Advanced steam, operational comparisons

something like "engine braking" as used by diesel trucks with mechanical transmission. probobly would not require much alteration to the valve gear to accomplish.

as an aside, Im not sure adiabatic compression of saturated steam would necessarily result in superheat, since both pressure and temperature increase.

While it was technically possible to admit steam to the cylinders for compression, such a move would require extraordinary care on the part of the engineer.

Such a move could easily bend the main rod, shear the piston from the piston rod, or blow a cylinder head off the engine... either way, NOT a good day.

As an aside... I don't know how many amps are needed to generate a field effect in a traction motor. But if its small enough, couldn't a steam turbo generator be wound for the right volts (74v) and motors hung on the axles of the tender? I mean seriously, why couldn't a steam engine be equipped with dynamic braking?

Even if a turbo generator couldn't handle the amp load of more than one traction motor, I would think the power generated by that one motor could be tapped to create the energy to engage other motors.

Just idle thoughts.

Allen Hazen wrote: Dynamic braking ... WAS possible on steam locomotives, and I think used on (at least some) ATSF 4-8-4. Saturated steam would be admitted to the cylinders, where the forward motion of the train would compress (& so heat: Boykle's Law) it, with the resulting superheated steam being exhausted up the stack.

Dear Allen,
No! Don't do this.
Only in case of emergency an engineer would admit steam in the cylinder to compression. This is made by i.e. forward idle switching the gears to backward motion and open carefully the throttle.
The steam will get compressed, but:
Right Bykle's Law -> The steam will get compressed and much heat will get created. Thus: under high compression and high temperatures steam will transform back from a fogy gas to a solid state, called water. Thus no superheated steam will be generated, more super hot water will be found on the peak of compresion in the cylinder, and you cannot compress water, thus will this lead to serious damage of the piston rod, cylinder lid and lid bolts, the piston rod glands, or all the drive bar and the even the crank.
I guess, you may look and browse for the Riggenbach counter pressure brake for steam engines... Go down read more

jgallaway81 wrote: But if its small enough, couldn't a steam turbo generator be wound for the right volts (74v) and motors hung on the axles of the tender? I mean seriously, why couldn't a steam engine be equipped with dynamic braking?
Even if a turbo generator couldn't handle the amp load of more than one traction motor, I would think the power generated by that one motor could be tapped to create the energy to engage other motors.

Gallaway81,
you do not need something realy aditional electric. A steamer has something, which powers enough force for brake effects, so powerfull, most people haven't seen it or realized.
Let's describe this dynamic brake and it's development a little further:
The Riggenbach Gegendruck Bremse in German language, or Riggenbach counter pressure brake for Steam engines in english translation.
Niklaus Riggenbach developed the first cog wheel mountain railroad in switzerland. Thus small steam engines push passenger cars on steep gradients uphils. For the downhill motion, he first acted with band brakes. Those iron bands had woody pads, which could be tied by a spindle around the main jackshaft, which propelled the cog wheel between the tracks. But: downhills those pads often started to fail and the load began to slip the brake, and the whole train get downhill much faster and in cases of emergency it would be impossible to stop a train. He let mount cog wheels in the axles of the cars, they had no tractive effort uphills, but brakemen could use band brakes on those cog wheels so support the brake of the engine.
But eve here, those brakes tend to fail and Riggenbach had the idea:
He used compressed air to slow down the train.
If a steamers idles, the cylinders act like air pumps, drawing in air from the exhaust and compress this in the cylinder rooms. A very bad effect, because dirt, ashes and clinkers could be drawn into the cylinder, disturb the grease film on the liners, increasing the wear of the liner and pistons, also have an abrasive effect in the material. This has to be avoid, by using snifting valves or other idling support systems.
Riggenbach used this effect of the bad idle. He build up a valve in the smoke box below the blow pipe, which cut of the blow pipe and opened the exhaust from the cylinders to a open tube for fresh and clean air.
So fresh air can be drawn by the motion of the pistons into the cylinders, by adjusting the valve gear, it could now be compressed, but pushed back the inlet way back to the throttle. To prevent damage to the super heaters and steam inlet tubes, special throttle valves are additionally mounted, which were opened, to let the compressed air from the cylinders leaf the steam inlet tubes through silencers into the free air. The engineer could adjust those throttle valves and thus adjust the brake power. Little water was taken from the boiler and injected to the cylinders, to prevent overheating and spend cooling effects to the liners, piston surfaces, valve gears, piston rod and the glands.
Now it was possible to nearly use the same power the engine created to push the train uphill for braking effects downhills, because the whole load pushed the engine and set the engine drive parts in motion.
Later, the GErman federal railways test and development department used large freight engines of series 44 and series 44 for load tests on diesel and electric locomotives. The steamer was behind the test and measurement car and the steamer was equipped with the Riggenbach counter pressure brake. Many of those steamers developed loads, which easily could bring the cooling system of a diesel to complete collapse or develop such braking loads, to let the electric locomotives main motor coils melt in overtemperatures. Many of those locomotives get 'warrior names' as diesel or electric locomotive killers, as the Riggenbach brake on those steamers developed continuos brake powers of nearly the same power the engine was able to develop as tractive efforts, thus loads of trains with more than 2000 up to 3000 tons could be simulated with only a single steam engine by adjusting the Riggenbach brake to full loads. On the gradients of the balckwood forrest nearly regulary those steamers killed the test engines by facts of overheating, because letting the test engine at the trains head continuos work on peak maximum power levels, which result many times compete engine failures. No problem: The steamer switched of the Riggenbach and pulled as steam locomotive the whole load and the killed test locomotive back to the shops… one bait more, the Riggenbach equipped steamer killed ;o)

