At the first "cabinet meeting," Mike Stearns says, "We got rail tracks leading most of the way from the mine to the power plant, but as far as I know there isn't a locomotive anywhere around. We may have to haul it by truck." (1632, Chap. 8)
The principal focus of this article will be on how the USE will design its first locomotives, but first I will explain what Canon (the entire set of 1632 series novels and anthologies) tells us about railroading after the Ring of Fire (RoF).
Mike decides that Grantville's best survival strategy is to use its "modern technology, while it lasts, to build a nineteenth-century industrial base." Mike muses, "Steam engines, steam engines. The railroads are about to make a big comeback in the world." (Chap. 11)
By the time of Becky's first cablecast (Sept 10, 1631), some kind of new track had just been laid to the new foundry, "but the first steam locomotive was still being built." (Chap. 33). That was still true as of the October 8 cabinet meeting (Chap. 40).
The next reference to railroads in "canon" is in the David Weber story, "In the Navy" (Ring of Fire). There, Eddie Cantrell lobbies Mike Stearns to turn over enough miles of salvaged railroad track to armor several ironclads, prompting complaints from Quentin Underwood about undermining the economy.
Nonetheless, the up-timers did lay steel rails between Grantville and Halle. Although incomplete, the line was in use as of a September, 1633 cabinet meeting (1633, Chap. 34). The trackwork was not modern steel T-rail, but rather "dinky wooden rails with an iron cap." Quentin is equally contemptuous of the motive power; the "pathetic" cargoes are "being pulled as often as not by 'locomotives' made up of a pickup truck—or even a team of horses."
By June of 1634, when Iona left Grantville, the trains were running all the way to Halle ("Until We Meet Again," Grantville Gazette, Volume 4).
Besides the civilian railroad, there is also a railway battalion in the U.S. Army, commanded by Major Elizabeth Pitre. Its mission is to build and operate narrow gauge military railroads (TacRail). Pitre's activities are described in "Elizabeth" (Grantville Gazette, Volume 4). TacRail will not be discussed further here.
However, there are a few important references to the civilian railroad in "Elizabeth." At the beginning of the story, in summer 1633, Frank Jackson complains that the rail line to Halle had not yet been completed. Nonetheless, at that point Charlie Schwartz had already "worked on the railroad link to the coal mine and helped to build the steam locomotive." The story ends in spring 1634, when the railway battalion rides civilian flatcars to Halle.
Having some track is nice, but it is not enough. We have to know how to plan out a rail network, manufacture and lay track, build locomotives and other rolling stock, and operate the railroad.
Naturally, there will be some information on railroads in the public libraries. Of the documented sources (those known to exist in Mannington, or mentioned in canon), the most useful from a locomotive design standpoint are the encyclopedias (especially the "Railways" [EB11/R] and "Steam Engine" [EB11/SE] articles in the Encyclopedia Britannica, Eleventh Edition) and Alexander's Iron Horses: American Locomotives 1829-1900.
There is more knowledge of railroads than just book knowledge stored in the libraries, of course. The first group to whom would-be railroad barons may turn for help are the retired railroad workers. According to the Up-timer Grid, there are ten such people in Grantville. These people have practical, first-hand experience with real railroads. They may also have souvenirs of interest. But bear in mind that a ticket taker isn't going to know how to build a firebox.
* * *
Next, there are the mineworkers. Some of them may have laid narrow gauge track to service the mines, or operated and repaired the mine cars or even locomotives. ("Elizabeth" says there were a couple of locomotives used in the Joanne mine.)
* * *
The third group are "rail fans." They may go out and watch (and perhaps photograph) real trains in operation, try to ride behind particular locomotives or on particular tracks, collect books, videos and railroad memorabilia, or build and operate model railroads.
There are at least three rail fans (Hardy, Pitre, and Szymanski) so identified on the Grid; there may be additional hobbyists. A town the size of Mannington (the model for Grantville) is likely to have five to seven model railroaders (Atlas Model Railroad Forum).
Of the rail fans, "Monty" Szymanski is of particular interest because he "helped restore locomotives for the Cass State Park Scenic Railway and had built several one-eighth scale models of steam locomotives." (Up-timer Grid)
Even up-timers who are not retired railway employees may have something to contribute. There are the steam engine buffs, of course. People who rode a scenic railroad may have home videos of the experience. Movie lovers who have videotapes of any of the many movies, including Westerns, mysteries and thrillers, which contain locomotive or other railroad footage. We know that The General (1927) is available; that is the movie which introduced Buster Keaton to the down-timers.
A train, running on rails, may be propelled by any of several different means. Despite Quentin Underwood's sneering, animal power is actually a pretty reasonable propulsion system, at least for moderate speeds and loads. A draft horse, with a body weight of 1,200 to 2,000 pounds, can, for as long as ten hours, exert a pull of 180 to 220 pounds. If the load is carried in a wheeled vehicle, riding on rails, the rolling resistance of the load is perhaps 1/100th to 1/250th of its weight. In other words, a 200 pound pull moves a 20,000 to 50,000 pound (ten to twenty-five ton) load, i.e., 1000% to 2500% of the body weight. (See Cooper, "Transportation Cost FAQ," www.1632.org .)
Teams as large as thirty horses were used in the American West to haul heavy loads. Even an eight horse team can move 80 to 200 tons on rails.
Clearly, steam locomotion is one of the options the USE is considering. In the early days, the greatest advantage of steam locomotion was that it had a lower operating cost. For the horse-drawn trains on the B&O railroad, the "crew" was 42 horses and 12 men, and the total operating cost was $33/day. The horses towed the train at a speed of 10 mph. In contrast, the 1832 locomotive Atlantic (0-4-0, 6.5 tons), which replaced the horses, could go 20 mph, and its operating cost was just $16/day. (Dilts, 196). (Alexander, PL4, says that it hauled 30 tons at 15 mph.)
Eventually, the locomotives became powerful to pull trains too heavy for normal draft teams. As early as 1839, a Gowan & Marx (4-4-0, 11 tons, 9 tons on drivers, driving wheels 42" diameter, cylinders 12 1/8" x 18," anthracite coal burner) hauled a train of 101 loaded four-wheeled cars, weighing a total of 423 tons, from Reading to Philadelphia at average speed of 9.82 mph. (Alexander PL10).
Why not jump directly to diesel-electric (DE) propulsion? Modern locomotives use a diesel engine to power electric motors; the latter turn the wheels. DE locomotives are more fuel efficient, and less labor intensive to operate, than steam locomotives. They can exert high tractive forces at high speeds, and they can be wired so that one DE's crew can operate several at one time.
The problem is that we lack the infrastructure to support DE's. A diesel engine requires diesel fuel, and we don't have it yet. The oil fields of Germany are small, and we probably won't have a large, reliable supply of oil until we have control of the North Atlantic and can import it from the Middle East, Africa, or the Americas. In other words, we have to win the war first.
Then there is the electrical system. We will need insulated copper wire. The best insulation is rubber or plastic and, in 1632, neither rubbers nor plastics are commercially available. In OTL, the natural rubbers and plastics were obtained from non-European sources.
