a design off an assumption of a sentence in a manual based off a past Q&A answer, you should probably ask it on Q&A for some form of further clarification

Re: Non-level bumpers
 

There is no explicit requirement that BUMPERS be perfectly parallel to the floor, however the requirement that BUMPERS be constructed per Figure 4?8, the vertical cross-section, does implicitly mean that a BUMPER should not overtly deviate from this orientation.

Emphasis mine. The blue box specifically states that the bumpers are IMPLICITLY required to be as close as possible to horizontal. Not explicitly required to be one way is not the same as specifically allowed to be another way. You're not explicitly required to use any particular fabric on your bumper, but a particular fabric is specifically allowed by implication.

Re: Non-level bumpers
 

I think it's still a gray area. In 2013, since there was nothing in the rules about angled bumpers, we showed our inspector at CMP the Q and A answer. He brought it to the LRI, who said that the rules permitted our bumpers (and the bumpers of 1114 and 67). This means that the current blue box (without any interpretation) permits bumpers, which the q and a contradicts. Normally, the rules from the manual would trump the q and a response, but the sentence in question is a blue box. So, which get used, the blue box, or a q and a (which references the blue box in question)?

Or, if magnets is right, and the meaning of the sentence has changed because they are now providing an interpretation of this sentence instead of just giving us a vague sentence, this means that the correct interpretation for this year (not legal) contradicts what they wanted teams to get out of it last year (angled bumpers are legal), which again, doesn't make too much sense.

I think they should address this in a team update.

Re: Non-level bumpers
 

Then, the bumpers of 1114, 67, and 236 were illegal in 2013.

I assumed that the interpretation given by the robot inspectors at the CT regional, GTR east, GTR west, Waterloo, Galileo, and the michigan district was correct and that robots that competed in the final match of their division at CMP (in a configuration that they had throughout the whole season) were not illegal. If we say that this interpretation could have been wrong, then it opens a huge door to changes

Re: Non-level bumpers
 

And the answer posted on Q268 as I look at it now (several minutes after your post) says:
Also, I read the question in 268 as probably referring to bumpers sloped so that the bottom of the bumper is not below the top of the bumper, since it is to " help aid the ball in rolling into our chassis". That is, sloped like snow plow or a cow catcher, not sloped so the bumper looks like a chevron when viewed from a distance.

Re: Non-level bumpers
 

sorry that's q199. It explicitly disallows angled bumpers. No doubt about it.

Re: Non-level bumpers
 

Or... the LRI made a mistake. Key volunteers do occasionally make a mistake--they're human, after all.

I agree--this needs to be either a team update, or a "better" Q&A. That said, I would advise any team considering angled bumpers to have a backup plan in case Q&A continues to disallow and no update addresses the issue. (BTW, I'm still waiting for someone to follow up on the "wheels are frame perimeter if they stick out from the frame" ambiguity.)

Re: Non-level bumpers
 

Before the championship, the LRI/all the inspectors have a conference call with FIRST, and they go over what's legal and not legal. That's how the robot inspectors knew that 118 was illegal in 2012. With the three robots (1114, 67, and 236), I'd be willing to bet the GDC must have seen a picture of one of them at least, and if the bumpers were illegal, they'd let the CMP/Michigan championship inspectors know they were no good.

Re: Non-level bumpers
 

And there still could have been a mistake made. Trust me. I've seen a situation where someone who should have been on all the conference calls and been at all the trainings and all that made a mistake--and just about everybody knew it was a mistake, except this one person--and it was pretty blatantly obvious from the Manual that it was a mistake. The mess created by the aftermath of that one resulted in three extra teams at Champs that year from that event. Stuff happens.

Besides the fact that the GDC does not rule on specific designs, only provides input to the people that do make those rulings when asked...


Either way, I think this needs clarification. I don't have Q&A access as anything more than an observer; anybody who does want to ask? Q268, I see as angled with respect to "we want our bumpers to slant towards the robot"; Q199 (the first part) appears to be "we would like our bumpers to go from 10" down to 7, is this legal" or some equivalent, and thus addressed by the blue box. That's the one to follow up on--but don't bring 2013 into it, because that'll simply get a "last year's rules have no effect on this year" response from the GDC and we'll get no other clarification.

