# Lip at ball chute opening

I have just read a disturbing thing (I think) in FIRST’s Q&A section:

"Q: Is there a seamless transition between the playing field and the ball chute? The kickoff video looks like there was a 1/2 inch steel bar or some structural support there.

A: No. There was an angled piece of 1-1/2" x 1-1/2" aluminum in the opening with the outside of the angle facing up (~1-1/8"). In the final configuration, there will be a vertical piece of 1/4" thick aluminum with the same vertical dimension as before. The ball dynamics are the same in either configuration. Drawings will reflect this change."

My quick energy calculations (with some simplifying assumptions) indicate that if the ball is travelling greater than about 3 ft/sec as it approaches the chute it will bounce up and hit the 16" high top of the chute without going in. Very rough empirical tests seem to confirm this. In practice, it seems to me that the robot must carry the ball all the way to the chute and can’t do so very fast at that. To get the ball over the lip moving slowly, the pusher must be closer than 6" from the chute wall. The problem is complicated by the fact that another Q&A says that a rule change in update #3 (not yet available) will prescribe a penalty if the robot breaks the plane of the ball chute. This has major implications for our robot design. Am I overlooking something?

Just a quick note about WHY the “lip” along the bottom of the ball corral is necessary. Without it, balls pushed into the ball corral bounce off the back of the corral and roll right back out. This would make it very difficult for the human player to collect balls to throw, as she (we all saw during the kick-off demonstration that girls make better human players for this game, didn’t we Jason? ) would constantly have to grab balls as they entered the corral, leaving little time for throwing.

Also note that the “lip” is actually set back behind the plane of the diamond plate of the player station, about 1-1/2" This means that the center of mass of the ball would have passed the plane of the diamond plate before it hits the “lip.” Most of the time it would bounce up behind the diamond plate, and into the corral, rather than back out on to the field. So this should not be too large of a concern.

-dave