Can anyone explain how steam engines coordinated power and brake operations when double heading or in pusher service?
Whistle signals, feel, and past experience.
Any chance of expanding on your answer? For example is it bake line pressure, or movement by leaning engine? If so how disk the trailing engineer know how hard to push?
Adam,First of all is EXPERIENCE. It is not like they just jumped on a locomotive and took off. These men have been at it a long time and learned a lot. They all, head end & pusher, know the road. They know where the signals are. They know the speed limits, They know the terrain. They know where the rear or head end of their train is at any one time, etc.
Let me provide a couple of examples. Here in Roanoke, Va., the eastbound trains had basically to only climb the Blue Ridge grade, just a few miles eat of Roanoke. A train be it coal of freight that needed a push over the grade would leave the terminal and stop just east of the town of Vinton at the pusher siding called Boaz.
Here, the pusher would couple up to the rear of the train behind the caboose . The air would be turned into the pusher (after he had cut his automatic brake out). When the pusher was ready to go, he would give a long whistle blast. This would let the head know that he was ready to go and he would start pushing in the slack as the air brakes released. The head end would start pulling and off they went. Each set of locos would pull as hard as necessary in order to try to attain the speed limit, then regulate the throttle to maintain that speed. As the grade increases each loco has to pull/push harder until they are at full throttle climbing the mountain. After the rear topped the hill, the brakeman would pull the coupler pin. Then the pusher would ease off of the power and uncouple from the train on the fly, then return back down the mountain to the pusher siding or another awaiting train.
Trains running north and south kept their pushers for a many more miles, if not the entire trip, because of numerous grades spread out over the division. These trains would leave the terminal with their pushers already attached. Because of the many miles to travel, these pushers would be placed ahead of the caboose for safety reasons. The crews knew, again through years of experience, when and how hard to pull/push in order to maintain the varying speed limits over the division. This all depending on the varying route profile. Northbound trains would normally cut their pushers off about 77 miles from Roanoke for them to return home.
Should the train need to stop enroute, the head end would give a whistle signal that they were ready to go. There would really be no need for whistle signal to stop as, it probably couldn't be heard and a heavy brake application trumps pusher throttle power. Even so, a good engineer will be keeping an eye on his air gauge to see just what the head end is trying to do, as in maintain speed or stop.
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Big Jim, of whom I'm not respectful , gave a lot of Good Stuff, in his response, oxymoron?
A rear-end or cut-in helper can't be positioned to crush cars ahead or to shove them off the outside rail.
Whatever power was necessary was assumed to be assigned to a train that was riskless....definitions of those risks were in the rules and special instructions.
Starting a train with a rear-end helper....SP required the head end to start the helper, pull on it, to insure that all the train's cars coupler's pins had dropped..
There' more to come but there is dinner....back later....
Big Jim, you told us how pusher service was worked; can you give us all information about doubleheading? I know something of it, but my knowledge does not extend far at all in the matter of details, other than that the engineer of the lead engine controls the brakes, and he communicated with the engineer on the second engine by means of whistle signals.
Johnny
Not much to tell Johnny. Being that both engines are on the head end, they can both see the signals and will know what to expect approaching the next signal as to how to proceed. There probably wasn't much need to communicate with whistle signals between the two engines unless one or the other had some kind of mechanical problem while running or when stopped to take on coal/water. Again, how and when to pull or let off will come from experience.
Caveat. I am not an engineman. This was told to me by the crews involved while I was railfanning in Japan half a century ago. The train consisted of a D51 class 2-8-2, twenty four-wheel wagons and a C12 class 2-6-2T.
When the signals cleared and the stationmaster pushed the buzzer, the lead loco whistled the start, but did not open the throttle. The helper repeated the whistle signal, then pushed in all slack. When the thrust of the pusher was felt on the lead loco, then the road d'raiba opened his throttle and the train attacked the 2.5% grade, which started just beyond the points of the station sidings. Speed was controlled as necessary by the lead loco - the helper operated at full throttle.
Since the grade didn't break before the home signals of the next station both firemen got a workout. No power stokers on those muzzle-loaders.
Chuck
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