pic: Custom Chassis 2576

[Gregor]

It looks like this frame is in violation of R26.

R26
BUMPERS must be supported by the structure/frame of the ROBOT (see Figure 4-10). To be considered supported, a minimum of ½ in. at each end of the BUMPER must be backed by the FRAME PERIMETER.

You're not supporting the edge of your bumper by at least 1/2".

[TheMadCADer]

Originally Posted by Gregor

It looks like this frame is in violation of R26.



You're not supporting the edge of your bumper by at least 1/2".

The way I understand it, you could make every robot compliant with R26 by putting a string all the way around the Frame Perimeter.

The string is now your Frame Perimeter. There are no gaps at all in the frame perimeter, so you don't need to worry about the 8" gaps or 1/2" edge gaps, and the 1/4" gap doesn't come into play either. There is nothing about structural integrity in their definition of "supported".

[Gregor]

Originally Posted by TheMadCADer

The way I understand it, you could make every robot compliant with R26 by putting a string all the way around the Frame Perimeter.There is nothing about structural integrity in their definition of "supported".

Would your grandmother, or a reasonably astute observer define a string as supporting your bumper? This rule exists for a very good reason.

[Woolly]

Originally Posted by Gregor

Would your grandmother, or a reasonably astute observer define a string as supporting your bumper? This rule exists for a very good reason.

So, how about a stand-off from the inner poly-carbonate plate to the outer poly-carbonate plate? One could even have the bumper mounts such that they hook over said standoff.

[Gregor]

Originally Posted by Woolly

So, how about a stand-off from the inner poly-carbonate plate to the outer poly-carbonate plate? One could even have the bumper mounts such that they hook over said standoff.

Perfect.

[Whippet]

Originally Posted by TheMadCADer

The way I understand it, you could make every robot compliant with R26 by putting a string all the way around the Frame Perimeter.

The string is now your Frame Perimeter. There are no gaps at all in the frame perimeter, so you don't need to worry about the 8" gaps or 1/2" edge gaps, and the 1/4" gap doesn't come into play either. There is nothing about structural integrity in their definition of "supported".

Originally Posted by Rule R2

The ROBOT must have a FRAME PERIMETER, contained within the BUMPER ZONE, that is comprised of fixed, non-articulated structural elements of the ROBOT. Minor protrusions no greater than 1⁄4 in. such as bolt heads, fastener ends, and rivets are not considered part of the FRAME PERIMETER.

(Emphasis mine.)

I would't consider a string to be structural element. However, if they put something like churro tube on it at the corners, it would probably be rigid enough to be considered structural.

[TheMadCADer]

Originally Posted by Whippet

I would't consider a string to be structural element. However, if they put something like churro tube on it at the corners, it would probably be rigid enough to be considered structural.

R2 apparently differs from the definition given in the glossary. The manual should probably be edited to provide a more consistent definition of the Frame Perimeter.

FRAME PERIMETER: the polygon defined by the outer-most set of exterior vertices on the ROBOT (without
the BUMPERS attached) that are within the BUMPER ZONE. To determine the FRAME PERIMETER, wrap a
piece of string around the ROBOT at the level of the BUMPER ZONE - the string describes this polygon.

Also, I wouldn't put it past some students to find a way to use structural string (it can be done, see: suspension bridges). That'd really tie the robot together.

Originally Posted by Gregor

Would your grandmother, or a reasonably astute observer define a string as supporting your bumper? This rule exists for a very good reason.

As far as this observer goes, it depends what part of the manual you quote for them. Glossary or R2? Because using the glossary to determine that the string is the Frame Perimeter, any observer can see that the string obeys the 3 stipulations of R26. If you look at R2, then you get a whole bunch of other questions. Just how thick of a string are we talking about here? Does the string provide structure to any part of the robot (since the determination of an item being structural in R2 is independent of supporting the bumpers. The string doesn't need to support your bumpers to be your Frame Perimeter).

The rule exists so you don't wreck your bumpers in a collision. However, there are many ways to wreck more than just your bumpers in a match. Why are bumpers special? This year, if a team's bumpers break they are disabled for the match (G20). If something like your drivetrain or scoring mechanism breaks during a match, you may not be disabled, but it's close to it.

It is absolutely possible to make bumpers that will withstand the collisions in a match without following these rules. Why not let teams try? I fully support maintaining a set of guidelines similar to the current rules, but I'd like to see people get a bit creative with more parts of their robot. One of my favorite things to see is a team with bumpers that provide structure for their robot, rather than the other way around, using the bumpers to offload some weight from the robot.