Finally, there is the issue of start-up costs; DE's are perhaps five times as expensive as a steam locomotive of equal horsepower. (NOCK/RE 203)
Even if we recreate the steam locomotive technology, that doesn't mean that it will be suitable for all purposes. During World War One, Major Connor warned against use of steam locomotives to directly supply the front line, because a "steam locomotive would indicate too clearly its position by its smoke."
As one possible alternative, Connor provides data on Vulcan gasoline locomotives. Even the smallest can haul over 150 tons. It therefore is not so strange as it seemed at first blush that the USE is using "a modified pickup truck cab section" to draw Iona's train. Canon doesn't specify the modifications, but it probably has been equipped with locomotive-type wheels so it will run on the rails.
Gasoline locomotives were first developed for coal mines (WLW). If the Joanne mine locomotives (Elizabeth) passed through the Ring of Fire, they were presumably narrow gauge gasoline machines.
Historically, fuel was the largest operating expense item for railroads, and the choice of fuel was based primarily on cost. The early American locomotives mostly consumed wood; it was not until 1870 that half the steamers in service were coal-burners (White 85). Fuel conversion was driven by both deforestation, and the opening of large new coal fields.
Early seventeenth-century Germany is experiencing a wood shortage because of the heavy use of wood as a fuel in home fireplaces and industrial furnaces, and as a raw material for carpentry.
On the other hand, because the Ring of Fire encompassed several up-time coal mines, and the up-time equipment for mining them, there is a readily exploitable coal supply in the Grantville area. There is also a lot of coal in Germany, notably west of Hannover, near Zwickau in Saxony, in Saarland, and in the famous Ruhr region.
So it is something of a no-brainer to prefer coal to wood. (What wood we have available for railroads is best employed in the wood-ties which support the rails.)
The USE is rich in coal but impoverished in petroleum. Consequently, we cannot expect to have large supplies of either gasoline or diesel fuel within a reasonable time. Our gasoline locomotives are likely to be limited to rebuilds of up-time vehicles, and used only as a stopgap. And we aren't likely to consider building a diesel locomotive at all—at least, not until we are importing oil in large quantities.
We have completed the first stage of the engineering process: conceptual design. The principal motive power for the new railroad is going to be a coal-burning steam locomotive.
Both the Encyclopedia Americana and the modern Encyclopedia Britannica provide a basic cutaway view of a steam locomotive. These diagrams show, and label, certain major components of the boiler system (the firebox and its grate, the water circulation, the steam dome, and the superheater tubes), the engine system (the steam chest, the valve, and the cylinder-and-piston), the transmission system (the crosshead, main rods, and connecting rods), the driving and leading wheels, the valve control system (the eccentric crank and rod), the exhaust system (exhaust pipes, smoke box and smokestack), and the control system (throttle valve, throttle lever, safety valve). Other parts are recognizable to a railroader (e.g., the ashpan), but are not labeled.
In a steam locomotive, fuel is burnt in the firebox, evaporating water in the boiler. The resulting high-pressure steam is directed by the valve slide in the steam chest to either the front end or the back end of a cylinder containing a piston. If the steam enters the back end, it drives the piston forward and, at the completion of this forward stroke, the steam is allowed to escape. Steam then is redirected to the front end, moving the piston backward. Then the front end is exhausted, and the piston is ready for the next cycle.
This to-and-fro movement of the pistons is converted by the rods and cranks into rotary motion, each piston turning the driving wheels one half turn on each stroke of the cycle. Another linkage, driven by the rotation of the axle, controls the position of the valve slide.
The process may sound simple, but it is important not to underestimate the difficulties of building a practical steam locomotive. There are no steam locomotives in Grantville. That means that the design for the USE's first steam locomotive must be based on inspection of books and videos.
The next engineering design step is called "preliminary design" or "embodiment design." That is when engineers decide things like the size and weight of the locomotive, the fire grate size, the desired boiler pressure, the diameter of the cylinders, the piston stroke length, the number of wheels, the wheel diameter and so forth. These in turn determine how much the locomotive can pull, how fast.
To make those decisions, we have to determine the tractive force (pull) necessary to overcome the expected train resistance to motion.
The "basic" resistance on straight, level track is the result of rolling friction between wheel and rail, friction among all the mechanical parts driving the wheel (cylinder and piston, bearings and axle, etc.), air resistance, and other factors.
The starting resistance is about 20 pounds per ton of load, but the engineer can bunch up the cars and then take advantage of slack, starting the train one car at a time.
Resistance drops once the train is moving slowly. It then climbs again as train speed increases.
EB11 provides some formidable equations, of dubious relevance, for calculating resistance. I instead quote two simple historical formulae which are likely to be known to model railroaders. The resistance, measured in pounds of force per ton of load, equals
(1) 2 + (speed (mph) / 4)(the "Engineering News" formula; Ludy, 131), or
(2) 3 + (speed (mph) / 6)(the Baldwin Locomotive Company formula; Connor, 89).
Equations (1) and (2) are useful at the speeds the USE will be operating. However, for high speed modern trains, air resistance becomes important, and this introduces a factor which is proportional to the square of the speed.
In nineteenth-century America, poorly capitalized pioneer railroads economized on track building by taking the path of least resistance: going up and down, or around, hills. As a result, American locomotives had to be engineered to cope with steep grades and sharp curves. This could be true in the USE, too.
Total train resistance is the sum of the basic resistance mentioned above, and extra resistance attributable to grades and curves.
* * *
Grade (Slope). If it is going uphill, the locomotive has to overcome gravitational force as well as rolling friction. This grade resistance is roughly 20 pounds per ton of load, for every 1% of slope. (Armstrong, 20)
* * *
Curves force the train to reduce speed (so it doesn't derail), and also result in an effective increase in resistance. A curve with a turning radius of 5,729 feet (called a one degree curve) increases resistance by 0.8 pounds per ton of load. Halve the radius, and you double the resistance.
EB11/R explains how to calculate the average tractive force (in pounds) exerted at the rail by the driving wheels of a two-cylinder steam locomotive engine: it is the product of the mean effective pressure (p.s.i.) of steam in the acting cylinder, the square of the piston diameter (inches), and the length (inches) of the piston stroke, divided by the diameter of the wheel. (See also Ludy, 131). The mean effective pressure at start-up is usually assumed to be 85% of the boiler pressure.
In this article, when I refer to "cylinder diameter," what I really mean is the size of the bore, which is, roughly, the piston diameter. Also, I may express the cylinder bore diameter and piston stroke length in shorthand form as, e.g., "16X24" (16 inch bore, 24 inch stroke).
The drawbar pull—which determines the load that the locomotive can haul—is its tractive force at the rail, less the resistance imparted by the locomotive itself.
The steam locomotive develops the rated tractive force made possible by its boiler and engine only if it can adhere to the track.
The effective tractive force applied to the wheel rims cannot exceed the "adhesion," which is the product of the weight which the locomotive places on its driving wheels, and the "coefficient of adhesion." This coefficient (Armstrong and others use 0.25; EB11/R, 0.2.) expresses how well the wheels resist sliding on the rails; higher is better. The engine can apply more force to the wheels, but they will just slip, not turn.
Consider the rail-riding pickup truck on the Grantville-Halle line. We are probably talking about a 200-300 horsepower engine, and a vehicle weight of around 5,000 pounds. At 10 mph, that engine could develop a pull of 9,000 pounds—if only the wheels didn't slip. But its maximum tractive force, thanks to the adhesion limit, is just 1,250 pounds. That means that it is way over-muscled, relative to its adhesion. Of course, "its muscles are designed for rubber tires on pavement, which have a much higher coefficient of friction." (Douglas Jones comment)
The desired tractive force can be calculated if we know how much tonnage the locomotive must move, over what grades and curves.
