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

[Al Skierkiewicz]

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.

[cabbagekid2]

Originally Posted by Al Skierkiewicz

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.

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).

[eugenebrooks]

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.

[Vikesrock]

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.

[eugenebrooks]

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

[Al Skierkiewicz]

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.

[Jack Jones]

Originally Posted by Al Skierkiewicz

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.

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.

[IndySam]

Originally Posted by Jack Jones

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.

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.)

[Jack Jones]

Originally Posted by IndySam

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.)

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

[Al Skierkiewicz]

Originally Posted by Jack Jones

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

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.

[IndySam]

Originally Posted by Jack Jones

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

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

[Rob]

Originally Posted by IndySam

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

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

[Daniel_LaFleur]

Originally Posted by Jack Jones

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.

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.

[Mike Betts]

Originally Posted by Vikesrock

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.

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

[Vikesrock]

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.