Bumper Zone Limitations

[Oblarg]

Originally Posted by BBray_T1296

Also, many bumpers wear over time. You see teams, probably including your own, when the bumpers are fresh and brand new they sit perfectly and look great, but after a regional or two, you look at them and they sag, if you put your hand on them, they seem kind of loose and are not what they once were. Some teams make bumpers really really well and this does not happen, but a large quantity of teams do not [see teams that have to rebuild their bumpers at regional]. with the bumpers 2" off the ground, this sag has clearance before the bumpers are being dragged around. If they were lower, teams with reversible bumper flaps or drape cloths for changing colors may effectively "trip on their own shoe laces" as it were. Yeah, if the bumpers sag they are technically against the rules at that point, but recall that they check your bumpers during initial inspection, but (so long as you don't modify them) you never get the bumpers reinspected, even if one side falls off in one match.
In 2011 we had our bumpers at the lowest point, 2" and we had one of those red skirts that wraps around the blue cloth, to change bumpers, and we had to be super careful to keep that thing velcroed down so we didnt run ourselves over.

No matter how well you make your bumpers, unless you have a source for ridiculously sturdy pool noodles (if you do, please share it) they will take significant damage if you drive aggressively. That foam can only take so many collisions before the compression becomes permanent.

[Nemo]

Interesting thought. I could see doing a 1"-9" bumper zone for a game with a flat field. For a game with a non-flat field (and possible incentives for bigger wheels), I think 2-10" has worked out well enough.

[EricH]

That's my thought too--non-flat fields require bumpers to be placed higher for design purposes; Aerial Assist was the first game with a truly flat field since 2007 (robot ramps not included) or 2002. All the games in between had something that would make you want higher bumpers or larger wheels if you could get away with it. Ramps, steps, bumps, carpet-covered plates in the field, you get the idea.

But, if you place the bumpers too high, you get a case of high hits/easier tipping (longer lever arm). Too low, and you hit those obstacles or the bumper isn't an obstacle to tipping, you just tip over the bumper.


I think it's best in the general area of where it is. High enough to clear obstacles, low enough to help keep the robot upright and not drag.

[BBray_T1296]

Originally Posted by Oblarg

No matter how well you make your bumpers, unless you have a source for ridiculously sturdy pool noodles (if you do, please share it) they will take significant damage if you drive aggressively. That foam can only take so many collisions before the compression becomes permanent.

I am pretty sure that all of our bumpers now feature pool noodles that are cracked in half along the vertical diametral plane

[Oblarg]

Originally Posted by BBray_T1296

I am pretty sure that all of our bumpers now feature pool noodles that are cracked in half along the vertical diametral plane

Our first set of pool noodles this past season was exceptionally flimsy for some reason. After our first regional, the ones on our front bumper were permanently compressed to about an inch thick.

The frame behind that bumper, incidentally, also developed some surprising curvature (we eventually had to swap it out with another, steel-reinforced piece).

[Lil' Lavery]

Originally Posted by EricH

That's my thought too--non-flat fields require bumpers to be placed higher for design purposes; Aerial Assist was the first game with a truly flat field since 2007 (robot ramps not included) or 2002.

*2009

[Oblarg]

Originally Posted by Lil' Lavery

*2009

2008, too. There was a big barrier in the middle of the field, but the actual driving surface was completely flat with no obstructions.

[BrendanB]

Originally Posted by Oblarg

2008, too. There was a big barrier in the middle of the field, but the actual driving surface was completely flat with no obstructions.

Games like 2008, 2011, & 2013 were technically on flat fields but around the bases of the 2008 wall, 2011 minibot poles, & 2013 pyramids they were raised up close to half an inch due to the field elements below the carpet.

[EricH]

Originally Posted by Lil' Lavery

*2009

Not going from the regolith to the carpet. And even the regolith could deform a bit, going into the carpet that was under it.

I draw a distinction between "flat" and "truly flat" for a reason. A "flat" field includes 2005, 2007*, 2008, 2009, 2011, and 2013; every single one of those had plates under the floor to support something, which affected the flatness (Exception: the loading zones in 2005, which were above the carpet), or a transition from one surface to another (2009). 2007 also had ramps, though those were on robots. Those shallow transitions MUST be accounted for when designing ground clearance, or you'll get slowed down/stopped. (I remember someone at AZ 2010 was a little annoyed at the transition plates next to the bumps--they'd been mentioned in the Manual all along.)

