vendors McMaster-Carr Small Parts Stock Drive Products principles stress-strain moduli elastic, plastic flow friction spalling force loops hysteresis backlash flexure elastic averaging kinematic coupling fasteners nuts bolts washers drive gears sprockets belts chains shafts rods nuts guide rods rails slides couplers shaft joint bearings ball thrust linear rotary sleeve rotary wheels pulleys casters cable ties carriers wire fiber springs liquid pipe tubing assignment design or modify a machine document the group project and your individual contribution make the passive parts and operate it manually