We then first ensure that the weight on the drivers is sufficient to generate adhesion at least equal to that desired tractive force. We distribute this weight across a sufficient number of axles so that the rail can handle the load.
Next, we must size the engine and boiler so that the rated tractive force is sufficient and sustainable. A logical starting point would be to use the design parameters of an old timeline (OTL) locomotive. EB11/R provides some useful comparative data for thirty-six different locomotives: wheel configuration, the position (inside or outside), diameter, and stroke length of the cylinders; the diameter of the driving wheels, the weights of the engine and its tender; the weight carried by the driving wheels; the grate area and total heating surface of the firebox. In fourteen cases, it also states the boiler pressure.
While EB11/R has something of a British bias, Alexander provides significant design parameters for over fifty American locos.
It should be evident from the discussion of rated tractive force that this can be increased (up to the "adhesion limit") by
1) increasing the mean effective pressure (usually by increasing the boiler pressure),
2) increasing the cylinder diameter or the piston stroke length, or
3) decreasing the driving wheel diameter
Decreasing the drive wheel diameter is the only way of increasing long-term tractive effort which does not require that the boiler and firebox be enlarged to pay for it. However, it, too, has a price: reduced speed.
Large wheels are reserved for express passenger service, while small wheels are used on freight locomotives to maximize tractive effort. But the wheel diameter cannot be made too small, because it must remain larger than the piston stroke length.
For a freight locomotive, 42 inch driving wheels are typical. On a general purpose locomotive, a typical wheel diameter might be 54 inches. A little more speed, a little less tractive force. For a dedicated passenger locomotive, wheel diameter is likely to be in the 60-90 inch range, resulting in a more pronounced tradeoff of hauling ability for speed.
If you want to increase the boiler pressure, you will have to evaporate water at a faster rate. This will require various firebox and firetube modifications. And to contain that pressure, you will have to use thicker boiler and firebox walls, which will make the locomotive heavier.
* * *
If you increase the cylinder diameter or piston stroke length, you increase the engine's steam requirements. If the boiler is mismatched to the engine, then the boiler pressure will drop, the engine will gulp for steam, and the tractive force will decline. So changes in the engine ultimately affect boiler and firebox design.
Increasing the cylinder diameter or the boiler pressure also increases the force on the piston so the piston rod must be made larger and heavier to withstand the stresses imposed by piston motion. Which in turn affects the size of the main rod, the coupling rods, the axles, and even the frames.
Making the reciprocating parts (e.g., piston) more massive will increase shaking, which will mean more wear and tear on the engine, the running gear, the wheels and even the rail.
Increasing the stroke length necessarily increases the length of the piston rod, and hence its diameter must be increased so it doesn't buckle when compressed. The rest of the running gear then needs to be scaled up, too. With the same consequences as before.
Any mechanical engineer (there are at least ten in the Grid) will have studied, and will have textbooks describing, the basic mechanics of columns and beams, crank-and-rod mechanisms, etc. and hence will appreciate the mechanical limitations on piston rod length and cylinder diameter. It is no doubt because of the forces at work that cylinder diameters and piston strokes on locomotives rarely exceed 30 inches, even though a more massive design would increase tractive force.
Because of the role of adhesion weight, lightening a locomotive is not necessarily advantageous. Indeed, in 1835 Baldwin built the first locomotive (The Black Hawk) in which the tender was integrated into the locomotive body, so that part of its weight would contribute to the traction. (Alexander, 50).
A locomotive is likely to be designed so that the weight it places on its drivers is at least four times the desired tractive force. Of course, its boilers and engines should then be sized accordingly.
However, the basic rolling resistance of a locomotive is still proportional to its total weight. There is substantial additional resistance, again proportional to total weight, when the locomotive steams up a slope, or accelerates.
We also need to consider wheel weight. The greater the weight, the greater the wear on the rail, and the risk of rail failure.
The quality of the track is the principal limit on wheel load. EB11/R (847) says that a weight of 37,000 pounds "could be easily carried on one axle," and that implies 19,500 on each wheel. The heaviest rail mentioned by EB11/R is 100 pounds per yard, so a conservative rule of thumb would be to allow a wheel load of 195 pounds per pound of rail weight.
A contemporary Baldwin Locomotive Company catalogue states that if steel rails are properly supported by cross-ties, they can support a maximum wheel weight of 225 to 300 pounds for each pound per yard of rail. Thus, if a rail is dimensioned so that its weight is forty pounds per yard, no more than 12,000 pounds weight should be placed on a single wheel.
For a given weight on the drivers, wheel load can be reduced by increasing the number of driving wheels. In OTL, there was an increase in the number of coupled driving wheels.
One 1893 locomotive (Alexander PL87) had 84,000 pounds on four driver wheels, and thus the individual wheel load was 21,000 pounds (suitable for 70 pound or heavier rail). In contrast, another (plate 90) had 172,000 pounds on the drivers, but it was spread over ten wheels, and thus it could actually run on lighter track.
The wheelbase is the distance from the first driven axle to the last one. If the normal axle spacing and wheel diameter are maintained, increasing the number of driving axles lengthens the wheelbase, which makes it more difficult for the locomotive to handle a curve. (Clarke, 122). Or turn around in a turntable or wye.
If the wheelbase is made too short, the locomotive becomes unsteady at high speeds. This was a problem with four-wheeled locomotives. (Clarke, 112-3).
* * *
There are constraints on height and width, too. The so-called "loading gauge" (the clearances provided by bridges, tunnels, road cuts, stations and neighboring track) comes into play here. In America, the rolling stock can be as wide as 10'10" and as high as 16'2." (NOCK/RE, 208-9).
The width is constrained, not only by the loading gauge, but also by the track gauge (the distance between the inside edges of the rails), as a large vehicle on a narrow gauge track may tip over when running a curve. The standard American track gauge is 4'8.5."
Likewise, the height not only cannot be so great as to be "clipped" by the roof of a tunnel, it cannot be disproportionate to the width, or the locomotive will topple over.
* * *
Increases in the dimensions of the locomotive will ordinarily mandate an increase in weight, too, unless a new, lighter structural material is employed. The materials presently available to the USE are wood, cast iron, wrought iron, steel, and a few other metals such as copper.
In nineteenth-century America, wood was used mostly in the cab and the tender frame, and as insulation. Copper was sometimes used for the heat exchange elements, because it conducts heat well, but it is structurally weak and thus copper tubing is thicker than the steel equivalent. Cast iron was used in cylinders, journal boxes, and valve boxes. For all other major components, the initial preference was for wrought iron, but this changed once the Bessemer process (1856) made steel affordable. By 1900, virtually the whole locomotive was made of steel. (White, 29-31).
* * *
We cannot put into a locomotive the most powerful boiler and the most powerful engine available, only those whose power is greatest within weight and size constraints. And the engine and boiler compete for the mass and volume allotted.