Re: Non-level bumpers
 

Fig 4-8 shows the bumpers being perpendicular to the floor. You really can't tell if they are parallel from the figure despite what the blue box says. I have always interpreted that rule to mean you cannot have "cow catcher" bumpers. We have never had a reason to mount one end of bumper lower than the other or have anything other than rectangular bumper so we never tested the exact meaning.

Currently you can have several bumper segments on on a side each one slightly higher. having the net effect of an angled bumper. Now as dX approaches 0....

Re: Non-level bumpers
 

Well, I thought I'd bring this back. Our team would really like angled bumpers (not like a cow catcher, but like 1114/67 in 2013), and we've been having quite an argument about the interpretation of the rule, and we were wondering what you guys thought.

There are currently three interpretations.

1.) The question and answer interprets the the blue box as saying no, so this year, the sentence in the blue box means the opposite as what it did last year, and angled bumpers are no good.

2.) The question and answer says that the blue box says no, and that sentence (which is a little ambiguous), means no, and 1114, 67, and 236 were all really illegal in 2013, but since the GDC never gave a clear response that year, no inspector could call them on it. (this is what I think)

3.) The q and a and game manual are in contradiction of each other.

Now, we may try some bumpers where the distance of each parallel segment is about 0.5" to get the same effect as angled bumpers.

If the GDC had put a rule in the original manual "bumpers must be parallel", then we wouldn't have had our sponsor waterjet an intake plate that only works with an angled bumper, or build a frame with an angled bumper, or build angled bumpers, or waste hours correcting the mistake. [/rant on bumper rules]

Re: Non-level bumpers
 

Here's hoping that the GDC doesn't take this on as a challenge. ;)

-Karlis

Re: Non-level bumpers
 

WOW! Let me explain all of this for you guys.
1. Angled means strictly the horizontal orientation as described by the lower edge of the bumper system. If the bottom of the bumper is higher at one end than the other the Q&A has responded it is illegal this year to date(as of Feb 5, 2014).
2. Bumpers must be completely vertical because they mount on the FRAME PERIMETER which is series of vertical planes described by the outer dimensions of the robot. So that means no plows, no angles that help you pick up the ball, no wedges.
3. The Q&A contains answers to specific questions as answered by the GDC and other individuals. When these answers seem to contradict the rules, they become the rule and should be followed up with a Team Update to insure the maximum number of teams/team members are alerted to the change.
4. Horizontally angled bumpers were allowed last year as long as the entire bumper system remained in the 2" to 10" above the floor dimension. This allowed different bumper sections to be mounted at different heights around the perimeter of the robot.
5. The Blue Box in R22 was added this year. That is the reference made in the 2014 Q&A you are discussing.
6. Inspectors will inspect as directed by the rules or the Q&A whichever is most recent. We are after all, an extension of the GDC and are expected to perform as such to keep inspections consistent across the world.
7. Please remember that some of the rules are written to give you a challenge that you would not normally have. This make the contest more interesting and challenging. It is the way this competition has operated from the very beginning.
8. Yes, we do make mistakes from time to time, even me. I hope when I do make an error it is in your favor.

Re: Non-level bumpers
 

Thanks for the clarification, but it's still not clear and really does need to be in a team update.

You stated that angled bumpers are legal in 2013. Go check the 2013 question and answer and look at question 42. They use the exact same sentence as what's in the blue box in the 2014 manual to allow angled bumpers for 2013. Now, this year, the same sentence is used again, but this time to disallow angled bumpers. So either angled bumpers weren't allowed in either 2013 or 2014, or angled bumpers were allowed in 2013, but not 2014, and the manual/q and a contradict each other.

Or, the definition of the words "overtly deviate" has changed.

Re: Non-level bumpers
 

What part of Q199 is not clear?

I didn't know the meaning of the word "No" needed clarification.

