legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Hi,

I should have thought of this earlier, but our robot design is such that our wheel brackets are flush against the surface of the chassis of our robot. To assemble the wheel brackets, we use 1/4-20 cap screws and 3/8" bolts and such. Our bumpers mount to the chassis such that the plywood is flat against the C-channel.

When the wheel brackets are mounted to the chassis, the heads of the bolts holding the wheel brackets together extend into the plane that is between the bumper plywood and the chassis. Is this going to cause a problem with the rules?

I really hope not...because only the bolt heads go through this plane. Even with the bolt heads, our robot (wo bumpers) is within the volume restrictions.

Thanks for your time!
windell

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

There was an update regarding this issue... main concern here is that you can fit within the sizing box. The other issue is covered in the update.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

According to the FRAME PERIMETER rules this year, these bolt heads will not be allowed. You will have to artificially inflate your frame perimeter (by gluing strips of wood, plastic, etc) around your chassis so the bolt heads that aren't within the BUMPER ZONE are within the FRAME PERIMETER.

It's a pretty dumb rule, but it is what it is. Hopefully it will be amended next year.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Here is a picture I made for training my inspectors...

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Mike,

You should add one more element to your excellent picture

The wood backing of the bumper sits on top of the bolt head without any kind of indention. In other words, the bumper is not firmly backed by the frame.

Many Robots will arrive violating R16
 

Judging from the many robot photos already posted, many teams have misinterpreted R16:

" During normal operation no part of the ROBOT shall extend outside the vertical projection of the FRAME PERIMETER, except as permitted by Rule <G30>.
a) Exception: To facilitate a tight, robust connection between the BUMPERS and the FRAME PERIMETER, minor protrusions such as bolt heads, fastener ends, rivets, etc that are excluded from the determination of the FRAME PERIMETER and are within the BUMPER ZONE are permitted."

I am afraid that teams read the "minor protrusions such as bolt heads, fasteners, ..." independent of the BUMPERS -- like last year's rule.

My guess is that 50% of the robots will arrive to week one events out of spec.:eek:

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Okay, some responses in this thread are causing me to be confused. I thought this year fastener heads and small protrusions were NOT considered part of the FRAME PERIMETER as per the definition provided in Section 8, Page 4:

Now my interpretation is that this means that bolt and screw heads are OK if they extend past the FRAME PERIMETER - regardless of whether they are within the bumper zone or outside of it (i.e, this exception is not limited to bolt heads and screw heads between 10" and 16" above ground level).

Why would I interpret this in this way?

1) Because the definition doesn't explicitly say the bolt head exclusion is limited the bumper zone area.

2) If the bolt head exclusion only applied to the bumper zone, robots with extended bolt heads above or below the bumper zone would just shim their frames to artificially extend the FRAME PERIMETER - exactly what Art Dutra suggested above - and completely counter to the intent of "encouraging a tight, robust connection between the BUMPERS and the FRAME PERIMETER."

However, these bolt heads and screw heads must STILL comply with the overall 36" x 28" maximum dimension. Meaning you might have bolt heads that stick out of your frame, but you still must FIT IN THE BOX.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

It says that the frame perimeter is defined inside the bumper zone (first sentence).

See also <R16>.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Thanks Joe, having one of those days... :rolleyes:

And yes Coach Tom, you're probably right that many teams will show up with illegal robots - it looks like I'm a prime example of one of those people who were confused!

But to avoid sidetracking this thread, I'd like to know then if the OP's situation is in fact LEGAL assuming all extended bolt heads are within the bumper zone, and the bumpers have been counterbored to allow the bumper to sit flush against their frame.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Ok, I'm a bit confused.


Frame Perimeter

R-16

Note Under R-16

These Three parts of the rules completely contradict each other.

The definition of frame perimeter is consistent with the first part of R-16, which would make bolts protruding perfectly legal.

