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This page contains information intended to help acquaint laymen and neophytes with the basic terminology and practices of the model railroading hobby. It is by no means a detailed "how-to" course, but only an explanation of the basic aspects of the hobby, what is meant by certain terms, and the rationale behind model-building and operation.
Frequently Misused or Misunderstood Terms
meet: A meet is a maneuver in which one train encounters and passes another train headed in the opposite direction. (Compare: pass.)
pass: Pass has a couple of meanings:
1. A pass is a maneuver in which one train overtakes and passes another train moving in the same direction. (Compare: meet.)
2. A pass is a card issued by a railroad authorizing someone to ride as a passenger on the railroad, usually for a single trip or a limited series of trips, either in performing a service for the railroad or as a guest of the railroad.prototype: With respect to modeling, a prototype is a real-world object or process which is replicated, usually in miniature form, with varying degrees of fidelity to the appearance and functionality of the original, depending on the objective. Examples of modeling prototypes include vehicles, rights of way, structures, scenery, control circuitry, operation schedules and timetables, communications and dispatching procedures.
train: A train is any coupled assemblage of motive power and rolling stock which has orders authorizing its operation on mainline or branch-line trackage. A car or group of cars in a switching yard is not a train, and a locomotive without train orders is not a train.
train set: There are two appropriate applications of this term, and one common misapplication of it.
1. Referring to prototype and model railroads, a train set is a group of matched cars used as a unit in a specific form of service. Examples are the Burlington's early streamlined Zephyr, the five-car streamlined heavyweight train sets of B&O's Cincinnatian, GM's Aerotrain, New York Central's Xplorer, and the multi-car consist of the American Freedom Train. Train sets of a different sort are used in freight service, such as unit coal trains, whose couplers are designed to pivot for sequential rotary car-dumping of the entire train, car by car, without uncoupling..
2. Referring to toy trains, a train set is a boxed group of a single manufacturer's products, typically consisting of a locomotive, a few cars, and a circle of track, designed and intended primarily for use by children, but sometimes collected by adults.
3. Misapplication: A model railroad is not a "train set." Model railroads typically operate several trains, the number and content of which vary from hour to hour as individual cars are collected, classified, coupled together, and hauled to an assigned destination, where the process is reversed, and cars are distributed to industries and transfer points—just as on a real railroad. A model railroad typically takes form as a gradual accretion and adaptation of many materials and pieces of equipment from a variety of sources; it is not a "set" in any sense of the word. If you prefer a shorter term than "model railroad," "layout" or "pike" will usually suffice.
Gauge or Scale?
What do the terms gauge and scale mean? Is there a difference? What's a "ho" train?
Gauge: In railroad terms, gauge is simply the distance between the inside edges of the tops of the track's two running rails. Obviously, this distance must remain constant throughout any rail system, so as to match the distance between the wheels on each axle of every car and locomotive that rolls on the track. In Europe, North America, and much of the rest of the industrialized world, the standard gauge for major railroads is 4 feet, 8 1/2 inches (56.5 inches, or 143.5 centimeters). Some low-budget rail operations operate instead on narrow gauge, typically 3-foot or 1-meter gauges, but as narrow as 2-foot gauge in a few cases. Narrow gauge both requires less real estate and permits tighter turns, and so is well suited to logging and mining operations in mountainous territory, as well as streetcar service. On the other hand, a few systems, such as the Trans-Siberian Railway, went the other way, to a broad gauge of 5 feet or so. To see how gauge translates into terms of toy and model railroads, however, we first need to consider the issue of scale.
Scale: When we create a miniature reproduction of a real-world object, such as a locomotive, we reduce all dimensions of the original (called the prototype) by some fixed proportion (the proportion of the prototype itself being 1:1). For example, we might decide to build a miniature of such a size that each inch of length on the model represents a foot of length on the prototype. In that case, the ratio is 1:12, since there are 12 inches in 1 foot. If we do this reduction precisely for every dimension of every part on the real locomotive, then our model should look exactly like the prototype, only one twelfth the actual size. If the prototype locomotive we're modeling is 50 feet long and 12 feet high, then our model will be 50 inches long and 12 inches high—uncomfortably large for indoor display, but usable outdoors in a large back yard. Miniature railroads don't become convenient for indoor use until the scale-to-prototype ratio gets down to the range of 1:24 (1/2 inch represents 1 foot) or below.