So, that's dynamic braking in steamers, long before diesels or electric locomotives ruled, or even had dynamic brakes... works pretty nice, even todays.
Watch my Achensee ride on youtube to find out how downhill actions works with Riggenbach adjusted: The trains chuggles downhills like a silent moped, without any hard braking noise... continuos braking power by the engine. That's even something, difficult for many diesels and electric locomotives

Steffen:

While this may have worked well in the application it was designed for, you have to understand that American railroads have a different approach to operations.

Today, our transcontinental truck trains utilize as many as five or six 4,00hp-5,000hp diesel electric locomotives to move 6,000tons at speeds approaching 70mph.

Our heavy coal-drags, counting 130 of the heaviest hoppers, can easily weigh in at over 19,000 tons. This exceeds the displacement of at least 4 different aircraft carriers currently in service by other countries. To safely drop this weight down the east slope of the Allegheny divide requires four 6-axle diesels on the head end and additional four 6-axle diesels on the rear. All these in dynamic braking are required in addition to a 8-10pound reduction on the brake line.

So, no, taking air into the cylinders and compressing it, while offering a resistance to rolling, is far insufficient to be of any use in our operations. However, electric traction motors are a very well understood principle. So is the technique of using those motors as generators to power a huge forced-air-cooled "electric heater".

It seems to me that the consensus these days is that the live steam injector, while functional, is not the best solution. Preheating the water precludes the use of an injector. Injectors don't work if the water is warm, and you could never keep the feedwater velocity high enough through a preheater to still overcome boiler pressure.

The solution is the use of one or more pumps combined with a preheater. It seems to me that using the tender water to cool the dynamic brake grid would allow for preheating, and the use of pumps, possible exhaust steam turbo pumps for maximum efficiency, live steam for necessity, to move the water into the boiler.

The downside to all this would be that you would have the added expense of an electrical traction system, without the benefit of being able to use it for propulsion, unless you also wanted to tug around a diesel booster. Perhaps a 4-axle diesel locomotive, rebuilt with the diesel/generator from a high-horsepower 6-axle could provide enough power for both itself and the tender's motors while in power, there by justifying the additional weight of dragging around an additional diesel.

Such ideas like this in the US would never see the light of day on a freight railroad, for freight service, but might be possible for use on long-distance mainline excursions.

The perfect test subject would be UP 844. equipping her tender with motors, and rebuilding the 6969 with twin diesels salvaged from a couple of the decommissioned 90MACs. Those prime movers would be powerful enough that one could provide power for the diesel locomotive, and the other for the motors on the tender.

All this combined with a computer interface connected to the steam throttle, custom made software could easily convert the steam notches to diesel notches. Add in a double-duty isolation switch which would allow you to cut throttle commands to all of the trailing units (counting the tender here), cut off the tender while leaving the trailing units online, or bring all units online. Another option would be to cut off throttle while leaving the dynamics online: Isolate, Isolate Tender, Online, Dynamic Only.

Sorry for going off topic, but its all interconnected, development wise.