The boiler is the stomach of the locomotive. It consumes fuel, air and water, and belches steam. The fuel is burnt to change chemical energy into heat energy; the air is necessary for combustion to occur, and the water is what is heated to generate steam. It is the expansion of steam which moves the pistons, and ultimately makes the wheels go round.
Coal is shoveled onto a horizontal grate in the firebox, which receives air from the "ashpan" below, as well as, intermittently, through the firebox door.
The first fireboxes were mounted "inside" the wheel lines, and were long and narrow (grate area 17-18 square feet). Later, they were placed on top of the frame, and were wide but short (30 square feet). Long, wide fireboxes (up to 90 square feet) were made possible by relocating them behind the driving wheels. (Forney; Bruce, 36-43)
The smoke puffing from the steam locomotive is photogenic, but it is also evidence that fuel is being wasted. In 1859, engineers solved this problem with two new elements, a brick arch and a deflector plate. Together, they controlled the airflow so as to improve combustion.
"Monty" should be familiar with these two firebox features.
* * *
There are two basic methods of using the released heat energy. Most railroad boilers were of the "fire tube" type, which means that the hot air rises from the coals and enters a multitude of pipes. These travel through the main section of the boiler, which holds the water. The heat brings the water to a boil, and the steam rises from the top of the water surface, ultimately collecting in the "steam dome." The fire tubes empty into the smoke box, and the smoke ultimately escapes through the smokestack. This creates a partial vacuum in the smoke box, which helps to draw in the air. EB11 "Boilers" shows two views of an express locomotive boiler (Fig. 10).
A few OTL locomotives were equipped with water tube boilers. Water is circulated in tubes through the firebox, rather than hot air through the water reservoir. Water tube boilers were much safer to operate, and potentially more economical, "but it was impossible to build efficient boilers of this type within the clearance limitations of the railway engine" (Sinclair, 691).
The most efficient boiler operation is at a relatively low rate of combustion, e.g., 30-60 pounds of coal per square foot of grate per hour, resulting in evaporation of 11-13 pounds of water per pound of coal, and a boiler efficiency of about 80%. Burning 100-180 pounds per square foot of grate per hour, we obtain only about 6-8 pounds of water per pound of coal, and the boiler efficiency is about 40-50%. (EB11/R) Forney says that the most coal which can be burnt is about two hundred pounds per square foot of grate per hour, and then only at most six pounds of water would be evaporated by each pound of coal fired.
The size of the grate determines how much coal can be burning at one time. So a big grate seems like a good thing. However, there are problems of increasing its size. First of all, it means increasing the overall size of the locomotive. Secondly, once the grate exceeds a certain size, it becomes too difficult for a single "fireman" to keep it "fired" properly. (This was a problem with hand-fired "Pacific" locomotives, NOCK/RE 175.) You either need to provide two fire doors, for two firemen, or engineer a "mechanical stoker."
The firebox is positioned within the boiler so that there are water spaces to the sides and in back of the firebox, to maximize the direct firebox-to-boiler surface area (Alexander PL79). There is also water above the top of the firebox, the "crown sheet," and indeed the most common cause of a boiler explosion is that the crown sheet loses this protective blanket, and melts.
Heat transfer takes place not only at those walls of the firebox which are in contact with the water reservoir, but also at the walls of the tubes. So having lots of small diameter tubes is good—unless you are the fellow who has to make sure that those tubes are tight.
The longer the tubes, the greater the heat transfer area, but the weaker the combustion-promoting draft in the firebox. Having lots of tubes increases the heating area, but weakens the tube plate of the firebox.
EB11/R discloses both the grate area and the total heating surface for 36 locomotive designs. Disregarding the Stephenson Rocket, the total heating surface ranged from ~1,400 to ~6,100 square feet, and the grate areas from 20 to 100 square feet. The average ratio was 71:1.
* * *
The steam passes up into the steam dome, from which it is released to the cylinders by the throttle valve. Some locos had two steam domes, or other provisions for storing more steam.
The boiler pressure is a function of the rate at which steam is produced (evaporation rate), the rate at which steam is used, and the size of the steam reserve. Taking advantage of a large steam reserve to briefly make faster-than-normal speed or pull an extra-heavy load is called "mortgaging the boiler."
If you are producing a lot of steam quickly, the boiler pressure will increase. The pressure which the boiler can tolerate is dependent on the thickness of the walls, as well as the nature of its construction. Thicker walls can hold higher pressure steam, but the boiler will weigh more.
Alexander provides only limited boiler pressure data. An 1860 engine had 130 p.s.i. (PL47); locomotives built as late as 1882 had 125 p.s.i. pressure (PL76-7); three later locos were 180-190 (PL80, 85, 96). The highest pressure in the EB11/R table was 235.
Bear in mind that since the cab is behind the boiler, a large boiler limits the crew's view of what is in front of them.
Usually, the locomotive will have a pair of pistons, which operate one-quarter of a cycle out of phase, so when one is in "neutral" the other is ready to receive steam.
The cylinders can be mounted outside or inside the main frame. In general, during the nineteenth century, the British preferred to use inside cylinders, and the Americans, outside ones (Nock/RE 164).
There are some locomotives which have a second pair of cylinders, in which case it is very common to have one pair on the inside and the other on the outside. However, both pairs can be on the outside. (EB11/R).
There was experimentation with other positions in the early days, but the cylinders of late nineteenth-century locomotives were mounted horizontally, and at axle level.
Looking at the locomotive data in EB11/R, and ignoring both the primitive "Rocket," and engines with more than one pair of cylinders, we can see that the cylinders are 18 3/8-23 inches wide, and the piston stroke is 26-30 inches long. For the American locomotives in the Alexander book, if we ignore the pre-1840 models, cylinder diameter is 12-22 inches, and piston stroke 15-30 inches (save for one "13/54" locomotive).
For both the British and American locomotives, the stroke length was, on average, 50% greater than the cylinder diameter.
In the standard "rod" locomotive, the pistons are connected to cranks on the driving wheels, so two power strokes by the piston, make one turn of the crank, resulting in one revolution of the wheel.
The driving wheels of a high speed locomotive may turn at a rate of more than five revolutions per second. During each half-revolution, each piston accelerates to full speed (say, 35 feet per second) and then decelerates to a full stop. The necessary force on it is the mass times the acceleration. The piston weighs, say, 500 pounds (Forney), and the maximum acceleration is proportional to the stroke length and the square of the wheel speed (EB11/SE 837). The piston transmits that force to the piston rods, cranks, and other elements. They all must be able to withstand the resulting stresses, and, unless they are balanced, they cause unpleasant, perhaps dangerous, vibrations in the locomotive structure.
The engine and running gear include both rotating and reciprocating masses (some parts do both). The perturbations caused by the rotating masses (e.g., crank pin) can be completely balanced by a wheel-mounted counterbalance.
However, the reciprocating masses (e.g., piston head, piston rod, crosshead, main rod, coupling rods) would still cause the locomotive to yaw right and left. This horizontal disturbance can be reduced by "overbalancing" the wheels, but at the price of causing a vertical imbalance (pitching up and down). This alternately hammers the rails, and lifts the locomotive.
Usually, the compromise is to balance all of the rotating mass and 25-50% of the reciprocating mass, so that there is both horizontal and vertical imbalance.