Gauge in Scale: Now, suppose we've created a model in a scale of 1:32—that's 3/8" on the model representing 1' on the prototype. And suppose we have the clever notion of turning it into an operating model, by installing an electric motor and a few gears in it. If we want this scale miniature to operate, and to do so reliably, then we must also create miniature track, reduced from prototype dimensions by exactly the same proportion. If we reduce the standard track gauge of 56.5 inches by a ratio of 1:32, the railheads of our miniature track will be 1.77 inches apart. For all practical purposes, we can call it 1-3/4 inches, and no one will notice the difference. And that's precisely what early electric train manufacturers did, dubbing the 1-3/4" rail spacing "#1 gauge."
Popular Scales: Later on, a scale of 1:48 (1/4 inch to the foot) was introduced. Unfortunately, this would have translated into a track gauge of 1.177 inches, and at the time no one wanted to bother with special measurements for a mere "toy." So a "close enough" track gauge of 1-1/4 inches was settled upon, and dubbed "#0 (zero) gauge." Number-0 gauge became the favorite of toymakers and consumers for many years, from the 1930s into the 1960s. As a result, the popular pronunciation of #0 gauge (zero gauge) soon became the simpler "O gauge" ("oh" gauge), and the official designation eventually followed suit.
O gauge turned out to be a convenient size for home modelers to work in, so early precision model railroading evolved around 1:48 scale, with wheel and track gauge adjusted outward to the prevailing toy standard of 1.25 inches (rather than try to buck established tradition). Precision models built to 1:48 ratio were dubbed "O scale," distinguishing them from their O gauge toy counterparts, whose modeling standards remained relatively crude.
By the end of World War II, miniaturization and precision machining had advanced to the stage that motors and mechanisms could fit into models about half the size of O scale. A new scale called "HO" (signifying "half-0," and pronounced "aitch-oh"—not "ho") was developed, allowing more complex layouts to be built in the same space. HO's scale ratio is a curious hybrid, with 3.5 millimeters on the model representing 1 foot on the prototype, which translates to a ratio of 1:87. For this new scale, developers determined to reduce the prototype track gauge by the same proportion as the rest of the model, to 0.650 inches for standard gauge equipment and track.
As miniaturization evolved further, an even smaller scale, "N," about half the size of HO, with a reduction ratio of 1:160 and a standard track gauge of 0.353 inches, became popular.
Other Scales: O, HO, and N are the most popular scales today; however there are also in-between scales, such as 1:64 "S" (3/16" = 1'), 1:120 "TT" (1/10" = 1'), and 1:220 "Z" (0.055" = 1'), which attract niche followings. There are hobbyists currently active in S and Z scales, but TT lost popularity after the introduction of N, and is seldom seen today.
| Visual Comparison of Popular Indoor Model Railroad Scales | |||||
| O | S | HO | TT | N | Z |
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| O 1:48 1/4" = 1' |
S 1:64 3/16" = 1' |
HO 1:87 3.5 mm. (0.138") = 1' |
TT 1:120 1/10" = 1' |
N 1:160 0.075" = 1' |
Z 1:220 0.055" = 1' |
At the larger end of the spectrum, G gauge is about the same size as the old #1 gauge, and suitable for outdoor use. G gauge contrasts with O and HO scales, in that it uses the same track rail spacing (45 millimeters) for both standard- and narrow-gauge equipment. Standard-gauge rolling stock is simply reduced more than narrow-gauge equipment, in order to keep the wheels the same actual distance apart. The 45-mm span between the rails thus translates to a 1:32 reduction of prototype 56.5" standard gauge, a 1:22 reduction of European prototype 1-meter narrow gauge, or a 1:20.3 reduction of American prototype 36" narrow gauge. Since G's scale ratio varies but its track gauge doesn't, it's properly referred to as "G gauge," not "G scale."
Narrow-Gauge Modeling: In each of the larger scales, it's feasible to model narrow-gauge operations (3-foot being a popular prototype gauge), such that the model track gauge is reduced correspondingly. In HOn3 (3-foot narrow gauge modeled in 1:87 scale), track rails are spaced 0.414 actual inches (36 scale inches) apart, rather than the standard-gauge HO's 0.650 inches. Operations get really interesting here, where narrow and standard gauge tracks intersect and intermingle!
Scale Speed: Most model railroaders prefer to operate their equipment at what's called "scale speed." Consider that a real train traveling at 60 miles per hour is doing "a mile a minute." That is, it moves 5,280 feet in one minute, or one sixtieth of that—88 feet—in one second. For modeling purposes, we reduce distance traveled by the very same reduction ratio that determines the size of our model equipment, i.e., 1:48 in O, 1:87 in HO, 1:160 in N, and so forth. Using HO (1:87) scale as an example, a scale mile is 5,280' / 87, or 60.79 actual feet, or 60 feet, 8 1/4 inches. So a 1:87 model train that travels 60.79 actual feet in one minute is traveling at a speed of 1 scale mile per minute, or 60 scale miles per hour, and will cover an actual distance of just over one foot (88' / 87) in one second. A 1:87 model train traveling at half that speed, 30 scale mph, will move half those actual distances in the same time interval, i.e., 30' 4-1/8" per minute, or just over 6 inches per second.