Gallaway,
I think you do not understand ;o)
If I have the adhession and power to pull a train on steam the slope uphill, I have with the counter pressure brake enough power to brake it!
The Riggenbach brake isn't something unusefall or impractical, this was something very valueable and very very important on many slope tracks in Germany. Many locomotives equiped for those lines had those brakes.

And your coal train: I don't think, that we are talking about a single steamer pulling those huge trains. Let's consider five or six steamers doing the job of the diesels, and with Riggenbach counter pressure brake, all those engines develop enough dynamik braking force to hold on the train, because Riggenbachs brake is a brake, with increases power as faster the revolutions go, so less brake power on slow motion, high brake power on high rounds.
So I guess you do not have seen those brake and cannot asume the power those dynamic brake found by Riggenbach can develop.

Also, if we talk about advanced steam, we must throw overborad our view or image of steam locomotive.


That's how modern steam locomotives will look like, if you start from a plain sheet of paper and start the construction.
And consider this engines in power close to diesels... even in performance.

Let's fix that:
I guess the Riggenbach counter pressure brake was uncommon in the United States, and I do only know a few countries which ever used it, so many if any cog wheel locomotive was delivered from austria or switzerland to there, but I do not think it was found in Britain, Canada or US.

Braking means: Decrease the rotation of the wheel. This can be done by pressing one, two or more brake pads to the wheel rim, which was commonly done. Later Disk brakes appeared and now pads were squeezed to the disc rotating between the pads. The disc was mounted on the axle or also disc brakes used the area of the wheel between middle and rim..
A special brake is the electromagnetic field brake: Heavy electro coils are mounted to the rotating brake disc, and if now high voltage was applied to the coils, the electromagnetic field influenced the disc, creating a braking force.
Also large coils were mounted on sliders, which hung straight above the track. If the coils were connected to electricity, their electromagnet field pulled them on the top of the track, which pressed braking pads hardly and very brute to the track head, resulting in a cruel braking force, damaging yards of the, that#s why those brake is only used for emergency.

In cog wheel railroads many locomotives have a jackshaft, were the drive rod is connected to. Here the brake pads are laid around and pressed firmly against the jackshaft crank wheel with a iron band.trackhead

Electric locomotives use electric brakes. If the engine rolls, the motor will create a field of electricity, which can be connected to resistors, which transfer the generated electric current into heat. This will result in a large electromagnetic resistance in the motor, which acts now as generator, thus a brake power is developed.
Later electricians found, that the current should be better switched back to the live wire. That resulted in curios situations, were loaded coal trains in China generated the electricity for the upcoming empty train on the same line. The live wire only supported one locomotive, the other one took the energy created by the downhill traveling train. Was there now downhill train, the train had to be divided into two halves, because only one locomotive could be supported by the lines electricity support, thus the large double headed trains only go, if a double header would be ready for their downhill ride.
Modern electric locomotives can adjust the electromagnetic fields to increase the brake power of the motors used a generated during a brake maneuver, but always such things result in increased heat development of the motor, which killed many electric motors on long downhill passages.
In diesel locomotives a slight brake effect can be generated by switching the gasoline supply to the injectors off. Now the pistons draw air, compress and exhaust the air.. This effect is little, compared to the engine power generation under traction, but better than nothing. Thus retarders or exhaust blockers were developed.
The Retarder is a hydrodynamic brake: A turbine moved oil to a non rotation able stator, the reflux of the oil through the retarder blocks the turbine wheel and creates brake energy, but also massive heat. Large retarders need special cooling supply not to die by overheating, which will result in boiling oil, increased retarder pressure, which will crack the seals to leak, oil will escape and the retarder will fail.
Exhaust blockers are seldom used anymore, because they damage the motors and long downhill rides. As we read above, the fuel injection is cut off, to the motor compresses the drawn in air, but after this, the piston moves down again (this is the fuel burning stage, which is non functional now, because of the non presence of fuel in the cylinders), the exhaust valve opens and gives the air in the cylinder free. Here the exhaust blocker set's in, and throttles the exhaust of from the cylinder, this counter pressure in the exhaust system will block the free run of the piston in the cylinder, thus creating a brake power... but also, this counter pressure can harm the exhaust bores of the exhaust chambers in the motor block, might apply to high pressures to the glands of the valve shafts in the exhaust, it creates again heat, which the motor has to struggle with and often the exhaust throttle blocks or fails, which can result in normal traction operation to a serious cylinder internal pressure rise, which often lead to serious motor explosions.

