communication/control during steam pusher locomotives

[gregc]

i'm guessing that when a train is helped by a pusher engine on the rear, that somewhere in the middle of the train the couplers aren't really pushing or pulling one another.   In other words, the lead engine(s) are pulling half the train and the trailing engine(s) are pushing half.

i'm curious if both engines are being pushed as hard as possible or if they are both working only so hard to work(?) half the train.

but how would either engineer know that they are pushing their engine just enough?   I assume whistles can be used to communicate between engines, but again how hard would each engineer know how hard to push their engine?

i assume with diesels, the diesels have some measure of engine output (e.g. horsepower) and can more easily communicate with one another so that they both, lead and trail engines are operating at the same horsepower.

[charlie9]

I am sure the technique would vary depending if the train was stopped on the grade or on a level stretch before the grade.  I have no practical experience in operating under those conditions but have talked with some old head who have.  They pretty much told me that in the absense of audible whistle signals or visable hand signals, when the pusher engineer saw the brake pipe pressure increase to the point the brakes released, he would lean against the train and then it was pretty much a seat of the pants operation from there on out.  Brakes were controlled by the lead engine.

In reference to your first paragraph, passenger trains almost univerally preferred to use head end helpers only since the in and out slack action you mentioned tended to make for a rough ride.

Charlie

[tomikawaTT]

Got a chance to talk to the d'raiba of the road loco (D51 class 2-8-2) and pusher (C12 class 4-6-2T) while their freight was waiting for a clear track from Agematsu to Kiso-Fukushima back in September of 1964.  The procedure, as described and as I saw it:

1. Road loco acknowledged clear start signal (and stationmaster's buzzer) with two short blasts.
2. Pusher answered with two short blasts and opened throttle, minimum cutoff.
3. When the slack was all pushed in (felt through the seat of the pants) the lead loco throttled up, minimum cutoff.  Smoke, thunder and a rain of cinders!
4. As the train pulled out, the lead loco stretched slack into about the 12 - 13 car point, about 60% of the train.  Both locos at full power - they had about 150 meters of level track before the start of the 2.5% upgrade.
5. As they approached track speed, the road loco d'raiba used cutoff to reduce power production to stay below the speed limit.  The pusher continued at full power.  (The route had been laid down using a snake for a straightedge, so track speed was only 40kph or so.)  In this mode the pusher would end up shoving the slack in to about the seventh car.

The reason for letting the pusher do most of the work was pragmatic.  After a 7.5 kilometer push the C12 would cut off at Kiso-Fukushima, where it could refill side tanks and bunker.  The road loco had to continue to Shiojiri, so saving fuel and water was a no-brainer.

(And now you know one specific reason why I model what I do.)

Chuck (Modeling Central Japan in September, 1964)

[gregc]

so by having the pusher doing most of the work, the lead engine not only saves fuel and water but controls the speed of the train.

thanks