The vertical imbalance increases with the square of the wheel speed (Addendum). The rails have to be able to withstand this dynamic load, not just the static weight on the wheels. And, of course, when the disturbance is upward, the locomotive must be heavy enough, and the balanced reciprocating mass light enough, so that the locomotive remains on the track.
Usually, with an outside cylinder, the piston rod fits into a crosshead, and the main rod connects the crosshead to the main crank pin, near the rim of one driving wheel. One driving axle is cranked directly, and the other driving axles are turned by the action of connecting rods, which run from one crank pin to another.
With an inside cylinder, the main rod will act on a cranked axle, rather than a crank pin. One advantage of an inside cylinder was that it could be mounted close to the center line, reducing the disturbances caused by the piston action. Another advantage is that the cylinder is warmed by the smokebox, and insulated by the frame. However, Ellis (51) warns the up-timers that "persistent breakage of crank axles" bedeviled inside cylinder designs. Crank axles were also expensive, large, heavy, and difficult to inspect and repair (White 208-9; EB11/SE 841).
The axle rotation also regulates the slide valve on the cylinders. EB11/R mentions five different mechanisms for this purpose, but for a description, you must turn to EB11/SE. The mechanisms are the Stephenson (Figs. 29, 32), Goochs (Fig. 30) and Allan (Fig. 31) type link motions, and the Joy (Fig. 36) and Waelschaert radial gears. EB11/SE also depicts the Hackworths (Fig. 33) and Marshalls (Fig. 34) valve gears. One 1887 valve control mechanism is depicted in Alexander (PL79); I believe this is a "link motion."
In the modern Waelschaert gear, the movement of (1) the crosshead, together with that of an "eccentric crank" connected to (2) the main crank pin, serves to move forward and back the valve rod (which directly controls which valve is open). However, the valve rod leads the piston rod.
In the EB11/R table, the driving wheel diameter ranged from 54 to 85 inches. Among Alexander's American locomotives, the range was 30 to 96 inches. In general, the bigger the wheel, the higher the intended operating speed of the locomotive. With typical locomotive designs, and adequate track, maximum speeds (mph) were usually 75-150% of the wheel diameter (inches).
Big wheels also have the advantage of a larger wearing surface (proportional to diameter). So the abrasion by the rail is spread more broadly.
However, if you increase the wheel size, you need to increase the size of the connecting rods, the cylinders, the frames, and so forth. Which means, given size and weight constraints, that much less room and weight allowance for the boiler. (Forney)
The wheel is not a single piece construction. Rather, there is a wheel proper, over which is mounted a metal "tire." This is the "wearing surface" of the wheel, the part that is gradually worn away by the action of the rails.
The tire also includes a flange, a thin, flat, short metal projection. A flanged wheel looks a little bit like a stovepipe hat; the crown is the wheel, and the brim is the flange.
In nineteenth-century America, the tires were made of wrought iron, case-hardened cast iron, or, once the price came down, steel. Steel tires were preferred because they lasted at least five times as long. (White, 175-83).
There are a number of little expedients used to make it easier for the driving wheels to hold onto curved track. One is to put non-driving pilot (leading) wheels in front of them.
Secondly, one or more of the axles may be allowed "sideplay," that is, the ability to shift left or right. The Bavarian Ep 3/6 had an inch or so of sideplay in several of its axles. Side play was even more marked in Baldwin's 1842 flexible-beam engine (Alexander PL14).
Thirdly, the wheels can be tapered. Wheels are slightly conical (standard "taper" is 1 in 20), with the narrowest diameter on the outside. As the train moves onto a curve, the wheels shift outward, so the outer wheel's diameter at the point of contact increases, and that of the inner wheel decreases. That corrects for the curve.
Finally, one or more pairs of driving wheels can be "blind" (flangeless)(Alexander PL20, 83, 84).
Locomotive wheels are mounted on axles; the transmission system turns the axles, which in turn rotate the wheels.
Some of the axles are driven, directly or indirectly, by the engine. Others turn passively as a result of the action of the car on the wheel. If your car has front wheel drive, then the front axle is a driven axle, and the rear one isn't.
Locomotives are described according to a standard wheel configuration nomenclature which, usually, but not always, uses three numbers, like so: X-Y-Z. The X value is the number of leading wheels. These wheels are not driven by the engine, but help to give stability to the ride. They are mounted on what is called a "truck" or "bogie," which can turn if the wheels encounter a curved track. X might be 4 for a passenger locomotive, 2 for a freight locomotive, and 0 for a switching yard locomotive. The American-style four wheeled leading bogie is mentioned in EB11/R.
The Y value is the number of driving wheels. Usually, the main rods directly drive one axle, to which the other driving axles are coupled. The driving wheels transmit the power of the engine to the rail and, by adhering to the rail (if there were no friction, the wheels would just spin in place), create the reactive force which impels the locomotive forward. A freight locomotive will usually have more driving wheels than a passenger locomotive of equal horsepower.
The Z value is the number of trailing wheels. Like the leading wheels, these are unpowered. However, by providing additional support, they permit a locomotive to enjoy a long, wide firebox. It can produce steam at a greater rate, and thus supply more power to the cylinders. Like the leading wheels, the trailing ones are mounted on a rotating truck.
If a train has both a leading and a trailing truck, that means that it can back easily into a curve. This can come in handy on a branch line serving a mining area.
Occasionally, a locomotive has a wheel configuration necessitating more than three numbers. This implies that there is more than one set of coupled driving wheels
For example, instead of a 4-8-4, you could have a 4-8-8-4, in which one pair of cylinders drives four driving axles, and a second pair drives the other four.
The waste steam leaving the cylinders passes through a constrictive blast pipe, and jets out. This creates a partial vacuum in the smoke box, which in turn elicits the draft which fans the flames in the firebox. The smoke box subsequently discharges the waste furnace air and steam through the smoke stack. EB11/R goes into an amazing amount of detail (see Figs. 18-20) as to the design of the smoke box, as well as that of its spark arrester (so the locomotive doesn't set the countryside on fire).
The basic problem with spark arrester design was that to be effective, it had to obstruct the smoke box, which in turn reduced the draft.
Just as the speed (in feet per second) at which you walk is the length of your stride (in feet) times the number of strides you take per second, the speed of a locomotive is the circumference of the wheel times the number of times the wheel turns each second-and it turns a half-turn on each piston stroke. For high speed, you need big wheels or fast-moving pistons.
The maximum speed is that at which the tractive effort exerted by the locomotive is only enough to overcome the movement resistance of the locomotive and its tender alone.
* * *
In 1911 (EB11/R), the following train weights (long tons, ignoring locomotive) and speeds were considered typical:
Coal train (GB), 800-900 tons, 18-22 mph
Goods train (GB), 430 tons, 25-30 mph
Express goods train (GB), 300 tons, 35-40 mph
Mineral and grain trains (US), 2,000-4,000 tons, ~12 mph
Goods train (US), 600-1,800 tons, 15-30 mph (with 40-60 mph bursts)
When the heat of burning coal converts water into steam, it's like putting money into a bank. The compressed steam stores energy, just like a bank stores money. When the engine uses that steam to move the pistons and, ultimately, the wheels, it's like withdrawing funds from your account. Some of the stored energy is used to do work, and the rest is lost.
Power is the rate at which energy is produced, converted, stored or used. If the engine is using "steam" energy faster than the boiler is producing it, then eventually it will use up whatever reserve the boiler had built up previously, and the locomotive will literally "run out of steam," and come to a stop. There is no overdrawing the energy account!