But equal which brake you use: The main thing is to reduce the rotation of the wheels. So the wheels will turn faster, driven by the weight and adhaesion, but their free motion is blocked.
So, in Riggenbach the engine is used to compress air. As because all parts can widstand the total backpressure, which could not be higher than approximately boiler pressure. So no harm the any part by the pressure to fear.
Usually the engineer was advised only to give 1/3 of maximum boiler pressure as maximum back pressure, but under test circumstances even 3/4 back pressure was kept over a long time period, without any harm the the engine, drive rod and coupling rods, even the bearings weren't much increased in their temperature.
So if I have a steamer going uphills with 5000 hp the Riggenbach counter pressure brake has the possibility to create nearly the same hp as braking load, without the need for any additional brake powers.
So if I pull a train uphills I need a adhaesive wheel rim power, this power is required to brake the load downhills, little more, to slow down, little less to accelerate. So if my train is not that heavy that I need maximum power output from th engine I can use the Riggenbach the same track downhills, without any further adjustment or addition air brakes. Because for adhaesion power it's equal if the train is pulled or if the train pushed the locomotive, the effort on the wheel rim has to be given: Uphills as power output in tractive effort, downhills as slow down power to the drive wheels.
As Riggenbachs brake for steamers throttles the free motion of the piston, it generated a negative power to drive rod and couples, creating a huge braking power to all drive wheels...
And you can believe it or not, but this works very well.
A single series 44 steam locomotive was able to simulate a hugh train of 2000 tons in weight, only by applying the Riggenbach counter pressure brake. Thus no brake pads had to be pressed against the wheel rim, or any additional brakes had to be used. So the steamer was pulled often hours over a track, which simulated for the pulling diesel or electric locomotive a long and for Germanys railroads a heavy train... the steamer did not need much effort, the Riggenbach counter pressure made the job as a full operational dynamic brake, the only thing was the maximum power output on the pulling test locomotive, which often overheated, thus being killed by the huge braking power of the Riggenbach brake at the end of the train...

Steffen, you are much more informative than I can be!
I tried, briefly, to find more about the ATSF 4-8-4 "dynamic brake" I remembered, but couldn't find anything specific. I did, however, find a general reference to this sort of braking, in Alfred W. Bruce's 1952 "The Steam Locomotive in America; its development in the 20th century." (Bruce was Ass't V.P. of Engineering and Director of Steam Locomotive Engineering at the American Locomotive Company: the historical review in his book was maybe a retirement project, since if the jacket blurb is to be believed he had started working for ALCo before 1910.)

He writes (direct quotations in quotation marks, linked by my paraphrase: my comments in {{}}):
"Cylinder compression brakes" were widely used prior to 1900. Early ones had used air as the compressive fluid, but this led to problems with heat and with cinders drawn into the cylinders. {{Heat? I don't know whether air would be compressed to reach a temperature higher than that of the steam used, but steam, I think, has a bit of a lubricating effect which air wouldn't. Anyway, high temperatures were more of a worry before 1900 than they would have been later: early steam locomotives didn't use modern lubricants! The theoretical advantages of superheating were known quite early, and a superheater pipe isn't complicated: the delay in the adoption of superheating was due to the lack of lubricants that could handle the higher temperatures.}}
Later cylinder compression brakes used steam. The best-known type was the Le Chatelier. It worked by admitting a small amount of hot water from the boiler into the cylinder exhaust passages, where it formed a "heavy vapor" which was drawn into the cylinders. You'd start an application of this brake with the reverse lever in neutral, then gradually move it into reverse until you got the braking force desired. And {{suggesting problems which may have led to the general abandonment of this sort of brake!}} "cylinder head relief valves were fitted whenever it was applied."

Allen,
I would never recommend something, which would be something not on the state of the art.
See, Riggenbachs counter pressure brake is still today in use. I guess most americans are very unfamiliar with this methode, but I was about certain engines running downhill with the brake, and this is truly state of the art today and would be the dynamic brake solution for any advanced steam engine.

Look, at the BRB in Switzerland. Those engines go the whole trip downhill without any air brake or other mechanical brakes, they only use the Riggenbach brake.
So here the full load is pushed uphills with steam power, and downhill hold by the Riggenbach brake only, even the same load.