When considering prototype practice, 60 mph was a typical cruising speed for mainline passenger trains in the 1950s; 40 mph (8.1 inches per second in HO) was typical for freight operations; and a long drag ascending a mountain grade might manage only 15 mph (3.3 inches per second in HO) or less. Now, to people accustomed to watching toy trains whiz around little loops and figure-eights of track at scale speeds of 100-200 mph, even 60 scale mph might seem painfully slow. But when you get your full-scale eyeball down to a scale eye-level at trackside, it actually looks much more like the real thing. And that's the goal of modeling.
Model or Toy?
Model railroaders often get miffed if people refer to their expensive and intricate treasures as "toys," to their magnificent empire as "a train set," or to their hobby as "playing with trains." The unenlightened observer, seeing a miniature replica of a real object, automatically thinks "toy." But there is a distinction between toy and model, though in some cases it's hard to know exactly where to draw the line.
In general, toys are intended as children's playthings, whereas models are accurately detailed representations of a prototype. Toys thus tend to sacrifice looks for durability, while models tend to be relatively fragile but far more realistic. In the case of operating models, such as remote-control miniature vehicles, this durability-looks-functionality trade-off varies over a considerable range. A crude toy could never be confused with the real thing, whereas a fine-scale model, photographed from an appropriate "scale eye-level" position with a wide-angle lens, might easily be mistaken for its real-world prototype.
"Scale" models adhere to a strict ratio that maintains proportion. In HO scale, that ratio is defined by the specification that each 3.5 millimeters (about 0.138 inches) on the model represents exactly one foot on the prototype. This specification produces a ratio very close to 1:87. Creating a miniature representation of any large object involves reducing any already small parts to extremely fragile dimensions, and thus entails a certain degree of trade-off between durability and accuracy. Toys maximize durability by sacrificing accuracy, while in models the compromise is in the other direction. |
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Here we compare two molded-styrene HO box cars of similar dimensions. The scale and overall proportion of both cars is about the same; the devil is in the details. Note that, on the toy car on the left, the end-rib design is not prototypic, featuring only seven full-width ribs, whereas the model on the right has the full nine-rib pattern of the prototype car. The brake wheel of the toy is a crudely embossed disk, while on the model it is a fully formed wheel with individual spokes. Although the plastic corner steps on the model are somewhat oversize (to resist breakage), the toy has none at all. (Click on the photo to enlarge.) |
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Major subassemblies of the toy car are molded as a single piece. The roof-walk and its end brackets are cast into the roof itself, and the joint between roof and body is crude. Grab irons, side rivets, and door guides are grossly oversize, and the door itself is not a prototypical design. The peculiar side "seams," mysteriously interrupted midway up the car side, don't correspond to any sensible freight car construction practice. The railroad herald (emblem) near the far end of the car is a stick-on paper print. The car number, "514," is simply the toy manufacturer's item number, not the number of a prototype Seaboard car. (Click on the photo to enlarge.) |
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Major components of the model car are created separately and fitted together, thus giving the appearance of a real car similarly constructed. Rather than being embedded in the roof as on the toy car, the roof walk "floats" a few scale inches above the roof on support brackets. The door guides, though slightly oversize for functionality, are reasonably close to prototype dimensions, and the door itself has simulated roller brackets attached to its lower edge. On the car's side, floor-to-roof rivet patterns give the appearance of sheet metal panels secured to interior framing, per prototype practice. All lettering and graphics are applied directly to the car body by means of printing, decals, or dry transfers, and the car number corresponds to that on the MP prototype. (Click on the photo to enlarge.) |
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Like the roof, the underside of the toy car is cast in a single piece. The major brake components are crudely represented, and there's no brake rigging or plumbing. (Click on the photo to enlarge.) |
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The underside of the model car is built up of several well detailed parts and assemblies. The air-brake components, rigging, and plumbing are clearly defined and positioned as on the prototype. (Click on the photo to enlarge.) |
The cars compared here are a low-grade toy (A. C. Gilbert) and a budget model (Train Miniatures). Were we to compare a crude toy with a fine-scale model, the differences would be even more striking. The crude toy would be seen to lack most detail and resemble the model in general shape only. The fine-scale model would have even more and finer (and thus more fragile) detail, including separately applied steps, grab irons, ladders, brackets, and handbrake linkage, with scale-size rivets and bolt heads. |
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But between the extremes, the distinction can get quite fuzzy. My own criteria for "toy" and "model" status reflect the level of resemblance of a miniature to its prototype. Specifics of these criteria, with respect to railroad miniatures, include the following:
- crude toy: little sense of scale and proportion; poor fidelity to prototype (if any); no significant detailing; just a step up from a toddler's pull-toy (e.g., 1930s Marx, Lionel, or American Flyer "tinplate")
- low-grade toy: roughly resembles prototype, but proportion inconsistent; many details absent or incorrect (e.g., 1950s American Flyer S- and HO-gauge)
- medium-grade toy: fair fidelity to prototype; includes basic details, but some simplified or oversize (e.g., 1960s Rivarossi and Mantua)
- high-grade toy: good proportion and fidelity to prototype; could pass for model with some addition or modification of details (e.g., 1960s Varney; 1980s Rivarossi, Bachmann)
- budget model: excellent scale and proportion; high fidelity to general prototype; some fine details missing (e.g., Athearn, Roundhouse, Bachman/Walthers Proto-1000)
- precision model: excellent scale and proportion; high fidelity to specific prototype; fine details, including some often hidden (i.e., underbody or interior) details, accurately reproduced (e.g., Camargo, Walthers Proto-2000)
- fine-scale model: exact scale and proportion; near-microscopic accuracy of exterior and interior detail, including running gear and other operationally functioning components.
