Fasteners extending outside the FRAME PERIMETER

[Al Skierkiewicz]

Kevin,
If it helps, bolt heads have always been tested with the box. If in the past you drilled out the back of the bumpers as allowed, the frame perimeter was still set by the maximum dimension of the bolts.

[Vikesrock]

Originally Posted by Al Skierkiewicz

Kevin,
If it helps, bolt heads have always been tested with the box. If in the past you drilled out the back of the bumpers as allowed, the frame perimeter was still set by the maximum dimension of the bolts.

The obnoxious part is that the axle bolts for many teams this year are not in the BUMPER ZONE and thus do not set the FRAME PERIMETER. If an upper frame supporting the bumpers and a lower frame supporting the wheels are the same width and the upper frame has no protruding fasteners the axle bolt heads on the lower frame will be outside the FRAME PERIMETER and will violate <R16>.

I was suggesting that a simple workaround if these lower fasteners are not declared legal through the Q&A may be to have identical bolt heads in the level of the BUMPER ZONE so they redefine the FRAME PERIMETER as you mention in your post. This vertical projection of this larger FRAME PERIMETER would enclose the axle bolt heads preventing the <R16> violation.

I'm hoping the GDC makes all this moot with an answer to 1771's Q&A, as this workaround is more like a loophole

[GaryVoshol]

Originally Posted by Al Skierkiewicz

Kevin,
If it helps, bolt heads have always been tested with the box. If in the past you drilled out the back of the bumpers as allowed, the frame perimeter was still set by the maximum dimension of the bolts.

Al, are you confusing FRAME PERIMETER and NORMAL CONFIGURATION? Normal configuration is the size that has to fit in the box, bolt heads and all.

The FRAME PERIMETER is a subset of that, the polygon defined by the string stretched around the robot at the BUMPER ZONE level. Even if the FRAME PERIMETER is only 20x30", nothing is supposed to be wider than it, not even a bolt head, whether that is outside 10-16" off the ground. Even if it would fit in the sizing box.

Now, are you going to be measuring for that? So the 1/4" extension of a bolt causes the robot to fail inspection? Or are the inspectors and refs only going to be eyeballing it?

[artdutra04]

The least nitpicky and anal retentive solution to this would be for the GDC to allow static (non moving) fastener heads to stick out no more than 0.25" from the FRAME PERIMETER, as long as they still fit inside the sizing box. This meets the spirit of the rule of the FRAME PERIMETER (it's not like having a button head stick out an 1/8" from the FRAME PERIMETER, but still within the NORMAL CONFIGURATION, will give that team magical super powers or some unfair advantage) while allowing leeway for teams that can't/won't buy flat head bolts and a countersink tool.

The GDC has been getting better about these kind of situations lately, with relaxed tape rules, relaxed pneumatic rules, etc so I'm hopeful this will be the outcome here.

Originally Posted by Vikesrock

I was suggesting that a simple workaround if these lower fasteners are not declared legal through the Q&A may be to have identical bolt heads in the level of the BUMPER ZONE so they redefine the FRAME PERIMETER as you mention in your post. This vertical projection of this larger FRAME PERIMETER would enclose the axle bolt heads preventing the <R16> violation.

If GDC is fervent that the FRAME PERIMETER means the FRAME PERIMETER and that means absolutely no exceptions whatsoever, not even for fastener heads, then this is exactly what we are planning on doing: just installing dummy bolt heads to redefine the FRAME PERIMETER. Fine, we'll jump through your hoops and sit and play dead, but we won't enjoy one second of it.

[Rich Kressly]

As an aside, and as a general rule, we always design out robot to be at least 1 inch smaller than max footprint in all directions, allowing for any covers or fasteners, or stuff that may happen later.

The thing that would make this easiest this year would be to design the "lower" part of your frame to be a little smaller than the "mid" or "upper frame" that your bumpers attach to.

[DonRotolo]

Thank you Rich. Our design has the 'lower' frame (at wheel level) just a bit smaller than the 'upper' (bumper zone) frame, about 1/2" on all sides. The upper frame is just under 27" wide.

