Interpertation on Bumpers: Do the bumpers need to display the team numbers?

[Team 2524]

We have some old plexiglass that has our team number on it and we were going to mount that on the robot. Do we also need to put the team number on the bumpers?

I was curious since on the 2011 FRC inspection checklist for Logomotion mentions:

"Team number displayed with 4" tall x 3/4" stroke, on the bumpers, 4 locations at approximately 90 deg spacing, in contrasting color or background."

Thank you:)

[nighterfighter]

Yes, it needs to be on your bumpers, both the red and blue.

[vhcook]

And for the contrasting color, as a scout/scouting mentor, I strongly recommend something in the white/silver/bright yellow range. Black lettering looks fine close up, but it's nearly unreadable in the stands.

[nighterfighter]

And for the contrasting color, as a scout/scouting mentor, I strongly recommend something in the white/silver/bright yellow range. Black lettering looks fine close up, but it's nearly unreadable in the stands.

Yes! We have used a bright white color, and it looks fine on both red and blue bumpers.

If you do use black letters, at least put a thin white outline around them.

[David Brinza]

We have some old plexiglass that has our team number on it and we were going to mount that on the robot. Do we also need to put the team number on the bumpers?

If the piece of plexiglass with the team number was fabricated prior to this year's kickoff, you aren't allowed to use it on your robot. ::rtm::

Is it really plexiglass or lexan? I wouldn't recommend using plexiglass on a robot: it will shatter upon impact.

[Team 2524]

If the piece of plexiglass with the team number was fabricated prior to this year's kickoff, you aren't allowed to use it on your robot. ::rtm::

Is it really plexiglass or lexan? I wouldn't recommend using plexiglass on a robot: it will shatter upon impact.

It is plexiglass and we still need to cut it.

[JaneYoung]

Why are you creating room for interpretation when there isn't any?

Jane

[EricH]

Plexiglass, AKA acrylic, shatters on impact. I've seen it happen, back in 2005 (and the robot that did the shattering drove up a steep angle to do it). That's why it's not recommended in any areas on the robot where it might get hit.

You may be thinking of polycarbonate, AKA Lexan, which doesn't shatter nearly as easily.

[Team 2524]

Well, the plexiglass will be located about 2-4ft off the ground. It will be connected the Arm frame which Doesn't hit something on impact >..<

[IndySam]

Well, the plexiglass will be located about 2-4ft off the ground. It will be connected the Arm frame which Doesn't hit something on impact >..<

I have seen supposedly safe plexi shattered.

There is no safe place on a FRC robot.

[EricH]

I have seen supposedly safe plexi shattered.

There is no safe place on a FRC robot.
Yep. That acrylic I mentioned earlier--the impact was at about 3.5-4 feet up. The "ramp" that was gone up could slow or stop a robot pretty well-- except that one. The other 3 sides of the tower shielding (running between arm supports) were Lexan and survived the rest of the season, as did the replacement Lexan panel.

[Cory]

The best place for acrylic is the trash can. There is never a situation on your robot where it would be a better choice than polycarbonate.

[GaryVoshol]

This isn't an interpretation. It's a reading of the rule:
<R09> Teams shall display their team number on the BUMPERS in four locations at approximately 90° intervals around the perimeter of the ROBOT. The numerals must be at least 4” high, at least in ¾” stroke width and in a contrasting color from its background. Team Numbers must be clearly visible from a distance of not less than 100 feet, so that judges, referees, and announcers can easily identify competing ROBOTS.See how many times "must" and "shall" appear? You have to do it - numbers on the BUMPER, regardless of wherever else on the ROBOT they appear. Period.

[Al Skierkiewicz]

Well, the plexiglass will be located about 2-4ft off the ground. It will be connected the Arm frame which Doesn't hit something on impact >..<

Let this be your guide... I predict 50% of the robots on the field will have an arm for scoring at least the center rows. That means at least one robot on the opposite alliance in every match will have extensions beyond their frame perimeter. Those arms will reach over six feet and can contact your plastic signage.

