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.