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How a steam engine works

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Posted by Lastspikemike on Friday, October 16, 2020 8:06 AM

gregc
 

 

... 

 

the art is recognizing that without cutoff, allowing as much steam into the cylinder as possible each cycle, results in a lower sustainable pressure and sub-optimal work from the cylinder.   at "optimal" cutoff, maximal work output results from the cylinder.   

i think(?) optimal obtains the maximum average cylinder pressure.

imagine trying to control a model that models this behavior, trying to find that cutoff setting while at the same time keeping track of boiler water level, fire and anticpating future needs

 

 

 

Hornby tried an electrically heated OO scale Pacific live steamer. I neariy bought one (sale price  CAD$1,000.00. [symbols removed by moderator]) it was so pretty. Quite the technological tour de force. 

The challenge you describe basically killed a really great idea.   The steam control was remote and probably servo or stepper motor electric. In theory it should've worked and the model is still reasonably popular in a devastatingly restrained way, price wise. Operation of this model is possible if one is geeky enough.

The main reason it was a commercial failure, I think, was that even the model railroading world is basically geek limited. 

Though this thread is shaping up to be providing a fair bit of contrary evidence to that idea.  

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Posted by Overmod on Friday, October 16, 2020 8:10 AM

Now look at what happens if you try full-stroke admission with the engine at any particular rotational speed -- in a low-drivered engine this might be no more than the 10 to 15 miles an hour where its boiler starts running out of volumetric effectiveness.  You have full thrust on the piston all the way to BDC ... as the rod starts to move around to the back of the crank and the lubrication starts to suffer ... then nearly instantly you relieve the pressure to exhaust and open the other end to steam.  Do not expect your rod bearings to survive this treatment very long, or your axle bearings or wedges or pedestals either.  

Meanwhile you had to make your rods very stout to absorb the monster thrust.  These have appreciable inertial mass, and momentum, and this appears in part as reciprocating augment (the thing overbalance is for).  These forces go up as the square of the peak speed, and while you can compensate for this somewhat by making the rods heavier still, you then have the overbalance guiding problems, including severe nosing and hunting, and very few cost-effective ways to deal with them.  

This method completely falls apart if you expect to run heavy trains at diameter speed or above, where any real interest in steam power starts Wink  Here the physical time available to get steam mass into and out of the cylinders effectively starts to matter; it would be physically impossible to move valves quickly enough to get long expansion (and in fact when N&W tried this with some of the best-designed Baker gear in the industry, it 'unraveled' with somewhat dismal predictability from inertial forces alone when let out to corresponding valve opening)  This is where the fast porting/unporting of poppet valves, and separation of admission and exhaust duration, come into their own, and while cutoff much shorter than 24% had little historical value, improved approaches can use shorter overall admission to good result in faster rotation (and hence higher horsepower per unit time).

I will take up effective compounding in the next post, as most people who haven't studied steam design don't really understand how it works or what to do to improve it.

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Posted by Overmod on Friday, October 16, 2020 8:24 AM

Lastspikemike
Hornby tried an electrically heated OO scale Pacific live steamer. I neariy bought one (sale price  CAD$1,000.00. !?!@#?) it was so pretty. Quite the technological tour de force. 

I did buy one of these, precisely because it was a tour-de-force probably never to be repeated, like those expanding tables on yachts from the same general era, or twelve-cylinder production cars from multiple makers.

The problem I had with it was that, like many live-steam models, what it actually did with the steam is not the same as in a 'real' locomotive.  The "throttle" is somewhat similar to how you do steam control in a once-through flash boiler: the more you pump in, the more goes out to the cylinders.  There is no adjustable valve gear at all, as on a donkey engine, and no care for balance at all.  In other words, cool as hell to do, but no more interesting that a typical putt-putt steam launch in complexity.  (And you can teach a kid how to set up, run, and put away one...)

The real problem with it was that, at the time, it was too expensive and too operationally limited* for 'serious modelers' -- it fell into a hole between geek tribes, as it were.  That is something I frankly didn't see coming, and it's a little sad there will likely never be a 're-run' in properly-improved form.

(* and then, there was the oil issue.  If you don't like smoke on a layout, you won't like oil...)

On the other hand, I've been crying for scale operating rodwork for many years.  That is not just scale rods and pin detail instead of soft-metal stampings and slotted screw heads; it's proportional valve gear actuation from reverse position right through to proper Walschaerts and Baker operation servo-driven proportional either to road speed and 'load' (for conventional model throttles controlling DC motors to get speed) or to an actual model power-reverse control with calibratable scale (and perhaps a simulated version of Valve Pilot) for the true tech nerds (and perhaps some geeks as well! Wink)  Note how very simple this would be to implement in its coarsest form (with gear moving either side of mid depending on direction, and spring-centering with power off).  But not one person here, including quite a number of model-railroading gods, sees even much need to replicate prototype valve-gear detail, let alone the finer points of its proportioning.  Some argue that robustness rather than fidelity is the mark of a good model, and I would be among the last to suggest that they, especially by their chosen standards, are wrong even if it produces (to me) toy-train-like appearance. 

