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Painting of LMS Royal Scot 6161 "King's Own" by Murray Secretan |
In service from 1930 to 1963. King's Own Royal Regiment Museum Lancaster has a page about this loco, as does Wikipedia.
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3 cylinder compound locomotive steam engine This is only image I could find of a three cylinder engine. Sad, very sad. |
In my mind, steam locomotives have two cylinders, one on either side of the front of the engine. The piston in each cylinder drives the wheels on that side through a connecting rod. Turns out that some locos have three and even four cylinders. The Royal Scot has three as shown in the drawing above. This means that the straight axle between the second pair of driver wheels has been replaced with a crankshaft. The center cylinder is slightly elevated so that the connecting rod clears the axle of the first pair of driver wheels.
The three cylinders are high on my list of unique designs that never took off over here in the US.
3-cylinder locos had a speacial exaust chuff as well, from the four chuffs per driver revolution on normal engines, 3 cylinders had six chuffs, making for some very interesting “stack talk”
While here in the US they never really took off, they became fairly common across Europe. Among some notable European 3 cylinders is the A4, thats right, the “Mallard” was 3 cylindered, along with her sisters who still operate today!
[3 tiny pictures that purport to show the center cylinder of 3 cylinder locomotive. They made no sense to me. Perhaps they would if you were familiar with these locomotives.]
The center cylinder yielded more power in a smaller locomotive, the #12 (pictures above) is an 0-8-0, but still produced more than 60,000 lbs tractive effort! Thats more than some 4-8-2’s and 4-6-4’s of the time period!
Unfortuantely, the 3rd cylinder was difficult to service, and the costs related to maintenance outweight those saved by fuel economy. These engines became known as “Roundhouse Queens” as they sometimes spent longer under repair than in operation.
This is probably more than you wanted to know,
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