Steam & Excursion > Double-Heading Steam Locomotives

How was this accomplished safely and efficiently? How much skill did it take? Could it be dangerous? Without radios, was there a minimum of communication--hand and whistle signals? Was much of it by the feel of the train? How did the handling differ from the lead and second loco engineers? Did one engineer only handle the air brakes for the train? In the event of an emergency brake application, could two locos stop the train quicker or did that have its own complications?


Victir Baird

Posted from Android



Edited 3 time(s). Last edit at 02/22/25 11:26 by wabash2800.

wabash2800 Wrote:
-------------------------------------------------------
> How was this accomplished safely and efficiently?

With VERY experienced Engineers who REALLY knew their territory.

> How much skill did it take?

A lot!

Could it be dangerous?

Not really.

> Without radios, was there a minimum of
> communication--hand and whistle signals?

Only whistle signals, plus knowledge of ones territory.

Was much
> of it by the feel of the train?

Yes, but more about knowing ones territory.

How did the
> handling differ from the lead and second loco
> engineers?

The second locomotive's Engineer generally worked full throttle, depending on the territory, while the lead locomotive Engineer controlled train speed.

Did one engineer only handle the air
> brakes for the train?

Yes. The lead locomotive Engineer controlled the air, and the train brake valve was cut-out on trailing locomotives.


> Victir Baird
 

HotWater Wrote:
-------------------------------------------------------
> wabash2800 Wrote:
> --------------------------------------------------
> -----
> > How was this accomplished safely and
> efficiently?
>
> With VERY experienced Engineers who REALLY knew
> their territory.
>
> > How much skill did it take?
>
> A lot!
>
> Could it be dangerous?
>
> Not really.
>
> > Without radios, was there a minimum of
> > communication--hand and whistle signals?
>
> Only whistle signals, plus knowledge of ones
> territory.
>
> Was much
> > of it by the feel of the train?
>
> Yes, but more about knowing ones territory.
>
> How did the
> > handling differ from the lead and second loco
> > engineers?
>
> The second locomotive's Engineer generally worked
> full throttle, depending on the territory, while
> the lead locomotive Engineer controlled train
> speed.
>
> Did one engineer only handle the air
> > brakes for the train?
>
> Yes. The lead locomotive Engineer controlled the
> air, and the train brake valve was cut-out on
> trailing locomotives.
>
>
> > Victir Baird

Even though the train brake valve was was cut out on the second engine, the second engineer still had the ability to place the train in emergency with it.

Brian Black
Castle Rock, CO
>  

tehachcond Wrote:
-------------------------------------------------------
> HotWater Wrote:
> --------------------------------------------------
> -----
> > wabash2800 Wrote:
> >
> --------------------------------------------------
>
> > -----
> > > How was this accomplished safely and
> > efficiently?
> >
> > With VERY experienced Engineers who REALLY knew
> > their territory.
> >
> > > How much skill did it take?
> >
> > A lot!
> >
> > Could it be dangerous?
> >
> > Not really.
> >
> > > Without radios, was there a minimum of
> > > communication--hand and whistle signals?
> >
> > Only whistle signals, plus knowledge of ones
> > territory.
> >
> > Was much
> > > of it by the feel of the train?
> >
> > Yes, but more about knowing ones territory.
> >
> > How did the
> > > handling differ from the lead and second loco
> > > engineers?
> >
> > The second locomotive's Engineer generally
> worked
> > full throttle, depending on the territory,
> while
> > the lead locomotive Engineer controlled train
> > speed.
> >
> > Did one engineer only handle the air
> > > brakes for the train?
> >
> > Yes. The lead locomotive Engineer controlled
> the
> > air, and the train brake valve was cut-out on
> > trailing locomotives.
> >
> >
> > > Victir Baird
>
> Even though the train brake valve was was cut out
> on the second engine, the second engineer still
> had the ability to place the train in emergency
> with it.
>
> Brian Black
> Castle Rock, CO
> >  
That's true...and even the caboose can create and emercency application with their cab valve. 

Double-heading may have different proposes.

On the old New York & Long Branch RR, a flat, commuter RR from suburbs
of NYC, schedules had imbalance of power: too many accumulated at one place,
—— and locos would double to re-balance the engines needed for next commuter
rush-hours.
( In-balances occurred on weekends where some locos would still be needed for the 
  lighter schedules and Monday mornings --- for workers living in North Jersey to
  get down to their jobs and businesses on the Jersey Shore).

The lead loco MUST have the full boiler pressure —- in order to safely control
the the train’s airbrakes.

In cases of doubling with light-weight trains, firing of engine 2 was tricky because lack of ‘draft’ —— the weight of the train being pulled determines the air intensity through the grates.

The two engineers would have to agree, beforehand , which loco has the train weight….
Always the lead lloco.

The critical factor is maintaining full-boiler pressure:  needed for ‘snappy’
operation of the air compressors.... and maintaining full control over 
train airbrakes.