And yes, I rack that up in no small part to 'steam technology' being boring to most model-railroad fans.  Perhaps this thread can start to change some hearts and minds...  

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Posted by Lastspikemike on Friday, October 16, 2020 8:35 AM

ndbprr

I suspect that most of this is far beyond basic concepts. Think of a steam engine as a teakettle. Heat is applied, water boils and produces steam. When enough steam is produced it builds pressure and the tea kettle whistles to say it is hot enough. Plug the opening and eventually the steam pressure will build to wear it blows up the kettle.  Forget who it was in England who made a steam driven pump to remove water from the coal mines which started the mechanical revolution resulting in primitive locomotives that replaced horse drawn rail carts.  Everything since then is ways to produce higher efficiencies just like cars today compared to model T Fords

 

What he said.

Steam does work in a piston engine by expanding, not by flowing.  Expanding results from pressure changes. The boiler is a compressor rather than just a furnace on wheels. The heat is used to manufacture a pressurized gas (the working fluid) , indirectly rather than directly as would be the case for an internal combustion engine (which creates compressed gas directly from air and fuel as its working fluid). The plug in the kettle is the throttle valve allowing boiler pressure and volume  to be controlled at a macro level.

(You can make a steam jet engine, apocryphally that was the first and more than 2,000 years old. Hooking it up to do useful work is the challenge there.) 

If the pressure expansion comes from the volume of steam all the way back to the throttle valve then the engine will produce the highest torque at the driver crank pin that the engine is capable of. The smallest expansion ratio. That will consume steam at the highest rate for any given wheel rpm, which is of course a consequence of developing maximum torque.

What may be slightly counterintuitive is that most steam locomotives are traction limited, not torque limited. It would be very rare for an engineer to try using maximum torque available until the train was rolling right along.

Hence the idea of steam cut off which also conveniently provided a reverse gear.

My point there is that the torque capability of a steam locomotive is not limited by cylinder displacement whereas an internal combustion engine is so limited (supercharging aside, which had its own limitations). No way a single gear ratio internal combustion powered locomotive could haul what a single gear ratio syeam locomotive can haul.    The gear ratio of a steam locomotive is one fixed speed ratio: crank pin offset to wheel radius. Freakin' amazing. 

That control conserves steam and gives finer control over cylinder pressure and hence torque at the driver than the throttle can. That results from switching over from "boiler pressure"  control to effective control of the actual expansion ratio inside each driving cylinder. 

So, the "throttle" on a steam locomotive does not compare to the  gas pedal. It compares more closely to a variable controlled safety valve, some turbocharged engines have a driver controlled boost pressure control which has a similar function.

The gas pedal in a steam locomotive is a combination of the cut off ("reversing lever" ) controlled by the engineer and the combination lever which is automatic and fixed in its pattern of operation.

The really fascinating part about all this monkey motion is the skill of the erecting engineers in matching the combination lever geometry to the reversing arm. The combination lever moves the actuation point of the  radius rod (the rod controlled by the engineer by actusting the reversing lever) on valve motion to keep in sync with the linear stroke of the crosshead by matching that motion to the eccentric motion of the valve gear crank which in turn is offset approximately 90 degrees off the  crank pin orientation. The length ratio of the combination lever is critical to the fine control of the reversing lever by the engineer.  

The whole thing is exquisitely arranged so as to give a puny little human direct and quite finely adjustable control over an immensely powerful machine. Long before internal combustion engines developed anything like that level of power there we were running down the rails riding an insanely powerful beast hauling a huge amount of mass with no brakes. If you think these things have brakes then you are mislead. The only way to brake a train is to do so BEFORE it gets going too fast. Those aren't brakes, they're just retarders. More like a parachute than a brake.

Amazing, and developed in less than 100 years.  Watt's engine could never have worked in a locomotive, far too weak. Watt only improved on Newcomen's atmospheric engine.

Trevithick was the man.

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Posted by gregc on Friday, October 16, 2020 8:39 AM

ndbprr
Everything since then is ways to produce higher efficiencies just like cars today compared to model T Fords

not sure what you mean by efficiency.    it typically means extracting the usefullness from something with minimal waste.

i've described how allowing steam to expand within a cylinder improves efficiency -- more work from the same volume of steam.  one way of evaluating this efficiency is the energy in the coal consumed compared to the work produced by the engine

automobile technology has certainly improved since the model-T.   internal combustion engine efficiency has certainly improved, but is still only 20%

i don't think it's accurate to say "Everything since then is ways to produce higher efficiencies".   there are different goals.

a major drawback of steam engines is the time required to obtain full power.   other technologies such as diesel or turbine engines minimize this time.   not sure the benefit is efficiency or less complexity and easier maintenance.

not sure how to evaluate the efficiency and benefits of electric vehicles.  efficiency may depend on the source of power: coal, nuclear, water, ...   Benefits may be zero pollution from the vehicle, zero startup time, higher torque, ...

while efficiency or fuel cost may be important, performance and other contraints may be even more important.   electric locomotives to go underground have a unique purpose

greg - Philadelphia & Reading / Reading

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Posted by Lastspikemike on Friday, October 16, 2020 9:01 AM

I'm pretty sure he means efficiency in the same sense as you do. You might be leaping to a conclusion or unwarranted inference there.

