This model of steam engine was the most common in past. The energy of the steam pressure is converted into the rotation of the flywheel by the piston. The moving of the flywheel alters the position of the valve, which redirects a portion of steam in one of cylinder parts and opens the other part to emit exhaust steam.
In theory, such type of engines was mounted on locomotives. Now such devices can be found, perhaps, in museums or as a steam-punk attributes.
Green Steam engine, in my opinion, is still quite exotic . The principle of operation has been taken from the inventor site (http://www.greensteamengine.com) Robert Green.
The engine consists of:
Despite the simplicity and cheapness , the engines of this type can operate at relatively low pressure steam.
The peculiarity of this engine is that its cylinder is not fixed statically, but swings in accordance to the wheel rotation.
As you can see on the model in a transparent mode, the cylinder is connected to the source by the right aperture and by the left to the exhaust pipe. In the other extreme position, the apertures are interchanged.
You can find a lot of practical implementations of steam engines with oscillating cylinder in the Internet. That’s because of the simplicity of its construction.