RESEARCH

I wanted to learn more about the various gauges, levers, and fittings in a steam engine cab so I did some research. The first good source I found is the classic book from Kalmbach Publishing Company, Steam Locomotive Cyclopedia. It covers every aspect of steam locomotive design and operating principles with excellent diagrams of piping for all air and steam fittings.

Another excellent source of information is Charlie Givens' Straight Talk About Bent Pipes series in the Narrow Gauge and Shortline Gazette. The articles ran from 1975 through 1977 but are now out of print. If you know someone with a Gazette collection, you might photocopy the articles. I did and I prize them highly; they are most useful. (I have suggested to Uncle Russ that Outdoor Railroader might request permission to reprint the series because of all the new modelers who could benefit from it. If you are interested, please write to OR. With enough support, we could all gain access to an excellent source of information.)

[Even if readers were unanimous in requesting the series, actually publishing it could impose very difficult problems. But if enough of you really do harangue me, I will promise to try.- Ed.]

PRINCIPAL HARDWARE

Many Porter and other small industrial and mining engines operated with "open air" cabs. I decided to remove the roof from the cab of a Lehmann Porter in order to model what I had learned about backheads.

Trackside Details' owner, Pete Thorp, loaned us the backhead he uses to display his detail castings. It clearly shows the general placement of the most common parts. Let's look at them:

The throttle is a lever on the back side of the boiler. Its handle points toward the engineer's (right) side of the cab. The lever connects to a rod that runs up to a valve in the steam dome (where the whistle is). The valve regulates the pressure of the steam going to the cylinders. The farther toward himself the engineer pulls the lever, the more steam goes into the cylinders and the faster the engine runs. Trackside's part number TD-29 is typical of the throttle on most engines.

The Johnson bar is a large lever on a rack. It mounts to the floor. The engineer uses it, along with the throttle, to control the speed and direction valve settings on the cylinders. I used TD-28 to represent the Johnson bar on my model.

All steam locomotives need at least one gauge on the backhead to indicate boiler pressure. If the locomotive has air brakes, it also needs a gauge to show the working air pressure. I mounted the TD-51 double gauge cluster on top of my backhead after removing the top air gauge from my casting. That is because my Porter has no air compressor or air brakes. I used the Lehmann stick-on gauge face for the steam gauge. [The LGB Mogul and Bachmann Ten Wheeler have air compressors so you would mount the casting without modification.- Ed.]

If you model does have air brakes, you will need a brake valve. The TD-46 valve has an attractive stand and mounts to the floor on the engineer's side, slightly behind the back edge of the firebox.

I thought the Porter's firebox door could stand some improvement. Since I had no plans to use the electrical connections there, I fitted a TD-50 door for better detail. It, and the new firebox door from Ozark Miniatures, would work well on most other small locomotives.

SECONDARY HARDWARE

Many engineers added a lube tray to the back of the firebox above the fire door because the heat kept the oil from becoming too thick in cold weather. The lube tray is a small shelf for oil cans and miscellaneous accessories. I mounted the tray on my Porter on the fireman's (left) side of the firebox because that was the only space remaining.

Steam engines required a lot of lubrication. The fireman used his oil can to fill various oil cups on the running gear, but other parts require oil while the engine is moving. A hydrostatic lubricator, such as Precision Scale's part number PS-9820, will handle that job. The fireman keeps it full. It has a small sight window so he may monitor the oil level. A steam line from the boiler attaches to the top of the lubricator. Lines from its feed valves run to the cylinders, air compressor, and other moving parts, usually under the boiler jacket. I mounted my lubricator high on the backhead so gravity can aid the flow of oil.

In order to make steam, we must get water into the boiler. The boiler operates under pressure and it is necessary to overcome that pressure so the water can enter. The device for that job is a calledan injector. It uses steam to force the water through a check valve and into the boiler. The injector has a steam line going in, a water line from the tender, saddle tank, or side tanks going in, a water line coming out, and an overflow line to blow excess water down through the cab floor. The injector usually, but not always, mounts on the fireman's side of the backhead. Trackside's number TD-52 injector works well on nearly all locomotive models.

Steam locomotives use a lot of water. Maintaining the proper water level in the boiler is critical. If the level is too high, the water will flood the cylinders and stall the engine. If the level is too low, it will expose the crown sheet. That will result in the condition we call an explosion and blow the engine and its crew all over the landscape.

So the crew has a double check system to monitor the water level. The first check is a sight glass. It mounts so the glass is half-full at the proper water level. Then, because colder temperatures may cause condensation and cloud the glass, three drain cocks at three different levels provide a backup. The correct term for those "faucet handles" is tri-cock valves. The lowest mounts three inches above the crown sheet. The next two mount vertically above the first at distances of at least three inches.

If the sight glass was unusable, the engineer could open a valve and see whether water, dry steam, or water flashing to steam escaped. The process may have been crude but it was an accurate check of the sight glass. A drip funnel under the tri-cock valves caught the runoff and directed it through the cab floor. Trackside Details has a set of three valves and a drip funnel (TD-48) and a sight glass (TD-49). Since the Lehmann Porter already has the tri-cock valves, I only added the drip funnel. Most Porters were so simple, they had no sight glass.

OPTIONS

Since I'm a sucker for beautifully detailed lost wax brass castings, I added a Fairbanks-Morse auxiliary water pump from Precision Scale to my Porter's saddle tank. It was steam-driven and pumped water from a tank, lake, or stream into an engine's tender, saddle tank, or side tanks. It could also pump fuel oil from a supply tank or drum into a fuel tank or tender if the locomotive was an oil-burner.

That, then, is an elementary look at a steam engine's backhead. I hope it prompts some of you kitbashers and scratchbuilders to add detail inside your locomotive's cab. Some people may miss it, but you will know it's there and it is very satisfying when a knowledgeable observer compliments your attention to detail.

I want to thank Pete Thorp for his help in preparing this article.