The example given is Model T to modern car. Not steam locomotive to modern car (or truck).

Steam locomotives are not less efficient than diesel electric but they do cost way more to run.

Sailing ships were way more efficient than steam ships (and, bonus, zero emissions rated) but far more expensive to run. 

In human economies, efficiency is measured by output per man hour (or per man horsepower if you prefer) which is quite different to real engineering efficiency. The leaf blower springs to mind as illustrative, for some reason I can't quite put my finger on.  

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Posted by Overmod on Friday, October 16, 2020 9:27 AM

Lastspikemike
That control conserves steam and gives finer control over cylinder pressure and hence torque at the driver than the throttle can. That results from switching over from "boiler pressure"  control to effective control of the actual expansion ratio inside each driving cylinder.

But don't make the mistake that this 'fine-tunes torque' exactly; it does adjust it, but makes it peakier at the same time, which contributes to both a propensity to stall and to spin at times ... not a fun place to be!

Better to think of the controls of a steam locomotive as double-salient in a sense: the throttle controls the admission effective pressure, and the cutoff controls the mass flow available for expansive working starting at that pressure.  There will be times -- plenty of times, on excursions! -- where you don't need more than 150psi or so throttle pressure, but you need to start a train without slipping on uncertain track and then operate it efficiently.  You do this by coordinating the throttle and reverse appropriately.  For fast or 'most efficient' running, you want minimum actual impediment in the steam flow ... and the poppets in a multiple front-end throttle are an impediment.  Then you crack it open and, once you're at a speed where surge and low-speed augment are no longer problematic, drive on the reverse ... until you get into the range of 'high-speed slipping'.  At that point things start to get interesting...

... some turbocharged engines have a driver controlled boost pressure control which has a similar function.

Be careful with analogies to internal-combustion engines.  The point of turbocharger boost is to increase the amount of fuel that can be burned during a stroke, and there will be diminishing returns at some point where the complications of higher peak firing pressure, peakier torque, and exhaust back-pressure outweigh the added boost.  That is not a complication with an external-combustion expander, which is not volumetrically limited in its ability to utilize pressure expansion.

It will not help when some astute readers find out about John Sharpe, Gotaverken, and 'steam turbocompounding'.  It does NOT help to recompress steam with exhaust-steam energy to get more thrust out of it.  The recompression is to get a phase change to lose some of the 'excessive' heat in exhaust steam so it can be run back through the boiler at 'liquid' density without losing the latent heat of vaporization ... something that would induce MEGO syndrome in most everyone here to explain Wink  (See also the glory that was Holcroft-Anderson 'recompression'...)

While we're on the subject of turbocharging, it is fun to consider the Velox boiler, a fascinating dead end in sophisticated design.  It starts with recognition that external combustion works ever so much better if the fire can be turbocharged -- pressurized up to 30psi as in some (ultimately misguided) electrical generation power boilers.  The Swiss neatly used a gas turbine(!) to perform this in a small boiler to generate steam; I can't do nearly the justice to it that Duffy did for the Newcomen Society -- or that Douglas Self did in a somewhat less enthusiastic way on his delightful site.

There is another perhaps interesting story about MEP in steam engines.  A man named Tuplin, in England, was something of a bore on the subject of high boiler pressure and superheat -- he thought them unjustifiable in terms of increased maintenance costs for the benefits gained.  He was fortunate to observe the crew of a NYC Niagara, probably doing a break-in run on local freight out of Harmon, performing the work of a relatively small 2-8-0 on the 2-8-0's consumption of coal and water.  That was done by carrying fire on only some of the grates, with careful firing attention, and sliding-pressure firing the boiler only up to what I recall being a peak of about 180psi.  Now this was something of a waste of the capital involved in a 6000hp high-speed passenger locomotive, but it demonstrates a different way of working a locomotive efficiently to task.

 

The gas pedal in a steam locomotive is a combination of the cut off ("reversing lever" ) controlled by the engineer and the combination lever which is automatic and fixed in its pattern of operation. The really fascinating part about all this monkey motion is the skill of the erecting engineers in matching the combination lever geometry to the reversing arm. The combination lever moves the actuation point of the  radius rod (the rod controlled by the engineer by actusting the reversing lever) on valve motion to keep in sync with the linear stroke of the crosshead by matching that motion to the eccentric motion of the valve gear crank which in turn is offset approximately 90 degrees off the  crank pin orientation. The length ratio of the combination lever is critical to the fine control of the reversing lever by the engineer.

I am not sure if you understand what the 'combination' lever in Walschaerts is actually there to combine.  It synchronizes some of the crosshead motion with the 'commanded' valve excursion through the reverse to get effective valve motion; it is only a baseline setting and doesn't affect 'fine control' over the valve motion at all, really only its phase relative to mid.  (The existence of the combination lever is the explanation for 'nightwalking' of locomotives left in mid position on the reverser but with slightly leaky throttles...)  It may be easier to see the 'result' on locomotives like the D&RGW M-64 4-8-4s which had variable lead adjustment.

