Southern Steam Locomotives

[RME]

SD70M-2Dude

I have some experience with a steam locomotive equipped with a 6ET, and the engine brakes work just as I have described above. On this particular locomotive the maximum independent brake pressure is 45 PSI, which from observation does not seem to be enough to skid the wheels,

I believe this is described as a function of the 6-S reducing valve in the 6ET equipment, and I believe it is intentional for just the reason you indicated.

[SD70M-2Dude]

I think you guys have got the doubleheading thing covered, so I will stick to the air brakes.

All versions of the automatic air brake I have had experience with (6, 24, 26, 30, & several EAB versions, but no ECP systems) feed air into the locomotive brake cylinders when the automatic brake is set (even if the independent brake handle is in the released position), proportionate to how heavy a brake has been set.  Just like Mac said. 

To keep the brakes released on the locomotives the Engineer must 'bail off' (the proper term is 'actuate' I think), on early systems like a 6 you do this by holding the independent brake handle to the far left, past the release postion.  On 24, 26 and newer systems you press down on the independent handle.

I have some experience with a steam locomotive equipped with a 6ET, and the engine brakes work just as I have described above.  On this particular locomotive the maximum independant brake pressure is 45 PSI, which from observation does not seem to be enough to skid the wheels, although applying the automatic and independent simutaneously will result in a higher brake cylinder pressure if one does not bail off (seen diesels go well over 100 PSI in the brake cylinder when in emergency with the independent fully applied).

No idea about how any of the early straight air systems worked with regard to these issues.

[RME]

PNWRMNM

I can not say when the No. 6 engine brake valve, which I have operated on a steam locomotive, was introduced, but expect that any predecessor design in service ca. 1900 operated the same way, that is also applied brakes on the locomotive until or unless bailed off.

I believe 6ET was introduced about 1909; its predecessor 5ET around 1905.  They work as you say, and there is some mention that earlier systems were more, not less, aggressive in applying the engine brake in concord with the train brake.  Here is a good reference (which can be downloaded as a PDF) of the 6ET when it was introduced, compared with the 5ET (p.205ff).

Reference is made to the adjustability of the tender brake (to accommodate loss of adhesion as fuel and water were used up) and there is automatic pressure governing in the driver brake cylinders so that slack or leaks will not vary the application pressure as the brakes apply. 

[RME]

Can we hear from Sue Berry whether what we've been discussing helps her understand what to write ... and what the specific 'literary' situation her engine crews encounter is?

[PNWRMNM]

RME,

In every locomotive air brake system I know of including 26, 24 and 6, an application of the train brakes also causes a proportional application of the locomotive air brakes. In normal train operation the engineer will "bail off", that is, release the engine brakes by depressing the independent brake handle to keep slack stretched.

In switching the cars' air reservoirs have been bled dry so all braking is provided by the engine's "independent" brake, which is a straight air system as you correctly noted. I can not say when the No. 6 engine brake valve, which I have operated on a steam locomotive, was introduced, but expect that any predecessor design in service ca. 1900 operated the same way, that is also applied brakes on the locomotive until or unless bailed off. I do not know if engines of that date had a braking ratio high enough to slide the wheels. I suspect some did and some did not. That is why sand is important and is where the idea of manipulating the independent to avoid sliding the wheels comes in.

I will defer to your superior knowledge of steam engine details and centering the reverser, aka Johnson bar.

Agree there was no MU of steam loco independent brakes. That is a diesel thing. Since train air was controlled by the lead engineer, if the rear engineer does nothing with his independent air after a set from the lead engine, the air will set up hard on his engine. Agree that if second engineer is slow to shut off steam he may run slack in at lead engine's tender, but will not "yank" on the first car in the train. Since the initial condition on the first car was draft, either draft would be reduced, or more likely slack would run in behind the second engine as the air set up on both due to the automatic application assuming either no bail off or part bail off and manipulation of the independent brake to avoid wheel sliding/maximize braking effort to shorten stopping distance.

If I planned to unload, I would dump the train air, turn on the sand, shut off the throttle, do nothing with the independent since the engine brakes will set up hard if I do nothing, and unload.

Mac

[RME]

PNWRMNM

At this point the air would set fully on both engines. That may or may not be sufficient to slide the drivers.

