Bumpers sticking out 1" beyond frame perimeter

[jamesmcip]

Originally Posted by EricH

I had a step by step response, but I suddenly had a "Eureka" moment. The key parts of the rule here are R21B, R21G, and R21A, as well as R26. But first... the part that triggered that "eureka" moment.

My apologies to Boltman for calling him out, and my thanks to same for helping me understand this little dilemma. He's wrong. "Hard parts" includes the plywood, angle used to clamp cloth, angle used to join plywood to plywood around a corner, AND the mounting system (what he refers to as "fasteners"). That's what R21B calls out. Don't believe me? Look at the rules it references. All that is measured off of the robot's Frame Perimeter. (The "minor protrusions" would refer to ends of fasteners embedded in the bumper to allow attachment to the robot.) You can have a gap in the support system (Frame Perimeter) of either <1/4" wide, and as long as you want (less the ends of the bumper), or <8" wide, and as deep as you want (less the other side of the robot).


I would say that under R21B, you're going to be found in violation if you use a block system attached to the bumpers (but not if the blocks are attached to the robot frame); R21A is potentially going to be hard to show legal with that big of a clearance hole (again, that'd be an inspector making the call at your event); R26 makes life interesting when it doesn't need to be.

You've got a few options here. I would start by exploring moving the motor. Not knowing how it's mounted, etc, I'd say a longer belt/chain would be in order. Or maybe rotating it 90* and using bevel gears. I might also look at moving the intake slightly backwards. Or how about moving the bumpers up or down to avoid the intake?

The really "interesting" option would be to reconfigure the entire Frame Perimeter to allow you to attach blocks to the frame, redefine the front end of the robot, and attach to the blocks with no additional problems. Of course, that might take another 4-5 weeks that you don't have, so that'd be the very last option you should take.

Thank you very much for your thorough response. We will definitely try moving the motor first, as we can CAD that and most likely accomplish it with a simple mounting plate. Well, after all this, our mechanisms will probably only work better by having a smaller bumper profile.

[Chris is me]

Originally Posted by EricH

My apologies to Boltman for calling him out, and my thanks to same for helping me understand this little dilemma. He's wrong. "Hard parts" includes the plywood, angle used to clamp cloth, angle used to join plywood to plywood around a corner, AND the mounting system (what he refers to as "fasteners").

I'm sure this is what you meant, but just to be clear for those who aren't aware, the 1" hard parts rule is extending outward FROM the FRAME PERIMETER (i.e. toward the pool noodle side). You are allowed to have your bumper mounting system extend INTO the frame perimeter as much as you want, there is no restriction in that direction. However, you cannot significantly offset bumpers from your FRAME PERIMETER with hardware - that hardware would then define a new FRAME PERIMETER if part of the frame.

Edit: I just skimmed the rest of the thread and apparently this was a needed clarification!

[Al Skierkiewicz]

First I think you can see how difficult answering questions on the Q&A can be based on this discussion.

As to the bumpers, mounting blocks, protrusions, etc. An inspector must determine the FRAME PERIMETER before making any decisions based on FRAME PERIMETER as a reference. In WCD, the frame is determined by frame extensions between wheels that will be used to support the bumpers. Whatever the design for bumper support, the FRAME is examined for openings and gaps that are greater than 8" wide or more than 1/4" deep, FRAME that is 8" or greater wide as measured from each corner and hardware extensions from the FRAME PERIMETER that do not exceed 1/4". When these determinations have been made, then and only them can a bumper design be evaluated. In my understanding of the OP, it is their intention to add blocks to the back of the bumpers to position the bumpers out 1" from the FRAME. On the surface this sounds illegal. A legal design would be to mount the blocks and/or a plate on the robot chassis which will then be evaluated for FRAME PERIMETER. These blocks can be used as long as they are less than 8" apart and satisfy all the other rules like the 1/2" minimum support at each end of the bumper. No matter what you design, you cannot ignore the gap rules in the FRAME PERIMETER as shown in Fig. 4-9, R26, or Team Update 05.
Clearance holes are intended to allow teams to get a nice tight fit of their bumper system to the frame of the robot when they have hardware protruding outside of the frame for things like bolts used to hold the wheels and spacers on the kitbot chassis. In no case will clearance holes be allowed for motors as you describe. In that case, the FRAME PERIMETER is actually the motor in the resting position and that now would be the reference for bumpers that must be mounted on the FRAME PERIMETER.