Perhaps the best way to see what goes on is to download and run Charlie Dockstader's old DOS valve-gear modeling programs, which let you play with the dimensions and see the effect on the valve motion and timing in realtime: a picture is worth a thousand prolix words.  They were updated for Windows XP and have been verified to run on VMs available 'free' in the cloud for those whose systems won't allow legacy software from that era to run.

Something that ought to be of interest is the device in the cab that controls the reverser position.  Even early versions of power reverse could have interesting precision combined with speed, an early example of high-power servomechanism without 'force feedback' much like the controls in a Hulett unloader (which you have to see operated to believe!)  The version on UP 3985 could be slewed from full forward to full reverse in less than a second, with locating precision 'locked' at any point in that travel when achieved (needless to say if you did that at speed you wouldn't enjoy the brief time for observing the results!) and there were several different approaches to getting the fine precision control over the reverse that could be implemented for control.  

There were two styles of Franklin Precision reverse -- one was a wheel type, as fitted to locomotives like NYC Hudsons; the other was a lever type that could be moved more radically in a short time, as on Nickel Plate 765.  The 'catch' is that it's difficult to do fine positioning of the lever type, or quick movement and recovery of the wheel type.  [Incidentally the reverse problems on Blue Peter are not to be found on any American locomotive with wheel reverser...Dunce]  

The British had a power reverse of equal precision, for locomotives in their practice that used vacuum brakes and had no 'cheap' source of power air.  This was the Hadfield, circa 1950, which used steam as the working fluid (much as steam was used for debounced valve return in British Caprotti poppets)  To my knowledge they did not evolve a better fine-or-fast control than Americans did.  

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Posted by Overmod on Friday, October 16, 2020 10:01 AM

gregc
i've described how allowing steam to expand within a cylinder improves efficiency -- more work from the same volume of steam.

Except that ain't what it does.  You get equivalent work from a lower MASS of steam which is allowed to expand into a (varying, but bounded by cylinder dimensions) volume.    The valve gear meters the amount of mass that is admitted, and the control is to adjust the timing and duration of that admission to produce the 'desired' power at speed with the minimum of confusion and delay.

Note that one problem is that conventional steam locomotives are designed around what the English called 'automatic action' -- as you opened the throttle and tinkered with reverse, the exhaust energy in the front end more or less controlled the fire efficiently to match the added or decreased power.  In some locomotives starting in the late '30s this got out of whack with improved low-back-pressure design: it got to the point that engines would make desired horsepower at high speed but not produce enough physical draft to keep steam generation going (some of the early UP double-stack 800s had this problem).  Sometimes 'good' can be too good...

Remember that an important way steam engines are better than IC engines is that they utilize the Rankine cycle, not something more simplistic like the Carnot or Brayton cycles that are 'more efficient' as heat engines but can't use recuperated waste heat effectively (no, I'm not going into entropy here!)  Even on locomotives it was possible to use exhaust steam for a wide variety of useful purposes, from very good feedwater heat to gas-producing firing or primary-air preheat.  This is brought to a fine edge in powerplant design (as anyone who has seen and comprehended a heat-balance diagram will know) and it accounts for much of the phenomenal overall efficiency of steam-turbine baseline power generation over "just about anything else".  The combination of Snyder combustion-air preheaters (which are basically passes of 2" pipe, like air-brake radiators, in front of the gap between ashpan and mud ring) and enhanced Cunningham circulators (which provide enhanced flow to delay DNB and other effects in the relatively thin waterleg spaces of a Stephenson firebox) are probably good together for a ~20% improvement in performance ... this is a percentage of the minuscule Generation 0 or 1 locomotive performance, starting at under 10% for even relatively modern designs, but still very significant in terms of improved efficiency and performance together.  

[quote[Internal combustion engine efficiency has certainly improved, but is still only 20%[/quote]It can get much better than that, particularly with the right transmission matched to a high-efficiency engine.  Even the best Rankine efficiency that will 'package' on a locomotive will not go near what a good IC engine will do -- within its limits.  We don't pretend to try ... other than to have a little fun from time to time, like asking 'what is the efficiency of a steam motor expanding from 7250psi @ 950C superheat down to some reasonable finishing pressure like 2bar'.  (You can put these on a Roosen motor locomotive chassis and avoid much of the expense of a large boiler...Wink

Of course that's not the system efficiency, only the expander, and a great deal of that power has to go to the BFP (not a wicked euphemism, but could be one) that recompresses the exhaust for the next 'pass'.  But it still works at the necessary scale...

A major drawback of steam engines is the time required to obtain full power.

The answer to this, in most practice that would be relevant to a service like Plandampf, is in the approaches used on locomotive 8055.  When idling at full pressure is done with only 35kW of cheap and long-lived water-heater elements, it makes little sense to use expensive rechargeable batteries to use 'grid electricity' appropriately for locomotive use...