The note under R -16 completely contradicts everything. I would be more inclined to believe that a part of rules would be more correct than a note underneathe, and I would also be more inclined to believe that something that appears in the rules twice would be more correct than a note that occurs once. Based on what I've seen and read I have no reason to believe that protruding bolts are illegal; true there is some gray area, but since two distinct sections say it is legal, I would think that I can fairly assume that it is legal.

To me the rules pretty clearly allow the bolts to protrude as neither of the first two quotes I posted have been removed from the rules.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Remember, notes are meant to clarify. They are not rules.

If the bolt and screw heads are in the bumper zone, you're fine. Just make sure the bumpers are pocketed to take the bolt heads.

If the bolt and screw heads are above or below the bumper zone, you're not fine and will have to either expand the frame perimeter or reduce the bolts' protrusion to zero.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

If in fact a robot had bolt head extending out of the frame perimeter, but inside the bumper zone, then when the bumpers were removed and the robot were pushed against a wall, the bolt head would hit the wall and not the frame perimeter, which would make this note not make sense.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I think the note was a good example in illustrating the general application of the FRAME PERIMETER, which was its original intent. It's not as good in illustrating the protruding bolt head exclusion, which was added later in a Team Update(?).

The note clarification does make more sense if you interpret that the protruding bolt heads in the bumper zone "simply disappear" because they are excluded from the FRAME PERIMETER. By magically pretending the excluded bolt heads no longer exist, your FRAME PERIMETER should be the first thing to touch a wall.

(That also means any protruding bolt heads above or below the bumper zone will cause a problem - they are NOT excluded, and still have to be taken into account in the example)

Kind of a weird assumption, and I've already shown in this thread that making assumptions is generally a bad idea. However if you do this, the scenario seems to better the reflect the actual rules as written.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I know that this is a complicated area of the robot rules. You must look at all the rules and the bumpers must satisfy all the paragraphs in R07. Fasteners and bolt heads inside the bumper zone are permitted to extend beyond the FRAME PERIMETER and in R07, par D, holes and pockets are allowed to be made in the backs of the bumpers to facilitate secure mounting of the bumper system. In no configuration may any part of the robot exceed the maximum dimensions of R10 whether that be inside or outside the bumper zone. As pointed out above those fasteners in the BUMPER ZONE that project outside the FRAME PERIMETER are permitted. Similar fasteners projecting the same amount beyond the FRAME PERIMETER but outside the BUMPER ZONE are not permitted.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I'm sorry to keep dwelling on this topic, but does anyone know the intent of this rule? What changed from last year to this year, or any other year that made this rule need to be changed?

I can't see anything harmful about having a bolt extend a little underneathe the bumpers. The only thing I can see is if they were sharp, but that is covered in R-04 and thus shouldn't make a difference in the determination of this rule.

(That said the rules are the rules and we have to follow them, I'm just curoius if anyone knows the intent)

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

What is the reasoning behind this rule?

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

It appears to me that the note does not contradict the rules, but rather clarifies them; the "minor protrusions such as bolt heads, fastener ends, rivets, etc... within the BUMPER ZONE" (in my view) are allowed in order to attach the bumpers to the robot, and when the bumpers are removed, so are said protrusions. Then "you should be able to push the ROBOT... up against a vertical wall, and the FRAME PERIMETER will be the only point of contact with the wall."

So, if my reasoning is correct, the only protruding bolts allowed are the bolts holding the bumpers on.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

The Protruding bolts most certainly are not the ones holding the bumpers on. They are attached to the frame, see my second post for some clarification on where the note doesn't line up with the rules.

I understand what the rules are saying, but the intent of the rule is still somehwere outside of my knowledge base.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I'm only speculating -- since this year's game has the bumpers very high off the carpet, R16 helps to limit perturbing fasteners, bolts etc. below the bumper zone.

Team Overdrive is already planning a quick fix to our robot since our wheels currently have bolt heads perturbing outside our frame perimeter. We already fit into the allowable dimensions.

