I built the ball machine because I thought my dog Jerry, might like it and that it would be something fun for me to build. So after two years of on and off work, with many safety features such as IR proximity sensors to protect Jerry and my son from the machine, I finally complete. Far from being a replacement for me, I was always right there with him enjoying his fun. And with all the troubles that I went through to build the ball machine, I still end up throwing more balls than that the machine could count! According to the computer, he played with the machine by himself only 3 times in his life.