Well, Allen, the thing is, what you write or quote, is that the old Riggenbach methodes really drwa cinders, ashes and dirt into the cylinders, as I told. Many tried to switch to steam, but this was unusefull, because of the compression heat, which later leads to the problems of water accumulation in the cylinders, and we know how harmfull the water inside the cylinder can be.
So Riggenbachs brake was modified, and I can tell you from a large german freight locomotive (in size not compareable to US locos): Here a pnematic valve is mounted below the blow pipe in the smoke box. If switched, the blow pipe is cut off and the cylinder exhaust channels are switched to a pipe below the smoke box inside of the frame. This tube has a filter inlet, to protect it from coarse dirt or oil cinders, This is the tube from which the pistons draw air into the cylinder spaces.
This air is free and clean.

Allen, today those brakes work on many steam locomotives day by day, without any problems. I would never recommend steam, air is enough available, has the best compression factors and is available, even if the steam factors are not promising. Because steam differs in it's compression factors in pressure, temperature and saturisation levels.
So, maybe this is, why those dynamic brake was in US unsucessfull, and made the european version of Riggenbach successfull till today.
Consider, that Retrofit steam locomotive 52 8055 is fitted with this brake?
Would a such reconstruction be done and fit a brake, which would not fit to all advanced operations or be something with is not the best technic or most advanced technology?
52 8055 bases on the technology of André Chapelon, which was used to the excess by Livio Dante Porta, who was the most legendary founder or advanced or modern steam. Within his ideas and experiences David Wardale reconstructed the series 25NC to the well known series 26 aka Red Devil.
And his apprentice, Roger Wardale is the father of 52 8055 and the modern cog wheel steam locomotives... so those people are the source of all advanced steam improvements or any improved steam technology ideas...
And that's why I believe in the Riggenbach brake, too. Beneath my own experiences riding on locomotives equipped with that technology - I know to trust those people and I know what those brake is able to do.

Ah, well, Allen, aditional:
We in Germany have many technical books on steam engine development and construction, and also the full conservation of the technical maintainace and construction instructions for german steam engines. In most books is the Riggenbach brake only described in words, but our railroad museum has all technical instructions and plans for the brake... and I do not now if such technical manuals exist in US bookstores, I searched, but found nothing.
The complete operation of the Riggenbach brake is described the German manual "Niederstrasser - Leitfaden für den Dampflokomotivdienst" which means translated to english: Niederstrasser (name of the author) - Guide for the employment on steam locomotives"
So many german railfans are very familiar with the brake, because of reading the book.
Such guides a very valueable...

Steffen--
Thank you for all the information about the Riggenbach brake. It sounds like a "species" of the "genus" cylinder compression brake" described by Bruce: one in which the problems that led to the general abandonment of this genus of brake in North America were overcome. (It wouldn't be the only time American railroads ignored technological advances in Europe: the Giesl ejector had one experimental application in the U.S. and then was ignored for the last ten years or so of mainline steam, and other multi-port exhaust systems had very little use despite the very clear European experience that they contributed to locomotive power and efficiency. And, more recently, I think the first North American diesel-electric locomotive with AC traction motors was about ten years later than the first in Germany!)

I may be overinterpreting the brief paragraph in Bruce's book, but it sounds as if American railroads in general became convinced that cylinder compression brakes were too much trouble to bother with and decided to rely on the independent air brakes on the locomotive. This seems unfortunate if the c.c. brake can be made reliable and trouble-free: why use brake shoes and all the rigging connected with them if you can use "dynamics" instead?

I haven't been able to find anything about the Santa Fe application of steam c.c. brakes I remember(*) reading about: I take everything you say about the undesirability of admitting damp steam to the locomotive cylinders (though perhaps, with a well-designed brake of this kind, when the compression raises the steam's temperature, condensation is not as much of a danger as you suggest-- Bruce's comment about the use of cylinder relief valves when such bakes are applied testifies to the danger with more primitive forms of steam c.c. braking). ... There's something funny about the shape of the cylinder housings on Santa Fe 2900 class 4-8-4: looks almost as if there was another, smaller, piston valve above the main one. I don't know if this is connected to "dynamic braking" or not.

--

(*) Memory is, of course, fallible: I know from sad experience that even a very vivid and detailed memory can be totally wrong!