The maximum sustainable horsepower is the product of the combustion rate (the number of pounds of coal burned per hour), the energy value of the coal (BTUs per pound), the combined thermal efficiency of the boiler and engine (typically 0.06), and a conversion factor (0.00039)(EB11/R, 843, 847). The combustion rate is the product of the number of pounds of coal burned per hour per square foot of grate), and the square footage of the grate.
Now power also equals force times speed. The power (in horsepower) corresponding to a particular tractive force at a particular speed is
Speed (mph) X tractive force (pounds) / 375
The tractive force when you start up the engine is determined by the formulae we looked at earlier. Initially, as you increase the speed, traction remains constant, so the power applied to the wheels increases.
Eventually, you reach the critical speed at which the rate at which the engine consumes energy equals the maximum rate at which the boiler can deliver energy to the cylinder. The latter determines the maximum sustainable power exercised by the engine at the rail.
Above the critical speed, the sustainable power is constant, so the sustainable tractive force must decline as the speed increases. (Krug)
* * *
A parallel equation dictates the horsepower required to move the train against level, grade and curve resistance; we just set the tractive force equal to the total resistance. A further complication is that, as speed increases, so does resistance. So doubling the speed could double the required tractive force and thus quadruple the required horsepower (Clarke, 127).
Just as we can construct an energy balance for the locomotive, we can do the same for the steam which carries that energy. We multiply the combustion rate by the evaporation ratio (pounds of water evaporated by each pound of coal burnt), to get a water vapor production rate in pounds per hour. And we multiply the steam capacity of the cylinders by the piston stroke rate, and the density of the steam at cylinder pressure, to get the steam demand rate in the same units. For a given water vapor production rate, there will be an equilibrium speed at which steam demand equals steam production.
Assuming that the fuel and the grate are satisfactory, the ability of the boiler to properly supply the engine with steam can be judged by looking at the ratio of the "rated tractive force" (pounds) to the total heating area of the boiler (square feet). According to the Baldwin Locomotive Company, this ratio is 8-16 for the most common locomotive types, and is 10 for the "4-4-0." The lower the ratio, the easier it is for the locomotive to sustain that tractive force.
The ratio can be calculated for fourteen locomotives in EB11/R, and is 4.2-17.5.
The nature of the coal available as fuel has an impact on the design of the firebox and, of course, on the overall performance of the boiler. (GW15, Sanderson, Robinson).
There are three basic types of coal. In order of increasing energy content, they are lignite ("brown coal," 9-17,000,000 BTU/ton), bituminous coal ("soft coal," 21-30,000,000 BTU/ton), and anthracite ("hard coal," 22-28,000,000 BTU/ton)(Wikipedia, "Coal").
All of the coal in Grantville is bituminous. U.S. railroads generally preferred low water, low ash, low sulphur content bituminous coal; it may be advantageous to test coals from different mines and seams to find the best "steaming coals."
While anthracite burns smokelessly, it combusts slowly and requires a firebox several times larger than for a bituminous coal burner to achieve the same heat production rate.
Coke (25,000,000 BTU/ton) is bituminous coal which has been processed to eliminate the volatiles. It was used on British locomotives because it burns without smoke, but it was too expensive for acceptance by American railroads.
We have to analyze what we need the USE locomotive to do. What loads must it pull, over what speeds, and in spite of what grades? Freight locomotive designs tend to emphasize tractive force over speed; passenger engines must reverse these priorities. A general purpose locomotive—and that is what we probably want to build first—is a compromise.
We also must consider what limitations on locomotive weight and size are imposed by the quality of the track, the sharpness of the curves, the load capacity of any bridges it crosses, and the clearances of those bridges and other structures.
Of course, since we are starting from scratch, our locomotive design will affect the planning of the line. The first line is likely to be from Grantville to Magdeburg. This is not a mountain region, and the line can follow river valleys to minimize grades. So I think it reasonable to assume a maximum grade in the 1-3% range.
My recommendation is that the USE first attempt to build a 4-4-0 rod locomotive. This "American" wheel arrangement was extremely successful as a general purpose engine. Even in 1884, 60% of the new engines were 4-4-0's, although that dropped to 14% in 1891 (White)
Alexander's Iron Horses has descriptions of a large number of 4-4-0's, starting with the 1837 Hercules (PL8), and ending with the 1893 locomotive used by the CB&Q (PL93). The first 4-4-0's obviously were able to cope with the light rails of the late 1830s.
My one reservation about using 4-4-0's is that our tractive force may be weight-limited if our rails are light. This could be a problem if the track is steeply graded. With forty pound steel rails (allowable wheel weight of 4-6 tons), the maximum weight on the drivers would be 16-24 tons, and maximum tractive force would be one-quarter that (4-6 tons). That in turn limits the maximum total train weight to 533-796 tons on level track or 107-161 tons on a 3% grade.
My suspicion is that the USE will not have great difficulty in achieving "standard" wheel diameters and cylinder dimensions, but that boiler pressure will be more problematic. With sixty inch wheels, and 16X24 cylinders, the rated traction is 87 times the boiler pressure (p.s.i.) So, to achieve six tons of traction at the rail, we need 138 p.s.i.
If that isn't enough pulling power to satisfy USE engineers, we can instead design a 4-6-0 "Ten Wheeler" (Alexander PL30), which, with the same driving wheel load, could have 12,000-18,000 pounds traction, and could handle 800-1,200 tons level or 160-240 on the 3%. We might scale up to 20X30 cylinders, allowing us to make do with only 106 p.s.i. But the larger reciprocating masses will increase hammerblow on the rails, especially at high speed.
* * *
After that we need to think about constructing more specialized locomotives. We will probably be more concerned about moving goods. Hence, the next locomotive might be a 2-8-0, which is the "Consolidation" type, first in 1875 to haul heavy freight. The first engine with this configuration in the Alexander book is the 1879 Uncle Dick (PL70), and the last one is the 1900 Number 1621 (PL96). An alternative is the 2-8-2 "Mikado," which replaced the "Consolidation" in the 1920s. If an "eight coupled" loco is too heavy for the relatively flimsy tracks we have in service, we could construct a "Decapod" 2-10-0 (the driving weight is spread over five axles instead of four) or a "Santa Fe" 2-10-2 (the trailing axle permits a larger firebox, hence more steaming capacity).
For passenger service, the 4-4-0 was eventually replaced by the more powerful 4-6-0. As a second generation general purpose engine, we might consider a "Northern" 4-8-4 (Sinclair, 681).
For switching purposes, the best choice may be the 0-6-0. An 0-4-0 could be used for light switching at an industrial site. For heavy switching, as in a hump yard, one might step up to a 0-8-0.
One of the maddening things about locomotive design is how interrelated all the components are. It means that one which works fine in isolation may work poorly when it is in a locomotive which is actually running over track.
It may be tempting to take advantage of late twentieth-century knowledge and technology and design a "new" steam locomotive. However, if it fails, then you may not be sure whether it is because of the novel features, or because you overlooked something more basic. Hence, it may be prudent to first build a conventional nineteenth-century locomotive. In other words, duplicate, then innovate.
