Over the years, the reciprocating steam engine has appeared in many forms. None is more unusual than the Oscillating Cylinder Engine. As the name suggests, the cylinder is arranged so as to pivot on the mounting frame. The piston rod connects directly to the crank, causing the whole cylinder to swing to and fro. The abutting mounting faces of the cylinder and mounting frame are provided with ports so that the movement of the cylinder opens and closes the appropriate ports to admit and exhaust steam at the correct time without the necessity for valve motion. Wikipedia has an article here which outlines some early industrial applications for this design.
Many people were introduced to oscillating cylinder engines through their use in live-steam toys made by 'Mamod'. Although I never had one of the models, I was fascinated by the simplicity of construction. I didn't realise how extensive the 'Mamod' range was until I read the Wikipedia article here.
In May 2011, my Friend Keith visited the U.K. and, on a visit to Peak Rail, we studied the 'vacuum motor'. This is powered by an Oscillating Cylinder Engine operating on vacuum from the locomotive’s braking system and, through suitable reduction gearing, can effortlessly turn the largest locomotive. There's a collection of pictures here.
On 13th February 2013 I visited Keith at his home in Perth, Western Australia. Keith had always been impressed with the simplicity of the ‘Oscillating Cylinder’ engine and he ran (on compressed air) an ‘Oscillating Cylinder’ engine he built many years ago to demonstrate how powerful this type of engine can be when properly engineered. There's a description of this part of my visit here.
Keith's demonstration 'Oscillating Cylinder' engine.
It wasn't until September 2015, when I was preparing the post Railway Turntables that I found that Messrs. Cowans, Sheldon & Co. Ltd. of Carlisle held a patent for this method of driving turntables by either vacuum or air from the braking system of the locomotive being turned.