Throughout these lessons, we will cover the calculations and methods of modeling a pair of spur gears that is used in a windmill water pump engine. We will begin this tutorial with a brief tour of the finished spur gear pair assembled onto a mounting stand while demonstrating how these two gears work together. After exploring an Excel spreadsheet of gear calculations, we will then insert these values into a design sketch, which will be used to drive the major features of each gear of our spur gear pair. To speed up the design process, we will then apply some design automation by embedding SolidWorks equations and global variables into some Smart Dimensions so that multiple gear designs can be created in just a few minutes. In the end, we create both our pinion and wheel gears of the windmill engine, assemble them together with our mounting stand, and then make them work along with a discussion of potential modifications that can be made to optimize our design. Ultimately, you will be leaving this tutorial not only with a good understanding and appreciation of how a spur gear pair is created, but also with a model that can be used for various other spur gear applications of your own design. Software required: SolidWorks 2012 and higher.