27-01-2014 16:32

cbale2000

Re: pic: Custom Chassis 2576

What thickness is that polycarbonate?

27-01-2014 16:34

josemagr

Re: pic: Custom Chassis 2576

6 millimeters = 0.236220472 inches

27-01-2014 17:00

Damiaen_Florian

Re: pic: Custom Chassis 2576

Was the only reason to switch the outer plates to polycarbonate because of the weight? Also let me say that the polycarbonate chassis aesthetically speaking is amazing as well

27-01-2014 17:37

josemagr

Re: pic: Custom Chassis 2576

We believe that the weight reduction was an attractive detail, so that made us switch the outer plates.

We wanted a square chasis because of the systems that we were prototyping and designing. If we use the AM14U by AndyMark, our team would need to have cut the plates and we didn't have the correct machines. Since 2010 Sabic Polymershapes Chile was one of our best sponsors and they are available to support us with materials and machining.

The polycarbonate is a special material, very strong and esthetically amazing. Because we had the oportunity to work with this material, we tried something new on the chassis, and the result was a strong and attractive chassis.

27-01-2014 17:41

Boe

Re: pic: Custom Chassis 2576

One step closer to having a transparent robot which is one of the cooler looks a robot can have

http://www.chiefdelphi.com/media/photos/37570
http://www.chiefdelphi.com/media/photos/36596
http://www.chiefdelphi.com/media/photos/34998
http://www.chiefdelphi.com/media/photos/32862

27-01-2014 22:23

Gregor

Re: pic: Custom Chassis 2576

It looks like this frame is in violation of R26.

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

27-01-2014 22:47

TheMadCADer

Re: pic: Custom Chassis 2576

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".

27-01-2014 22:57

Gregor

Re: pic: Custom Chassis 2576

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

27-01-2014 22:59

Whippet

Re: pic: Custom Chassis 2576

(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.

27-01-2014 23:01

Woolly

Re: pic: Custom Chassis 2576

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.

27-01-2014 23:03

Gregor

Re: pic: Custom Chassis 2576

Perfect.

27-01-2014 23:58

TheMadCADer

Re: pic: Custom Chassis 2576

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.

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.

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.

28-01-2014 00:13

EricH

Re: pic: Custom Chassis 2576

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.

28-01-2014 00:39

TheMadCADer

Re: pic: Custom Chassis 2576

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.

Or, modified for bumpers:

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.

28-01-2014 01:10

EricH

Re: pic: Custom Chassis 2576

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."

28-01-2014 02:31

TheMadCADer

Re: pic: Custom Chassis 2576

PM'ed. This isn't the place.

28-01-2014 02:43

Duncan Macdonald

Re: pic: Custom Chassis 2576

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.

28-01-2014 07:36

jsasaki

Re: pic: Custom Chassis 2576

Make sure you grease your gearboxes!