Bumper Rules on a U Bot Chassis

[alexpell00]

Hello,

We have a U bot design with 5" wide walls at the each end of the U. I wanted to know if we can just cover each 5" section and still be ok with the 8" bumper rules. Does the 8" rule change if there is no chassis there, or do we need to have some internal bumpers? Internal bumps would be pointless but if it is what we need.

[M.O'Reilly]

Before the other sharks get you on this forum, let me answer your question real quick:

You must have 8 inches of bumper extending in both directions from every perimeter-defining corner. The bumper must be backed by the robot frame, so 5 inches is not enough. Internal bumpers are not necessary, and would not be counted.

You can see the game manual for example cartoons. There are also many other threads on ChiefDelphi that explain the rules.

Good Luck!

[Jon Stratis]

Please read the bumper rules carefully. The bumpers sit along the FRAME PERIMETER, not just the chassis. The FRAME PERIMETER for a U shaped robot is a rectangle - there is no opening or gap in the FRAME PERIMETER. You cannot have "internal bumpers"- they are not bumpers at that point, but part of your robot.

You will need to extend your frame another 3" into the opening of the U in order to get 8" of bumper properly mounted from each corner.

[ASmith1675]

In section 4.7 in the game manual, reference "Robot Frame Perimeter C" as an example of exactly what your are referring to.

[Rockant]

So, the bumper rules won't actually change, regardless of the size of your chassis. Basically, your bumpers need to extend at least 8" from each corner of the robot. But, yes, read the bumper rules. They will tell you all you need to know.

[alexpell00]

I read the rules just wanted to make sure before we redesign a bit. Thanks for the clarification!

[ICE_Bear]

We were going to have an open front for our robot that's short enough to go under the low bar... We will have about 4.5 inches on each side of the front of our robot that's actually our frame. So we will have nowhere to connect the bumpers on the front. And since our chassis IS our frame since there is no other metal or anything other than electrical wiring above the chassis. What do we do? We have no mentors to help us interpret the rules and help us change our design if we need to.
So basically right now, we have all of the electrical and mechanical stuff set up very basically. We just have a chassis, so with the wheels, the top is at about 5" from the ground. We weren't planning on having a front part of the chassis so that we'd be able to have an attachment to help open the portcullis. So now I'm kinda stuck now trying to understand the bumper rules and see if we can still use our design at all.

[David Brinza]

We were going to have an open front for our robot that's short enough to go under the low bar... We will have about 4.5 inches on each side of the front of our robot that's actually our frame. So we will have nowhere to connect the bumpers on the front. And since our chassis IS our frame since there is no other metal or anything other than electrical wiring above the chassis. What do we do? We have no mentors to help us interpret the rules and help us change our design if we need to.
The bumper rules are clear on the 8" minimum bumper segments from each corner of the frame perimeter. Unfortunately, as described, your current design will not pass inspection.

If you post a drawing or photo of your existing robot chassis, you might get some suggestions from CD on how to bring your robot into compliance without a major redesign.

[ICE_Bear]

Wouldn't you just have to cover the entire piece that IS there? per R19

[MrBasse]

Wouldn't you just have to cover the entire piece that IS there? per R19

Read the sentence just before the one you are thinking of in R19 and you'll see why you need at least 8" covered.

[GaryVoshol]

That's not how "side" is defined. The side is from outside corner to outside corner, including any gaps that happen to be in that side. See ROBOT FRAME PERIMETER C (lower left) in Figure 4-3. The FRAME PERIMETER follows the black line around the ROBOT, including the portion spanning the gap. It is marked "NOT OK" since that bottom "U" is less than 8 inches.

[ICE_Bear]

That was labeled "NOT OKAY" because the corner wasn't covered, not because it was less than an 8" piece of the side.

Since it's our chassis piece that's only 4.5 inches long, wouldn't each individual piece be a side?

[David Brinza]

That was labeled "NOT OKAY" because the corner wasn't covered, not because it was less than an 8" piece of the side.

Since it's our chassis piece that's only 4.5 inches long, wouldn't each individual piece be a side?
There are two "NOT OK" labels for Figure 4-3 C - one for an uncovered corner, the other for a segment <8".
You are receiving replies from experienced mentors and robot inspectors, you should consider how to address your design issue. If you are not satisfied with the responses from CD, you should post on FIRST Q&A for official clarification.

[Boltman]

Its fairly simple to determine what size bumpers you need.... use walls and string

Place your robot against wall (without bumpers) that defines a side THEN for each side at least 8 in. of BUMPER must be placed on each side of each outside corner. IF a side is less than 8" entire side must be covered.

So for a U shaped bot the front side would require 8" bumpers per front corner. Thats assuming traditional U-shape with two front corners.

For odd shapes... or to verify corners

Simply wrap a string around the bot (in bumper zone)..any corner of that string shape (frame perimeter) needs an 8" bumper per outside corner side. So its hard to get around 8" rule even with very unique shapes. Either each comer needs 8" bumper side or the entire side <8" needs a bumper, your choice. Anything inside the frame perimeter shape does not need a bumper.

