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.
Geared Locomotives
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.
Second Generation Locomotive Concepts
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.
Other Locomotive Design Features
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.
Conclusion
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."
Select Bibliography
*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,"
Ludy, Locomotive Boilers and Engines: A Practical Treatise on Locomotive Boiler and Engine Design, Construction, and Operation (1920), available online at
Self, "Balanced Locomotives,"
http://www.dself.dsl.pipex.com/MUSEUM/LOCOLOCO/balanced/balanced.htm and "Ho
w To Articulate Locomotive," .../articult/articult.htm
Baldwin, "Calculations, Delineations, Classifications,"
Forney, "The Limitations of Fast Running,"
[WLW] "Whitcomb Locomotive Works,"
http://www.absoluteastronomy.com/encyclopedia/w/wh/whitcomb_locomotive_works.htm
Netherwood, "Operation of Locomotive Type Boilers and Associated Fittings" (2001)
[GW] Great Western Archive,www.greatwestern.org.uk
Robinson and Associates, "Hand Firing of Locomotives,"
http://www.grandscales.com/downloads/Hand%20Firing%20of%20Locos.pdf
Sanderson, "Coal, Combustion and Front End Design,"
* * *
Cooper, "Locomotive Addendum," www.1632.org
(*documented source)
Images
Note from Editor:
There are various images, mostly portraits from the time, which illustrate different aspects of the 1632 universe. In the first issue of the Grantville Gazette, I included those with the volume itself. Since that created downloading problems for some people, however, I've separated all the images and they will be maintained and expanded on their own schedule.
If you're interested, you can look at the images and my accompanying commentary at no extra cost. They are set up in the Baen Free Library. You can find them as follows:
1) Go to www.baen.com