Mac, unless I'm badly mistaken, the Westinghouse does not apply on the drivers at all, and no one sane would arrange it to do so.  [EDIT: Yes, I was badly mistaken: see the reference in my following post for the details of contemporary 5ET and 6ET Westinghouse brake setups, which work as Mac indicated.]  Only the independent 'straight' brake would act on them, and that would have to be applied and then held on in proportion to the amount of braking setting up on the train as the Westinghouse came into full application -- I believe the straight brake applies more quickly, and certainly releases quickly when not held in application [EDIT: it does not; it will stay set when desired, and it is not difficult to set or coordinate] and would be used to modulate the engine brakes for quickest stop (based at least in part on the engineer's experience).  A considerable amount of very good thinking went into the detail design of these ET brake systems.

The reason for working the reverse is that compression with any degree of condensation will run the risk of locking the drivers, blowing off a cylinder head, or bending a rod if the throttle is just closed at longer cutoff with no adjustment.  The chance of that is likely related to the conditions under which the train was operating when the emergency was 'detected'.  This was one of the nominal reasons for putting Wagner bypass valves on some large ATSF steam power.  It was also a known issue for systems of ATS which just arranged to close the throttle after setting a 'penalty brake' application on the automatic brake of steam-powered trains.  Note that it is technically easier to put an adjustment to center a power reverse in an ATC system than to put a stop valve or servo in typical mechanical dome or front-end throttle linkage. 

A couple of further notes: there is no "MU" of independent between steam locomotives, so if the train brakes are setting up and the independent is applied hard to the lead locomotive, the second locomotive may remain coasting inertially, running in the slack to the lead engine's tender while yanking on the first car of the train.  And if the crew of the lead engine decides to 'join the birds' the independent on the lead engine will start releasing when the last hand leaves its handle ... this might result in some interesting forces on the second locomotive, including greater required independent brake application right up to slipping and tire heating to get the 'expected' level of braking.

[PNWRMNM]

While I am not, and never have been a locomotive engineer, I have ridden in loco cabs and observed the manipulations and asked why they did what they did, and have also read extensively about modern car and engine brake systems and their design parameters. To the best of my knowledge the physics of braking were known by 1900.

I know of nothing unique to the Southern ca. 1900, so would assume power would be nothing larger than 2-8-0, and could be 2-6-0 or 4-6-0. A heavy freight train on the main line would likely be two 2-8-0 engines.

Control of the train brakes, including those of the second engine, would be by the lead engineer who would also have the best view of what was going on. For simplicity, assume the rear engineer is blind.

The initial state would have some small effect. For simplicity assume both engines working steam in an effort to maintain some speed.

The lead engineer upon seeing a threat would big hole the air, apply sand, and close the throttle immediately. I do not know why he would fool with the Johnson bar. The whole "set and centered" thing is a 21st century FRA rule, so obviously not in play at the time. Applying the sand is a big deal since it increases the coeffecient of friction by about 1/3 over the initial value, whether on wet or dry rail and as the train moves forward more and more of it will be on sand.

The trailing engineer would instantly detect the application of the air by sound and see and feel the cesation of lead engine's exhaust. He would not know what was going on but he would know it was bad.

At this point the air would set fully on both engines. That may or may not be sufficient to slide the drivers. Sliding the drivers is bad because it makes flat spots, but more importantly sliding drivers generate less braking force than rotating drivers. The ideal amount of braking is just a bit less than what would slide the wheels.

Each engine has an independent brake. In normal power braking the independent is released, or bailed off, to keep the slack stretched in the train. Since the objective of the moment is to stop ASAP, the only reason to bail off is to avoid sliding the drivers. Not knowing the braking characteristics of the engine(s) I do not know if bailing off and working the independent to apply less than emergency braking would shorten the stopping distance or not. The real engineers probably had at least some idea, and the good ones would have known the answer to the question which may well have varied by class of engine.

One thing skilled engineers would not have done is to throw the engine in reverse and spin the drivers backwards. The retarding force would be less with reverse spinning drivers than with forward rolling drivers subject to maximum brake force. This practice is Hollywood BS!

Mac 

[RME]

Deggesty

Would the engineer of the lead engine simply give two shorts on his whistle (which means, when running, stop) so the engineer of the second engine would apply his independent brake?

I was hoping that someone with actual Southern Railway rules would say something in this thread.

In normal doubleheading, I would expect the whistle signal to be ONE blast (two being, I thought, the signal to start the train) which would likely be interpreted as 'close the throttle and expect air-brake application'. 

