Bumpers sticking out 1" beyond frame perimeter

[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. We assumed, as per rule R26, that if we supported the bumper at least every 8" we could have a gap between the frame perimeter and bumpers as long as we wished, within common sense of course.

However, we just realized that this may be a violation of R21B, which essentially states that hard bumper parts must not extend more than 1 inch away from the frame perimeter.

Is it legal to extend the bumpers in this manner?

[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.

[jamesmcip]

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).

Sorry for asking, but what specific rule would this violate? Unfortunately as it stands our frame perimeter cannot be any larger so we would have to modify the bumpers to make it work. One thing we could do is cut 1" x 6" "clearance holes" as defined by R21A to help with clearing our intake motor.

[Boltman]

Originally Posted by jamesmcip

Sorry for asking, but what specific rule would this violate? Unfortunately as it stands our frame perimeter cannot be any larger so we would have to modify the bumpers to make it work. One thing we could do is cut 1" x 6" "clearance holes" as defined by R21A to help with clearing our intake motor.

Just make it "the gap" 1 inch or less considering the hard parts/fastner of your front bumper. 1" is not more than 1".

"Hard BUMPER parts allowed per R21-A, R21-E, R21-F, and R21-G must not extend more
than 1 in. beyond the FRAME PERIMETER with the exception of minor protrusions such as
bolt heads, fastener ends, rivets, etc"

[Dave McLaughlin]

I'm guessing R21G...

[jamesmcip]

Originally Posted by Boltman

Just make it "the gap" 1 inch or less considering the hard parts/fastner of your front bumper. 1" is not more than 1".

"Hard BUMPER parts allowed per R21-A, R21-E, R21-F, and R21-G must not extend more
than 1 in. beyond the FRAME PERIMETER with the exception of minor protrusions such as
bolt heads, fastener ends, rivets, etc"

It believe that includes the 3/4" of the plywood for the bumper, meaning the gap must be less than 1/4". Clearance holes it is...

[EricH]

Originally Posted by jamesmcip

Sorry for asking, but what specific rule would this violate? Unfortunately as it stands our frame perimeter cannot be any larger so we would have to modify the bumpers to make it work. One thing we could do is cut 1" x 6" "clearance holes" as defined by R21A to help with clearing our intake motor.

You might want to post a picture, but I wouldn't exactly call a motor a "minor protrusion" allowed by R2--which would mean that you're potentially already over the frame perimeter. If I could see a picture, I could tell pretty quickly where your perimeter is and where you think it is.

The rest of the response will follow shortly, I'm taking some time to get it right.

[jamesmcip]

Originally Posted by EricH

You might want to post a picture, but I wouldn't exactly call a motor a "minor protrusion" allowed by R2--which would mean that you're potentially already over the frame perimeter. If I could see a picture, I could tell pretty quickly where your perimeter is and where you think it is.

The rest of the response will follow shortly, I'm taking some time to get it right.

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.

[EricH]

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.

And... you can't move the motor on the intake? Just a thought.

That's a legal move, by the way. I'll modify my response to cover that note, and post it in a few minutes. I can get mighty detailed sometimes...

[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.

[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.

[Boltman]

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.

Figure 4-9 clearly shows a 7" gap covered by a bumper as OK along with a 1/4" gap..are we absolutely sure a 1" gap as OP described is not allowed?

BTW thanks for the clarification, I just want to get to the bottom of this for the OP.

[EricH]

Originally Posted by Boltman

Figure 4-9 clearly shows a 7" gap covered by a bumper as OK along with a 1/4" gap..are we absolutely sure a 1" gap as OP described is not allowed?

BTW thanks for the clarification, I just want to get to the bottom of this for the OP.

There's a big difference in a gap in support and a gap between the Frame Perimeter and the Bumper.

= is bumper. _, -, and | are support and robot structure. Let's see if the ol' TextCAD can convey this.

What the OP is talking about:

==============
___|______|_____ 1" gap between bumper and frame, 8" between supports. This is legal in one configuration and illegal in another. I'll explain below.

What you're talking about, and what the Manual is talking about:

==============
----|______|----- Where the gap in the narrow areas is <1/4" bumper to frame, up to infinitely long, and the gap in the wide area is <8" long and infinitely deep


Now, that first situation is legal IFF the supports are part of the frame of the robot. Standard move to put bumpers on a WCD and all that. But, the supports count towards the Frame Perimeter. But let's switch that up.

===|=====|======
___|_______|______

Now the supports are on the bumpers. They're NOT part of the Frame Perimeter determination, they're part of the bumper hard parts (R21B), and at that point, you basically have 1/4" before your plywood goes beyond your 1" allowance (R21B, combined with R21A's plywood requirement). OP is talking about a 1" gap, so you've got hard parts (plywood) almost 2" beyond the Frame Perimeter. Sorry, folks, that's not going to fly...

[Jon Stratis]

If I understand the description correctly, the plywood on the bumper in question would not touch the frame perimeter at all - it would be 1" off it, with the brackets holding it in place being the only part to touch.

This really, really does not meet the intent of the rules, and as an LRI I could easily point to many of the rules referenced in here. But really, I think it comes down to R26 and figure 4-9. Figure 4-9 shows the bumper plywood resting along the robot frame, but there being gaps in the frame. The intent of the rule is to allow those gaps in the frame of the robot. It is NOT to allow you to essentially have an oversized robot. As an example, lets take it to the extreme... what if I build a set of bumpers with 6" deep blocks on the back every 8", and attach that to my frame perimeter? I'll end up with a robot that, when interacting with other robots, has an effective frame perimeter of 168" - it would be HUGE. Clearly, that's not what we want on the field.

I also would not consider a 1"x6" "clearance hole" to be "small", and I would suspect that something that large would "significantly affect the structural integrity of the BUMPER", as described in R21-A. The intent of the clearance holes in R21-A, as I understand it, is to allow a flush, rigid construction of the bumper. It's so you can account for any bolt heads or slightly protruding axels and still have a bumper that is snug and tight against the frame perimeter. It's not so you can get more motion in your mechanisms.

I strongly suggest looking at any options for moving that motor to a better location.

Edit:
You could also ask a question on the Q&A. Something specific, like "Is it legal to have a bumper mounting system that holds the plywood 1 inch outside the frame perimeter, so long as there are hard mounts to the frame every 8 inches?" Asking a very specific and clear question like that and getting a positive response is really the only way to be sure you'd be fine at competition.

[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.