Wednesday, October 14, 2020
Two Birds with One Stone...
The second challenge that is solved in the locomotive shown on this post card was the need for power. Some of the grades the Southern Pacific faced were as much as 2.5%. Getting through the steep grades required either many engines linked together - or this solution. This engine is called a "Mallet" (pronounced mal-ay); it was invented by a Swiss (think lots of mountains) engineer Anatole Mallet who lived from 1837 to 1919. A Mallet engine has one boiler that is connected to two sets of driving cylinders; this is also called an articulated engine. What makes this a Mallet engine is that the steam goes through one set of cylinders (rear) at high pressure, the exhaust from those cylinders is at a lower pressure, but strong enough to still be used in the second set of cylinders (front set) before it is sent out the exhaust.
Again, this is an Edward Mitchell post card as indicated by the back of the post card.