This book will guide you step-by-step through the process of building three low temperature differential (LTD) Stirling Engines for less than $30 each. Two of them are efficient enough to run from the heat of your hand. And all three of them can be built using common hand tools with material available at your local hardware store and hobby shop. The hot air engine (aka: "Stirling engine") has been around for a very long time. Interest in the technology has been revived in recent years by those exploring new methods for producing "Green Energy." An LTD Stirling engine is efficient enough to run from the waste heat that is discharged from other appliances or from the warmth of direct sunlight. The most efficient of these will run from the heat of your hand. Until now, if you wanted to build your own heat of the hand Stirling Engine you had to either spend several hundred dollars for an expensive kit or you needed access to a precision machine shop. This book breaks both those barriers for you. Now you can build your own working models that will run from the heat of your hand, without the aid of a machine shop. Whether you are a student looking for a winning science fair project, or just a home hobbyist looking for a fun project, you will find this book to be a helpful guide in creating your own LTD Stirling engines. You will find detailed instructions, tips on finding parts, and over 130 illustrations to help you recreate Jim Larsen's original designs for these highly efficient small models.