spur gear training tool

thingiverse

This set of spur gears is intended as a training tool for spur gear theory. large teeth to allow easier observation of tooth contact two thread holes are provided to show that gear tooth contact follows the 20 degree pressure line from the intersection of the pitch diameters. One face of the tooth follows one string, the opposite face follows the other string. Fundamental gear parameters (in inches) diametral pitch (DP) = 3 inch number of gear teeth (N) = 12 pressure angle (phi) = 20 degrees then using standard spur gear equations: pitch diameter (PD) = 4 inch outer diameter (OD) = 4.666... inch Note that the units above are provided in inches however the .stl files are provided in millimeters. references: a .pdf from Boston Gear discussing both spur (& other) gear theory:http://www.bostongear.com/pdf/gear_theory.pdf another .pdf providing additional information and clarification on both spur and spiral gears: "Parametric Design of a Spiral Gear Process" by Jeffery Baker, Jason Reynolds and Stephen Tecce of Worcester Polytechnic Institute:https://www.wpi.edu/Pubs/E-project/Available/E-project-042811-130543/unrestricted/Final_Report-Parametric_Design_of_a_Spiral_Gear_Process.pdf Instructions print two of each part: gear_4_DP3_N18_150116a.stl gear_4_DP3_N18_150117_link.stl use care when gluing the parts together to avoid binding the gears. see the link picture place glue (I used acetone) only on top of the post and in the socket hole assemble parts insert string as shown in the gear assembly picture to show line of contact for teeth