Dear Allen,
to be honest: Not everything good was also introduced and used in Germany. There was only one try with the Kylchap Exhaust and certain tries with stokers, but all were abandoned and not further developed. The Giesl Exhaust is a problem on many steam locomotives, because having some problems in high power output and low power output stages, if it's usually adjusted to intermediate power outputs... So the Kylchap was most promising, but german federal railways did not used it. As you can see: Soon after World War II it was clear, that steam would not be the tractive power for the new federal german railroad company, so the switch to diesels and electric locomotives was only a question of time, so development of steam was threaten very badly and not all good things were used in new build locomotives, but the development of new diesels and electric locomotives, as the establishment of more and more lines with live wires for the electrics was highly forced.
Thus, to be honest: In such circumstances a development of a real good steamer is impossible, so most things were more tuning ups, rather than good developments, and some new developments one can consider as complete failures in technology, despite all experience and knowledge from export locomotive developments, like for the SAR, India, or some asian countries.
So usually the steam locomotives with the counter pressure brake were more rare than regular, because steam was dying, so why incorporate something really advantageous?

Also, let's look about combustion. Look, to burn any fuel you need air, because air is the source of oxygen for any combustion, even slow reactions, like iron corrosion (rust) needs oxygen, if you get fine iron dust, be careful, because if you get this burning, if will get a high explosive reaction, so rusting in a very fast reaction
In steam locomotives combustion was always a problem, because air inlet was done below the grate, and usually the volume was not that good for a good or optimum combustion.
If i have no smoke, usually I have an optimum combustion, or rather more air as to less. This air I need for complete combustion is figured with the lambda factor. If I want to burn coal, I have to consider the lambda factor to 1,1 or 1,2... so a little air excess is desired, while other combustion processes were more closely to 1 configured.
In our steam locomotives the lambda was often less than 0,7... that's means that combustion was often inferior, compared to a well designed boiler. So all black smoke from the chimney is a sign of wasting energy and combustable fuel. Most stoker locomotives with high drought systems, like czech railroad steam locomotives smoke often and undesirable, wasting energy, because the fine coal dust was nearly unburned drawn through the tubes out of the chimney. The Gas Producer Combustion System was to overcome this process, invented by Livio Dante Porta and mainline tried by David Wardale on Red Devil. Even in Germany there were some trials with those GPCS boilers, but the system was found to be to complex for the most steam personals, so it was abandoned.
Still today, most of our museal steamers smoke... Railfans like it, but for me, this is a sign of a bad fireman. I was often n tours, were the fireman just switched the fire of oil burning steam locomotives to excess oil, just to generate as much black smoke as possible, just for the railfans... and I was shocked. Because the most railfans get the pictures burned into their mind of the smoking, stinking, energy wasting steam locomotive in their head, because of those narrow minded fireman. A fireman duty isn't as putting on a tour in an amusement park, so the black smoke what railfans like, should better remind all of us on wasting energy, and often done by bad firemans duties, rather than bad fuel or on the edge combustion circumstances.
So less smoking is desirable, it saves fuel, thus saves costs, is much economically, less stinky and less bad for our environment. Railfans dislike this, but I am not in duty to be liked by photographers or video filmers, who do not spend on buck for the preservation of the steam engines, so I save energy, thus save fuel costs for my railroad society, and save any buck of fuel costs I am able to, to help to preserve the steam locomotives in operation.
But did any technology to do a better combustion were incorporated into new developed steam locomotives, like additional air inlets, maybe especially to the combustion chamber or from the sides and the back slight above the fire, to increase combustion?
No... The combustion of a steam locomotive is still that inferior as nearly in the beginning of the stephenson boilers... Hard word, but true. Only with oil burning locomotives, it was tried to incorporate some additional air inlets, but on coal fired engines, it was still in the hands of a fireman.
So advanced steam begins right here, at the combustion, and many of us should remember, that smoke is still true sign of wasting energy, a bad fireman and incomplete combustion, rather than good steam locomotive performance. So improvements should be undertaken at this foundation part of the steam locomotive, as usually most boilers today, coal or oil fired, have much better combustion performance as steam locomotive boilers would reach. So modern boiler development would be the step to archive the goal of advanced steam, and after this huge part, one can see, how to design the right steam engine for

I would not recommend a turbine, because turbines need to run for prolonged periodes under a given load, and steam electric drive would not make the goal, because why transfer energy to another form of energy?
Diesel electric makes sense, because here I can run the diesel in various rpm ranges, without inferior performances, but most steam turbines only to well in a very small rpm range, and still turbines a usually unswitchable in directions and very prone to high load changes, like full steam ahead uphill on heavy freight train load, and on the summit, switching of all load from the turbine, because of the downhill idle...
So the piston steam engine has got advantages for those given basic factors, but we have to abandon outside bars and rods, because of high masses in motion and high maintainance...