While we are on the subject, if your team is using the kitbot chassis and they are using the standard bolts for wheel axles, please remember that the nylock nut and washers go on the inside of the chassis. The bolt should be mounted so that the head is facing out. The standard bolt head is less than 1/4". That is one of the intentions of the 1/4" gap rule for bumper mounting. If a team still wants to mount their bumpers with no gap, then the bumper can have clearance holes to reduce the 1/4" gap caused by the "bolt heads" as stated in R21.B.

[Boltman]

Originally Posted by jamesmcip

The motor is only an issue when the intake is fully extended, when retracted it is fully contained within the frame perimeter. I cannot post a picture as of now as we do not have access to the school until Tuesday.

The way I read it is the hard parts "plywood" can not be thicker than 1"
As for fasteners it looks like an up to 1" gap is allowed as the picture shows a 2" gap as not allowed meaning to me at least a smaller <= 1"gap is otherwise there is no point in that picture. The gap is spanned not by "hard parts" but by fastners.

[waialua359]

Originally Posted by EricH

I think you'll have more trouble with R21G than with R21B. Your bumpers are supposed to be attached to the Frame Perimeter. If your mounts are part of the bumpers, I would not consider your bumpers to be constructed in compliance with R21 (in total).

Of course, the "easy" way around this would be to build the mounts onto the robot... but that changes what your Frame Perimeter is and lengthens it.

Has the rules changed in recent years based on your interpretation?
Why would it matter if your mounts are part of the bumpers vs. the robot frame if the exact position of the bumpers is on the frame perimeter?
This allows robots to meet weight requirements and moving the weight of mounts to the bumpers who has a max weight of 20lbs. We have done this for years and passed inspection before.

[EricH]

Originally Posted by waialua359

Has the rules changed in recent years based on your interpretation?
Why would it matter if your mounts are part of the bumpers vs. the robot frame if the exact position of the bumpers is on the frame perimeter?
This allows robots to meet weight requirements and moving the weight of mounts to the bumpers who has a max weight of 20lbs. We have done this for years and passed inspection before.

The rule hasn't changed.

But the implementation specifically called out WAS a change from the norm. Specifically, the bumpers (other than the mounts) were NOT on the Frame Perimeter. As in, the normal, standard, FRC bumper, that we all know and love, was being proposed to be mounted on blocks, as is normal on the sides of a West Coast Drive, except that the blocks would be mounted on the bumper, and THEN mounted on the front of the robot (you know, where the classic WCD has a frame member nicely defining the Frame Perimeter). And therein lies the problem. R20, Blue Box: If a multi-part attachment system is utilized (e.g. interlocking brackets on the ROBOT and the BUMPER), then the elements permanently attached to the ROBOT will be considered part of the ROBOT, and the elements attached to the BUMPERS will be considered part of the BUMPER. Each element must satisfy all applicable rules for the relevant system.
(Emphasis mine)

EDIT: I've attached two pictures. One is of the WCD "standard" bumper mounting, with the attachment points being hardmounted to the robot. The other is of the proposed bumper mounting, with the attachment points being on the bumper. One is legal. One is not.

And the legal one would extend the frame perimeter, which per the OP would make the robot illegal under a different rule altogether.

[waialua359]

Originally Posted by EricH

The rule hasn't changed.

But the implementation specifically called out WAS a change from the norm. Specifically, the bumpers (other than the mounts) were NOT on the Frame Perimeter. As in, the normal, standard, FRC bumper, that we all know and love, was being proposed to be mounted on blocks, as is normal on the sides of a West Coast Drive, except that the blocks would be mounted on the bumper, and THEN mounted on the front of the robot (you know, where the classic WCD has a frame member nicely defining the Frame Perimeter). And therein lies the problem. R20, Blue Box: If a multi-part attachment system is utilized (e.g. interlocking brackets on the ROBOT and the BUMPER), then the elements permanently attached to the ROBOT will be considered part of the ROBOT, and the elements attached to the BUMPERS will be considered part of the BUMPER. Each element must satisfy all applicable rules for the relevant system.
(Emphasis mine)

EDIT: I've attached two pictures. One is of the WCD "standard" bumper mounting, with the attachment points being hardmounted to the robot. The other is of the proposed bumper mounting, with the attachment points being on the bumper. One is legal. One is not.

