BUMPER PERIMETER
 

I haven't seen this discussed much yet. This year we have a new definition, the BUMPER PERIMETER:
Then we have
Teams need to be very careful about how they design their frames. If you have concave sections of the frame, you cannot attach bumpers to that section. In the extreme, consider a robot frame in the shape of a Maltese Cross:
The Bumper Perimeter forms an octagon connecting all the vertices - and the frame touches the Perimeter only at those vertices. There would be no legal way to connect Bumpers to the Bumper Perimeter. Beware!

Re: BUMPER PERIMETER
 

I saw this rule but I did not read this as a cannot. I just read it as a permissive rule--i.e., you can avoid putting bumpers on up to 1/3rd of your bot.

Suppose you had a chassis like this:



Are you saying that you cannot put bumpers on the inside (i.e. the concave) part of the chassis?

Or (and I do apologize for the crudeness of my drawings here),


You're saying that the bumpers in green are legal and the bumpers in red are illegal? Because the way I had read the rule was that the bumpers in green were necessary and legal but the bumpers in red were superfluous but legal.

Or am I misreading you entirely and you're simply making sure that teams know they need to protect 2/3rds NOT of the outside of their robot, but rather 2/3rds of the imaginary line described by the vertices of their robot?

Re: BUMPER PERIMETER
 

Bumpers on the inside are allowed, but will not count as standard bumpers, as they are not mounted to the BUMPER PERIMETER, and as such will not cover 2/3 of robot. Also not that you can't just attach the bumpers at the vertices and have them along the imaginary line that is the BUMPER PERIMETER, as they wouldn't be supported along the entire back side and violate letter M of the bumper rules.

Re: BUMPER PERIMETER
 

Does this mean that a trailer striking these bumpers would be in violation of the rule that it needs to hit bumper first?

In other words, if the rear of your robot is concave in the way I diagrammed above, and you kept the trailer nestled in close, would it be against regulations because the bumpers within the concave shape are not "real" bumpers because they lie within and not along the perimeter?

This seems like a very confusing rule!

Re: BUMPER PERIMETER
 

Yes, which pretty much destroys any attempt to protect the trailer. Yay for offense!

Re: BUMPER PERIMETER
 

The green bumpers in the above illustration could count as standard bumpers, with all the benefits and requirements of such: Not included in weight and size, must cover 2/3's of the Bumper Perimeter, etc. The red bumpers would not count as standard bumpers, and must be included in size and weight. Nor would they have to follow all the bumper build rules in <R08>. (Actually, a small corner of each red bumper is outside the bumper perimeter, and would have to be trimmed off.)

No, I don't believe so, as long as you're not talking about the trailer you're towing.

If the trailer you are talking about is the one attached to your bot, well Team Update 1 took that away from us. You can't attach the Trailer Hitch in the concave section of the illustration, between the red bumpers, because the Hitch has to be on the Bumper Perimeter.

Re: BUMPER PERIMETER
 

That's what I was talking about; our original plan was to store the trailer nestled in that space to help stabilize its motion. But
Exactly.

Re: BUMPER PERIMETER
 

Instead of a recess on the rear to help protect your trailer, what if you made a hexagonal cutout on the front that would that act as a guide to help your robot more accurately dump into an opponents trailer? Is this allowable? We couldn't find any specific rules against it... you aren't attaching to the trailer, only "fitting" up to it momentarily to dump your moonrocks. Bumpers could line the recess, but they wouldn't count as legal "bumpers" and lessen chances of inadvertant attachment or damage to the trailer. Does anyone know if this would be legal? There is a rule that robots must contact bumper to bumper, but what about the trailer?

Re: BUMPER PERIMETER
 

I don't see any problems with this, but you should check Q&A to be sure.

You still would not be allowed to contact the upper structure of the trailer, under the liberal <G29> interpretation found in Team Update 1.

Re: BUMPER PERIMETER
 

Rules update 2 seems to confirm the legality of this, but they note that the bumper rules limit the size of the opening 26" centered on the front of a "wide" robot (minimum 6" bumper on each side of opening).

From update 2, section 8:

Re: BUMPER PERIMETER
 

There are still major interpretation issues that need to be addressed by the GDC ASAP.

Namely, the GDC wants us to only put bumpers on the BUMPER PERIMETER, and yet corners must be protected on both sides. This would preclude a LOT of the designs I have seen on Delphi this year.

Re: BUMPER PERIMETER
 

They did address it, in their round-about way.

It appears that half of the robots in the game animation are illegal, because they don't have BUMPERS on both sides of every corner of the ROBOT PERIMETER.

Re: BUMPER PERIMETER
 

Our team is having similiar problems with this rule. It seems that to comply with all the bumper rules AND the trailer tongue rule, pretty much the only shape the back end of a robot can be is square? What is the length of the trailer tongue that extends out of the trailer? The trailer BUMPER to BUMPER rule really limits the shape of the back end of the trailer.

Re: BUMPER PERIMETER
 

The back does not need to be square

The back can bulge out, but not in.

Re: BUMPER PERIMETER
 

does anyone know if the space for the trailer hitch on the robot is included in the 2/3 required for the bumpers?

