vendors McMaster-Carr Stock Drive Products Amazon Industrial Misumi principles stress-strain stiffness, strength, hardness Maxwell criterion moduli elastic, plastic flow friction spalling hysteresis backlash force loops elastic averaging kinematic coupling accuracy, precision materials plastic metal rubber foam garolite wood cement ceramic adhesives fasteners nuts bolts washers heat-set inserts rivets pins framing metal plastic t-slot self-aligning drive gears involute cycloidal helical herringbone planetary harmonic rack and pinion lead screw ball screw threadless chain belt thread wire capstan guide shafts rails slides couplers shafts joints bearings ball thrust linear rotary sleeve pillow blocks skateboard V slot groove preload rotary wheels pulleys casters omni OmniBot lubricants cables ties hook and loop carriers wire fiber liquids pipe tubing fittings pumps conveyors springs mechanisms flexure, stage, OpenFlexure series elastic linkage movements whippletree windlass pantograph deltabot hexapod CoreXY Sarrus Hangprinter Hoberman Strandbeest group assignment - design a machine that includes mechanism+actuation+automation+application - build the mechanical parts and operate it manually - document the group project and your individual contribution