How a steam engine works

[Overmod]

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...

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...   It is arrangements for the careless to operate motor vehicles that constitute the necessary (and if you ask, less 'efficient') alternative arrangements for practicality.

[Overmod]

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.

[Overmod]

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... 

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... )

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

[SpaceMouse]

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.

[rrinker]

 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

 

[BigJim]

"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.

[Overmod]

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.

[BigJim]

Now for something totally irrelevant,

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

[SpaceMouse]

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. 

[Neptune48]

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

[SpaceMouse]

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?

[Overmod]

SpaceMouse

Anyone know this book?

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

[BigJim]

SpaceMouse

That book costs $72.

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

[BigJim]

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!

[Overmod]

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).

[Overmod]

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.

[DR DENNIS GORDAN]

Model Railroader Cyclopedia, volume one, steam locomotives, probably has the level of information you seek. The first part of the book is devoted to the anatomy of all those appurtenances that you see, including valve gears, air pumps, etc. Although it is out of print, it is probably in some libraries.

[Overmod]

DR DENNIS GORDAN

Model Railroader Cyclopedia, volume one, steam locomotives, probably has the level of information you seek.

This is a book he should own, but the problem I had with it is that it's geared to modelers.  So it has discussions of the physical form of many of the devices and auxiliaries, but very little about how they actually work (which I understood to be the OP's question).

One example: in many of the drawings, you can see the 'can' of the receptacle for 'sparks' at the bottom of the smokebox that was in vogue before the introduction of self-cleaning front ends.  Nowhere will you see this mentioned, let alone discussed, even though there are interesting details between the length of smokeboxes, the arrangements to handle cinders, and the arrangement of internal baffles and screens in them during the period in question.

[Overmod]

Lastspikemike

If you find a copy I recommend you buy it.

A couple of the paperback copies can be had relatively cheap:

https://www.amazon.com/gp/offer-listing/0890240019/ref=tmm_pap_used_olp_0?ie=UTF8&condition=us

eBay currently has one listed, ending Sunday, for under $10.

[Hillyard]

SpaceMouse

So I'm looking for a book or books or other reference materials that shows the history, development and implications of all said dohickies.

Hello Spacemouse,

Check out "The Iron Horse" by Henry Comstock, (2nd ed 1993).  I see several copies avaible via a internet search.  I received a gift copy (actually a library remaindered outcast) which I never looked at much until the other day, with your questions in mind.  Has a discussion of two types of valve gear with drawings of all the linkages.  I think this is where the magic happens, regulating how much steam enters the pistons etc.  I found myself wanting additional diagrams to the three that are shown.  But it's a start.

I don't know about you, but some of the earlier discussion in this thread reminds me of the Chrysler Turbo Encabulator video.  

Good luck.  

[Overmod]

Hillyard

some of the earlier discussion in this thread reminds me of the Chrysler Turboencabulator video.  

With the slight difference that the earlier discussion isn't intentionally doubletalk BS...

Incidentally the original turboencabulator was part of a secret Naval program in WWII ... to determine if the various levels of ONR personnel were on their toes.  The gist as related to me was a top-secret communications improvement.  Research had indicated that static in radio was the result of bad electrons.  The turboencabulator filtered or separated these (cf. Maxwell) and charged a large 8" diameter capacitor with them.  The idea was then to fire this from one of the ship's 8" guns; while the drift speed of bad electrons back through salt water was fairly great, it would still offer a 'window' of time in which clear communications would be possible.

I was not told how far up the chain of command this got before someone exploded laughing or cursing, but it was said not to have been caught early.

Incidentally neither the Chrysler presentation nor subsequent parodies of it spell 'wainshaft' correctly, one of the problems with Anglo-American technology transfer (to say nothing of proofreading!) in those fabled years...

[BigJim]

If for no other reason, you buy "The Iron Horse" by Henry Comstock because of the ARTWORK!!!

[Overmod]

BigJim

If for no other reason, you buy "The Iron Horse" by Henry Comstock because of the ARTWORK!

One of my very favorite books!  And I note you can still find copies inexpensively!

I am STILL trying to find the lyrics to the song about the different locomotive bells that I first read about in that book... 

[steemtrayn]

Surprised noone mentionedthis one.

https://www.ebay.com/sch/i.html?_from=R40&_nkw=Catechism+of+the+Locomotive&_sacat=0&LH_TitleDesc=0&LH_PrefLoc=1&_fsrp=1&_sop=15

Suggested reading while studying for my fireman's license.

[Overmod]

steemtrayn

Surprised noone mentionedthis one. https://www.ebay.com/sch/i.html?_from=R40&_nkw=Catechism+of+the+Locomotive&_sacat=0&LH_TitleDesc=0&LH_PrefLoc=1&_fsrp=1&_sop=15

 Download your own PDF copy of the 1911 edition from the 'ebook free' button here:

https://books.google.com/books/about/Forney_s_Catechism_of_the_Locomotive.html?id=cugsAAAAYAAJ&hl=en