Balls under the bumper
 

Has anybody noticed the balls tend to roll under the bumpers rather than bounce off of them. Even with the with the bumper at the 2" height?

Re: Balls under the bumper
 

Yeah we are working on ways to prevent this. Add in trying to go over the bridge and this makes for one more thing to work into the design.

We might get some of those Uncle Sam mudflaps and put those around the bot

Re: Balls under the bumper
 

We haven't got that far yet...thanks for the info. Might be that we want a full bellypan.

Re: Balls under the bumper
 

We've also found that the balls like to go under the bumper, even with a 3.5-4" ground clearance.

Re: Balls under the bumper
 

I guess we shoulda spent more time playing before we designed our robot...sigh...

Re: Balls under the bumper
 

I am interested to see how hard/liberal they are with the penalties for getting a 4th ball "into" your robot. I think some teams with 3 balls already in possession are going to end of playing dodge ball on the field in hopes of not gettings a penalty.

Re: Balls under the bumper
 

I guess it depends on whether or not you're "controlling" the ball under the robot

Re: Balls under the bumper
 

In 2010 there ended up being a lot more ball entering the frame perimeter penalties than expected, as many of you may remember. Towards the end of the season, they changed the rules to be a bit more generous and I wouldn't be surprised if they do something like that again.

Re: Balls under the bumper
 

I would be a bit surprised if they did this considering every team can drop their bumpers low enough to prevent any incursions (at the cost of mobility, potentially). Also because a team can always just carry 2 balls when driving around the field, they do not have to carry 3.

In contrast to 2010 where incursion was a specific rule as you say, in 2012 a robot can legally drive over a ball, only other choices/avoidable scenarios make this potentially illegal.

Re: Balls under the bumper
 

I guess we need to try it ourselves, to see which of you is correct?

Re: Balls under the bumper
 

We tried with some older bumpers, anything much below 3" seemed to work quite well. Maybe something in one of our respecitve test setups wasn't quite legit?

Re: Balls under the bumper
 

It may be bumper fabric has something to do with it. We are using a generic heavy cloth frabric. Or maybe how tight the fabric is pulled up the noodle. I think ours is fairly loose. We tried it with our locomotion bot (low bumper) & the ball goes right under it.

Re: Balls under the bumper
 

Our old bumper was a little loose, but very, with the suggested bumper material.

Our bumper was mounted to a fixture (two chairs and a piece of c-channel) and we pulled some carpet+a ball underneath the bumper and we'd set the bumper height with a measuring tape. We might get different results if we moved faster or had a looser bumper.

Can you quantify "low"?

Re: Balls under the bumper
 

It was the locomotion bot. Bumper Height 2" from the ground. The ground was the build site carpet which is generic commercial carpet, seems close to the field carpet

Re: Balls under the bumper
 

Did the ball get pulled under the bumpers, or did the bumpers ride up over the ball? If the bumpers ride up over the ball, how heavy was the bot? Would a heavier robot just shove it out of the way?

Re: Balls under the bumper
 

We first noticed this with our mecanum test bed which has last year years bumpers on it. Its bumpers are at 5 inches & the balls just compresses & rolls under it. Robot is around 40-50 lbs. The Locomotion bot is 119.9 lbs. (Don't ask how that happened :) ) It was unpowered & pushed to the ball. The ball compressed & started under the bumper. We stop when it was clear that it was not going to bounce off. We will play with it (oops investigate) more tomorrow.

Re: Balls under the bumper
 

This is strange. Our low bumpers do not eat balls anymore. Currently not even close. :confused: The balls still go right under the high ones.

Re: Balls under the bumper
 

What if you just make sure that your bumpers can't actually "control" the ball, hence make the bumpers as high as possible so that you can't actually have a ball catch under them. Thus when it comes to the bumper, weather in or outside the frame it will pass under. Thus no mater how hard you tried to grab it with the bumper it would pass under. I would consider that would not be being in control of a ball.

Re: Balls under the bumper
 

A bumper is 5 inches tall, and the bumper zone extends to 10 inches. Thus, the highest you can elevate the bottom of the bumper off the ground is 5 inches.

Re: Balls under the bumper
 

We also played with (oops...investigated:) ) our 2011 bot on mecanum wheels. We had a 5 inch bumber height, but we realized that because the bumper is curved on the bottom, that curve aided in sucking in the ball. I believe you need the center of the ball to be higher than (or at least equal to) the midline of the lowest pool noodle in your bumper. This will prevent the curve of the bumper from "collecting" the ball. Unfortunately, it may also prevent you from driving over the midfield bump.

With a little geometry, you can calculate a desired bumper height of 2 and 3/4" maximum. If your bumpers are any higher than this, you will want to look into some sort of deflector on the non-intake sides of your bot.

Re: Balls under the bumper
 

I wonder how bumper cover material affects this? Seems to me that the balls get "sucked under" because the friction between the ball and the cloth covered bumper is pretty high. I wonder if a smoother bumper cover material (vinyl?) might change things.

Re: Balls under the bumper
 

The point was not that the ball would have full clearance (8 in.), but that every time it came to a bumper, it would be sucked under. If at 5 in. it always passes under (weather in or outside the frame), you wouldn't have any control over it, thus complying with the rule. However you want to be sure that it will always go under 5 in.

Re: Balls under the bumper
 

I expect to see some robots with high bumpers ride up on the balls and roll over this year without a deflector of some sort... or, get pushed over by those with low bumpers... A la Breakaway:eek:

Re: Balls under the bumper
 

In the section of the rules about the game fouls, it says that fouls caused by the opposing alliance will not be counted. Nothing against one of your team-mates jamming a ball into your robot.

Re: Balls under the bumper
 

If the bottom of the bumper is above the centerline/middle of the ball (above 4 in) then the balls are much more likely to get caught under the bumpers.