The presented engine design with an external piston combines the advantages of a classic engine with a gas turbine, i.e. high efficiency, low weight and small dimensions. It is a multi-fuel engine and it allows the use of high pressure compressed gases. The presented engine with an external piston and flexible cylinder is a slow-speed engine and is practically possible only now in the era of nanotube technology, such as carbon nanotubes, boron nitride. Flexible cylinders made of high-strength fabric made of carbon nanotubes, boron nitride and other nanofibres are fixed on the outer race of the roller. The above-mentioned materials for the flexible cylinder give us high fatigue strength, over one million bends and temperature resistance of over 1000 ° C in oxidizing conditions with boron nitride nanotubes. The cylinders are easily replaced. The gas inlets and outlets of the cylinders are offset by a certain angle with respect to the radius of the arms connecting the outer pistons to the axis of the engine so that the pistons pass the feed holes at different times. The gas under high pressure falls into a flexible, sealed cylinder in an oval form and as a result of the set pressure, the gas, through the deformed fabric, presses against the external pistons, moving them.
This type of solution gives us the maximum torque from zero revs and in many cases does not require the use of a gearbox. It does not require an oil system.