Bumpers sticking out 1" beyond frame perimeter

[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...

[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 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.

Thanks, I will definitely ask the Q&A to make sure.

[GeeTwo]

As I read OP, this could be perfectly legal. I'm ignoring the other three sides (where the bumpers are against the "frame" and seem to be exactly what the rules envision).

How I read it: On the front side, the bumpers would be located 1" forward of the "frame". Then, at least once each 8", there is a (substantial) protrusion from the "frame" which is part of the robot (not the bumper) that supports the bumper. These protrusions then define the FRAME PERIMETER. As long as the FRAME PERIMETER is still no more than 120" after including these protrusions, this would be a legal FP/bumper combination. On the other hand, if the protrusions are part of the bumper (that is, they come off the robot when bumpers are changed), they are illegal, as the hard parts now extend beyond 1" from the FRAME PERIMETER.

In a practical sense, this is the same as the bumper brackets used on many West Coast style drives, just on the front face rather than a side face.

[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.