Operating a steam locomotive demonstrated with a modified Accucraft Ruby, G scale radio control Ruby

This is part 4 in the series on the Ruby live steam locomotive operating on the Oyster Creek Garden Railroad. Today we will discuss operating strategy for steam locomotives, both model and full size.

Two places in you can operate a steam locomotive:

Nevada Northern Railway Museum: https://nnry.com/pages/engineer.php

Southern California Railway Museum: https://socalrailway.org/run-one-prog...

There are 3 controls used to operate a steam locomotive. A way of regulating fuel - a valve regulating gas to burner (Show burner), a throttle for distributing steam to the cylinders which power the locomotive. And a leaver for selecting the direction of motion/Engine brakes

When steam is made faster than used, the boiler pressure increases until the safety valve opens to limit boiler pressure. Excess steam cannot continue to be stored as increasing pressure and it is lost. Lost steam reduces run time which is already limited on live steam models. If steam is used faster then it is made, the pressure will drop and the locomotive could will stall. On a full sized locomotive, the fireman and engineer know their rout.

When approaching a grade the fireman increases the fuel stoked into the firebox to increase the rate at which steam is generated. This is done in anticipation of the engineer needing more steam when climbing the grade. Conversely the fireman stokes less fuel before drifting down a grade where by balancing steam supply and demand.

Often live steam modelers avoid the need to adjust the burner and throttle on the fly by operating on a flat and level track with generous curves where steam usage is constant and throttle and burner adjustments are not required.

This strategy does not work on the OCRR which has grades and curves. The single track main line has a reversing loop at each end and a horseshoe curve in the center. The change in elevation over the 100 foot distance between the reversing loops is about two feet. This Ruby is not fitted with a servo on the burner valve. So I manually set the burner set to generate steam for steady speed on level track, and allow the pressure to build to 50 psi. As the train climbs the grade steam is used faster than generated. Pressure drops to 40 psi half way up the grade and the throttle is opened to compensate. At the top of grade the pressure dips to 30 psi. This is enough for the train to circle the loop and drift back down the grade. Drifting down uses very little steam and the boiler pressure returns to 50 psi by the time the train circles the lower reversing loop and is ready to climb the grade again. The train can travel the length of the railroad and back three times before running out of fuel.

On a full size locomotives, or sophisticated live steam models, the Reversing Lever, often referred to as a Johnson Bar, regulates the timing of the valves that direct steam to the cylinders. The Ruby has a simplified valve gear. The lever shifts a valve which reverses the direction of steam flow to the cylinders rather than actually changing valve timing. (note location of reversing valve Steam line length)

Some radio controlled live steam locomotives only have a servo for the direction leaver. When the lever is moved only part travel, the valve isn’t fully engaged. This restricts steam flow and acts as a throttle as well as controlling direction. But there is little travel from full open to full closed on the Reversing Leaver, so fine control of speed is difficult on a rod driven locomotive with small cylinders. The throttle has a much greater range of motion. This makes small changes in the steam flow easier. In practice I use both. I regulate the steam with the throttle, but if I need to stop quickly or want to be sure the locomotive stops completely, I shift the Direction Lever to center.

One locomotive I do operate with only a servo on the Direction Leaver is the Accucraft two cylinder shay. This locomotive is driven by gears. The gearing favors power over speed. This helps to smooth out changes in speed and allows good control just using the Direction Leaver.

Another technique that engineers use when running a full sized steam locomotive is to listen to the “stack talk”. When the throttle setting is changed it takes time for the train to react noticeably. But the exhaust sound instantly gets louder letting the engineer know the locomotive is working harder. Also changes in the speed of the train can be gradual and nearly imperceptible. But even the smallest change in speed makes a noticeable change in the frequency of the exhaust pulse. The original exhaust pulse from the Ruby was not crisp or loud enough to hear the stack talk. However this Ruby was retrofit with a Summerlands chuffer. Now the exhaust pulse is loud and crisp enough to provide feed back to the engineer, just like on a full size locomotive.