[Part 3]
The Black Hills Central Railroad (BHCR) is a standard gauge, steam-powered (mostly) "heritage railroad" that operates over a ten-mile route between Hill City and Keystone, North Dakota, U.S.A. Its route is part of the former Keystone branch of the Chicago, Burlington, and Quincy Railroad, originally built to support gold mining operations in the South Dakota Black Hills.
Carla and several of her fellow Red Hatters rode the line round trip. Their train was pulled by the line's flagship locomotive, BHCR no. 110, a 2-6-6-2T tank Mallet locomotive, originally built in 1928 for Weyerhauser Timber Company. We see it here just as it has pulled into the station at Keystone to load passengers:
Carla C. Kerr:
BHCR no. 110 pulls into the station
Canon PowerShot G16, ISO 80, f/2.8. 1/400 s
Sadly, the circumstances were such that Carla couldn't get a good clear shot of the locomotive from the side, so I will resort to pictures snagged elsewhere for illustration later in this essay.
The Mallet type of locomotive is names after its designer, Swiss engineer Anatole Mallet. He was a French-speaking Swiss, and accordingly it is the custom to say the name of the locomotive type with the French pronunciation, approximately "mal-LAY".
The Mallet locomotive has two unique features:
• It is an
articulated locomotive. It actually comprises two "sub-locomotives", each with its own stem engine driving six driver wheels, both under a common frame and fed by a common boiler. The frontmost of these sub-locomotives is able to pivot under the frame, thus giving the beast the ability to negotiate curves of relatively small radius (often encountered in the tricky right-of-way found in mining operations).
• It is a
compound locomotive. That means that the steam from the boiler, initially at full boiler pressure, first works in one or more cylinders of relatively-smaller diameter. Then, exhausting from these "high pressure" (HP) cylinders, now at a lower pressure, it then works in one or more cylinders of relatively-larger diameter (the "low pressure"–LP–cylinders). For reasons that are beyond the scope of this note, this gives a greater efficiency to the overall system.
In the Mallet implementation of this concept, the HP cylinders are on the rearmost sub-locomotive, and the LP cylinders on the frontmost.
We get a bit better looks at some of the arrangements in this photo of that same locomotive (found someplace on the Internet):
Notwithstanding the perspective, we can see that the cylinder on the frontmost sub-locomotive has a substantially larger diameter than that on the rearmost.
Then rusty-looking pipe carries the steam exhausted from valve of the the rear cylinder to valve of the front cylinder. It has swivel joints in it to accommodate the movement of the frontmost sub-locomotive. This pipe is of substantially larger diameter than would be needed just for the conveyance of the steam. In that way, it large volume provides a reservoir to deal with the fact that the "puffs out" of the steam from the HP cylinder are not (necessarily) synchronized with the "puffs in" of the steam into the LP cylinder.
The "T" in the type designation means that this is a
tank locomotive (yes, just like Thomas). That means that it carries its own supply of water (in this case in curved tanks around the boiler, blue in the picture just above), rather than depending on a separate tender for that. As for the coal (also carried in the tender for conventional locomotives), that is carried in a small "bunker" at the back of the locomotive, rather like a car's trunk. We see it in this shot of that same locomotive from the Internet:
BHCR no. 110 showing coal bunker
It might seem that there is a big disparity between the size of the coal bunker and the size of the water tanks, but in fact typically a steam locomotive of this type consumes (by volume) about five times as much water as coal.
But enough of locomotive machinery, and back to cute girls. Here we see a batch of 'em in car 112, "Oreville":
Carla C. Kerr:
Red Hatters aboard
Canon PowerShot G16, ISO 200, f/1.8. 1/30 s
This car was originally built in 1913.
[to be continued]