And the legal one would extend the frame perimeter, which per the OP would make the robot illegal under a different rule altogether.

Now I see where you are coming from.
Ours is a different case. Our frame perimeter is not extended, but instead our bumper has attachments that extend into the frame perimeter resting on a flat point, providing the bumper support that the 8" rule asks for. This allows us to transfer the weight of robot mounting points to the bumper weight instead. Its also easier when removing the bumper, because it is already being fastened at other points. The main purpose for doing this was to meet the bumper support rules while not adding to the weight of our robot for certain sections on the side of our robot.
Again, our bumper is mounted on the frame perimeter.

[EricH]

Originally Posted by waialua359

Now I see where you are coming from.
Ours is a different case. Our frame perimeter is not extended, but instead our bumper has attachments that extend into the frame perimeter resting on a flat point, providing the bumper support that the 8" rule asks for. This allows us to transfer the weight of robot mounting points to the bumper weight instead. Its also easier when removing the bumper, because it is already being fastened at other points. The main purpose for doing this was to meet the bumper support rules while not adding to the weight of our robot for certain sections on the side of our robot.
Again, our bumper is mounted on the frame perimeter.

And we're doing something similar, to a point (we do have hardware on the robot side, but only to lock down the bumper). I think you'd be interested in the other thread, discussing using bumper attachments as cross-bracing.

[waialua359]

Originally Posted by EricH

And we're doing something similar, to a point (we do have hardware on the robot side, but only to lock down the bumper). I think you'd be interested in the other thread, discussing using bumper attachments as cross-bracing.

Thanks for the info.
Actually, ours serves another purpose, but I cant say.....yet.

[GeeTwo]

Originally Posted by waialua359

Now I see where you are coming from.
Ours is a different case. Our frame perimeter is not extended, but instead our bumper has attachments that extend into the frame perimeter resting on a flat point, providing the bumper support that the 8" rule asks for. This allows us to transfer the weight of robot mounting points to the bumper weight instead. Its also easier when removing the bumper, because it is already being fastened at other points. The main purpose for doing this was to meet the bumper support rules while not adding to the weight of our robot for certain sections on the side of our robot.
Again, our bumper is mounted on the frame perimeter.

As I read this, your bumper has "hard parts" that are more than 1" outside the FRAME PERIMETER, violating R21 B.

[waialua359]

Originally Posted by GeeTwo

As I read this, your bumper has "hard parts" that are more than 1" outside the FRAME PERIMETER, violating R21 B.

"Inside" the frame perimeter, not outside.

[GeeTwo]

Originally Posted by jamesmcip

Today we have finally made our bumpers and decided to have it flush with the frame perimeter on all sides except for the front, which would have a gap of 1" between the plywood of the bumper and the front of our chassis.

Originally Posted by waialua359

"Inside" the frame perimeter, not outside.

At first, I didn't see how to de-conflict these two statements. As you are located some 5,000 miles from OP, you are probably describing completely different situations. This makes it virtually impossible to help either of you, as both of you are responding as though you are teammates.

Mounting brackets that reach inside the FP are allowed (Q744), but if extensions of the "chassis" cause the hard parts of the bumper to extend more than 1" outside the chassis, the extensions to at least within 1" of the edge of the hard harts of the bumper must be permanently mounted parts of the FRAME PERIMETER for the configuration to be legal.

[Nate Laverdure]

Originally Posted by GeeTwo

As you are located some 5,000 miles from OP, you are probably describing completely different situations. This makes it virtually impossible to help either of you, as both of you are responding as though you are teammates..

Glenn and the OP ARE describing completely different situations. Please be careful not to overlook the context in your eagerness to help.