Features: 1.A Stirling Engine is a heat engine that operates by cyclic compression and expansion of air or other gas at different temperatures, such that there is a conversion of heat energy to mechanical work. 2.It is forbidden to add oil for lubrication, because the oil will mix with dust in the air and become oily, which will eventually increase the friction and prevent free running. 3.This good-looking low temperature stirling engine could be a great gift for your friends or families or yourself. 4.The engine is like a steam engine in that all of the engine's heat flows in and out through the engine wall. 5.Suitable for students' engine principle educational toys, teaching experimental equipment, training students to like physics, live science, brains. specification: Speed up to 180-200 RPM Start temperature difference:20 oC Color:Silver Bottom Gold Flywheel Material :Steel and Glass Size:100X100X120mm Weight:250 Grams Use pencil to lubricate it Just use pencil powder tolubricate this stirling engine if need. Prohibit to add oil to lubricate.Because the oil will mix with dust inthe air, and become a oil-dirt, finallymake the friction to be even bigger.The stirling engine can't runfreely. Package included: 1 x Stirling Engine 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 contrastto 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'suse of water in both its liquid and gaseous phases as the working fluid,the Stirling engine encloses a fixed quantity of permanently gaseousfluid such as air or helium. As in all heat engines, the general cycleconsists of compressing cool gas, heating the gas, expanding the hot gas, and finally cooling the gas before repeating the cycle. This good-looking Low Temperature Stirling Engine could be a great gift for your friends or families or yourself. It is almost ready to run: you will have to install the flywheel. After 30 seconds of installation, put it on a cup of hot water, then it will run like Forrest Gump. Note: the various parts of the crankshaft and connecting rod can use pencils to lubrication, never oil lubrication, once produce oil dirties, friction is very huge, and not easy to clean up!!!!