... not sure how to evaluate the efficiency and benefits of electric vehicles.  efficiency may depend on the source of power: coal, nuclear, water, ...   Benefits may be zero pollution from the vehicle, zero startup time, higher torque, ... while efficiency or fuel cost may be important, performance and other contraints may be even more important.

The best answer I have is to look at the existing well-to-wheel studies for various plug-in and BEV systems -- and scale them correctly for build-out and sustained maintenance.  One has to ensure the electricity fairy makes the necessary magic to support the electric transportation on top of all the regular -- and more time-shiftable -- consumption of grid power elsewhere in society.  Sometimes that is no fun, and sometimes people you thought were your 'allies' start screaming and making devil signs (especially when you point out how much of 'renewable power' is more or less a scam) but -- as with the calculations for 'successful' hydrogen-powered transit vehicles (all of which are battery cars with carrier-hydrogen fuel-cell 'recharging' but work primarily because governments can assure proper supply chains for the fuel) -- you need a hefty dose of political expedience to go along with nominal 'thermodynamic efficiency' or whatever metric you're adapting.

Personally I think any obligate BEV is a disaster waiting to happen.  Any sensible long-range 'solution' for American use really either needs some onboard sustainer power or a connection for some version of sustainer power -- and ideally will continue to be usable if the battery degrades with time, as on so many original hybrids, and plans to replace it expen$ively weren't factored into its adoption.

It is difficult to argue with straight electric transmission in the presence of Ludicrous+.  Especially when repeated use of the feat can be arranged with minimal battery damage... Big Smile  It is arrangements for the careless to operate motor vehicles that constitute the necessary (and if you ask, less 'efficient') alternative arrangements for practicality.

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Posted by Overmod on Friday, October 16, 2020 10:14 AM

Lastspikemike
Steam locomotives are not less efficient than diesel electric but they do cost way more to run.

They are far, far less efficient than diesel-electric, and in some uses (flat switching being one) compellingly so even if designed to be as 'diesel-like' as possible (see the N&W M-2 'Automatic' for a poignant example).  It is almost astounding how much more effective a pair of 4400hp 'power-by-the-hour' modern diesels is than any 8800-hp external-combustion equivalent ... it takes a great difference in fuel, and care with other support provision, to make them economically competitive with diesels, which is a very, very different thing from efficiency.  They can be made roughly 'as cheap' to run mechanically, but it takes lots of work and detail design to make it so.

Sailing ships were way more efficient than steam ships (and, bonus, zero emissions rated) but far more expensive to run.

Sure, if you don't mind ridiculous lack of actual cargo space if you want any kind of speed, and don't care when the cargo gets to port reliably, and can keep well out of the track of storms ... and there are interesting automation schemes for much of the expense of running traditional multimast sailing ships, but they ain't cheap and not always good in 'anomalous conditions'.  The British took over the trade of the world with dirty iron tubs ... and remade the Scots into respectable engineers in the process, by making the actual things constituting 'efficiency' in shipping cost-effective (or more reliable).  

Note that subsequent attempts to utilize 'the power of the wind' for commercial shipping, some of them very sophisticated, have not panned out, in any service requiring profitability.  I have always thought it strange that Flettner rotorships were never tried; they do involve some motorization but far less than what would be needed for equivalent propulsion.  I guess it is what it is; I have known a number of shipowners and none of them would give revised sail the time of day (although they were interested in the technology involved) -- much as railroad owners don't like modern steam even though they be steam buffs in private life.

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Posted by Lastspikemike on Friday, October 16, 2020 1:56 PM

Possibly not the best idea to take up the efficiency issue  about sailing ships.  They were of course much more efficent cargo carriers.  No steam engine gubbins, no fuel bunkers or tanks and so on.  Size limits had nothing to do with the sailing technology. It took a long time for steamers to pack more cargo and deliver it faster. Just BTW the hard driving skippers made a point of not avoiding storm tracks. Ever heard of the roaring forties?

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Posted by Lastspikemike on Friday, October 16, 2020 2:02 PM

Superchargers have nothing to do with adding fuel. They force air in, the fuelling is handled by carburetion or injection.

Supercharging results in a variable displacement engine, able to ingest more air than atmospheric pressure can provide.

It is this added pressure that corresponds exactly to the throttle in a steam locomotive, when controlled by the driver.    Automatic boost control works better but that wasn't my point. Steam locomotives are also pressure limited just as supercharged engines are. Supercharged engines operate at much higher pressures than steam locomotives, a point you make elsewhere although perhaps unconsciously. 

Steam locomotives also use more fuel at higher operating pressures.

Duh. 

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Posted by Overmod on Friday, October 16, 2020 2:34 PM

Lastspikemike
Superchargers have nothing to do with adding fuel. They force air in, the fuelling is handled by carburetion or injection.

The point is that the additional air is worthless without proportional fuel.  There actually are applications that added fuel through the supercharger in the past (some because evaporation of the fuel helped cool the charge) but I can't imagine a modern engine using anything but direct injection, probably with pilot injection for promotion.  Pilot injection carefully adjusted to avoid supersonic shock in the combustion chamber... Dunce

I stand by the hard limits on gain from supercharging + additional fuel imposed by engine structure and balance.  On the other hand it's been fun watching those limits get raised over and over as technology improves!