Re: Non-level bumpers
 

Right, so the answer is no. Maybe the reference is unclear when you compare it to 2013, but that's in the past so it doesn't matter.

Re: Non-level bumpers
 

The No part is very clear. I understand very well that we are not allowed to use angled bumpers. The same sentence used this year to disallow angled bumpers was used last year to allow angled bumpers, which is the bad part.

Most teams don't read every single q and a response. When they see the blue box below r22 that has the sentence used to allow angled bumpers in 2013 (in q42 of the 2013 q and a), they will assume that angled bumpers will be allowed again. However, the meaning of the words "overtly deviate" has changed, and it would be nice to let teams know that this definition has changed so that they can design around the new meaning, as opposed to the 2013 version.

I'm not trying to contest the fact that the definition of a very, very vague sentence has changed from one year to another. r22's blue box is pretty ambiguous, and the q and a clarifies it. I just really feel that it's not going to be clear to a team who reads the manual, but not every q and a response. But I guess that's their problem, just like it was our problem that we didn't ask a q and a, and assumed the 2013 interpretation would stay.

Re: Non-level bumpers
 

Then isn't it that team's fault for not reading the Q&A for clarification on (what you see as) an ambiguous subject?

Re: Non-level bumpers
 

Sure, but (I hope) the point of the q and a and updates isn't to confuse teams and make it harder for them to pass inspection (though historically, it seems that this may be true).

When the GDC changes the definition of words in the manual, it would be really nice to see them outlined in an update(of the first draft of the manual). Would you be happy if you turned up to your competition and discovered that the type of tread used on your wheel was suddenly considered a traction device and was illegal? If nobody had asked the bumper question, then teams would have shown up to competition with angled bumpers, and would have been unable to use their intake mechanism that relied on angled bumpers.

Re: Non-level bumpers
 

Now you understand 118's pain in 2012. Their solution was legal using the definition of Grapple from 2011, and there were no changes to the rule in 2012, and yet their robot was ruled illegal.

118's robot passed inspection as it was not illegal from inspection standpoint. The Head Ref is the person who enforces the game rules and the definition of Grapple.

Re: Non-level bumpers
 

Magnets,
It is irrelevant at this point that the interpretation was different last year. It is this year's Q&A that has answered the question as it applies on Feb 5, 2014 to 2014 robots.

Re: Non-level bumpers
 

"No" is unambiguous, but if bumpers have to be parallel to the floor, why does the manual say bumpers don't have to be parallel to the floor? Why not just change the blue text to say "bumpers must be as close to parallel to the floor as reasonable"?

Obviously angled bumpers are illegal if they say they're illegal, but I don't understand how the GDC would expect teams to interpret identical wording differently in different years.

Re: Non-level bumpers
 

Q199 said the bumpers had to be parallel to the ground. It also said the different bumper segments could be at different heights.

Maybe that gives enough room to creatively build the robot to meet your needs without lawering the rules?

Re: Non-level bumpers
 

I don't believe the GDC changed their mind between last year and this year. Nothing I've read indicates that the 2013 bumper rules permit angled bumpers. I think the Lead Robot Inspectors who gave angled bumpers a pass last year were not interpreting the rules the way they were intended. Since it was in teams' favor to accept that interpretation, nobody went up the chain of authority to get an ultimate ruling, and the LRI's word was final.

The answer from the GDC this year is clear: bumpers should not be angled. It's basically the same answer they gave last year, with the addition of the explicit "no".

Re: Non-level bumpers
 

Our bumper sections are 0.5" long, aren't angled, and function as an angled bumper would for our intake.

Your dx approaching zero comment gave us the idea. Thanks! :]

Re: Non-level bumpers
 

We all do need to remember that the 2013 rulebook is completely nullified and 100% irrelevant for the 2014 game. Any rulings made in 2013 do not "roll over" into the new season. Just because they can Copy/Paste year to year, it doesn't mean we get to.

And next year in 2015, any arguments that are based on "how it was in 2014/2013/1992" will have no traction.