[EricH]

Originally Posted by TheMadCADer

R2 apparently differs from the definition given in the glossary. The manual should probably be edited to provide a more consistent definition of the Frame Perimeter.

It doesn't. The string is a visual aid. If I wrap a string around the exterior vertices of the frame and stretch it tight, the string describes the frame perimeter. Not "is", "describes". A suitable comparison: You getting fitted for a suit--are you trying to say that because a tape measure is wrapped around your waistline, it is your waistline? Didn't think so.

Bear in mind, I've been dealing with bumper rules since '06. Some things are obvious to me because I've been dealing with 'em so long, but that particular definition/description has been in there since at least '08, if not '06. (I can't quite remember whether "bumper zone" or "frame perimeter" came into play first, or if they came in at the same time.) The key thing about the bumpers is that they serve 3 purposes: Protect the robot against impact with other robots/field elements, Identify the team by number, and Identify the alliance by color. If you've got a suggestion for the GDC that will result in looser bumper rules, while still fulfilling these three purposes, I suggest that you let them know. With all the restriction-easing going on, they might welcome the suggestion as one less place the inspectors have to inspect.

[TheMadCADer]

Originally Posted by EricH

It doesn't. The string is a visual aid. If I wrap a string around the exterior vertices of the frame and stretch it tight, the string describes the frame perimeter. Not "is", "describes". A suitable comparison: You getting fitted for a suit--are you trying to say that because a tape measure is wrapped around your waistline, it is your waistline? Didn't think so.

Bear in mind, I've been dealing with bumper rules since '06. Some things are obvious to me because I've been dealing with 'em so long, but that particular definition/description has been in there since at least '08, if not '06. (I can't quite remember whether "bumper zone" or "frame perimeter" came into play first, or if they came in at the same time.) The key thing about the bumpers is that they serve 3 purposes: Protect the robot against impact with other robots/field elements, Identify the team by number, and Identify the alliance by color. If you've got a suggestion for the GDC that will result in looser bumper rules, while still fulfilling these three purposes, I suggest that you let them know. With all the restriction-easing going on, they might welcome the suggestion as one less place the inspectors have to inspect.

You've misunderstood what I'm talking about regarding the string. This string is a fixed part of the robot, not the visual aid. The string used to identify and measure the Frame Perimeter is different and irrelevant. By your suitable example this would be more of a belt for your pants than a measuring tape for the fitting of said pants.

I'd suggest removing the need for specific supports for the bumper (basically removing R26) by opting for a rule more similar to the safety of robot mechanisms, like G3.

G3
ROBOTS whose operation or design is unsafe are not permitted.
Violation: FOUL & DISABLED. If the issue is due to design: Re-Inspection.

Or, modified for bumpers:

G20
ROBOTS must be in compliance with Section 4.6: BUMPER Rules throughout the MATCH.
Violation: DISABLED. If the issue is due to design: Re-Inspection.

We're already doing the first half by disabling failed bumpers. All we need to do is implement the second half (teams need to prove the problem is solved to re-enter match play) if we want to allow more restriction-easing.

[EricH]

Originally Posted by TheMadCADer

You've misunderstood what I'm talking about regarding the string. This string is a fixed part of the robot, not the visual aid. The string used to identify and measure the Frame Perimeter is different and irrelevant.

I was directly responding to your saying that R2 and the definition are at odds--no other part of your post, or any previous post. They aren't--and they still aren't. If you wrap a string, and it remains part of your robot, it isn't structural (unless you know of uberstrong string that I don't), and therefore is not the frame perimeter.

Let's break R2 down into what it's ACTUALLY saying.

The ROBOT must have a FRAME PERIMETER polygon defined by the outer-most set of exterior vertices on the ROBOT (without
the BUMPERS attached) that are within the BUMPER ZONE, contained within the BUMPER ZONE, that is comprised of fixed, non-articulated structural elements of the ROBOT. Minor protrusions no greater than 1⁄4 in. such as bolt heads, fastener ends, and rivets are not considered part of the FRAME PERIMETER. [Replaced "Frame Perimeter" with its definition and removed a repetitive section.]

Now, what part of that would allow a string, which is not made of unobtanium, to define even part of the frame perimeter? Nope, I'd call it a minor protrusion. It's not structural--strings don't exactly push well, and it's difficult at best to build a frame completely in tension--and the argument could be made that it can articulate. You tryin' to use the tailor's measure as a belt?

They aren't saying different things. They're saying the same thing in two slightly different ways. If someone were to show up at inspection and try to claim a string as a structural element, they'd be rebuilding that part of their robot if any other bumper rules--particularly support--were violated.