I still predict that more than 50% of the robots will arrive at their first regional out of spec per R16. This will delay the regional for sure.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I'm going to guess about 1/3 of the robots will have trouble with this rule, although I wouldn't be surprised for it to be as high as 50%.

The thing I definitely disagree with is that it will delay regionals. The events will go on, even if some robots have not passed inspection.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Team Overdrive is assuming that welds at perimeter joints (or below) are not protrusions -- otherwise we will be grinding down some metal. What fun!

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I'm afraid your assumption will be wrong. It might be easier to make shims to move your perimeter out a bit to cover your welds.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

There has been much discussion about this topic in this thread.

As for why, there has been much discussion about the why of rules in this thread.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Thank you for steering me to the prior threads. Woo ... What a discussion.:ahh:

I noticed that Team Overdrive's Rules Captain "Scout Master" (a student) chimed in on the thread in late January. At the time, it appeared that bolt heads could protrude beyond the vertical perimeter below the bumper zone (at least that was her conclusion). So, we proceeded with our design. By sheer luck, I stumbled onto this thread today. Team Overdrive can fix our robot to comply within the strictest compliance, but it will take about one hour of valuable time at the regional. We will grind down our welds and counter sink our shaft bolt heads.

I agree with the Mentor from Wildstang (111), clarification of this issue came way to late in the build season. Team Overdrive gives 100% of rule compliance responsibility to our students. After week four, they thought this issue was settled -- especially since common sense seemed to be obvious. Fortunately, we have a relatively quick fix. Many other teams will not. Also, depending on a team’s bumper design, "adding a shim" is not always possible.

I sure hope the local regionals give some grace on this otherwise I still see a lot of out of spec robots.

Respectfully, Coach Tom (FRC 2753)

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

After installing shims to expand our frame perimeter on our wide dimension to deal with this issue I strongly hope that regionals DO NOT give any grace on this issue.

The rule is certainly obnoxious (and perhaps a bit confusing), but it is obnoxious for everyone and I see no reason why other teams should be excused from following rules we put in the time and effort to adhere to.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I'm glad you had an easy shim fix. My fear is that many robots were completely designed and well into fabrication by week 4.

Good luck.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

we have a low frame that is 27.5 by 37.5, then a foe frame made out of velurite (corrugated lexan) glued to C channel to avoid this problem.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Yeah, I had that fear too. My team had that problem, and still does. We didn't pick up on the ever so slight change in the wording from last year, and our drivetrain was fully fabricated week 4, so we have to fix that on Thursday at WPI.

I read the other threads and still don't quite understand the intent. If I extend my frame perimeter out a quarter of an inch to cover the bolts, the bolts are still protruding, they're just a quarter inch further in in relation to the bumpers, which makes practially no difference except that it causes a lot of teams the trouble of the fix it on the first day of regionals. I'd like to see the GDC change the rule to save a lot of teams the hassle, It would have no negative effect on anyone, it just save people wasted time and effort.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I would just like to say that use of "etc." in a rule is generally a bad idea in my opinion. To try to pin down an exact meaning of a rule written with it is maddening.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

we riveted 1/8" aluminum strips to either side of our frame, because we couldn't counterbore due to the space in the middle of the 1x2 8020

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Without pointing fingers or fanning flames, in my humble opinion, and we all know what opinons are worth in todays market, this is an example of an area in the rules where graphics would be extremely helpful.

I know the GDC is probably up to here with opinions and I respect what they have to do each year, and I have no doubt they put a lot of time and effort into this to ensure that the playing field is level for all, but this would probably remove a lot of the questions that inevitably arise from taking ideas that are expressed in text only and the resulting confusion from interpreting these ideas.

Mike

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

The sad thing is as I look through the pictures posted of team's robots, I would be willing to bet that >75% are illegal due to this stupid ruling.

