prusa i3 Zonestar p802 z axis upgrade

** This version is no-longer being maintained **
please use the V2 linked below as it is soo much better.
Even if you only use the updated top plates it's still so much better.

** V2 is here http://www.thingiverse.com/thing:1470886 **
many improvements.
new parts include updated top plates with more adjust-ability for belt length, and a 18t stepper pulley and updated 36t pulleys for the z lead screws (so a 2x improvement in torque)
you may wish to refer back to here for construction ti