Supercharging results in a variable displacement engine, able to ingest more air than atmospheric pressure can provide.
Far more common to see it used to restore baseline 'atmospheric' pressure in high-altitude conditions -- the two-speed arrangement on the Merlin being a further technical example.  No few 'turbo' engines turn out to produce laughable actual boost without tinkering - the GM 6.5TD being an unsung example.  (It could in fact have its 'electronic' wastegate control altered to produce sufficient boost to justify the famous #9 resistor and marine injectors, for a whopping ~315hp, but you weren't going to get far with twins... Laugh)

Pity Juniatha is gone from here... she'd love a good sailing-ship discussion...

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Posted by SpaceMouse on Friday, October 16, 2020 5:09 PM

Whoa! I'm totally overwhelmed. 

Bear--great intro videos. I was surprized to learn that steam pushes the pistons in both directions.

Overmod
have not yet found a better 'on video' explanation than the one ATSF prepared, as I recall circa 1922, using the then relatively new technique of animation to show with technical correctness some of what was going on.  Fortunately at least some of this was preserved by Herron Rail Videos and a portion of it can be seen here: https://m.youtube.com/watch?v=QYNRhL0ddDQ

You're right. I'll probably come back to this. 

I haven’t seen this manual, but it may be the go.   https://www.amazon.com/Locomotive-Enginemans-Manual-W-James/dp/1935327828

Overmod
That manual was one of the better ones, but suffers from a fate more than usually common to steam-technology books: they were copied and reprinted in the era before Google Books and are therefore considered 'copyrighted' even with regard to the historic originals and hence not available as Google Books or archive.org scans even though the original editions are long out of copyright.

Looking at the simple pages, it seems like you would have to sort through a lot of regulations to get to the technical stuff. Still, I'm sure I can borrow it from inter-library loan.

gmpullman

The PRR T1 Trust has made this excellent training book available as a .pdf file. It is quite worthwhile.

https://prrt1steamlocomotivetrust.org/bookclub/download.php

Good Luck, Ed 

Downloaded to my personal archives. 

Overmod
This reminds me that CSR/SRI went to some trouble a decade ago, when they were developing their 'Project 130', to prepare some white papers on modern steam technology, which can still be found with a little looking.  Here is an example: 

https://static1.squarespace.com/static/55e5ef3fe4b0d3b9ddaa5954/t/55e6373fe4b04afd122b821d/1441150783767/%23+DOMS-1_Chapelon.pdf

 

 
Also downloaded.
 

Kevin
My suggestion would be, if at all possible, to look into live steam locomotive contsruction manuals and maybe find a group. These are sort of a "real thing", and these guys love to chat about their builds.

Good suggestion.

ATLANTIC CENTRAL
Chip, you really did it this time, I hope you are having fun and following this because you will learn a lot if you do. I will give you the really simple practial description, that skips a lot of details.

You got that right. I'm following some of it. How much is indeterminate, because how much I think I understand and how much I actually do may be as disperate as Chinese Trade Practices and a rudamentary understanding of the Chinese Global Warming Hoax. 

pav

Another good book that is easy to understand is 'Model Railroader Cyclopedia Volume 1: Steam Locomotives'. Eric

Thanks. I'll check into it.

ConfusedConfusedConfused

Well, my brain is full. I'll get back to when I find a way to reduce my brain valve stroke distance to 41-43%. 

 

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by rrinker on Friday, October 16, 2020 11:26 PM

 They haven't given up on sailign cargo ships yet:

https://www.maritime-executive.com/article/swedish-collaboration-unveils-world-s-largest-sail-powered-car-carrier

Many years ago, there was featured in MR an O scale locmotive that has moving valve gear as well as a moving throttle quarant inthe cab (and the linkage on the boiler moved as well. Among other things. The bell actually moved as well. The whole insiode of the boiler was packed with servos to make all the motion work. It was pretty impressive.

                                            --Randy

 


Modeling the Reading Railroad in the 1950's

 

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Posted by BigJim on Saturday, October 17, 2020 9:04 AM

"Whoa! I'm totally overwhelmed."

SpaceMouse,
If you hang a round here long enough, you will quickly learn that there are those here that just can't help but take a simple question and turn it to something so totally complicated that they don't even understand it themselves! It is like they are having a battle of the brains amongst themselves. Such is life. Some like it, some good filters out of it, yet, a lot of times it just gets in the way.

Let me add, if it hasn't already been suggested, a book by Karen Parker..."How Steam Locomotives Work". It is easy to understand. There is a minor mistake or two, but, a novice will never notice and it will teach you a lot.

Do try to be aware of what you buy! I am pretty sure that there is another book out there by the same title, but, it deals with British locomotives.

.

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Posted by Lastspikemike on Saturday, October 17, 2020 9:54 AM

That's why I posed the question early on. 

There's how a steam locomotive works and how you work a steam locomotive.

For me I was more interested in how you drive a train than how the steam power was converted to motive power. 

