pic: Legal Frame ????????????????

Is this a legal frame design. Last year we saw a robot in the shape of a “T” and it was almost the same rules and it passed inspection.

I would ask the Q and A for an official ruling, but my understanding is that the bumper perimeter has to be a convex polygon as defined by the definition of frame perimeter:

This has come up in past years and was not allowed, but you could always try running it past the Q&A again.

This is kind of on that same track:

If that “T” had any concave areas, it shouldn’t have passed inspection.

This looks illegal. A FRAME PERIMETER cannot be concave (barring the allotted cutouts)

You are correct Chris, and in the FIRST Forums thread there they talk about how it should not have passed.

i would say yes as long as the bumpers are ok.

Then you might want to spend some time reading the robot rules. Specifically, see Section 1 of the Game Manual, read the definition of FRAME PERIMETER. Also study section 4, specifically the information about bumpers.


That’s very interesting considering your signature. The FRAME PERIMETER of this frame would be a rectangle with the 4 outermost vertices as corners. The bumpers need to be placed along this FRAME PERIMETER with the maximum unsupported distance being 8".

We were the team that had the tee design last year and won an award for it at our first event. At the first event the ref’s questioned the design but concluded that they couldn’t see that it was positively in violation of any rule. But asked if we would ask the GDC to verify and we did here: http://forums.usfirst.org/showthread.php?t=15188 As you can see they never responded even after many phone calls. We showed up at our second event and they told us we couldn’t compete. We could have fixed it in the fix it window if they had responded. But instead were forced to fix it at the event. Redoing the frame and bumpers was not easy.

The whole thing was handled very badly with FIRST. I was very sad to see the rule in the rule book again this year. It is a very confusing rule that really should just say “no inside corners are allowed”

After much arguing at the event they finally told us what part we were in violation of. They interpret it as: The outer-most exterior vertices (aka corners) are the perimeter. Thus if you have an inside corner it is not outer-most and thus is not allowed. :ahh:

They tell us not to lawyer the rules but then they don’t write them like an engineer would and it forces us to lawyer them.

Here are this years rules:
BUMPER PERIMETER – the polygon defined by the outer-most set of exterior vertices of the BUMPERS when they are attached to the HOSTBOT. (To identify the BUMPER PERIMETER, wrap a string around the BUMPERS at the level of the BUMPER ZONE - the string describes the polygon.)

FRAME PERIMETER – the polygon defined by the outer-most set of exterior vertices on the HOSTBOT (without the BUMPERS attached) that are within the BUMPER ZONE.

In blue: To determine the FRAME PERIMETER, wrap a piece of string around the HOSTBOT at the level of the BUMPER ZONE - the string describes this polygon. Note: to permit a simplified definition of the FRAME PERIMETER and encourage a tight, robust connection between the BUMPERS and the FRAME PERIMETER, minor protrusions such as bolt heads, fastener ends, rivets, etc are excluded from the determination of the FRAME PERIMETER.

I’m an engineer, when I read the rules it’s easy for me to understand that they mean “no inside corners”.

If you’re not an engineer, yeah, I can see how it could be confusing. Although it was discussed to death here on CD…

Apparently it is better to not have a concave bumper system than to have an aluminum mechanism drop down after start to give the same desired contact design. That will mean other robot will be running into our mechanism through the match and the bumper behind it will be just for looks and rules

We had already asked the GDC about this design (yes, we thought of doing it as well). The answer was no.


Totally agree

You got an award for blatantly breaking a rule?

I understand it’s by no means your fault, and you obviously didn’t mean to, but how could that happen in FIRST?

We couldn’t get penalties for the soccer balls going more then 4 inches under the robot because the robot/frame was only 4 inches wide. That idea is what we got the award for.

It’s not likely that many judges have studied the rules…they are not the robot inspectors, after all.

what about a curved bumper?

I find it odd that they are taking away creativity when there is an award for it! I personally don’t see the harm in having a concave design. Where is the fun in building a box (rectangle) on wheels? Our team is known for doing things in a strange way!! We love that about us. Joe should be on the GDC because of his creative mind. He has inspired dozens of kids being a “wild and crazzzzy guy”!! The kids are bummed but we will go build a nice box on wheels!!

You don’t have to create a box. You simply have to have all external corners. A triangle is perfectly legal. A trapezoid (Wider on one side, narrowing down) is allowed. There are a number of shapes that are perfectly legal that don’t break any rules. Obviously, I’m not a part of the GDC, I have no bearing on the rules, but I imagine that the idea is to reduce the risk of entanglement and to ensure that things aren’t going to be as easy to break.

The string example was in the rules last year, it is a simple rule and if you REALLY struggle with doing it in your head get some freaking string and drive some nails into plywood. If the string doesn’t touch the nail it isn’t a valid vertex on your bumper perimeter.

As for it being handled poorly at FIRST’s end I have to agree, the inspectors at your FIRST event should not have allowed you to compete at all and it sucks that they lacked the understanding of the bumper rules. I was at that event and I also saw teams competing without batteries secured down and with black bumpers. I admit, my brother got sick of my picking at least one team a match that shouldn’t be allowed on the field because they shouldn’t have passed inspection. (This was Saturday and is only a SLIGHT exaggeration)

You’re right, but it is hard to give a robot that isn’t on the field an award and 326 should NOT have been on the field.