Package:Sunnytech package, Sunnytechtech LOGO printed, great gift for boy or girl friend, parents, kids,etcSunnytech Hot Air Stirling Engine Model Education Toy Electricity Power Model SC004Features: Single Flywheel Hot Air Stirling Engine MODEL:SC02 Speed:1300 to 1500 RPM Size: 155*80*90mm/ 6.10 * 3.15* 3.54 in Material: Steel,copper and Aluminium Weight:471.4 g color: silver (not black) With the help of the single flywheel, this engine run madly. Many of our ustomers comes from school,colleague,etc. What is the stirling engine? A Stirling engine is a heat engine that operates by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work.The engine is like a steam engine in that all of the engine's heat flows in and out through the engine wall. How it works? This is traditionally known as an external combustion engine in contrast to an internal combustion engine where the heat input is by combustion of a fuel within the body of the working fluid. Unlike the steam engine's use of water in both its liquid and gaseous phases as the working fluid,the Stirling engine encloses a fixed quantity of permanently gaseous fluid such as air or helium. As in all heat engines, the general cycle consists of compressing cool gas, heating the gas, expanding the hot gas, and finally cooling the gas before repeating the cycle.