A "truly flat" field does not have those plates underneath or other irregularities, just floor, tape, and robots. 2002 and 2014 are both in that category; 2009 is not because of the regolith/carpet transition.

*This one is on a technicality--the floor base for the Rack was in a place no robot could be expected to come even close to it. But the robot-mounted ramps tip it to just flat, or even out of that altogether.

[Chris is me]

Originally Posted by EricH

Not going from the regolith to the carpet. And even the regolith could deform a bit, going into the carpet that was under it.

Every field has tape on it, so therefore it's not flat, right?

The regolith was no more than 1/8" thick. At this point saying a field with a 1/8" depression "isn't flat" is just being pedantic. The miscellaneous hardware and debris that people build ground clearance into drivetrains in order to avoid is generally more than 1/8" tall. You would have to try very, very hard to design a drivetrain that would be issue free on a "truly flat" field that wouldn't work on a 2009 field (ignoring the wheel rules). 2009 is flat.

[scca229]

Originally Posted by Chris is me

Every field has tape on it, so therefore it's not flat, right?

The regolith was no more than 1/8" thick. At this point saying a field with a 1/8" depression "isn't flat" is just being pedantic. The miscellaneous hardware and debris that people build ground clearance into drivetrains in order to avoid is generally more than 1/8" tall. You would have to try very, very hard to design a drivetrain that would be issue free on a "truly flat" field that wouldn't work on a 2009 field (ignoring the wheel rules). 2009 is flat.

Several bots at the Arizona Regional this year would challenge that assertion. As an inspector, I had to accompany no less than 3 back to their pits to help them figure out why the aforementioned "flat" tape as well as carpet strings... LONG ONES ...were being carried back with them in a huge mass in their drive train. Each of them had elements on the bottom mounting board that were exactly equal with the plane of the wheels, tangent to the ground. Any deviation from a "truly flat" field would have been even worse, say a 1/8" edge to climb.

One possible reason was the underlay beneath the carpet wasn't a surface like hardboard to protect the gym floor but 4'x4' foam tiles, like you put in a shop that gave the floor a slight cushioning effect. The deflection from a bot was very slight, but enough that quite a few bots were pulling up carpet and not just the tape. Those 3 just happened to be the worst ones I witnessed and could finger point that needed to be corrected before being allowed on the field again. A solid layer of packing tape across the bottom fixed the issue in all cases.

Because the field was "truly flat" with no built-in height deviation,

Originally Posted by EricH

A "truly flat" field does not have those plates underneath or other irregularities, just floor, tape, and robots. 2002 and 2014 are both in that category; 2009 is not because of the regolith/carpet transition.

many bots I witnessed during inspections were designed for the undercarriage to be as close as possible without actually touching... much more so than I witnessed in previous years. Some took it too far and didn't account for the possibility that the floor wouldn't be concrete underneath the carpet.

[jimbo493]

Well, I just got a new helmet and it had a warning that if you had a severe hit to the head with it, it should be destroyed and replaced. That is because the hard foam breaks down, but its impossible to see. And i'm very certain this would happen with our pool noodles, because the are beat up so much. Maybe we need a better way as far as the foam. Because Im sure some of the sagging caused is a result of the foam breaking down. Just an idea, and I have alot of bad ones

[FrankJ]

Realize the helmet lawyers write that warning. You are also protecting a difficult to repair brain. Pool noodles are also considerably springier than the Styrofoam that goes into helmets. We have torn bumpers, but they have not sagged appreciably.

[Qbot2640]

Not intending to derail this thread...just to interject...that this is a great time to buy pool noodles for the upcoming season. At least here in the Southeast, retailers are more interested in selling their stock off at a slight loss, than putting such a bulky item into storage where (by January 3) they will become largely inaccessible.

Our local Dollar Tree has them currently for $1.00. Last season they went down to $0.50 at Walmart.

I'm thinking about asking everyone to bring a noodle to the next meeting...kind of an "ice-breaker"/quick supply tactic.