Description: Stirling engines are unique heat engines because of their theoretical efficiency is almost equal to the theoretical maximum efficiency,Called the cycle efficiency. This is an external combustion engine in which the fuel is burned continuously,and the piston is moved by the expansion of air (or helium or hydrogen) as a medium,and the expansion gas is cooled in the cold chamber,and the cycle is repeated.Only a small alcohol lamp,you can make it fast rotation and strong power. As the external combustion engine to avoid the traditional internal combustion engine of the explosion to do work,in order to achieve a high efficiency,low noise,low pollution and low operating costs. Aerodynamics are rich in knowledge of physics,single cylinder combustion engine.Engine principle is intuitive,educational toys,teaching experimental equipment can effectively cultivate children's interest in learning can also be used for classroom teaching,more intuitive and easy to understand. The engine model on the horizontal position by hand toggle the flywheel to see if smooth,if there is a strong sense of astringent,check the connection rod is normal,whether the cylinder oil and dust,and if so,please use toilet paper to erase Not smooth.Toggle the flywheel feel pressure within the cylinder body is a normal phenomenon,the cylinder is sealed. Specification: Assembled size: 16x8x9cm / 6.29x3.14x3.54inch Material: Metal Package Includes: 1 Set Hot Air Stirling Engine DIY Model Kit Note: Please allow 1-3mm measuring deviation due to manual measurement. Due to the different monitor and light effect,the actual color of the item might be slightly different from the color showed on the pictures.Thank you!