Also, I would not recommend on dynamic brake to use steam instead of air. Because: I you set steam under pressure, the steam, which is the appearance state gas of water, it will take up heat. So this causes a cooling effect of the surround walls and atmosphere, but will also change the appearance state of water from gas to liquid form, were instead of steam I will get a very hot water in my cylinder... and because the piston is in motion, maybe there is not enough room to get more compression applied, thus one cannot compress water by hydraulic laws, thus the incredible force will apply now a pressure force to cylinder lids, piston seal rings, valve seals, cylinder and valve lids or even rod packings, and the danger of a water blast is present.
This makes the Riggenbach brake tricky, because even here boiler water is injected for cooling purposes, but: The pressure applied by the piston in motion is controlled by the extra exhaust valves, thus in case of water formation in the cylinder by high compression rates, the water will rush through the brake throttle valves directly into the silencer and the free air.
This shows than a typical steam formation on the silencer exhaust, showing the Riggenbach at work.
Watch http://www.youtube.com/watch?v=tAEx1ZckGAo from 2:20 mins to the end, to see and hear Riggenbach brake at work... Note the steam from the silencer exhaust nozzle from below the cab.
So I would never recommend from all my experience and knowledge to inject steam into the cylinder for dynamic braking.

Steffen wrote:Gallaway,
I think you do not understand ;o)
If I have the adhession and power to pull a train on steam the slope uphill, I have with the counter pressure brake enough power to brake it!
The Riggenbach brake isn't something unusefall or impractical, this was something very valueable and very very important on many slope tracks in Germany. Many locomotives equiped for those lines had those brakes.

And your coal train: I don't think, that we are talking about a single steamer pulling those huge trains. Let's consider five or six steamers doing the job of the diesels, and with Riggenbach counter pressure brake, all those engines develop enough dynamik braking force to hold on the train, because Riggenbachs brake is a brake, with increases power as faster the revolutions go, so less brake power on slow motion, high brake power on high rounds.
So I guess you do not have seen those brake and cannot asume the power those dynamic brake found by Riggenbach can develop.

Also, if we talk about advanced steam, we must throw overborad our view or image of steam locomotive.


That's how modern steam locomotives will look like, if you start from a plain sheet of paper and start the construction.
And consider this engines in power close to diesels... even in performance.

Does the locomotive illustrated use a steam piston driven geared transmission (like the many geared steam locomotives built for logging and mining service in the US)?

The illustrated locomotive is considered to have a geared transmission and a typical hydronamic gear and torque transmission, from the gears the power is transmitted with typical power shafts, like in many todays Diesel locomotives with diesel hydraulic power transmission.

Considered is a monoblock multi piston triple expansion steam engine, a so called steam motor. Such compact steam engines were build soon after invention of easy control able valve controls. Such steam motors doesn't look much different than modern multi cylinder diesel engines.... expect needing a boiler

See, if we talk about advanced steam, we have to follow the guidelines of Livio Dante Porta. And simply there is one rule, he found, to overcome:
As much tractive effort as possible, so no needless bogies or non-powered axles. If we look to a typical Northern type, we found two leading axles with no power, followed by four powered axles and the cab is resting on again two non-powered axles, followed by a huge tender with a various number of non powered axles.
So the engine, watched as engine with tender, has more axles without tractive possibility than having axles which produces the overall tractive power. So most axles of the whole engine consume this tractive power... This means: Advanced steam reduces the non powered axles, and if possible: As much axles as possible generate tractive power.
This is, as we can find, in most Diesel and electric locomotives done. All trucks of the typical diesel locomotives are powered, all axles generate tractive power. Same for the electrics, were usually each truck if not each axle has it's own electric motor, to drive the wheels.

So compared to a steam engine, it's clear why those engines pull like hell. There are no non powered wheels!
So if we consider a new and most advanced steam engine, means to replace the outside drive gear and switch to a modern frame, resting on trucks, and all trucks are powered, so all wheels of the trucks generate power... and on the frame, we simply mount a small, but efficient steam power plant with a modern boiler, electronic controls, modern fuel burners, economical feedwater heaters and if possible as much condensation power as possible, so conserve as much water as possible. All packed and bundled in a modern shell, so u get a double locomotive: Locomotive with engine, boiler and gear, and a powered tender, with condensation, feedwater supply and fuel tank, all resting on shaft powered trucks from inside the frame mounted hydro gear boxes...

