The approach we used with our triangular pendulum kicker was based on the fact that a professional soccer players only remains in contact with the ball for ~1/100th of a second. So, our goal was have our kicker rapidly reach a high velocity BEFORE contacting the ball. The only way to accomplish this was to sustain a high force
THROUGHOUT THE TRAVEL of the kicker, BOTH before AND during contact with the ball.
To produce this result, we preloaded our bungie set so that there was at least 20 lbs force at full extension. We then went for about 10" of winder retraction of the kicker to build up to a force level of between 80-100 lbs. Having a kicker mass at about 1.5 times the ball's, this produced some serious acceleration of the kicker and very high energy transfer during kicks.
FROM AN EMAIL SENT TO MY TEAM EARLIER IN YEAR ON A FANTASTIC WEB BOOK:
This web document has the most in depth math/physics analysis of ABSOLUTELY EVERYTHING relating to soccer!!
=>
http://www.scribd.com/doc/6726997/ScienceofSoccer
Their analysis of kick, bounce and spin are useful, and worth reviewing briefly.
Some items covered include:
1) good kicks go 70 miles per hour & contact with foot lasts ONLY 1/100 of a second
2) ball spin of around 10 RPS can accelerate a ball on landing by 5-10 miles per hour
Based on my read of this info, I am starting to think that kicks traveling the length of the field will not be so easy to accomplish.
We likely need to have a minimum 3lb mass traveling at ~30+ MPH impacting the ball to have it travel the length of the field, clearing both bumps.
Remember that we also need to instantly absorb the momentun impact of this 3LB. mass against our robot frame too.
-- Dick Ledford