IMHO, the GDC made a hasty ruling, and instead of eating crow and retracting or changing it like they have in the past when such a thing happened (like the "no band saws in the pits" ruling), and correct it to the obvious and rational ruling, they are sticking with it and it's going to really cause a ton of problems at the early regionals.

All for nothing.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Stupid ruling? Hasty ruling? Not the correct or rational ruling?

... seems to me that we have been given a requirements specification list from our customer (rules from FIRST) that we need to comply with. Whether you agree with these requirements or not, you accepted them as a part of your terms so that you could compete and now that you've shipped your product and it doesn't comply you call the requirements stupid?

Doesn't make much sense to me. Seems your time would be better spend figuring out how to comply with the requirements and not bashing them.

JM(NS)HO

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Rules don't become not stupid just because we have to follow them. Of course everyone's going to follow and accept the rules, and most if not all of the people complaining have made their robots compliant. I don't see why we have no right to complain over something that was legal week 3 and then illegal week 4.

If no one ever complains, how would anyone ever know anyone had a problem with any rule? The rule IS stupid and hasty, even though we do have to follow them. Yeah, in the real engineering world, complaining that your boss or client gave you a requirement isn't a good idea, but I'd rather not jade my teammates into the philosophy that there's no use expressing an opinion on anything. Just yet.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

And I think you missed my point completely.

Our robot is bagged and meets the requirement. If I was only worried about our robot, then I wouldn't be spending my time "bashing it".

But, I have a broader view of the problem outside of just my team and I'm thinking of the 75% of the robots that show up at the competition and have to really work hard to make their robot legal due to a stupid ruling instead on focusing on better things...if they can even make their robot legal.

Now, if the ruling was just changed to allow fasteners (welds, strings, etc.) outside the bumper zone...we can stop bashing...and I can stop worrying about all the teams that have no idea that this problem will be there when they go to inspection on Thursday/Friday...

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Segue to the real world for a moment… I agree that simply complaining is not a constructive approach for resolving issues (requirements or otherwise) but communications is absolutely essential in engineering. My experience has been that in complex projects there is almost always a two-way communications channel between the engineer and the customer. Requirements are an abstraction of what a customer wants (by the way this leads to the distinction between system verification and validation). Said another way, requirements are a powerful communication device but they don’t always perfectly reflect the customer’s desires. Many times the customer’s need can’t even be fully articulated. That is where direct dialog with a customer is crucial to ensure that we aren’t spending disproportionate time and material resources on meeting requirements that don’t really represent the customer’s need in the first place. As an engineer, when I don’t understand the rationale behind a particular requirement that really means that I don’t fully appreciate the customer’s problem and means I better spend more time communicating. So please don’t think that in engineering requirements always come down from high engraved in stone.

I think the frustration that we see in many of these requirements "debates” is that we have a limited communication channel for understanding the rationale behind non-obvious requirements. As practicing engineers, we are trained to think critically about requirements, figure out how to make improvements, and then communicate this back to the customer. Friction results when we can’t “close the loop” between our thought processes and our customer’s. In FIRST, the GDC obviously has the authority to define the requirements any way they like. I would like to think that they aren’t intentionally trying to irritate their engineering mentor base with arbitrary rules, but the question remains how can we bridge the gap in our understanding without an appropriate communication channel? Since we haven’t been able to carry on an effective dialog with the GDC, we instead turn to our peers on Chief Delphi in hopes that maybe they can set us straight.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Rules and laws are just contracts between people, and when we find them to be misguided, we continue to follow them but heavily lobby for their repeal (hopefully with the pen and not the sword). Right now, I can't see any logical reason why a bolt head that sticks out a quarter inch past the FRAME PERIMETER (but remains inside NORMAL CONFIGURATION) is illegal except for "because the GDC said so". I never accept "because we said so" as a valid reason, because it reeks of arrogance on the part of the person or entity making the rule and only seeks to downplay the intelligence of those to which the rule is given.

