A Rio Grande, err, uhm, Mountain?? D&RGW 1501, Otto Perry photo, Salida, CO, 1940. The boilers of the D&RGW 1500-class engines were enormous; in fact, they were the largest boilers ever mounted to 4-8-2 running gear. LaMassena said they were 96" in diameter, and a PRR 4-8-2 boiler would fit inside with 12" clearance all around!
Is it just me, or is that D&H engine's firebox simply MASSIVE? For such a small engine, it has a huge firebox, reminiscent of Northern Pacific's engines, burning low-grade Rosebud lignite coal.
The D&H steamers were noted for having extra wide Wooten fireboxes. The Wooten design provided a much larger grate area than seen on most steam locomotives. The extra grate area was required for burning anthracite coal. A few other small northeastern roads also used Wooten fire boxes, Lehigh & New England and Lehigh Valley come to mind. But the D&H had the most, IIRC. As Hemi mentioned, some western roads also used Wooten fireboxes. Those roads had access to only very low grade coal which needed a large grate area to get enough heat energy to make steam. I've always felt the D&H steamers looked weird, sorta like the tail wagging the dog.
John Wootten invented his firebox for the Reading Railroad to enable the line to utilize culm, or anthracite waste, as an economy measure.
Applying his PhD in Engineering and a ready source of cash, D&H President Leonor F. Loree knew few limits in locomotive design. His triple-expansion 1403 was loaded with every efficiency feature he could apply. Note the cylinder under the cab; there were four. Even a tender booster was thrown in. Boiler pressure was 500 PSI!
500#'s!!!! At that pressure, any steam leak would be invisible until it cooled down a bit. In other words, anything close would be cut severely or in two! That is amazing!
An ordinary boiler wouldn't stand up to that kind of pressure. Multiply 500 lbs by the number of square inches around and you're in bomb territory (think Mythbusters blowing up water heaters at just 300 psi) . Simple explanation: instead of the standard fire-tube boiler where hot combustion gases were piped through a big water heater, they used a water-tube boiler, where water was piped through a large chamber filled with hot gases. Small pipes can better withstand that pressure than a huge boiler. Basically, the visible boiler was just an extension of the firebox, filled with pipes carrying water to become steam. In the LF Loree, steam went to the first cylinder at 500 psi, then to the second at 290 psi, and finally the last two at 145 psi each. All four turned all drivers at once. Just getting the push-pull forces of all four cylinders even and in sync must have been quite an engineering challenge. 1403 was the summit, preceded by three other prototypes, each at progressively higher pressures. This was the steam era's high tech.
Those would have been fun to see and fuss with. Being aware of the power of steam, and having worked around it, makes it all the more fascinating. I do wonder how many mechanics went crazy trying to time those events. And I wonder just how much the "Johnson" operation would affect things. Probably not too much, but a poor engineer could really cause issues running it in the wrong notch at speed, causing loss of pressure and / or excess fuel consumption. Anyway, these unique steamers would have been fun to be around and see.
