[Culvan Van Li]

So my question is how much force should a robot mechanism be able to withstand to survive contact with the ball? I'm leaning towards 25lbs, but I wanted to solicit feedback since this isn't my strong suit. Has anyone got a good number for how much force the ball is likely to impart when it bounces off of a robot? Does anyone have a force plate they could drop a ball on to get us some numbers? We could also get some good calculations from high speed camera footage of the ball bouncing.

Here's the current model I'm working on:
A ball launched at a 45 degree angle rises to a height 2 meters above it's launch point and falls the same distance before it impacts the robot of interest. Energy at the time of impact can be calculated as Mass*Height*Gravity/(Sin Angle) = 1.136*2*9.81/(sin 45) = 31.53 joules. From there I can work back to figure out the incoming Velocity = sqrt( 2 * Ke/mass) = 7.449 m/s (downward). Observing the ball as it bounces, our ball seemed to bounce about 50% of the height is was dropped from utilizing the equations above I come up with a departing velocity of 3.97m/s (upward). The total change in velocity is 11.42 m/s. Force = Mass * Acceleration and Acceleration = Change in Velocity / Change in Time. Unfortunately I don't have the ability to measure how long the ball is in contact with the ground. I guessed at a quarter of a second (does anyone have a better number?) That gives us an average force of 51.9N or 11.7lbs.

I know I'm not taking air resistance into this equations and many other smaller factors, but I think the numbers I have listed above will dominate the equations. I also think that it is entirely possible to have balls thrown harder than I've listed. Additionally the ball will act like a spring and the force it exerts will be defined by the equation F= K*x where K is the spring constant and x is the amount it has been deformed. This implies there will be a linear variation to the force as it bounces. That probably means that maximum force would probably be double the average. That implies that the max force asserted based on my model is over 23 lbs.

Andy