The conversion of fire into motion is fairly straightforward. It's all the gubbins you need to control the process that fascinates me.  

No gearbox and yet variable speeds up to well over 100 mph. Hauling ability was, and remains, staggeringly huge.  

Say what you like  about old fashioned stuff but it remains amazing what was   achieved with some pretty simple fabrication techniques and a lot of ingenuity.

In a blink of an eye historically speaking. 10,000 years of animal power and then inside 100 years technology advanced from lifting water out of mines to inter City travel at 60 mph....that's a mile a minute you know, 

Alyth Yard

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Posted by Lastspikemike on Saturday, October 17, 2020 10:02 AM

Sailing ships were always very efficiently built to purpose. The ultimate cargo carrying hull shape developed rapidly in the early 19th century from the "American Clipper" the fastest ever of which was a Canadian design. Modern cargo ships still use that design. 

Speed is irrelevant to ocean shipping. Think of these ships as huge floating warehouses. Truck to train to ship to train to truck is just a very flexible pipeline and treated as such by manufacturers and their customers. Of these, it is actually the  train that earns its keep most.

And freight has been containerized forever: from barrels to boxcars there's  nothing really new about intermodal freight.     It's all about eliminating the labour costs of longshoremen  and other manual handling of product from mode to mode. 

Alyth Yard

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Posted by Overmod on Saturday, October 17, 2020 11:52 AM

Lastspikemike
That's why I posed the question early on.

He's compressing nearly 220 years of practice, over 150 of which occupied the talents of very skilled people when it was one of the most relevant subjects on earth, into a week or two.  It would be possible, as Big Jim indicates, to give him a simplistic view of it -- like that other ATSF training video on YouTube, that I pointedly didn't link to.  In my opinion, if he does not appreciate the complexities and practicalities early, he'll be stuck with having a great deal to unlearn later, when it will be harder to distinguish the good from the myth or the outright BS.

He originally asked specifically about all the complicated details of modern steam power -- the stuff lastspikemike amusingly terms 'gubbins' -- and discussing many of those without detailed background may not advance his desired knowledge very meaningfully.  So far he seems to be agreeing with learning the complex along with the simple; I think if he thought he didn't need or want the added detail, he would simply say so.  (Others who want a more simplistic view of steam can easily establish their own thread and get it.)

There's how a steam locomotive works and how you work a steam locomotive.

We have barely touched on the latter.  Personally I think he would do better to understand the construction and physics involved before getting to technique; otherwise he won't understand why a considerable amount of technique is done as it is, particularly with respect to starting and drifting.  Many PRR engineers went most of their careers without seeing an engine with a modern front-end throttle, then found themselves stuck without real advance warning or retraining behind the throttle of not only modern power but modern duplex power.  This caused a great deal of ultimately somewhat convenient trouble, and it has not been remarked yet but may be important that the opposite concern, that a modern engineer may not appreciate how to run an older American type with riding cutoff, might also apply...

For me I was more interested in how you drive a train than how the steam power was converted to motive power.

This is directly relevant here, as this community has perhaps the greatest potential interest outside the train-simulator and gamer community into operating steam 'prototypically'.  I would start a thread exclusively on this as a 'companion' to this one for Chip if you are that interested.

The conversion of fire into motion is fairly straightforward

However, the efficient conversion ... let alone most cost-effective conversion ... is anything but.

And getting things wrong by oversimplifying for children or beginners will not be doing them any service should they have an actual interest in the subject beyond Freeman Hubbard level.

No gearbox and yet variable speeds up to well over 100 mph.

But not ultimately very safe speeds much over 100mph ... something relatively overlooked in the days reciprocating steam was the 'only' choice for passenger trains, but quickly recognizable when even fragile and expensive alternatives came about.  Something that has not yet been mentioned is how quickly a great many reciprocating designs hit a performance wall at high speed/high load.  The C&NW E-4, a formidable-looking 84"-drivered 4-6-4, could not even get the late-'30s AAR test train to 100mph.  The even more formidable ATSF 3460 class could easily get to around 100mph (whjch was, to be fair, its intended highest speed) but was in trouble getting even to 105mph and would likely need the vertical assistance of gravity off a bridge to reach 110mph.  These were not technically irremediable 'conditions' but they illustrate how nearly designers of the late Thirties were to the practical limits of reciprocating power.

It might be added that the inclusion of a transmission did solve many of the issues with other kinds of steam power.  Westinghouse patented a reversing two-speed planetary to fix the issues with direct-drive turbine power like PRR6200; the adaptation of the Bowes 'tugboat' drive to the V1 mechanical turbine gave that design a new grip in life for a couple of years after the war -- allowing much higher practical top speed without compromising starting TE at lower steam consumption.  Reducing effective water rate at high speed and keeping an engine from exceeding the capacity of its port and valve arrangement are other reasons for less direct drive; geared duplex conjugation is another reasonable example (when done right).