The simple solution is not adding dummy fasteners, but a 1/4 (or 3/8", whatever) strip along the outside of the frame perimeter. Nothing says it can't be birch plywood (lightweight) strips.

In theory, the lower frame could be as much as three inches smaller, eh?

[Al Skierkiewicz]

Gary,
I believe, as you suggested, that the FRAME PERIMETER in the strict definition is the outside of the frame including any fasteners in the bumper zone. It is those dimensions that would also define the extent to which fasteners and other parts can extend out from the robot body because that now defines the NORMAL CONFIGURATION. I think it will be fairly easy to tell with the robot in the sizing box with no bumpers. As the rules allow clearance holes and pockets in the backing of the bumper (R07, D), I believe the GDC is allowing the fasteners and therefore the FRAME PERIMETER to merge with the inside of the bumper as they have in the past. Depending on individual design, it may be necessary to have a team rotate their robot to test all sides to insure compliance with these rules as the sizing box really has only two solid sides.

[martin417]

Everyone keeps focusing on the sizing box. This question has nothing to do with the max legal size for NORMAL VOLUME. Only with frame perimeter. The sketch below is of a 12" square bot, which could never have issues with the sizing box. However, as the rules currently read, is not legal. Since we have not yet recieved an answer, the only alternative is to desigh the bot so that this does not occur. If this is truly illegal, I would expect a great deal of trouble for some teams at inspection this year.

[thefro526]

Originally Posted by martin417

Everyone keeps focusing on the sizing box. This question has nothing to do with the max legal size for NORMAL VOLUME. Only with bumper perimeter. The sketch below is of a 12" square bot, which could never have issues with the sizing box. However, as the rules currently read, is not legal. Since we have not yet recieved an answer, the only alternative is to desigh the bot so that this does not occur. If this is truly illegal, I would expect a great deal of trouble for some teams at inspection this yer.

I read through the discussion here and we ran into the same problem last night which resulted in us narrowing our chassis by about .5".

Now that I've thought about it more, I think that there should be some sort of concession made for bolt heads extending outside of the frame perimeter, but within the maximum sizing volume. I know the last two robots we've built on the C-base had bolt heads extending outside of the frame perimeter and I'd assume most teams using it this year would have the same issues...

Hmm.

[Al Skierkiewicz]

Martin,
As I look at your drawing, there are no fasteners in the bumper zone and so those dimensions (12 x 12) become the FRAME PEERIMETER. Therefore the fasteners at the bottom of the chassis extend beyond those dimensions. If this robot was placed in the sizing box, the fasteners outside the bumper zone would contact the vertical sides of the box before the frame in the bumper zone and would therefore not meet the definition (as I understand the rules at this date) even though the robot is significantly smaller than the sizing box.

[MrForbes]

Originally Posted by artdutra04

The least nitpicky and anal retentive solution to this would be for the GDC to allow static (non moving) fastener heads to stick out no more than 0.25" from the FRAME PERIMETER, as long as they still fit inside the sizing box.

Won't work too well if you used 3/8" axle bolts...the heads are more than 1/4" thick. Wonder what the magic dimension is?

It's an interesting can of worms, it's good to see this much discussion about it, because this is an issue that many inexperienced teams will probably overlook.

[Vikesrock]

Originally Posted by squirrel

Won't work too well if you used 3/8" axle bolts...the heads are more than 1/4" thick. Wonder what the magic dimension is?

It's an interesting can of worms, it's good to see this much discussion about it, because this is an issue that many inexperienced teams will probably overlook.

All the 3/8" hex cap screws on McMaster seem to have a head thickness of 15/64".

[MrForbes]

What about the kit bolts? Seems to me that the 3/8" bolts usually have a head around .290" thick?

We're using 1/2" axle bolts this year

(the heads are welded to the frame, and the threads stick out not quite as far as the FRAME PERIMETER, but still.....)

[Andrew Y.]

im almost positive that in past years, the robot perimeter has included static boltheads...otherwise there will be A LOT of counter sinking on our hands

[Vikesrock]

Originally Posted by Andrew Y.

im almost positive that in past years, the robot perimeter has included static boltheads...otherwise there will be A LOT of counter sinking on our hands

In past years these bolt heads were inside the Bumper Zone