Weekend Steam: Inner Workings Of A Triple Expansion Launch Engine

The first video shows the engine not-quite-done, so you can see the pistons and valves mechanisms up close. The second one shows the engine in operation for the first time.  There are six power strokes per revolution in a triple expansion engine.  Note that it takes a while to warm up the engine so all the petcocks can be closed.  The steam has to work its way through three cylinders and power strokes before it's exhausted.