We're smart people. If the GDC gave us a logical reason why bolt heads couldn't extend past the barrier, then most rational people here, myself included, would accept it and move on. Until then, I think this is a pretty dumb rule.

If this was the real world, and a client specified that no bolts could stick out, I'd personally ask why. For all I know it could just be that the boss of said client's company thinks flat head bolts look nicer than socket head bolts, but would compromise with button head bolts in order to save the costs of countersinking lots of bolts. When engineers know why specs are the way they are, they can better design systems to meet the genuine intent of the client, as opposed to the what the client thinks they want/need.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Last time I checked, we are a part of a high school robotics competition meant to inspire young students into science and technology careers. FIRST is a lot of fun and it keeps us all in it.. but that does not mean we should have to deal with rules nobody can comprehend the reasoning behind. I don't blame anyone for being upset about this rule. Saying "I'm sure GDC has a sound backing behind this rule" soothes no one. Fortunately, our robot was relatively simple but I pity teams who have to re-build parts of their robot at the regional... or rebuild an entire robot at regional because of a shipping mishap.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Art,

First off, I don't like the ruling anymore than the next guy, but ...

Asking your customer for the reasoning behind a spec is all well and good (and actually very wise), but posting on a unofficial, public forum that their specifications are "stupid" is niether proactive nor wise. This is neither the proper forum, nor the proper way to get an appropriate answer ... hence my "whine" comment.

Also, when asking for the reasoning, you might want to consider "because we said so" as a valid answer, lest your customer take his multi-billion dollar buisiness elsewhere. You see there may be many possible reasons why they cannot disclose information to you (IP issues?). Consider this just a design constraint.

All in all, you might consider just putting your efforts into making sure that those who didn't follow the letter of the rule still get on the field, rather than bash those who put the design constraint in place.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Wait.. FIRST is our customer?? :ahh::ahh::ahh::p

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I understand the idea that real world engineering has to respond to a customer's constraints, but in the real world, how often can customers change an extremely important facet of the their specifications 75% through production without having to pay some sort of price or be told they need to wait a bit longer?

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

After this ruling came out, I took a look at our design and pointed out where we were in compliance and where we were not. The lead mentor looked at me like I had two heads. I told him "We either change it now, or change it on the first day of the competition. Your choice." We changed it then and there, while we still had the luxury of making the change in the shop, and not the pressure of a competition starting in a couple of hours. I agree that the perhaps the ruling could have been handled better, but teams were given the chance to respond to the ruling and make the needed design changes. So file this under "life isn't fair" and move on.

Adding to what Daniel said, so now we have a different issue, and one that has some degree of urgency. The week one competitions start in 60 hours from now. We have recognized that this year, more than most years (in our case, due to Snowmeggeddon primarily), we will need to be organized and ready to assist other teams to help get them ready to compete. We have communicated with the other teams at the Chesapeake regional to see who has the ability to help, and who needs help. My suggestion would be - get a bunch of pre-cut plywood strips and bring it to the competition and be organized and ready to assist as soon as you can. Maybe next year things can be done differently, but doubt we will see much movement on the change to this rule this year. Think of this as a major glitch, barrier, crisis, etc... and find a way around it/fix it/solve it. Who knows, maybe the GDC wanted to introduce some crisis and see how everyone responded? I know half the major projects I manage, that usually happens too!

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Al, the rules allow you to pocket the bumper to allow for bolts, etc sticking out of the frame perimeter, but is it REQUIRED or just allowed? I thought that by being excluded from the frame perimeter, bolts, tie straps, etc can stick slightly out of the perimeter and the bumper sit flush (with the exception of the fasteners) without being pocketed.

For our case, we just have tie straps wraping around the frame in the bumper zone. Will we be required to have 10 vertical and horizontal notches on our bumper to allocate for these tie straps to allow the bumper to be perfectly flush? Or is it okay to just slap the bumper on the tie straps? The tie straps being used are small (similar to the vex ones).

