Let's Make Robots!

Legally blind veteran needs some help building a robot

Please help me. I need a small robotic device that can periodically pull on a string with enough force to move a suspended weight approx 300 lbs . Then accassionally give another pull to keep the weight moving at a very easy rate. This needs to be very quiet operating and weather proof. It will be used to keep targets in motion at a range. DC POWER must operate for at least 1 hour on a small battery. The movement only needs to be 12 ibches or so, not a lot. Contact ne directly asos@verizon.net. We used to use a old baby swing to make it work but now need something more professional.