However, I think the OP is asking about a different situation, when there is an emergency too immediate for whistle signals "first" before responding -- and even at that, with insufficient time to get much 'way' off the train.  In that situation I'd expect the engineer in the lead unit to close his throttle and apply the train brake before 'signaling' anything to the trailing engine, and I suspect there are rules about keeping the locomotive independent 'bailed off' when the train brakes are in emergency, or setting up to be fully applied ASAP in emergency.  Now, whether an engineer would choose to risk flatting the drivers or whatever by applying the independent is one of those unanswerable Euclid questions, which could go either way, but one has to wonder what whistle signal the lead engineer might use -- my speculation would be that he would remember the old 'down brakes!' signal and send that: a repeated series of short toots with one hand on the whistle cord while using the other one if necessary on other controls.

I, personally, do not think that the first reflex of an engineer would be to send a whistle signal to get the following engine to shut off steam -- it would be to brake, and do the other things associated with braking hard, and only afterward confirming something that would become obvious within seconds to the following engine crew 'anyway'.  However, for literary purposes here is a lovely opportunity to 'show, not tell' how the particular engine crews in this instance think, and how they choose (or react!) to respond: if the narration involves interior monologue, the author might even go over a couple of the choices that are made and the physical results (e.g. the second engine banging the first as the slack runs out, then perhaps slipping as the train air sets up).  I don't think there is much likelihood of the second engineer using his independent until comparatively very late, especially since there will be a great deal of uncertain slack run-in and run-out and figuring out 'how much' independent to use, and listening for the signs and symptoms of 'too much', might not be too easy.

Now, the author hasn't indicated whether one or both crews might want to 'join the birds' depending on what is happening in front of them.  The point here is that neither a Johnson Bar 'reverse' nor an application of the independent will long outlast the engineman's hand on the lever, so that if the crew elects to jump the engine will likely stop any practical 'retardation' fairly quickly, again leaving the job up to the train brakes which are really best qualified to do the job.  Situation a bit different with a screw reverse, which if allowed to 'wind' itself may do what happened on Blue Peter as the radius rod drops down to full 'whatever'.

I get the impression the 'period' of this story is prior to the adoption of Schmidt superheaters on the Southern, so there won't be much if any flashing carryover to keep the wheels spinning after the throttle is closed.

[Deggesty]

RME

Doubleheading (in fact, multiple heading) has always been possible, and in fact is remarkably easy because there are no necessary  'disproportionate' effects on one locomotive when another one is making more or less power.

With turn-of-the-century power -- I assume you mean 'turn of the 20th Century' as there was no Southern Railway or indeed any high-speed steam locomotives at the turn of the 19th --  the effect of a 'first locomotive' trying to slow down without warning the following engine would be little different from the same thing with a proportionally longer or heavier train.  The first question that needs to be asked is this: the leading engine necessarily controls the air brakes, which are the train brakes and not the 'locomotive's' brakes (aka the 'independent brake') -- is one of the steps taken to 'reverse or slow' the train the application of the Westinghouse brake?

If so, the progressive application of the brakes on all the cars produce far more retarding force, within a few seconds, than that second locomotive would develop even with full steam pressure and perfect adhesion.  So what will happen is that, at some point related to the effective factor of adhesion (FA) of the trailing locomotive's drivers, the drivers will start slipping.  When this happens, the coefficient of friction goes down dramatically so they will keep slipping, perhaps even speed up their rate of rotation -- and this will rapidly be compensated for by the second engine crew, who will first try to stop the slip in the 'usual' ways, and then fairly quickly bow to the inevitable and close the throttle, center the reverser, open the cylinder cocks, etc. so that the engine rolls with as little resistance or slip as possible.  At this point they may apply their independent brake to help stop the train, if they realize that's necessary or desirable.

If the first locomotive tries to use 'reverse' to help stop the train (this was far more common in much earlier eras of steam power, where independent brakes were minimal and it was apparently common for skilled enginemen to use reverse not only for train braking but a measure of 'dynamic braking' to aid the work of manual brakemen) it is likely that the train momentum and contribution of the second locomotive will induce first a slip and then the spinning with lower coefficient of friction mentioned above.  That won't do much to slow things down.

Now, in practice what would almost certainly happen would be that among the first things the leading engine crew would do upon seeing a 'too short of a distance' disaster looming would be to whistle 'down brakes' (I don't know the exact signal used on Southern, but I would expect a series of short toots), followed by "big-holing the Westinghouse" (application of the emergency-brake feature of the air brakes).  Both those things would 'ideally' be completed before the engine crew even started moving the reverser toward mid (central) or closing the throttle, as it's understood that the air brakes are far more important in stopping the train than anything the locomotive, or its brakes, will do.