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Here is a QandA that does not address this question directly,
but is quite close.

Join Date: Jan 2010
Posts: 1
Warped Bumpers
We manufactured two sets of bumpers early in the build, to the specifications of <R07>. Since then, we have mounted the bumpers on the robot and found the 3/4" plywood has warped, making them slightly convex. Do the bumpers have to be in contact with the frame through the entire length of the robot?
#2
02-15-2010, 11:35 AM
GDC
Game Design Committee

Join Date: Jan 2006
Posts: 2,401
Re: Warped Bumpers
Yes. Please refer to Rule <R07-M>. The BUMPERS have to be supported along their entire length.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Thanks for posting that Eugene, I had managed to skip over or miss that one.

I'm going to guess that at least 50% of robots and potentially many, many more will not be in compliance with that response when they come out of the crate.

I hope the inspectors show some common sense and let small gaps (less than 1/8"), due to slight warping of the plywood or parts of the frame that aren't perfectly square, pass.

I may be heavily arguing for a piece of foam as a frame member if inspectors don't take it into their hands to be reasonable with this one.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

1/4 inch Styrofoam bumper spacers may be pretty popular
this year, considering the vagaries of the rules and fact that
robots are almost always weight challenged. We will see
what happens.

Eugene

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Kika and others,
The bumper design is intended to protect your robot. The GDC looked very hard at the effects on last year's damage and saw that bumpers, as designed, indeed protected our robots. Part of that design is the backup frame structure that prevents the bumpers from damage due to extreme flexing. Robot inspectors will evaluate each bumper implementation to determine if, in their opinion, the bumpers satisfy the rule. If anyone thinks that a 3/4" slab of plywood can absorb the hit of two 150 lb objects by itself should look for a post from Dave Lavery last year on this subject. The bumper system includes the backing frame structure and will be evaluated with that in mind. To that end, the GDC has allowed you to "pocket" the bumper (not drill holes through the material that will weaken the plywood) to allow the bumper to use the backing of the frame to strengthen the system. If you have two bolt heads at each end of the bumper that cause it to be separated from the frame for 35", some failure will occur. If your inspector asks you to make four small pockets, I don't think he/she would be out of line. Please be prepared to remount your bumpers during the inspection process following weigh and size. This step will be needed to evaluate the bumpers, check for height and ball intrusion and kicker extension if any.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

If the GDC has looked very hard at the bumper design, then how is it they overlooked the most critical element - the plywood? There's a whole lot of difference between the 13 ply Baltic Birch plywood we use and the 5 ply soft-wood junk they sell at Home Depot. The ruling spends just one word, "plywood", on the most important part, but goes into great detail and updates about trivial air gaps. It just doesn't make sense!

Al - I'll bet you a dollar to a doughnut (no Krispy Kreme please) that a 35" slab of our plywood will take that hit. ;)

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

In 2007 we had a bumper of high quality plywood unsupported over about 30 inches. It snapped like a twig our first match. We replaced the wood and it happened again so we played the rest of the regional with a broken bumper. At our next regional we replaced it with cheep Lowe's plywood and it lasted almost the entire regional before it broke (it had more spring.)

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Ah - there's our mistake, we should go to Lowes instead of Home Depot. :)

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

No comment...
Agreed on plywood type. Most teams are going to opt for the cheapest available or what ever is left over from another construction project. Sam's experience is what the GDC is trying to avoid and what we are trying to inspect.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I'll take your bet ;)

In 07 we snapped our front bumper 3 times, including once with 4 pieces if 1/2" angle aluminium. It took less than 30 seconds to snap it and we couldn't move faster than 6'/sec.

* Bumper was unsupported across 35" of frame giving a 1" space behind it.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Not that I don't like Home Depot I just cant stand all that orange.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I would rather deal with sickening orange than the terms "FRAME PERIMETER" and "BUMPER ZONE"...