In a blink of an eye historically speaking... 10,000 years of animal power and then inside 100 years technology advanced from lifting water out of mines to inter City travel at 60 mph....that's a mile a minute you know, 

It was quicker than that.  Even the jump from Trevithick in 1801 to Trevithick in 1802 is astounding - and that is one man without benefit of sophisticated equipment.  Much of railroad improvement follows the story of industrial improvement, including Webb's showing Henry Ford how to build his Rouge plant about half a century earlier (even if what was built in Webb's facility could be a bit dotty at times).

Far more of course was possible than was actually built, beginning with the true high-speed steam railroads.  I believe the original M&O, or something very like it, was planned for 150mph service before the American Civil War; the high-speed trains to run on it were patented right after that war.  An interesting speed competition developed long before the streamlined lightweight train years, in the service between Philadelphia and Atlantic City which quickly evolved into the fastest trains in the world.  One can only wonder at what would have run on the Ramsey-survey NYP&C, or the PRR Sam Rea line to compete to the West, or the revived Gould line that nearly saw construction in the late '20s ... the duplex passenger power was shaping up to fill that niche effectively, and I think it was only the lightweight-gear better-balance movement, from Eksergian to Timken, and then Glaze and Langer, that nipped it so conclusively.

A great fascinating thing in United States practice was the 'late' development of practical steam support, notably on NYC and N&W.  This did not always involve expensive fabrication (although it is hard to imagine modern steam without GSC engine beds, which were not born of 'railroad' technology) but it represents a valiant effort to make steam cost-effective to evolving alternative forms of power and the industrial and political forces behind them.

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Posted by BigJim on Saturday, October 17, 2020 5:56 PM

Now for something totally irrelevant,

SpaceMouse, Your avatar looks exactly like Mike Love of the Beach Boys!

.

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Posted by SpaceMouse on Saturday, October 17, 2020 7:18 PM

BigJim
Your avatar looks exactly like Mike Love of the Beach Boys!

I don't hear that as often as I used to. Heard it starting in college. 

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by Neptune48 on Monday, October 19, 2020 11:17 PM

How a Steam Locomotive Works by Karen Parker.  Available at Amazon and other book sellers.  I highly recommend it.

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Posted by SpaceMouse on Wednesday, October 21, 2020 9:55 AM

Neptune48

How a Steam Locomotive Works by Karen Parker.  Available at Amazon and other book sellers.  I highly recommend it.

That book costs $72.

However, I found: 

American Steam Locomotives: Design and Development, 1880–1960 (Railroads Past and Present) by William L. Withuhn (Author)

Anyone know this book?

Chip

Building the Rock Ridge Railroad with the slowest construction crew west of the Pecos.

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Posted by Overmod on Wednesday, October 21, 2020 2:49 PM

SpaceMouse
Anyone know this book?

It's good in my opinion.  It goes with Parker Lamb's Perfecting the Anerican Steam Locomotive.

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Posted by BigJim on Wednesday, October 21, 2020 7:08 PM

SpaceMouse
That book costs $72.

Wow! I had no idea of the exorbitant prices being asked for that book! Highway robbery!!!

.

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Posted by Lastspikemike on Thursday, October 22, 2020 8:45 AM

BigJim

 

 
SpaceMouse
That book costs $72.

 

Wow! I had no idea of the exorbitant prices being asked for that book! Highway robbery!!!

 

 

Welcome to the wonderful world of "rare books". 

Prices can get so high you wonder why a reprint isn't a no brainer. 

Then you go looking for a copy of the book and realize that only several hundred were printed in the first place and now only a few are left in "circulation", say 10% so it only takes a relatively small demand to drive the prices way up. 

Oddly, the more unreasonable the price seems the more likely the used book is of very good quality, content wise. Unlike new books where bad and good are initially released for similar prices. 

Model locomotives show similar patterns.

And old Ferraris for that matter. Now in that case those are all way overpriced having regard to how they actually drive.....

Alyth Yard

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Posted by BigJim on Thursday, October 22, 2020 6:43 PM

SpaceMouse,
If you want to learn about steam locomotives, go to the following web site: http://www.icsarchive.org/icsarchive-org/bb/

Scroll down to ics bb 501 and start clicking on those links. Keep in mind that they are mostly large files (a few won't take you to anything), so wait for them to load and start your education!

.

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Posted by Overmod on Friday, October 23, 2020 8:11 AM

BigJim
If you want to learn about steam locomotives, go to the following web site: http://www.icsarchive.org/icsarchive-org/bb/

I am delighted to see that a considerable number of new lessons were added in April 2020; they're using the pandemic 'downtime' to excellent advantage.

Start with 510c  section 2504.  This doesn't have a couple of the key 'insights' that made their lesson on 'entropy, heat and steam' as effective as it was, such as how heat is converted into pressure in practical calculations involving 'entropy', but is otherwise excellent in establishing much of what you need to know.  Read this with 455 section 0000 at your elbow, which explains much of the nature of steam (and its quirks in expansion engines).

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Posted by Overmod on Sunday, October 25, 2020 5:19 PM

Consider Prior's 1925 Modern American Locomotive book.  This is another of those rare-book-price-inflation things but I see AbeBooks has a couple listed for between $15-$17.

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