And I am sure: Would someone only tell, to want one of these locomotives, there will be one build, and no one would look at it and tell by looking, that this is a steamer...
But as long as the picture of the old steamers is in our mind and in the minds of the most railroad responsible persons, an advanced and modern steam locomotive would not be constructed from plain... So all modern steamers, like those in Switzerland and Austria, look like old steamers, because the customers wanted them to look like this... so this compromise abandons use of more advanced options, but is what the customers expect and want...

I have to say I disagree.

A steam-turbine electric would be the perfect mode of transportation (aside from a direct electric driver from overhead catenary).

As you said, a turbine is most efficient in a very small RPM range. If this turbine was designed so that its most efficient rpm range was perfectly matched to a set multiple of the RPM which produces maximum power in the generator/alternator.

Using modern electronic systems, such a power source could be controlled electronically instead of via standard RPM-voltage manipulation. Either AC-frequency modulation or a DC pulse-width modulation could be used in combination with a steady-speed turbine.

Further, a turbine might not be the most efficient use of the steam. I will admit that this possibility exists and further research in fluid dynamics and hydrothermal mechanics would be required to determine the most efficient means of transforming the heat energy into rotational energy. My thought would be a 2-stage compound 8-12 cylinder diesel-like-block turning the generator... perhaps using 12 total cylinders, four triple-compound engines could be used to turn the generator.

With enough generator capacity, there is no reason that the tender couldn't also provide tractive effort.

As for a hydraulic or a hydrostatic drive, neither of these would have the capability to meet American railroading demands. I believe UP & SP both tried such engine and found them incapable of standing the abuse of our mainline freight operations.

You can disagree, of course, but this shows how the things differ and why any advanced steam technology might be not come up today, because there are still things like 'would not match' or 'cannot displace'...
So there is no chance to move on or start from a plain sheet of paper.

Turbines a very prone to motion, what causes difficult bearings, watch this in shipyards if the large turbine tankers comes for repaiers. Even the slight rolling and swinging on the ship influences the bearings and the oil films, so the hydrostatic bearings are very, very special.
In Railroads those motions are much higher and some motion influences, like certain switch passages and other partial track 'improperties' might result in serious problems. Consider: Steam Turbine / Electric locomotions were tried, but widly abandoned, because usually of the proplem of improper steam quality and turbine problems due the often rough service.
So a Turbine ist very good in stationary electric power plants, or in certain ships, but on the rough railroad, the power plant is often a serious problem, what is a high advantage for piston driven engines.

Consider, modern power plants use steam in pressures of around 1750 psi and temperatures of more than 950° F!!!!

For steames this improper steam quality is the advantage of the piston steam engine, which depends not on the streaming power or flow or the expanding, more on the expansion of the steam in small rooms, so the flow isn't the thing, more the pressure.
So good pressure of about 290 psi up to 440 psi will be very successfully be useable in monoblock pistion steam engines, even multi piston compound engines.
So I agree here with you, that a four triple expansion monoblock steam engine, a so called Steam motor might be better than the turbine. But not to turn the turbine.
Such steam engines generate enough torque power to go directly by power shafts to the trucks, so the switch to electricity is not need, alternating the efficiency of the machinery. Because transfering the heat power into shaft or rotation power is often very improper, because often less than 40% of the energy of the fuel source can be given to the shaft. Even modern diesels are prone to this, because having only a very narrow rpm/power output range, were the engine efficiency is higher than 38 or 40% efficiency, otherwise to much heat is generated or fuel wastet...
That's why oil firing power plants usually use still steam turbines and not diesels, only power plants with gas turbines, exhaust heat boiler and additional steam turbine use most of the power of the fuel, so have an efficiency of over 80% in output....
So the couples to the generator consume efficiency, the generator consumes efficienty, the electronic traction controls consume efficency... this won't match up.
Direct coupling the engine to a hydraulic gear and direct couple the gear to the trucks avoids most losses, because the gear can be mechanical 'bridged'.
So the loss of efficiency of the gear can be avoid over a wide range of engine power outputs, is only need to switch the gears, adapt the rotation or in certain cases try to compensate the rough torque outputs from the engine to the more lazy truck wheels
And with such an engine you still can use the Riggenbach counter pressure brake, having a very, very strong dynamic brake... so long downhill rides do not really consume much fuel