Bumpers and the Frame Perimeter

[HammadB]

Do wheels define the frame perimeter? Our team has cantilevered wheels so they jut out the width of the wheel from the "frame". Or do we have to create a surface to which the bumper mounts that is the same distance out from the frame as the wheels?

See the attached picture for further clarification, except picture the wheels as top down not laying flat so that they only protrude approx. 1 inch (Width of wheel) from the frame.

[LinuxArchitect]

Your wheels must be inside the robot frame.

[R01-2] The Robot must have a Frame Perimeter that is comprised of fixed, non-articulated structural elements of the Robot.

The bumpers then directly attach to that frame. Standoffs are not allowed.

[R33] Bumpers must be supported by the structure/frame of the Robot (i.e. each end of the Bumper must be rigidly attached to the Frame Perimeter, the gap between the backing material and the frame must not be greater than ¼ in. and no section of Bumper greater than 8 in. may be unsupported).

[GaryVoshol]

Standoffs would be allowed provided they are no more than 8" apart. You can have up to 8" unsupported plywood on the bumper. The ends of each bumper segment must also be supported (they don't want them cracking off).

[Jeff Pahl]

The frame perimeter is defined by wrapping a string around the outermost vertices of your robot. This means you need to have hard corners that stick out farther than your wheels for the string to wrap around. These hard corners will also serve to support the ends of your bumper segments, as required. Then, as mentioned, you have to have structural support standoffs with a spacing of less than 8" between them. They need to be structural enough for the inspectors to believe that there is no risk of them collapsing or causing the bumpers to fail.

For example, it would be hard to convince me that a standoff that was a single 1/4" bolt or rod on an 8" spacing was structural.

So no, your drawing is not legal. You don't have to bring frame out all the way around your wheels, but you have to bring something out at the corners and out past the wheels every 8" to support the bumper. This should not be too big an issue unless you are using 8" or larger wheels.

[Bob Steele]

I would have to respectfully disagree with the idea that the wheels have to be within the frame.

They do have to be within the frame perimeter (which is a fictional line found with a piece of string.)

You could have wheels outside the frame as long as your attachments for the bumpers (which could be place above the wheels or between depending on the wheel size) allow for bumpers that are of the correct height, construction and proper support as detailed in the rules.

The frame perimeter doesn't have to have anything in common with the actual
"frame" of your robot...it usually does but it doesn't have to.
Take a look at the West Coast Drives from the past several years...
the wheels are cantilevered outside the "frame"

I think your drawing is pretty good except that the "string" would mean that the corners of your robot would have to have another "stand off" to support the bumpers there also...

good luck!!

[Tristan Lall]

The disagreement in principle detailed above is simply a reflection of the fact that FIRST has failed to define the frame.

I'm inclined to believe the frame is whatever the team tells me it is, within reason, seeing as it's their design. I'm not too concerned about how structural it is.

(Whether the bumpers are securely fastened to that frame with a tight, robust connection system is a separate issue—there structural integrity might matter.)

[nnfuller]

Can you please quote a rule that says the bumpers must be supported on the corners? I do not see this in the bumpers section. Also, as a good practice, quote rules when asked about legality.

[bhsrobotics1671]

See Team Update on January 17

[R33]
Bumpers must be supported by the structure/frame of the Robot (i.e. each end of the Bumper must be rigidly attached to the Frame Perimeter, the gap between the backing material and the frame must not be greater than ¼ in. and no section of Bumper greater than 8 in. may be unsupported). See Figure 4‑7.

[Steve W]

[R02]
The Robot must satisfy the following size constraints:
A. horizontal dimensions must not exceed 28 by 38 in.,
B. the absolute height must not exceed 84 in.,
C. the height of the Robot at the start of the match must not exceed 60 in.,
D. any appendage may not extend more than 14 in. beyond the frame perimeter, and
E. no other part of the Robot may extend beyond the vertical projection of the Frame Perimeter (with the
exception of minor protrusions permitted per 0).
Expect to demonstrate the Robot’s ability to constrain itself to the envelope defined in
Rule 0 to Inspectors.
Please refer to Section 3: The Game for Robot spec ific dimension constraints during the
Match.
If a Robot is designed as intended and pushed up against a vertical wall (with Bumpers
removed and appendages retracted), only the Frame Perimeter (or its minor protrusions)
will be in contact with the wall.

As an LRI it seems clear to me. The bumpers are to be fastened to the frame so how do wheels fit in?

[EricH]

Originally Posted by Steve W

[R02]
The Robot must satisfy the following size constraints:
[...]
E. no other part of the Robot may extend beyond the vertical projection of the Frame Perimeter (with the
exception of minor protrusions permitted per 0).
[...]
If a Robot is designed as intended and pushed up against a vertical wall (with Bumpers
removed and appendages retracted), only the Frame Perimeter (or its minor protrusions)
will be in contact with the wall.

As an LRI it seems clear to me. The bumpers are to be fastened to the frame so how do wheels fit in?

I would like to remind the LRI of the definition of Frame Perimeter found in [R01-2]. This definition allows wheels to extend beyond the frame, provided that they do not cross the Frame Perimeter ([R02-E] as quoted) and the gaps are under the size allowed by [R33] for adequate bumper support (and the bumpers are attached as per [R28-E]).

However, the OP's attached design shows a rather octagonal frame perimeter. This may make compliance with multiple portions of the bumper rules rather difficult. The question in the drawing is which frame perimeter is the real one; the answer is that without something structural (per the attachment rules for the bumpers) out in front of the front wheels and behind the back wheels, neither is the actual one. There's a diagonal portion from the corner of the frame to either the wheel or the standoff, most likely the standoff because the frame perimeter cannot have articulating elements (and this diagonal could easily cause a violation of [R02-E] and [R27]'s 8" coverage requirement from a vertex). Structural elements other than the standoffs would probably not be necessary on the sides due to the gap allowance and the definition of frame perimeter; however, all gaps should be checked for compliance with [R33] and extra structure planned for accordingly.

To answer the OP shortly: No, the wheels would not define the frame perimeter due to being articulated/moving; they would exceed it instead. You'll need something to extend the frame perimeter (as defined by the rules) beyond the wheels.

[Al Skierkiewicz]

Gentlemen,
Without ruling on the bumper design we have to first establish a Frame Perimeter. That is determined by wrapping the virtual string around the frame in the critical zone of 2" to 10" above a flat floor. In the above example, I see nothing that would support the string such that the Frame Perimeter encloses the wheels as shown in the drawing. Bumpers aside, this design does not meet the Frame Perimeter rules.

[LinuxArchitect]

Originally Posted by Bob Steele

I would have to respectfully disagree with the idea that the wheels have to be within the frame.

True, you could have the wheels located in the allowed frame gaps. Not sure why such a design would be desired, but who knows.

The wheels only have to be inside of the frame perimeter.