The final engineering design step is the "detailed design." That is the blueprinting stage, and specifies, e.g., whether the boiler plates are lap welded or riveted.
After design, you build and test a prototype. If it works, you move on to the production phase. If it doesn't, you rethink the design.
Of course, our heroes are starting almost from scratch here. They not only have to do the system-level (locomotive) design, but also designs for virtually all of its components, even such seemingly simple ones as steam pressure gauges.
* * *
I would strongly advise USE engineers to first build a reduced-scale steam locomotive, which would run on a scaled-down experimental track, first. That would allow them to discover some of the inevitable mistakes after only a limited investment in valuable materials. And lives.
What I have in mind for initial prototyping is what model railroaders would call a "garden railroad" with "small-scale live steam." This is most commonly operated on #1 gauge (45 mm) track. These have working boilers and engines. However, they burn either alcohol or butane, not coal. (Miller) It is possible that one of the model railroaders in Grantville already has one of these setups.
The garden railroad will be helpful not only for testing the engine design, but also for showing down-time smiths (and investors!) what we are working toward.
The next step up might be a "ride-aboard," coal-burning locomotive. This still need not be a full-size machine; think amusement park ride. If it is built to two foot gauge, it can use the TacRail track.
Finally, we build the real thing. Expect surprises.
On "rod" locomotives, there is a limit to how much wheel size can be reduced. The stroke length is equal to twice the crank radius, and the latter is necessarily smaller than the diameter of the driving wheel. That implies that at some point, driving wheels cannot be made any smaller without reducing the stroke length, which would defeat the purpose of increasing the tractive force.
The solution to this conundrum is a geared locomotive, which uses the piston to drive a geartrain. If the piston applies a torque to a small gear, whose teeth engage a larger one, then the larger gear experiences a higher torque, but turns more slowly. (This is what is literally meant by "gearing down.") You get even more tractive force, at the expense of speed. A geared locomotive with forty inch diameter wheels, and a 2:1 gear down, will have the tractive force of an equivalent rod locomotive with twenty inch wheels.
But wait. What about the adhesion limit on tractive force? A rod locomotive applies a strongly pulsating torque, and it is its maximum torque which determines the adhesion limit. A geared locomotive applies an almost constant torque, and thus it has a higher effective coefficient of adhesion. Since geared locomotives are intended to operate at low speeds, they are designed so that all of their wheels are drivers, thus maximizing the adhesion.
Because gears replace most of the rods, there is less mass flying about. This reduces the hammer on the rails, and hence geared locomotives can be used on lighter track. It is safe to assume that the up-timers know something about geared locomotives. Grid character "Monty" Szymanski, Sr. overhauled locomotives of the Cass Valley Scenic Raiload, which operates geared "Shays." There are also photos of Shays in two books in the public library (Ellis, 109; Rails West, 12). The documented sources don't explain the differences between the Shay and the other common geared locomotives (Climax, Heisler, etc.)
Some knowledgeable members of Baen's Bar have strongly urged that the first USE steam locomotive should be geared.
I disagree. It is important to remember that in OTL, geared locomotives occupied an important but small niche (perhaps 3,000 were built). Geared locomotives were developed in the late 1800s to meet the needs of the logging industry for a high traction engine that could ride on temporary tracks (sometimes mere logs) which were curvy, steep and rough. What about the mining industry? Geared locomotives were used if the branch serving the mine had a steep enough grade. However, mining companies typically planned for longer-term operations than loggers. They expected to work the mine for years, and therefore were usually willing to go to some trouble to reduce the grade of the track. In contrast, nineteenth-century loggers expected to "saw and scoot," so they tolerated a steep route.
Now, I just don't see there being a great deal of logging activity in early seventeenth Germany. And, to service mines, I expect that USE railroad entrepreneurs are going to cut-and-fill as needed to provide a reasonably graded roadbed for permanent track, just as was done in OTL. According to a Mannington Public Library book, in Minnesota, the Shays were used on logging railroads, but iron ore was transported on 4-4-0's. (Rails West, 12, 14).
So geared locomotives service a niche which probably won't exist. But it is possible that they will be used on a rough-and-ready narrow gauge rail connection into the Thueringerwald hill country, which is a source of both ore and timber.
Geared locomotives are not well suited to hauling passenger and perishable goods trains. They had a top speed of 10-15 mph, which is inferior to even an 1830 0-4-0 rod locomotive (Alexander PL42; 21 mph).
But will the down-timers care? After all, they are accustomed to the pace of draft horses, mules and oxen.
In OTL, without knowing that they were even possible, investors, shippers and passengers clamored almost from the beginning for higher speed trains. In 1831, the B&O held a contest whose entries were required to draw 15 tons at 15 mph over level track—already in excess of what horses could do.
Moreover, in this timeline, people will know what they are missing. They can read in the library that an 1893 4-4-0 supposedly set a speed record of 112.5 mph (Alexander PL85). (Its true speed was probably 82 mph, but steam locomotives can exceed 120 mph.) Down-timers can see high speed movement on the occasions when a modern automobile barreling down the asphalt roads of Grantville.
So, thanks to popular demand, the main lines, at least, will be dominated by fast-moving rod locomotives.
Compound Expansion. The steam can be expanded in two or more stages. Typically, compound locomotives have two pairs of cylinders, a high pressure pair and a low pressure one. The exhaust steam from the former is directed into the latter, and each pair of cylinders drives one set of driving axles.
Theoretically, compound working increases thermal efficiency (EB11/R). However, in actual practice, "it was discredited for reasons of higher first cost and troublesome maintenance problems." (EA)
* * *
Articulation. The locomotive data table makes reference to "articulated engines." These have essentially two separate but flexibly connected engine-and-wheel sections, each mounted on a bogie. This is essentially a way of having the advantages of a long wheelbase (high tractive effort with low load per axle) without the disadvantage (being "curve-shy"). EA says that articulation "made possible machines of extraordinary size and length." The modern EB is also approving, and mentions the 600 ton articulated "Big Boy" 4-8-8-4 (135,400 pounds traction; over 6,000 hp at 75 mph).
In the original "Mallet" configuration, the boiler was rigidly attached to the rear "power bogie," and the front power bogie pivoted on the rear one. In the "Meyer" configuration, both power bogies were connected by pivots to the overhead boiler. And in the "Garratt" configuration, the boiler was in-between, rather than above, the power bogies. (Self; *Gordon 97).
Superheating. EB11/R commented that the "application of superheaters to locomotive work" is "exceedingly promising." The steam which is initially generated by the boiler is what is called "wet steam," because it contains water droplets as well as water vapor. If more heat is applied, the temperature remains constant until the water is all evaporated, and then you have dry steam. And if you heat that even more, the temperature rises, and you have superheated steam.
It has two advantages. First, it avoids wasting water by delivering it to the cylinders in liquid form. (It is only the compressed water vapor which, by expanding, moves the pistons.) Secondly, superheated steam occupies a greater volume than wet steam of the same pressure. That means that you can use bigger cylinders, which in turn allows you to either increase power, or reduce the boiler pressure (and fuel consumption). (Netherwood)
EA says that superheating increased horsepower and reduced fuel costs by about 25%. Unfortunately, EB11/R doesn't explain how superheating was carried out, and EA contents itself with a cryptic, "this mechanism returned the steam through the fire tubes of the boiler for reheating."
