Sometimes Bumpers & Kickers don't mix

Yesterday when we put bumpers in the correct position on our kicker prototype and kicked , we found out the ball hit the bumper and deflected noticeably. When we did the math we found out why. Our ball is 3 inches deep in the robot when kicked. That makes the top of the ball another 1 1/2 inches outside the perimeter. The bumper is a 2 1/2 pool noodle on a 3/4 piece of plywood. The bottom of the bumper could be as low as 10 inches above the ground or only one inch above the top of the ball. Doing the math a triangle with a base of 1 3/4 (3 1/4 - 1 1/2) with the other side of 1 inch has an angle of 30 deg. That means a ball leaving the robot at an angle of more than 30 deg is going to hit. If the top of the bumper is 16 inches above the ground then the triangle other side is 2 inches. That makes the angle a little over 45 deg. That means if you kicker is designed for max range (ie 45 deg) it’s probably going to hit also. Bottom line is you really ought to try out your kicker with bumpers in place before you finalize your design. We’re redesigning our kicking shoe for a flatter kick. I’m glad we found this out now rather that we tried to kick the first time we had the robot completely together

I get the feeling that the evil GDC really has their act together this year.

GDC- smarter than we ever thought they were!

No doubt. I’ve had more than one vision of GDC lunchtime sketches and right triangle math followed be maniacal laughter from the insidious ones.

I must be misunderstanding what you’ve written. It sounds like the radius of the ball you are using is 4.5" This is not regulation.

Thanks!

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6.3.1 BALLS

While playing Breakaway, ROBOTS manipulate BALLS to accomplish the objectives of the game. Each BALL is a standard Size 5 soccer ball. The BALL weighs between 14 and 16 ounces, has a circumference of 27 to 28 inches, and is inflated to a standard pressure of approximately 9psi.

let’s see…28" / 2 pi = 4.45" so the spec ball radius could be pretty close to 4.5"

at least to within the accuracy that you can measure the position of the lower front corner of the bumper!

You are correct. My bad. I was going from memory. Not a wise thing to do at my age.

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You’ll regain a wee bit on the curve of the pool noodle profile. I remember quantifying this back in Aim High to calculate our approach angle for the ramp.

This problem has been on my mind as well but I have yet to test it. Does your kicker stay inside your chassis or does it go out the full allowable distance?

What do you mean specifically by a flatter kick?
Changing the kicker point of contact design with the ball mechanism or the angle in which the current kicker makes contact with the ball.

Hi Glenn…I mean by flatter that the ball will leave the kicking mechanism at a lower trajectory angle. We’ve been playing with different angled kicking plates all afternoon and still haven’t got it right. The next thing we may do is play with where the kicker plate makes contact with the ball. Currently we’re contacting the ball about 2 inches off the floor. The other thing that’s making the situation worse is back spin from the dribbler. We’ve finally got the ball to miss the bumpers with the dribbler off. With it on the ball climbs the kicking plate and increases loft which means its still hitting the bumpers.

they measure the 3" from the frame perimiter

You could perhaps modify the bumper brackets to give you more clearance. That’s if you still want to maintain maximum trajectory. How high up are your bumpers?

The bumpers are 5" tall, and the bumper range is 10-16" above the floor. So couldn’t you move them up a little and get 2.25" of clearance above the ball?

The bumpers are also rounded, so the ball can go “through” them a little.

And unless you’re getting really far under the ball with your kicker, its pretty hard to get 45* anyhow…

Martin,

Not really…

Many teams are eventually going to find hitting the bottom of their bumper an issue…

JMHO,

Mike

When you have your “ball magent” adding back spin it is actually real easy to take off well higher then 45 degrees and even with mounting the bumpers as high as legally possible we are still running into an issue. The only solution it looks like we have is to not allow the ball as far into the robot.

Edit: didnt want to hijack the thread so here is our kicker playing some what nice with our bumpers after tonight’s modifications http://www.chiefdelphi.com/forums/showthread.php?threadid=81914