Actual air compression, in the compressor, occurs only at the last 1/2” inch of
their pistons's power strokes.   Air only moves from the compressor when the
cylinder pressure exceeds the pressure in the Main Reservoir — that only occurs
at the end of the piston’s stroke.

The engineer needs full boiler pressure in order to be able to get quick-recharges
of brake-pipe pressures ( after a brake application and the drop in train line pressure).

With little or no draft, the fire stays relatively ’cold’. — no air-flow.
If the engineer tries to increase the draft, he simply gets the train
going faster…; but, no commensurate increase in air flow…. it’s still a “cold”fire.

The preferred arrangement is a heavy-enough train so that both
locos get strong drafts, heavy loads and slow speeds…. and uphill fights.

Flat and down hills are very difficult to produce roaring-hot fires.

Fire-boxes are proportioned so that the hottest fires are available with
the maximum designed train-load, for hours on-end.

Lighter trains are harder to fire, because of low-draft volume &
low air velocity.

Passenger locos’ furnaces were proportioned differently when it came to drafting.
So, Steam draft is determined solely by train-weights being hauled.

Hotter fires, with light trains = gets you TOO MUCH speed increase… for timetable allowances.

In my experience, i've never seen the engineer of loco 2, be the main power source.
The lead-engine always controls the air brakes and trainline air pressures,
which requires that snappy air compressors perform at their
fastest cycle speeds. Sluggish compressors mean longer times
to bring the MRs back to Full Pressure.

To aid in re-capture times, later model compressor Steam governors
had 2 different control pressures:
140 psi in MRs—- for normal
pressure maintenance.

150 psi MRs—— For anticipated
excess volume, ( pressure-bubble) after the
engineer had made a ‘reduction’ and would be placing
the brake handle in “running”, thus, sending release air pressure
charge down the train-line — to release the trains’ brake shoes.

The extra MR air quantity allowed for quicker re-charge of the depleted
train lines. Back in lower settings, MR returned to 140 psi .

W.

Posted from iPhone



Edited 7 time(s). Last edit at 02/22/25 17:13 by wcamp1472.

And another insite as to how things other that you pull this hear lever. All these years never thought about that 1/2" deal about an air compressor and I worked with them in my profession as an HD mechanic too. 

When doubleheading with a diesel, i've noticed some engines are equipped with MR lines, so the diesel can better maintain the MR pressure on the steam engine, and not having to worry about a sluggish steam pump struggling to keep up.

That's a doubtful possibility, but a possibility.

 The main advantage with using equipped diesels, is the 
employment of dynamic braking, down-hill.

Only ONE Loco can have the controlling brake valve for the 
trains' air brake system.  You cannot have two Automatic Valves 
"on" feeding the train-line.  Any attempt at a brake pipe 'reduction'
will have the other supply system blow air in the trainline, and
no air will be moved out of the train, ....so, you'll have 2 control 
valves in conflict.  Not possible.

So. where dynamic-equipped diesels are and advantage going 
down hill, is that the engineer can keep the Automatic brake valve 
keeping the train fully charging ( against continual leakage), while
having the diesels' traction motors doing the braking, while descending.
The coaches in the train remain fully 'charged".
A big advantage.

When using the train air brakes, the engineer's brake valve supplies the 
air into the train. and acts to apply the brakes on each car.
Every car has storage tanks that hold air that will be used 
to apply the brake shoes on that car.   If you are running 
100 psi for train air systems, the most pressure that can be applied
to the brakes at each car is 50 psi--- equalization---.  The pressure 
available to flow, only flows until the two volumes have equal tank 
pressures. .

The problem is that brake applications occurr very rapidly, once 
the lowered BP pressure has been set by the engineer.

When making brake-pipe reductions, the air flow rushes towards the 
loco in 'waves' of pressure ..... flowing unevenly....
The couplings and bends in the trainline form hundreds of 
restrictions, so air flowing to the engineer's brake valve,
is constantly varying in flow-rate and pressure..... impossible 
for an engineer to manually regulate a smooth reduction in BP 
pressures.

George Westinghouse invented a system that automatically controls 
the amount of air exhsusted, at steady rate, regardless of wave 
pressure flows.   He used an 'equalization resrevoir' and an equalization 
valve.

The valve acts as a blalance between the desired trainline pressure,
and allowing reduced, but controlled release of air down to a 'new' 
steady brake-pipe pressure.  The engineer sets the brakes by 
reducing the trainline pressure:   say, from 100 psi ( release) ,
down to 90 psi.   The system must control the reduction so that 
the trainline remains at 90 psi.   That applies all the car's brakes 
at a moderate brakeshoe pressure to the wheels.

A regular, full brakeshoe-pressure is reached with a 20-psi 'reduction'
at the engineer's control valve, that's when the car's storage tank pressure
equals the pressure in the car's brake cylinders.   Once those 2 pressures are equal,
trying to get more brakeshoe pressure is Impossible.

The challenge is that the car's air system has lost pressure, and now 
has less possibility for greater brake-shoe pressure.   If the train's speed
slows, as the engineer intended, he may initiate a brake-shoe release, and 
re-charge the BP back to 100 psi.  

