There is always more than one solution to a problem. Simple engines use steam on one power stroke before it is exhausted, and compound engines were invented to improve economy by using steam on a second stroke. Cross compound engines had separate cylinders on individual cranks. Industrial and maritime engines went to triple-expansion technology, using steam three times before it was spent. Tandem compound engines like this Port Huron had both the high pressure and low pressure cylinder on the same rod, which simplified the crankshaft considerably. Several steam engine manufacturers used a layout similar to the Port.
This Russell tandem compound is a real eye catcher. The high pressure cylinder where steam is first used is closer to the crosshead, which is reversed from the layout we are used to seeing.
Steam is exhausted from the high pressure cylinder to the larger, low pressure cylinder where it expands a second time, yielding more power before it is sent up the stack.
Cross compound engines, with their cylinders on separate rods and crankshaft throws, can have live steam sent straight to the steam chest from the throttle for extra power, and for starting without being stuck on dead center. Tandem compounds have the same starting characteristics as single cylinder engines, which means that the engineer must pay attention to the location of the crankpin when starting, and use the reverse lever skillfully to make the iron beast go.
Man, that's cool.
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