IMHO, having angled bumpers (relative to the vertical plane) is quite ridiculous. I would compare it to people in 2012 trying to "balance" on the bridge by driving up the Lexan guards underneath.

Re: Non-level bumpers
 

Alan,
This specific ruling was discussed during multiple LRI meetings and conference calls. The answer in 2013 was any and all bumpers located between 2" and 10" above the floor were legal. I personally inspected several at each event.

Re: Non-level bumpers
 

Bumpers designed using calculus, well played.

Re: Non-level bumpers
 

Well, I'm both proud and ashamed to say it, but we finally picked up a ball tonight, and dropped it into fairly stable well where we could "kick" it over the truss or into a goal. (Proud that we did it, and ashamed at how little time is left to tweak and tune the controls and give the drivers practice) We did it with vertical plywood backing the bumpers, and horizontal bottom lines and pool noodles (at 2.5" off the floor to the lower edge) coming in 8" from each corner. We did do some interesting miter/bevel stuff with the track INSIDE the frame perimeter once we pulled it over the bumpers, and the final mod that made it work was made in time-saving/desperation, and involved using pool noodles inside the frame perimeter. The noodles were intended as a filler, but they apparently also served as a traction device, moving us from "almost working" to "that's it". Given the late date, we're locking this in as a solution, and are forging ahead towards stop build day.

Re: Non-level bumpers
 

In the Q&A I asked
Q. As Per rule G27 robots can not use a wedge mechanism in order to flip other robots, but can we put our bumpers on an angle in order to help aid the ball in rolling into our chassis?
2014-01-31
A. BUMPERS must be backed by the FRAME PERIMETER and may not go inside the FRAME PERIMETER (see Figure 4-5). Please see the Blue Box on R2 for help determining the FRAME PERIMETER of the ROBOT.

and with the response it seems to sound like they dont approve of it but they dont say no to it but i could be wrong.

Re: Non-level bumpers
 

I believe you are wrong. The FRAME PERIMETER is not angled. A bumper backed by it will also not be angled. An angled bumper will not be backed by the FRAME PERIMETER and will not comply with the rules.

Re: Non-level bumpers
 

To be more specific, there seems to be no question that bumpers angled from the vertical (that is, like cow catchers) are illegal. As for bumpers angled with respect to the horizontal (that is, across the frame perimeter): they were allowed in 2013, but they are questionable to forbidden in 2014 based on the Q&A, despite the rules being the same. Unfortunately, none of the questions has clearly defined the axis of slope, so at this point, the ruling is uncertain. Since I feel that my team's bumpers are beyond reproach, I'm not going to put this question to the judges; if you're not so sure, you should ask a VERY specific question on Q&A.

Re: Non-level bumpers
 

There's nothing in the rules that requires that the frame perimeter polygon be parallel to the floor (if the robot is appropriately shaped). Also, it is uncertain whether a skew polygon (as opposed to a planar polygon) satisfies the rule.¹

Also, while the rules require that (certain parts of) the bumpers be backed by the frame perimeter, that doesn't create a constraint in which the entire vertical projection of the bumper has to lie directly above that locus of intersection. For example, one might conceive of a twisted bumper that was vertical at the ends and reclined in the middle. (But R21 and figure 4-8 may have something to say about that, on different grounds.)

That Q&A response doesn't follow from figure 4-5, but R21 and figure 4-8 may offer clearer guidance, if interpreted using the same standard as in R22. Of course, consistency of enforcement will be difficult, given that FIRST's guidance (about another, similar rule) is to look for overt deviation.

¹ Would FIRST really want to prevent a robot from passing inspection because its only possible frame perimeter is a skew polygon? Would it serve any purpose to interpret the rule that way? As usual, I'm inclined to give teams the widest possible latitude within the precise letter of the rules. And given that FIRST already allows curvilinear polygons, I see no particular reason to infer that they object to skew polygons.

Re: Non-level bumpers
 

As I said before I am not the one that is going to be inspect your robot. The person inspecting your robot might not have passed calculus. You robot inspector might also reasonably expect you bumper segments to be discrete. As Dx approaches 0 you might run afoul on the rule that requires you to be able to change your bumpers in a reasonable amount of time. Also keeping your numbers in order, (that would have to span extremely small bumper segments), will be problematic.