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Maybe I should have stressed more that issues in life like this are never white-and-black, but usually blurry grey areas that need context on a case-by-case analysis.

Doing any kind of classified work with need to know basis obviously means you don't ask questions and just do your job. But for non defense/classified work, I've seen first hand or heard of many other stories where the given specs were indeed misguided, and upon further back-and-forth questioning, a mutually beneficial agreement was found.

One such case a professor of mine told me recently, was of a large manufacturing corporation contracting out work for a french fry sorting machine. But when one did the math, their requested weight tolerance for the bag of french fries was 1/4 the weight of a single french fry. How would you bag something as multifarious as french fries and keep a weight tolerance of 1/4 of a french fry? Had my professor's company simply accepted these specs without asking questions, they would have had to create an unnecessarily complex sorting machine to sort individual french fries by weight and bag them one at a time, possibly with a french fry slicer to cut fries in half to get within the given weight specs. This would have been a much slower and more expensive machine than would have been necessary, and would have cost the client more money (both initially and in annual O&M costs) and possibly would have cast the contracted company in a bad light for coming up with an unnecessarily complex and expensive solution. But...

When they asked their client and showed them the math that the given specs were +/- 1/4 of a french fry, the client acknowledged the error and redid the specs to allow a wider error range.

For myself personally, I've worked for a company which produced an integrated system for clients that lacked X feature which all competitors had, but only because our integrated system was better designed to eliminate the need for X feature without any side effects other than a cheaper bottom line. Because most competitors had X feature, bids would often come in requesting this given feature, despite the fact that X feature was notorious for never actually working in the environment they were subject to. Nearly all of the time, when we talked to the clients and explained that our system was designed in a way to eliminate the need for X feature, saving initial and O&M costs, and that most competitors' X feature would almost always fail within three months of installation (and would then be bypassed anyway by the client's technicians), the clients would come to a mutual understanding and accept our bid.

Thus, it's all about context. Sometimes it's appropriate to question the given specs to better serve the customer (potentially saving them money), other times just do your job and don't ask questions.

Both can be done without negatively affecting each other. And I understand your reasoning on this; plenty of times in the past I've posted that teams shouldn't whine when other teams have "better" robots or "better" facilities, but they should instead work harder to become one of those said teams. But for those cases, that's an example where the cause for the individuals' whining can be directly attributable to their own specific actions (e.g. if they work harder, they can fix the situation they are in). In this case, no matter how hard one works, the bumper rules are still the bumper rules, and thus it's acceptable to "whine" to make sure those who could rectify the situation have a true understanding of the impact of said rule on the community at large.

I've personally always been one who calls things like they see it. Maybe it's blunt, but it's better to get right to the point than dance around the tree sugarcoating problems and hiding how they truly impact the affected people or entities. Bolt heads behind bumpers are completely understandable, and so is the allocation for small pockets in the plywood backing to allow bumpers to sit flush for strength reasons.

But when the rules as written would not even allow for a 1/16" high button-style rivet head above or below the bumpers... that's just a needlessly restriction on FIRST teams. 50-75% of robots should not show up at their first event unknowingly illegal; if it does occur, then that's obviously a sign the rules were too bloated and/or full of ambiguities to be comprehended by the average Joe FIRSTer.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Robots shall have a base-plate of prefabulated plywood, surmounted by a malleable logarithmic casing in such a way that no two spurving bearings can be in a direct line of contact with another robot's pentametric fan. ...:D

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

At risk of going even farther off on a tangent, I thought I’d clarify this sentence. Working in this type of environment does not prohibit communication instead it limits how and with whom that communication occurs. If anything, communication within these projects can be even more crucial because we are frequently pushing the envelope of technological feasibility. My experience across a spectrum of projects with security restrictions is that engineers maintain an almost constant dialog with program management, peer engineers, customer engineers, R&D labs, subcontractors, etc. Within really complex systems, it is nearly impossible for any one person to be an expert in all detailed aspects. Thankfully, we work in integrated teams so that we don’t have to. There are definite down sides of working in restricted environments such as this but you can also do some really cool engineering.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

