Mike Hord, just mention the rope. I'm trying to figured out a mathemathic model of the rope when a climber falls. I have the mass, the spring, and I feel aplying Hooke and Newton laws I can solved but I have a lot of little obstacles like spring constant when the rope has a dynamic elongation of 33,1%, like "bluewater accelerator 10.5 rope". Well,... I'm working on that, any help on math is well come. Dennis Crawley. ps: I've download "Rope System Analysis" by Stephen Attaway,... looks good but he doesn't state the system in Transfer words. (In/Out) ___________________________________________________________ 1GB gratis, Antivirus y Antispam Correo Yahoo!, el mejor correo web del mundo http://correo.yahoo.com.ar -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist