Modern trains when double headed link electronially how did steam engines do this to match power output?

Question

I know that modern diesel locomotives use some electronic connection to ensure that when two engines are coupled they both operate in perfect union with one driver. However how was this managed with steam locomotives when `doudle headed' as they had two drivers, two firemen etc, etc. How did they ensure equal power output and braking?

Can anyone out there answer that please, there is a major discussion going on here about it.

Answer 1

Sorry this is long - but it's the BRITISH version!

As this is the UK site I assume we couldn't really care less what they did/do  over the water. In the UK, when trains were "double headed" it meant that two engines were coupled to the train and co-ordination between the crews was done by whistle signals, these being "set down" in the Rule Book.

Under certain circumstances - e.g. when a heavy train needed assistance to climb a long bank (rising gradient), it was sometimes more expedient to literally drive another engine onto the back of the train at pre-arranged places - these were known as "banking engines" - and would simply push the train from the rear until the main train had got to the top or "over the hump" when the banking engine would simply stop pushing and would drop away from the train. It would then be signalled into a refuge siding whilst the main train went merrily on its way. The banking engine would then wait in the siding either until it was required to assist a train going down the gradient when it would join the front engine and assist with braking. If there were more than one train going "up" the slope, any number of banking engines could meet in the sidings, and all return to base coupled together as a single train.

Some companies - mainly the Great Western Railway - always insisted that whatever the circumstances, the main train engine would always remain at the front of the train, so that in the event of double-heading being necessary, the second engine was always just that - the second engine, although other companies who weren't necessarilly so well off weren't too particular exactly where the help came from - front or back ! ! !

Answer 2

With steam engines there were no remote controls, each locomotive unit had a separate crew and they communicated via hand signals and radio.  This is partly why it wasn't done all that often, mainly in mountain territory to assist a one-engine train over a hill.

They don't need to operate in "perfect union", there is no need to ensure equal power output and braking.  Each unit just does its best; and that helps the train move along.  The locomotive will be forced (by the couplers) to go the same speed as the rest of the train; at that speed it simply applies the best power it can.   It all just works.

Car and Driver magazine once made a dual-engine Honda Civic.  They took the powertrain from one Civic and put it in place of the rear axle on another Civic.  They both had automatic transmissons.  One throttle worked both engines, one shifter worked both trannies.  What put them in perfect sync?  The road!

Answer 3

In the UK, the leading locomotive is the train engine and is in control of the brakes.

The leading locomotive would create the vacuum using the large ejector and then maintain the vacuum using the small ejectors.

Braking is done by admission of air into the vacuum train pipe, this is done by the crew of the leading locomotive, except in emergency, when the guard would use the 'clapper' value in the guards compartment to admit air to the system and apply the brakes. Normally the guard would pulse 'clapper' to alert the locomotive crew, so that they could bring the train to a safe stop.

The passenger communication cord, when operated admits a small amount of air into the train pipe, to lower the vacuum to around 15 inches from the normal running vaccum of 18-21 inches (of mercury) (Except for GW engines that operate at 25 inches). This is done to signal to the loco crew and guard, it does partially apply the brakes, but the loco crew can overcome this, so that they can bring the train to a halt in a position of safety (ie not on a bridge, or in a tunnel).

Balancing power output is a skillful task, done by feel, listening and the occasional whistle signal.

Answer 4

Braking wasn't a problem because the two locos and their train were connected by a continuous vacuum pipe.  The braking could therefore be controlled by the pilot engine alone.

With regard to power-matching, this was done by experience and a "feel" for the going by the driver of the second loco.  Drivers could "connect" with their engines much more easily than is possible with diesel or electric and any discrepacies in the power output or wheel slip would be felt by the driver and corrected accordingly.  It was real "seat-of-the-pants" stuff.

Answer 5

Lots of good answers above.

To make sure we're on the same page, "double headed" meant that there was a helper engine added to the point of the train.  It was easy for the engineers to keep in sync, since most of the time a helper double heading is done in grade territory and this usually meant both engineers would have their power reverses "in the corner" (wide open).  Even today, with the brake pipe the only connection between two manned consists is double heading.  Otherwise, the locomotives are not dounle headed, but MUed "multple unit" engine.

When the helper(s) were cut into the train, or ahead of the caboose, they did communicate with whistle signals.  But, the rules provided for some consistencies as well.  As an example, the rules of the SP required that when helper engineer(s) saw a rise in brake pipe pressure, they were to start shoving, whether they could move the rain or not.  A release of the brakes signalled "here we go."

As a little tip for the hoggers amongst us, when a helper is cut in, use your marks and run the same as if on the head end.  If at the rear of the train, use your marks but run as if 20 cars ahead.

Answer 6

You had to have an engineer and fireman for each engine, and the two engines communicated through whistle signals.

Answer 7

Skill, coordination and experience. Exact output wasn't a big issue. They would both either brake or pull, and as long as they didn't fight each other, they worked together. Most of the braking was done by the brakemen along the train.