Parametric Sprocket

• http://www.thingiverse.com/thing:87647/#files - has a good 15 tooth example - Bike Sprocket
• The above was derived from http://www.thingiverse.com/thing:7918

How to Design a Sprocket for Bulldozer Drive

• The sprocket generator in OpenSCAD creates a proportionally correct sprocket.
• How do we know how to scale it to match our specific case?
• We note that the pin spacing on our track is 3"
• We note that the roller OD is 2.2"
• The parameters we have control of are:

• the number of teeth,
• spacing between the rollers

Bulldozer 2015 Usage

Hint: The bulldozer from 2015 used an 8 tooth sprocket, generated with sprocket(8,5,7.5,2,0.2); in the last line of the Editor

Exporting DXFs from 3D Objects in OpenSCAD

• Exporting DXFs - [1] - essentially - load and flatten, then export DXF

• Note: stock Export DXF does not work for 3D files - they need to be projected first.

• To project - projection(cut=false) import("sprocket.stl"); STL file must exist in same directory

• Sample file for exercise in OpenSCAD - the sprocket STL and the .scad file that loads the STL and does a 2D projection. Note that the directory must be correct. File:Sprocketexample.zip
• Note: original srocket was generated using Parametric Sprocket Generator using sprocket(12,5,7.5,8,0.2);

Links

• Sprocket geometry for a correct sprocket pitch and roller diameter - example - File:Sprocketgeo.dxf

• Uses Sprocket Generator