Now, with respect to the rest of your last post: Woefully inadequate. After all, what's to prevent someone from showing up with bumpers on a post on a corner mounted in such a way that the first hit leaves them disabled for a bumper rules violation? I don't know if you've ever inspected, but I have--if you open up the support rules like that, an awful lot of teams will be missing their 2nd matches due to inadequate supports, just trust me on that. If simply re-inspecting is going to be the solution, sorry, but I really hope that you're volunteering, 'cause by the time teams come looking after their first match with inadequate support, the few inspectors still "on duty" will be focusing in on teams with more pressing issues--like an illegal motor, or a faulty pneumatics system, or their first match is in ten minutes and they need a full inspection.

Support needs to be defined in such a way that it's relatively simple for an inspection team to determine that a team is good or not. "Looks good" from an inspector may or may not be adequate validation for a design--I can think of several inspectors that I'd trust that from, because they've been around a while; others that I've heard of, not so much. Try writing the rule such that the support test is included in the rule--say "RXXXX: Bumpers shall be adequately supported. Inspectors will check by dropping a 5-lb weight onto the bumper from 5' above it; if the bumper moves or breaks, it shall be rebuilt until it passes."

[TheMadCADer]

Originally Posted by EricH

I was directly responding to your saying that R2 and the definition are at odds--no other part of your post, or any previous post. They aren't--and they still aren't. If you wrap a string, and it remains part of your robot, it isn't structural (unless you know of uberstrong string that I don't), and therefore is not the frame perimeter.

Let's break R2 down into what it's ACTUALLY saying.

The ROBOT must have a FRAME PERIMETER polygon defined by the outer-most set of exterior vertices on the ROBOT (without
the BUMPERS attached) that are within the BUMPER ZONE, contained within the BUMPER ZONE, that is comprised of fixed, non-articulated structural elements of the ROBOT. Minor protrusions no greater than 1⁄4 in. such as bolt heads, fastener ends, and rivets are not considered part of the FRAME PERIMETER. [Replaced "Frame Perimeter" with its definition and removed a repetitive section.]

Now, what part of that would allow a string, which is not made of unobtanium, to define even part of the frame perimeter? Nope, I'd call it a minor protrusion. It's not structural--strings don't exactly push well, and it's difficult at best to build a frame completely in tension--and the argument could be made that it can articulate. You tryin' to use the tailor's measure as a belt?

They aren't saying different things. They're saying the same thing in two slightly different ways. If someone were to show up at inspection and try to claim a string as a structural element, they'd be rebuilding that part of their robot if any other bumper rules--particularly support--were violated.


Now, with respect to the rest of your last post: Woefully inadequate. After all, what's to prevent someone from showing up with bumpers on a post on a corner mounted in such a way that the first hit leaves them disabled for a bumper rules violation? I don't know if you've ever inspected, but I have--if you open up the support rules like that, an awful lot of teams will be missing their 2nd matches due to inadequate supports, just trust me on that. If simply re-inspecting is going to be the solution, sorry, but I really hope that you're volunteering, 'cause by the time teams come looking after their first match with inadequate support, the few inspectors still "on duty" will be focusing in on teams with more pressing issues--like an illegal motor, or a faulty pneumatics system, or their first match is in ten minutes and they need a full inspection.

Support needs to be defined in such a way that it's relatively simple for an inspection team to determine that a team is good or not. "Looks good" from an inspector may or may not be adequate validation for a design--I can think of several inspectors that I'd trust that from, because they've been around a while; others that I've heard of, not so much. Try writing the rule such that the support test is included in the rule--say "RXXXX: Bumpers shall be adequately supported. Inspectors will check by dropping a 5-lb weight onto the bumper from 5' above it; if the bumper moves or breaks, it shall be rebuilt until it passes."

PM'ed. This isn't the place.

[Duncan Macdonald]

Did you actually put it on a scale to verify the weight savings? I would be surprised if there was a significant savings by using a material ~45% as dense and twice as thick.

The frame as configured does not pass bumper rules and needs additional thickness in the corners. It does just squeeze into the size limit but how do you expect an inspector to measure 0.005 or 0.020 with a tape measure that probably measures in 16ths? Do you lose that much usable space by making the frame a quarter inch narrower? I promise it will get you through inspection faster.

Do you have your manipulator mounting planned? One of the nicest features of the kit frame is that there is a mounting point every inch.

It took a long time for one of my teams to learn that just because you have resources available doesn't mean it is smart to use them.

[jsasaki]

Make sure you grease your gearboxes!