[kws4000]

The best place for acrylic is the trash can. There is never a situation on your robot where it would be a better choice than polycarbonate.

For the past, what, 3 years now, we have used plexi for the electrical box, becouse it doesn't bend under load. Never had a problem. Asides from that, true, lexan is much more resilient under shock.

[Mike Betts]

For the past, what, 3 years now, we have used plexi for the electrical box, becouse it doesn't bend under load. Never had a problem. Asides from that, true, lexan is much more resilient under shock.

Back in the 90's, Plexiglass was explicitly forbidden on the robot by rule. When the ban was lifted, I bought a small sheet at the HD for an electrical panel. When it shattered during routine tooling, we went back to polycarb and never looked back.

No team I have ever mentored has ever had Plexiglass on their robot.

To the original poster: If the rules don't persuade you, note this quote from this document (http://usfirst.org/uploadedFiles/Robotics_Programs/FRC/Game_and_Season__Info/2011_Assets/2011FRCInspectionChecklistRevX.pdf):

Team number displayed with 4” tall x ¾” stroke, on the bumpers, 4 locations at approximately 90 deg spacing, in contrasting color or background.<R9>Without the team number on the bumpers as specified, you will not pass inspection.

Regards,

Mike

[Thermal]

Let this be your guide... I predict 50% of the robots on the field will have an arm for scoring at least the center rows. That means at least one robot on the opposite alliance in every match will have extensions beyond their frame perimeter. Those arms will reach over six feet and can contact your plastic signage.

It's more than just that. Simple vibrations will crack the acrylic where the bolts go through to mount it to your backing. Acrylic is not acceptable for a FIRST robot under any circumstances. If I won't use it in my computer for waterblock tops (where there is negligible vibrations and no movement), you definitely shouldn't ever use it on a FIRST robot.

Theres a few companies (Thermaltake) that used to make waterblocks with acrylic tops and meager 10°C changes to the acrylic along with the pressure the barbs put onto the threadings to maintain a watertight seal caused many of these blocks to crack and leak water over the users video cards and motherboards.

[Matt C]

I find it interesting that this post has turned into a post on acrylic vs polycarbonate.

With students, I normally do the "vise test" . .

Give a student (with safety glasses of course) a small piece of polycarb and tell them to smack it against the vise.

Then give them a piece of acrylic and tell them to do the same thing.

That'll teach em. :D

(and yes, you need to put your numbers on your bumpers . . silver Sharpie works GREAT!
http://www.amazon.com/Sharpie-MARKER-SHARPIE-METALLIC-SR/dp/B001GXFNYI)

[Grim Tuesday]

We used plexi (acrylic) to make a mounting bracket for our C-Rio, since we have access to a laser cutter, which can't cut polycarb. It allowed us to precisely "drill" the holes for the bottom of the C-Rio, and mount it in a way that it won't crack.

But then we took it off for weight and made a smaller bracket by hand out of polycarb :P

[Wayne TenBrink]

Is there any difference between "plexiglass" and "acrylic"? I have seen stuff marketed as "plexiglass" that was very brittle and virtually impossible to drill holes in without cracking. We have had decent success with "acrylic" sheet (as marketed by Ace Hardware), for non-structural, flat panels that are well supported along the edges. It drills fairly well, and is quite flexible, but will break before it bends. In 2009 we had 3 large panels (30" x 44") of the stuff and they held up very well despite impacts that bent the supporting structure (yeah, I know - that was Lunacy and there weren't arms and impacts weren't like they are on carpet).

We have three small, non-structural panels of it on the robot this year (because I had a tightwad moment and it was in stock), and we are taking bets about how long it holds up. Will replace any broken sections with Lexan, though.

[Matt C]

We have three small, non-structural panels of it on the robot this year (because I had a tightwad moment and it was in stock), and we are taking bets about how long it holds up. Will replace any broken sections with Lexan, though.

I got my money on 2nd practice round.

