Gizmo CAD Software
April 23, 2005
I'm writing this custom CAD software package to help me lay out gear trains for gizmos. The goal is to have an application that will let me easily add high-level "parts" to a project, and then arrange them. Most of the parts will be things like gears, and the software will take care of calculating part dimensions, making measurements, etc. You simply specify the number of teeth and the module of the gear, and the program will calculate the tooth form, and parameters for the spoking, draw the gear, and let you drag it around anywhere you like. Gears being dragged will automatically snap to the appropriate distance from other gears so that the teeth mesh properly. The little yellow stars you can see in the pictures indicate that the two gears there are snapped to the same center position (as if they shared an arbor). There is also a subtle green line between the two yellow stars indicating that the large blue gear is snapped to the small dark one.
All the numbers are stored in inch units, and scaled to pixels at draw-time. The small text box in the bottom left corner of the window lets you change the number of "pixels per inch" that are used when rendering the mechanism, so you can basically use it as a "zoom" control to see details of any particular part. Here's a close-up of the place where the blue & green gear teeth cross.