Balls under the bumper

[JamesCH95]

Originally Posted by squirrel

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

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?

[FrankJ]

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.

[JamesCH95]

Originally Posted by FrankJ

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.

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"?

[FrankJ]

Can you quantify "low"?

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

[SteveGPage]

Originally Posted by FrankJ

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

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?

[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.

[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.