[Al Skierkiewicz]

We used plexi (acrylic) to make a mounting bracket for our C-Rio, since we have access to a laser cutter, which can't cut polycarb.

We cut poly on our laser cutter all the time. We have even used it for wheels in the distant past also cut by the laser. It does require some serious deburring operations and the smell takes a while to get used to.

[sanddrag]

I thought I've read polycarb is dangerous to laser cut, due to toxic gasses produced? Can anyone confirm or deny?

[Al Skierkiewicz]

The laser bed we use has fume removal built in.

[Racer26]

1075 used plexiglas on our 2003 electrical board. We had to remake that board several times, and the competition robot had chunks missing from where it had cracked and we couldn't fix it.

Never again have we used it. We switched to some super-thin aluminum sheeting (in the neighborhood of 0.008", IIRC) for our electrical panels since then.

[PAR_WIG1350]

1075 used plexiglas on our 2003 electrical board. We had to remake that board several times, and the competition robot had chunks missing from where it had cracked and we couldn't fix it.

Never again have we used it. We switched to some super-thin aluminum sheeting (in the neighborhood of 0.008", IIRC) for our electrical panels since then.

??? Aluminum foil???

Also, why not use polycarb? You won't short stuff out by drilling into it, and you can mount your crio directly to the polycarbonate which can then be directly attached to the frame without any additional insulation.

[Matt C]

Also, why not use polycarb? You won't short stuff out by drilling into it, and you can mount your crio directly to the polycarbonate which can then be directly attached to the frame without any additional insulation.

Most teams I've worked with use plywood to mount electonics . . .

[Bill_B]

Is there any difference between "plexiglass" and "acrylic"? I have seen stuff marketed as "plexiglass" that was very brittle and virtually impossible to drill holes in without cracking.
There is a drill for plastics that has a steeper angle at the tip. I have no recommendation but you could try here (http://www.rplastics.com/plasticdrill.html) for at least the claim of flawless holes in plastics.

[MagiChau]

Most teams I've worked with use plywood to mount electonics . . .

Polycarbonate is what my team uses every year now. It worked fine for us and saves plenty of weight.

[Chris is me]

We cut poly on our laser cutter all the time.

A small, benchtop laser cutter found in many schools would be unable to do this - only huge ones in plastic shops.

[Racer26]

??? Aluminum foil???

Also, why not use polycarb? You won't short stuff out by drilling into it, and you can mount your crio directly to the polycarbonate which can then be directly attached to the frame without any additional insulation.

Its not aluminum foil. Its actually fairly rigid, and its significantly lighter than polycarb. We punch all the holes needed into this sheet, and ziptie most things (speed controllers especially) to it. Makes changing dead speed controllers a breeze, not having to deal with the tiny but long #6 screws. Cut two zip ties, and undo five wires.

We've been happy with it, but you're right, when the cRIO came out, we had to be a little careful with the shorting it to ground issue, and I think we DID use polycarb in 2010 IIRC.

[Al Skierkiewicz]

We use light aluminum perf stock and mount most everything with wire ties. Makes changing stuff a snap.

[The Lucas]

We use light aluminum perf stock and mount most everything with wire ties. Makes changing stuff a snap.

Same here, thin aluminum perf. Bend the edges down and it is very sturdy.

[wsansewjs]

The best place for acrylic is the trash can. There is never a situation on your robot where it would be a better choice than polycarbonate.

May I suggest that you could turn the plexiglass into your own clipboard used for the strategy planning during the game?

-Josh

[Wayne TenBrink]

I got my money on 2nd practice round.

So far, so good. No failures yet, despite a few battle scars. The brand of the stuff is "Optix" by Plaskolite, Inc.

[sithmonkey13]

One test 1178 did in 2010 on Plexiglass (to see if we should use it to protect our bot from the balls) was to attach a piece to two chairs, and kick a ball at it (while everyone was far back and wearing safety glasses). The piece shattered on impact, telling us what not to use.