Re: BUMPER PERIMETER
 

I count 2 of the 6 being clearly illegal - Cannonbot and Dave's favorite Bulldozerbot. Tennisbot is questionable; it would be interesting to see why the GDC would think it legal or not. The opening is not between two faces of a flat side, which compares to 842's Carmen, the only difference being the angle at the opening.

Re: BUMPER PERIMETER
 

Apparently it isn't. If you aren't sure, ask Q&A.

Re: BUMPER PERIMETER
 

Let's be careful to define the question here.

A robot's BUMPER PERIMETER is measured independent of the Trailer Hitch (measured as if the hitch wasn't there). Two-thirds of this perimeter distance must be covered with BUMPERS. At least 7" of space at the location of the Trailer Hitch cannot be covered with a bumper. Therefore some other location on the frame will have to have bumpers to make the total at least 2/3's.

Re: BUMPER PERIMETER
 

I think Gary is right about this.

On a related note: this year, FIRST HQ is continuing its effort to improve consistent application of rules at all events. One way they are doing this is by inviting (read: requiring) all 40+ lead robot inspectors to participate in training on site at HQ this coming Saturday. Rumor has it that the training includes special breakout sessions on key topics, and that BUMPERS are one of those topics.

So, early next week there will be 40+ key volunteers who have received intensive training on (among several other topics) how to correctly interpret <R08>. This makes me feel much better about prospects for the new rule being uniformly applied at all 2009 FRC events. :)

Re: BUMPER PERIMETER
 

I would like to call attention to the QandA copied below as it clarifies the situation for allowed shapes for the bumper perimeter.

#1
01-11-2009, 02:17 PM
FRC1270
Junior Member

Join Date: Dec 2008
Posts: 0
Bumpers and acute corners
In update #2 the robot is a rectangle with the front of the robot allowing for a 26” opening in the center. The two 6” front sections are perpendicular to the side rails and on opposite sides of each other. Would it be a violation of rule <R08-A> if the two side sections were angled 45 degrees towards the center of the robot – still covered with a bumper. Would the bumpers attached to the 6” angled section be considered enough protection to the corners and not in violation of rule <R08-C>?

#2
01-12-2009, 12:08 PM
FRC341
Junior Member

Join Date: Dec 2008
Posts: 0
Bumpers for Concave Designs
We have a question about exterior corners of the robot that are less
than 90 degrees. For clarification, this is one specific illustration
of this design, but our question refers to these sorts of corners in
general: http://www.chiefdelphi.com/media/photos/32317?

It seems that there are four possible ways to interpret the rules about
such corners:

1. Bumpers must be present on either side of the corner (per this Q&A
response: http://forums.usfirst.org/showthread.php?t=11159). Thus, the
interior angled sections of the robot must have bumpers.

2. Bumpers must be located on the BUMPER PERIMETER (<R08>). Thus,
bumpers cannot be present on the interior angled section, as they are
not part of the convex hull of the robot polygon.

3. These sorts of exterior corners are not permitted because (1) and (2)
cannot simultaneously be satisfied.

4. The interior angled sections of the robot must be padded so as not to
damage the trailer (preserving the intent of the bumpers in the first
place), but since they are "bumpers" rather than "BUMPERS", they are not
exempt from weight and size withholdings.

Which is the correct interpretation? Thanks.

#3
01-16-2009, 12:28 AM
GDC
Senior Member

Join Date: Jan 2006
Posts: 1,664
Re: Bumpers and acute corners
Based on previously provided information, you have correctly concluded that all exterior corners must be protected by BUMPER segments (Rule <R08-I>). Each BUMPER segment must be a minimum of six inches in length (Rule <R08-A), and must be attached to the BUMPER PERIMETER (Rule <R08-L>). Effectively, this means that an exterior corner of the ROBOT can not be at an angle that is more acute than the coincident corner of the BUMPER PERIMETER. It follows that the example configuration you cited would not be permitted.

Re: BUMPER PERIMETER
 

Thanks to the GDC for answering this question directly.

Re: BUMPER PERIMETER
 

does anyone know what the minimum distance between the rear BUMPER and the trailer hitch would be on a square-backed robot so that the first point of contact is BUMPER to BUMPER?

Re: BUMPER PERIMETER
 

I just had this same thought today. Can anyone give a good estimate for a robot with a 28 inch back?

Re: BUMPER PERIMETER
 

That is fairly simple with some trigonometry.

The hypotenuse is the trailer tongue. The shorter end is the distance between the tongue and the first point of contact. The bumper is a known thickness. The bumper hitch is a known length, of which you need half. The pivot point is a known distance out from the bumper perimeter, which will effectively decrease the thickness of the bumper. What you need to know is part of the distance of the third side.

The main question is, at what angle will the tongue contact the bumper, and will the trailer's bumpers contact first at that angle?

Re: BUMPER PERIMETER
 

Right, but we weren't sure what that distance was, or how to find it - Does anyone know this/ know the answer to this question?

Re: BUMPER PERIMETER
 

If I didn't have homework, I'd run some numbers for a typical robot back. I'll get back to you if somebody doesn't beat me to it, though it could take a day or two.