Balls under the bumper

[FrankJ]

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.

[FrankJ]

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

[commonsense]

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.

[Tom Line]

Originally Posted by commonsense

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.

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.

[one4robots]

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.

[MrForbes]

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.

[commonsense]

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.

[mrlg220]

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

[jon-s]

Originally Posted by 1493kd

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.

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.

[jon-s]

Originally Posted by FrankJ

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

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.