Your extension zone is now 15" beyond original frame perimeter with same shape.

[MrBasse]

That was labeled "NOT OKAY" because the corner wasn't covered, not because it was less than an 8" piece of the side.

Since it's our chassis piece that's only 4.5 inches long, wouldn't each individual piece be a side?

Don't rely on pictures, READ the rules. If you just look at pictures you'll never get the whole story.

Earlier you referenced r19. Read r19. Then re-read r19 just to be sure. I'm on my 7th time through the full manual plus all the other times I have check little items in between. If you read it you'll get your answer and notice every side that is less than 8 inches must be fully covered. You'll also see that you need a minimum of 8 inches covered from each corner.

[mastachyra]

Word of this change needs to be spread more loudly, or many teams are going to have a major issue at competition. Our robot has been driving and picking up balls for two weeks and now we need to widen our chassis. This is a huge waste of time.

I'm currently looking at the rules we printed out on kickoff day, and this rule is unclear. I guess I interpreted the words "side" and "frame perimeter" to mean different things. The frame perimeter was clearly an imaginary line around the robot, but I took "side" to mean a physical side of the robot.

It was especially confusing because the rules say "If a side is shorter than 8 in., the entire side must be protected by BUMPER"

I can take a picture of the old figure 4-3: BUMPER Corner Examples if anyone is interested.

[Chris is me]

Word of this change needs to be spread more loudly, or many teams are going to have a major issue at competition.

This isn't a change. This is how the rules have been written since the beginning - the only "change" is the addition of a picture to better explain the rule. The rules have been like this every year we've had openings in bumpers, going all the way back to at least 2009.

[dradel]

I find it hard to understand why teams are having so much problem understanding the bumper rules?

[engunneer]

I find it hard to understand why teams are having so much problem understanding the bumper rules?

especially this year, there are two years of "Bumper Rookies" because there weren't bumpers last year.

There are a lot of bumper rules, but it's very hard to explain clearly in a way that doesn't get lawyered. I wonder if there is a white paper yet on how to check your bumpers for legality with pictures and a step by step procedure. That might be helpful for the rookies.

[Karthik]

I find it hard to understand why teams are having so much problem understanding the bumper rules?

A few reasons.

1. There are twice as many teams this year who have never had to build bumpers. Both 2016 and 2015 rookies have never had to deal with the bumper rules.
2. This is the first season since 2012 that most teams have really needed an opening in the front of their chassis for an intake. In 2013 intakes were rare, in 2014 the ball was so large an opening was irrelevant, and in 2015 there we no bumpers. So we have 4 years worth of teams who have never dealt with the difficulties of having to have 8" of bumpers on each corner of your robot.
3. The bumper rules are not generally intuitive. If you don't give the manual a detailed review and analysis, it is very easy to misunderstand the definition of a Frame Perimeter

With all the questions about bumper openings I've seen on the Q&A, CD, and our team inbox, I worry that we're going to have a lot of teams who are rebuilding bumpers and/or their frame perimeter after their first attempt at passing inspection.

[ChuckDickerson]

I find it hard to understand why teams are having so much problem understanding the bumper rules?

As do all of your friendly robot inspectors every year (except last year). Bumpers should be easy. There are several pages of bumper specifications and illustrations that have changed little over the last several years. In my experience as an LRI most bumper issues stem from teams not thoroughly reading and comprehending the bumper specifications in the beginning (at kickoff) and including them in their robot design from the start. Way too many teams put bumpers off until a build season week 5 or 6 after thought and then try to figure out how to make bumpers fit on their now locked in stone robot design instead of considering them a design constraint and including them in their robot design from the beginning. Even worse are the teams that walk in the door at their first competition with no bumpers and think they are going to design, build, and properly attach their bumpers at competition with materials they don't even have.

[engunneer]

With all the questions about bumper openings I've seen on the Q&A, CD, and our team inbox, I worry that we're going to have a lot of teams who are rebuilding bumpers and/or their frame perimeter after their first attempt at passing inspection.

RIs at every event would be really happy if teams with a little extra room in the truck could bring the bits to events to help teams make bumpers. Most events have a few bumpers worth of spare bits, but I expect the need to be higher this year.

If you have rookie teams in your area, and you know the bumper rules down pat, offer to visit and check compliance. Late in the season is better than at the first event!

[mastachyra]

3. The bumper rules are not generally intuitive. If you don't give the manual a detailed review and analysis, it is very easy to misunderstand the definition of a Frame Perimeter.

I don't think it was clear that the word "side" referred to the side of the frame perimeter and not a side of the robot structure.

[dradel]

I didn't think of the two years of bumper rookies.

[ChuckDickerson]

A few reasons.
If you don't give the manual a detailed review and analysis, it is very easy to misunderstand the definition of a Frame Perimeter.

Karthik makes a great point here. As an LRI I also find too many teams that don't understand the difference in their robots "frame" and the FRAME PERIMETER. The former is defined by the team and their robot design. The later is defined explicitly in the rules. Sometimes they are one and the same but often they are not.