Make has a great post about these animations on mechanical linkages – they are actually pretty cool/mesmerizing to watch.
Mr. Đức thắng Nguyễn (Duc Thang Nguyen) is an engineer from Vietnam. Since his retirement in 2002, he has being working on an amazing animated 3D catalog of mechanical contraptions.
Using Autodesk Inventor as a tool, he has documented over 1,700 mechanisms. All from gears, couplings, clutches, differentials to detailed examples of movement conversions. For every mechanism Nguyen has generated a corresponding animated YouTube video. These videos are an invaluable source to understand some of the more convoluted and challenging mechanisms. The video-clips portray a mesmerizing collection of kinetics sculptures on their own and can be enjoyed for their sheer aesthetic value.
Through a file-sharing website, Nguyen generously provides an overview of all his contractions nicely organized into mechanical themes. The PDF files include pictures, short descriptions, and direct links to the videos. I strongly encourage you to visit Nguyen’s YouTube Channel and spend some time studying his work. You will find a treasure trove of ingenious solutions to a wide range of real life mechanical applications. If you own a 3D printer and want to improve you CAD skills, pick a compelling mechanism. Model and print it.