The engine crew would do two primary things: center the reverser and close the throttle.  Those things might be done in either order, depending on which control the engineman had his hand on at the time; it's easier to move some forms of reverser with lower steam pressure on the valves, and the throttle has a more definite 'stop' position than the reverser, so I'd close the throttle first, but it would be up to how a particular engineer responded in extremis.  I would NOT expect the engineer to try 'throwing the engine in reverse' as he would understand that would just produce a slip, especially with a doubleheaded locomotive still pushing, and there would be little time to mess around with trying to pull the sanders on to increase traction on reverse-spinning drivers, but you never know what someone might try with death looking them in the eye ... one of the things tried in the Federal wreck in the '50s was trying to reverse the GG1 (the breakers just tripped with overcurrent before any real braking could be developed).

 

Would the engineer of the lead engine simply give two shorts on his whistle (which means, when running, stop)  so the engineer of the second engine would apply his independent brake,?

[RME]

Doubleheading (in fact, multiple heading) has always been possible, and in fact is remarkably easy because there are no necessary  'disproportionate' effects on one locomotive when another one is making more or less power.

With turn-of-the-century power -- I assume you mean 'turn of the 20th Century' as there was no Southern Railway or indeed any high-speed steam locomotives at the turn of the 19th --  the effect of a 'first locomotive' trying to slow down without warning the following engine would be little different from the same thing with a proportionally longer or heavier train.  The first question that needs to be asked is this: the leading engine necessarily controls the air brakes, which are the train brakes and not the 'locomotive's' brakes (aka the 'independent brake') -- is one of the steps taken to 'reverse or slow' the train the application of the Westinghouse brake?

If so, the progressive application of the brakes on all the cars produce far more retarding force, within a few seconds, than that second locomotive would develop even with full steam pressure and perfect adhesion.  So what will happen is that, at some point related to the effective factor of adhesion (FA) of the trailing locomotive's drivers, the drivers will start slipping.  When this happens, the coefficient of friction goes down dramatically so they will keep slipping, perhaps even speed up their rate of rotation -- and this will rapidly be compensated for by the second engine crew, who will first try to stop the slip in the 'usual' ways, and then fairly quickly bow to the inevitable and close the throttle, center the reverser, open the cylinder cocks, etc. so that the engine rolls with as little resistance or slip as possible.  At this point they may apply their independent brake to help stop the train, if they realize that's necessary or desirable.

If the first locomotive tries to use 'reverse' to help stop the train (this was far more common in much earlier eras of steam power, where independent brakes were minimal and it was apparently common for skilled enginemen to use reverse not only for train braking but a measure of 'dynamic braking' to aid the work of manual brakemen) it is likely that the train momentum and contribution of the second locomotive will induce first a slip and then the spinning with lower coefficient of friction mentioned above.  That won't do much to slow things down.

Now, in practice what would almost certainly happen would be that among the first things the leading engine crew would do upon seeing a 'too short of a distance' disaster looming would be to whistle 'down brakes' (I don't know the exact signal used on Southern, but I would expect a series of short toots), followed by "big-holing the Westinghouse" (application of the emergency-brake feature of the air brakes).  Both those things would 'ideally' be completed before the engine crew even started moving the reverser toward mid (central) or closing the throttle, as it's understood that the air brakes are far more important in stopping the train than anything the locomotive, or its brakes, will do.

The engine crew would do two primary things: center the reverser and close the throttle.  Those things might be done in either order, depending on which control the engineman had his hand on at the time; it's easier to move some forms of reverser with lower steam pressure on the valves, and the throttle has a more definite 'stop' position than the reverser, so I'd close the throttle first, but it would be up to how a particular engineer responded in extremis.  I would NOT expect the engineer to try 'throwing the engine in reverse' as he would understand that would just produce a slip, especially with a doubleheaded locomotive still pushing, and there would be little time to mess around with trying to pull the sanders on to increase traction on reverse-spinning drivers, but you never know what someone might try with death looking them in the eye ... one of the things tried in the Federal wreck in the '50s was trying to reverse the GG1 (the breakers just tripped with overcurrent before any real braking could be developed).

[sueberry]

I am looking for someone who is knowledgeable on the operation of Southern Railway (or Central of Georgia or comparable) steam freight locomotives, particularly as to the running of two locomotives back around the turn of the 19th century. Was it possible? What would happen if the first locomotive tried to reverse or slow (stopping not possible because of too short of a distance) without warning to the locomotive behind?