The requirement for 100% full, CONTINUOUS, intimate contact of bumper plywood with the entire perimeter of the frame is rather excessive. Especially when there is no similarly draconian requirement for exactly where within the 5" height of the plywood that the frame makes contact. If frame only touches at the top or bottom 1" of the plywood, the bending torque force with a 4" cantilever of unsupported plywood at middle of side is also very serious with dynamic impacts!
It would make much more sense to have a simple spec for a maximum allowed spacing distance between points of support of frame in contact with bumper's plywood. If this spacing distance was between 3-6" the chance of breaking plywood would be minimal.

We currently have three aluminum plates on all four of our bumpers, one at each end and a 3rd in the middle. They are mounted with flat head screws going both ways, outward into T-nuts on plywood and inward into T-nuts inside frame slots. Screw heads are all countersunk into the thickness of the aluminum plate. The plates also stick up higher than the top of the bumper so that we can access the mounting holes for the plate-to-frame screws.

We were assuming that these plates were part of the bumper, since they fit within the 1" max. thickness of plywood plus mount H/W, but now we have the issue of plates only giving intermittent contact with frame-to-plywood. We also have the issue of plates sticking up past plywood. Is this still legal, as long as the aluminum plates still remain within the 10"-16" above floor bumper zone?
Perhaps we should consider treating the plates as part of the frame, and then filling in the gaps between the plates with similar thickness aluminum bar along the frame face, to give a 5mm expanded frame perimeter. Fortunately, we are not at the max 28"x38" size already and have some room to do this.
-Dick Ledford

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Somehow, I prefer the days of battle scars to the bumpers of today.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Dick,
I am your Lead Robot Inspector in Chicago. I will lead you through the fine points in two weeks. We will get you playing, guaranteed.
BTW, I assisted the original Francis Parker team, Frank's Garage and came to the school then to check on progress.
See you in a few weeks or you can come up to Milwaukee next week and see how things go at a regional event. If nothing else, come up on Saturday and check out other teams and watch the game play. I will be inspecting there as well. Just ask for Big Al and someone will point me out.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

I like to imagine my robot with mensur schlager scars.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Flashes to a darkened shop, late at night, candles burning and the sound of swishing blades in the air...

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Kevin,

It is not an issue of being sensible. As an engineer, I abhor specifications without tolerances. As an event volunteer, I must do as I am told.

Robot inspectors, referees and other key event personnel do not have the ability to post to the official Q&A. Only the teams can do this.

The official Q&A is, in my opinion, a perfect republican governance. The teams paid good money to compete. Only they can question the authority via the official Q&A.

If you wait until the event to try and complain to the inspectors about the non-sensibility of a rule (or the GDC's interpretation) you are virtually guaranteed to lose the argument.

I hope this makes clear the path that you and other teams must take to insure that you have no problems at robot inspection.

Regards,

Mike

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Mike,

I definitely do not envy the role of inspectors this year, especially after doing "preliminary inspections" at a pre-ship event. I fully understand the role/position the inspectors are put in, and arguing the sensibility of a rule that the inspector neither made nor has the authority to change is a waste of my time and theirs.

I plan to post a Q&A to see if teams can get a clarification on the tolerance of the full width support, but I am not particularly hopeful for a clear, unambiguous answer.

We will be ready to make that tiny gap disappear if necessary to pass inspection on Thursday, and we certainly won't be complaining to the inspectors who donate their time to help us compete if we are required to do so.

Re: legality of bolt and screw heads breaking plane of chassis meeting bumpers
 

Kevin,

If more teams posted to the Q&A about rules which are silly, contradictory, wrong and/or not in the best interests of the teams, I would imagine that all of our lives will get easier come competition time.

Best of luck to you and your team...

Mike