As for an angled frame perimeter goes. In order to be on the frame perimeter, when you push your robot against a wall, the point must be able to touch the wall and be in the bumper zone. If a point cannot touch the wall, it is not on the frame perimeter. (absent the minor projections of course.)

Re: Non-level bumpers
 

Tristan,
I am confused by your response, the FRAME PERIMETER is a series of planes, that are essentially perpendicular to the floor when the robot is in the Starting Configuration. As such, the backing of the bumper system that is mounted on the FRAME PERIMETER must also be perpendicular to the floor. There is no occasion where any part of the bumper system can be skewed or angled with respect to the plane(s) of the FRAME PERIMETER. The FRAME PERIMETER is determined by the outer most section of the Frame as determined by string test in the bumper zone. Once the FRAME PERIMETER has been established, it can be measured and the bumper system can be inspected. It is not possible to meet the rules with respect to bumper mounting (i.e. backed by frame with no gap greater than 1/4" be wider than 8" and supported at the ends by at least 1/2") on a skew polygon unless said polygon was skewed vertically by 1/4" or less in the bumper zone.

Re: Non-level bumpers
 

The frame perimeter definition refers specifically to a polygon, not to a series of planes:
Perhaps the series of planes to which you refer is the "vertical projection of the FRAME PERIMETER" (although that could include curved segments which are not strictly planar):
Since the bumper rules refer to the frame perimeter, but not to its vertical projection, I have to assume that they should be evaluated with reference to that polygon (whether it be rectilinear or curvilinear, and planar or skew¹).


To expand on what I'm talking about, consider a robot with four sides, each with an outermost edge running the whole length of the side within the bumper zone (i.e. the major protrusions relevant to the frame perimeter). If in the starting & playing configurations, the left and right edges are at 9.5 in from the floor, and the front and back edges are 2.5 in from the floor, there's no planar polygon that can satisfy the string test. I'm skeptical that FIRST means for that robot to be illegal, and the only way to maintain any measure of fidelity to both the rules and geometry is to allow a skew polygon—i.e. a figure composed of segments that do not necessarily lie in a plane.

That's the "skew" to which I refer, but when I speak of "twist" I mean something else. When I describe a twisted bumper, I conceive of one in which the backing material is bent out of the vertical plane. I argue that if the bottom edge of the bumper backing lies on the frame perimeter polygon, and the top edge lies inside of it, then R21 is satisfied, except—depending on interpretation—for the part about the vertical cross-section (including figure 4-8).

Now, as for the vertical cross-section, R22's blue box offers a suggestion about how to interpret figure 4-8 in a different context:
I think it's fair to apply the reasoning found there to R21, even though the blue box is attached to R22. After all, they're referencing the same figure and FIRST has never given any indication that they mean for a distinction to exist. The Q&A seems to be consistent with that interpretation of the constraints imposed by R21.

But note the distinction between "may not go inside the FRAME PERIMETER (see Figure 4-5)" and "should not overtly deviate from [vertical]". Figure 4-5 does not establish any constraint upon verticality (or flatness, for that matter). If they meant instead to refer to figure 4-8, and we interpret it as above, we're still left with a question of how much deviation is overt. That's why I express concern about consistency of enforcement: if it's 10° at one event, and then 2° at another event, we might have a bit of a problem.

Finally, "may not go inside" is phrased very strongly (compare "should not overtly deviate"), and this is an impossible constraint if there's any twist at all—as one might expect in a real physical part. I therefore contend that the Q&A is probably wrong in that respect, because we can't reasonably presume an intent to impose a practically impossible constraint upon a mandatory feature. Accordingly, I fall back on the necessity for officials to judge overt deviation.

¹ To avoid skew polygons (and other issues), I've previously suggested that the frame perimeter definition could be improved if it were based upon the convex figure formed by the projection of the outermost extents of the robot (within the bumper zone) on to the floor, in the starting configuration.