The Unofficial LEGO Technic Builder's Guide, by Pwel Kmiec, from NoStarch Press, is an excellent reference on mechanical stress and parts techniques, as well as

The Unofficial LEGO Technic Builder's Guide, by Pwel Kmiec, from NoStarch Press, is an excellent reference on mechanical stress and parts techniques, as well as guides for suspensions, gearboxes, transmissions, steering, and so on and so forth. I highly recommend it.