The double acting or multiple cylindered Beam Engine
The double acting high pressure beam engine was initially the power that turned the wheels of Great Britains of industry during the Industrial Revolution, pumped the water supplies (and the concomitant sewage) or in some cases propelled ships until replaced by faster, smaller or more efficient reciprocating engines. Some survived long enough to be replaced by turbines or electric motors and a precious few have survived into preservation.
A beam engine is generally defined as an engine having a rocking beam or lever interposed between the cylinder or cylinders and the load, there are a few generic types, with the overhead, centrally (or near centrally) pivoted rocking beam representing the majority of those built as in this single cylinder example above, designed to drive a textile mill from the teeth on it's flywheel.
The grasshopper beam - where the beam pivots at or near one end
The sidelever or bellcrank where the beam is at a lower level than the cylinder top being the main types - these were more popular in marine service than on land.
The construction is also often referred to, the housebuilt engine has the beam pivoted on a structure which is built into the walls of its building. This example is a housebuilt Woolf compound rotative pumping engine, Woolf introduced a system where the high pressure steam is used initially in the smaller diameter high pressure cylinder, when exhausted it is then used in the larger diameter low pressure cylinder, both of which are on the same side of the beam pivot.
Another variant of this is the McNaught compound where one cylinder is placed on the opposite side of the beam pivot to the other cylinder.
Free standing engines do not rely on the structure of the building for support, this is another Woolf Compound and the beam is supported on an A frame.
Another Woolf compound but this time the beam is supported on four cast columns supporting an entablature for the beam pivots.