The toy-model distinction carries over to layout design and operation as well. Toys are typically run continuously around a loop at breakneck speed. In contrast, die-hard model enthusiasts prefer to operate trains point-to-point at scale speed on a timetable schedule, with stops and switching moves to serve depots and industries along the way. Of course, there are many gradations in between, allowing operation to be tailored to personal preferences. With appropriate controls and reliable automatic couplers, toy equipment can be operated in prototype fashion (indeed, this was common in the early days of model railroading, when good models were hard to come by), and scale models can be run dizzily around toy-train loops and figure-eights, provided the curves aren't too sharp.
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Toy-to-Model Conversion Not all toys are suitable for conversion to models, but there are some that can be refined by various modifications to resemble a certain prototype. The following series of pictures shows (1) a mass-produced toy locomotive with decently proportioned major features (e.g., size and configuration of boiler, cylinders, and running gear), but rather crude and minimal detailing; (2) a prototype locomotive to which the toy's general proportions and major features are acceptably close; and (3) a modification of the toy that is distinctly more than a toy and an acceptable (to me) representation of a specific prototype, though falling short of being a high-quality model. |
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 Off-the-shelf Tyco Pacific, mass produced by Mantua Metal Products in the 1960s (Photo: eBay) The popular HO-scale Tyco
"Pacific" locomotive was
a "Christmas train-set" engine mass produced in the 1960s, and priced
from $20 to $30 during that period. It roughly represented large
"Pacific" type (4-6-2) steam locomotives in passenger and express service
on mainline North American railroads from the 1910s through the early
1950s, and was offered in several road names. The Tyco unit's cab,
pilot, and tender body are cast styrene. The locomotive has a die-cast metal
boiler on a metal frame, and the cast-in details are sparse and crude. Though not modeled after any specific prototype, the Tyco product fairly resembles a few specific engines, Baltimore & Ohio's class P-7c (with 8-wheel riveted tender) and P-7e (with 12-wheel welded tender) among them. |
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 Prototype B&O class P-7e number 5314 after rebuilding from class P-7 in the 1940s (Photo: Baltimore & Ohio Railroad, Mt. Clare) |
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 Tyco "Pacific" type modified and detailed to resemble the B&O prototype |
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| Modifications so
far: filed down casting ridge lines on boiler and
cylinders; *details not visible in photo |
Details yet to be added:
front (pilot) and rear (tender) coupler cut levers; Where I draw the line: I like a model to be well enough detailed to evoke the feeling of viewing the actual thing, but I don't care to obsess over every last detail. On my P-7e there are no drive-wheel springs, since they'd be virtually invisible behind the scale 80-inch wheels. The pop-valve cluster isn't positioned correctly for the chosen prototype, the connecting rods aren't fluted, the sides of the walkway ladders aren't slotted, and there are no air pumps behind the pilot deck shields. In addition, the existing cab is undersize, and the tender should be larger and of a welded (not riveted) design. Such features will not be addressed for a number of reasons, such as degradation of mechanical integrity and functionality, unavailability or expense of commercially made parts, insufficiency of my own skills to create details of the desired quality, and my judgment that the overall result is "close enough" to give personal satisfaction without the frustration of striving for unobtainable perfection. In this case, taking into account the mediocre running qualities of the engine, I feel a more extensive cosmetic makeover isn't justified by the operational platform. |