But for ALL the individual cars to get back to full pressure, takes a long time
the recharge pressure is only a 10 pound difference..full recharge at each car
and can take more than 20 minutes.

Because as the car's air tank pressure increases, the applied pressue stays 
the same.  So, if you had started with a 10 psi 'reduction', that would leave 
a partially lowered pressure in the car's storage tank.  Say, 90 lbs remains 
in the car's tank, with 100 psi trainline, that's only a 10 lb differential pressure,
to do the recharging.

As the car's tank gets back, up to 95 psi, that's only a 5 lb difference, so the charging 
rate slows even further, the closer you get to the full-100 lbs prsssure.
The control valve then closes and 'laps' the 2 ports.

There's more to the story.

​W.




 



Edited 1 time(s). Last edit at 02/23/25 12:20 by wcamp1472.

On the Santa Fe/bnsf where I worked for a couple million miles, we used a 90 lb brake pipe on freight. If I remember a 24 psi reduction was a "full reduction", everything was equalized, there aint no more to be had. But, if you had too, you still had Emergency, and that got you approx 20% more brake cylinder pressure, because that side of the reservior still had 90 psi piped to the brake cylinder over what was already there from the full service.

LocoPilot750 Wrote:
-------------------------------------------------------
> On the Santa Fe/bnsf where I worked for a couple
> million miles, we used a 90 lb brake pipe on
> freight. If I remember a 24 psi reduction was a
> "full reduction", everything was equalized, there
> aint no more to be had. But, if you had too, you
> still had Emergency, and that got you approx 20%
> more brake cylinder pressure, because that side of
> the reservior still had 90 psi piped to the brake
> cylinder over what was already there from the full
> service.

26psi = full service on a 90 pound brake pipe.



Edited 1 time(s). Last edit at 02/24/25 07:35 by train1275.

When we did the EAS for BNSF, they put a new diesel behind 1522 as a company billboard.  We shut down our compressor and just used the diesel's to save wear and tear on ours.  We were also MU'd with the diesel.  Our MU system didn't have the dynamic capability, but usually the BNSF conductor was back there or one of our 3 engineers.  I think we used dynamics once.
On one stop, I got a wild hair and cut in the booster and used the diesel to see how quick we could get away.  Like a streak! Booster needed some exercise.
On a Topeka RR Days trip, at KC they put a new SF diesel behind us leaving Argentine. The pilot engineer was a younger guy and showed up in overalls, blue denim shirt with a red bandana and engineer's cap. He rode back in the diesel and the road foreman rode in the cab.  1522 had been sitting all night and got little running the day before so I asked the RFE if he could have the guy go in dynamic so we could work enough to sand the flues. I started working 1522 hard and felt the dynamics working and felt him notching it up.  Pretty soon he was on the radio yelling 'I'm all the way into the dynamic and it's still accelerating".  We all got a kick out of that. Newer guys always thought steam engines just made noise and smoke. We showed 'em.

Dynamic brskes, are just that ----- they retard acceleration.
BUT, the braking comes from electrical current generated
by the motors, wheh cinnrcted to a fixed 'resistance", Load.

Motors do 'work', when in power-mode.
The traction generator produces current fed to the motors,
and the generator's current output is LIMITED' by 
control circuitry ---- to the rated power of a specific unit.
So, a 3,000 hp diesel, can power the motors, consistently,
so each motor is limited to 500 hp.

Limited, because at higher track speeds, pulling the train, the
power needed by the motors could exceed their current-limit.
And, so, the Main Geretstors' power output is limited to protect 
the traction motors.

During dynamic braking, the traction motors are changed to 
'generators' ----  on older DC diesels, the motors' field windings
were fed lower current power and fed the motors' modest 
field current,  

The the rotating armatures' output wires are routed to fixed-power,
steel resistance --- whch get very hot when braking.
As In all electric generating circuits, the amount of current, in AMPS,
increases as the armature spins.  The current produced increases
as the square of the currrnt flow.   So, 3,000 hp of braking current 
on DC locos is reached at about 13 mph.

That means that the combined power output to the grid-resistors,
is limited to that track-speed.   If the train accelerated by gravity 
( down hill), the motors will spin faster, generating more current,
land higher electricity to the resistance grids and gets them 
glowing from the heat!

To prevent the grids from being overheated & damaged, the excitstion
current-flow from the diesel generator --- to the motors--- is reduced to
each motor's excitation-field to reduce the current/heat generated....
sent to the" dynamic brake grid" on each equipped engine.

Typically, the maximum dynamic braking force has its' greatest 
motor-braking effects at about 13 MPH.  As train speed increases,
the power generated also increases.... soon you will be overheating 
all the braking traction motors, and possibly burning-out the 
dynamic brake grid.

So, loco's circuits protecct the electrical components, by lowering the 
applied braking current from the Main Generator.   
Actual traction braking is reduced, and virtually non existent, above 
35mph.

A good steamer is JUST getting going--- and headed to 50 or 60mph.

​W .