In a fire tube superheater, the upper rows of fire (hot air) tubes are made large in diameter. The wet steam from the steam dome is fed into narrow tubes which enter the top row of superheater tubes from the smoke box end, make a U-turn at the firebox end, and exit. They may then enter and leave a second or third row of superheater tubes the same way before delivering the now superheated steam to the steam chest. (GW10).
For superheating to be practical, the cylinder and boiler must be able to resist the corrosive effect of superheated steam, and the cylinder lubricants must remain functional. Heavy mineral oils (in short supply in Grantville) were needed for lubrication (EB11/SE 829). The necessary advances in the iron and oil industries will take some years, which is why I see superheating as a second generation feature.
Headlights, Bells and Whistles. These made travel, especially at night, safer.
* * *
Cowcatcher. Cheaper than fencing the whole line, and helps to clear track of debris or light snow.
* * *
Sanders. These were used to release sand in front of the wheels, to increase adhesion (especially when trying to start a train). EB11/R (p. 646) says that the sand is blown onto the rail by a steam jet. A sand box and sand pipe are shown by Alexander PL79 for a 1887 2-8-0 class R; here, the sand seems to just drop down. Sanding increases adhesion to about one-third (Clarke, 121).
* * *
Water quality. Minerals in the water can deposit on the boiler pipes. This fouling slows heat transfer and can result in tube failure. Impure water may also foam up if the boiler suddenly loses steam, intruding into the cylinders and damaging them (White, GW14). The solution is to purify or treat the water, either before loading it in the tender, or with an on-board system. Or you can "blow down" the boiler regularly, to clean out the scale.
* * *
Tenders. Fuel and water can be carried behind the locomotive in a "tender." A typical one might carry 3,000 to 7,000 gallons of water, and 5 to 10 tons of coal. (Connor, 91).
Water was originally conveyed by leather or canvas hoses; these were replaced by rubber ones in the 1850s. (White 223).
* * *
Water injector. Alexander PL79 shows the use of a steam jet (Giffard, 1859) to force water into the boiler. Previously, axle-driven pumps were used (Nock/RE, 150; Clarke, 116).
* * *
Feedwater heater. Exhaust steam may be used to warm the water before it enters the boiler. (NOCK/RE, 150; EB11/SE," 841).
* * *
Mechanical stokers. A fireman can shovel only 2-2.5 tons an hour; this limited steaming capacity. Mechanical stokers could handle ten times as much coal. (Sinclair, 673; Gordon, 48; EB11/B 150). The EA article shows one type, a screw conveyor for moving coal from the tender to the grate. The fireman could use steam jets to redistribute the coal on the grate.
We will need mechanical stokers only after we are building locomotives which are large enough to overburden a fireman. Even then, since labor is cheap, we might want to first experiment with a two stoker firebox.
Integral tank. Instead of using a tender, the locomotive may carry its own water and coal. Such a "tank locomotive" is more efficient (the stored water is preheated as a result of proximity to the boiler), able to move in either direction (a tender can't be safely pushed backward, at least at high speed), more compact than the engine-and-tender combination, and capable of exerting a greater tractive force (because the weight of the fuel and water contributes to the weight on the driving wheels).
A "tender locomotive" design is better if the locomotive must go a long distance without refueling, because the storage capacity of a separate tender is greater than that of a "tank locomotive."
Suspension Systems. In the first locomotives, the driving axles were mounted in a rigid frame. Alexander describes an improvement; in the 1837 Hercules (PL8), the driving axles were placed in a truck of their own, the center of which was connected to the main frame of the locomotive.
In the bogie holding the leading wheels of the 1842 Mercury (PL13) the axle boxes hung from springs, which dangled from a bolster, which in turn was attached underneath the front of the engine. Apparently, these axles could move up-and-down if the track was uneven. Alexander says that the driving wheels were also equalized, without providing details.
Ellis (113) also discusses bogie design, and makes the key point that it is desirable to provide a "three point suspension." How is this accomplished? Ellis doesn't say. If there are two driving axles, then the springs on each left side are connected by one equalizing lever, and those on the right side by another. These levers are in turn connected to the bottom of the locomotive frame, one on each side. The leading bogie, on the other hand, was centrally connected to the bottom of the locomotive. The three connections form a triangle, which makes it easier for the locomotive to "stand" on uneven road. (Clarke, 4, 114).
Insulated cylinders. Some steam is lost through condensation in the relatively cool cylinders. White (207) says that "the insulation of cylinders might appear to be obvious for reasons of thermal economy, yet, from existing evidence, it was not employed regularly until the 1850's." This is an example of one of the hundreds of fine details of locomotive design which are unlikely to be spelled out in the books available in Grantville.
In Action Comic #1, published in 1938, readers were told that the new hero, Superman, "could run faster than an express train" (i.e., more than 80 mph). Later, he was described as "more powerful than a locomotive" (which by then could muster 3,000 hp). The point of mentioning all this is not, of course, to quantify the superpowers of Superman, but to observe that the locomotive was thought to epitomize both speed and power.
With its ability to haul great loads at high speeds, across vast distances, the USE locomotive will be, in the words of Jessamyn West, "a big iron needle stitching the country together."
*Alexander, Iron Horses: American Locomotives 1829-1850 (1941)(all refs are to plate #).
*[EA] "Railroads," Encyclopedia Americana
*[EB11] Encyclopedia Britannica, 11th ed. (1911), [EB11/R] "Railways," [EB11/B] "Boiler," [EB11/SE] "Steam Engine;" see also "Rolling Mills," "Brake," "Traction," "Coal," "Fuel," etc.
*Ellis, Pictorial Encyclopedia of Railways
*Gordon, Trains: An Illustrated History of Locomotive Development
Armstrong, The Railroad—What It Is, What It Does: The Introduction to Railroading (1978).
Bruce, The Steam Locomotive in America: Its Development in the Twentieth Century (1952)
Clarke, et al., The American Railway: Its Construction, Development, Management and Appliances (1972)(reprint of 1897 edition)
[NOCK/RE] Nock, Encyclopedia of Railroads (1977).
Sinclair, Development of the Locomotive Engine (1970)(reprint of 1907 edition with additional material)
White, American Locomotives, An Engineering History, 1830-1880 (1968).
Connor, Military Railways (1917), available online at http://www.trainweb.org/girr/military_railways/military_railways.html
Krug, "Steam versus Diesel," http://www.railway-technical.com/st-vs-de.html
Ludy, Locomotive Boilers and Engines: A Practical Treatise on Locomotive Boiler and Engine Design, Construction, and Operation (1920), available online at http://www.sdrm.org/faqs/boilers/index.html
Self, "Balanced Locomotives,"
http://www.dself.dsl.pipex.com/MUSEUM/LOCOLOCO/balanced/balanced.htm and "How To Articulate Locomotive," .../articult/articult.htm
Baldwin, "Calculations, Delineations, Classifications,"
http://www.catskillarchive.com/rrextra/blclas.Html
Forney, "The Limitations of Fast Running,"
http://www.catskillarchive.com/rrextra/stspdlo.Html
[WLW] "Whitcomb Locomotive Works,"
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[GW] Great Western Archive,www.greatwestern.org.uk
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http://www.grandscales.com/downloads/Hand%20Firing%20of%20Locos.pdf
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(*documented source)