Definitions and Glossary of Common Railroad Terms


Q. What is a boomer?

A boomer is (was) any transient RR worker. At one time, there were more jobs than skilled railroaders, especially in times of "boom"ing traffic (wheat harvest, etc) or a local boom, say due to a mine opening. Some men travelled, habitually, from road to road. They were a figure of some romance, and figured popularly in RR fiction. One could have boomer operators, boomer conductors, boomer anythings.

Q. What are "craftsman" kits?

A craftsman kit implies that more time (and perhaps skill/experience) is needed to assemble the kit. They often include parts made of wood, metal, plaster, and paper/cardstock in addition to plastic, requiring knowledge of what adhesives should be used for different materials.

The benefit of this extra work is that the model typically looks much more realistic and detailed if properly assembled; such kits are often made in small runs and correspond to a specific prototype rather than simply giving a general impression. Many structures are available as craftsman kits in addition to models of rolling stock, with Westerfield being probably the best known supplier of cars in HO scale.

Q. What is a "turnout"? What is a "frog"?

The frog is the part where the curved rail for the diverging line crosses the straight rail for the straight ahead move. In Australia (and the UK) it is more usually referred to as the 'crossing'.

The frog number simply refers to how sharply the diverging line is diverging. For all practical purposes, you can consider it as the number of inches it takes for the diverging rail (at the frog) to diverge one inch from the straight rail. So a #4 frog takes 4 inches to diverge 1 inch, and is sharper than a #6 frog which takes 6 inches.

A frog is the 'center part' of a switch where the diverging rails cross. The frog number is a ratio of the length to width of the frog. A #4 frog is 4 times as long as it is wide. With a little bit of geometry you can figure the angle of the frog. A #4=14.36 degrees, a #6=9.56, a #8=7.187, and a #10=5.73 degrees. As you can see a #4 is a sharp turnout.

This table is taken from "Track Planning for Realistic Operation" by John Armstrong. This book has been recomended as a source book for operation and planning basics for modeling. Because one of the goals of the book is to design and layout a model railroad there are a lot of details needed for drawing a plan in detail.

Turnout Frog. No. Degree Angle N scale HO scale S scale O scale
4 14.25 15 3/4" 29" 39" 53"
4 1/2 * 12.5 36"
5 11.4 24" 44" 60" 80"
6 9.5 30" 56" 76" 102"
8 7.15 60" 110" 150" 200"

*Atlas "No. 4" HO Custom-Line turnout is actually a No. 4 1/2

The curved leg of a standardized railroad turnout is not of uniform radius. A short section through the frog is made straight to improve the action of the wheels at that critical point and to allow the same frog to be used in right and left-hand turnouts alike. The switchpoint is not shaped to a perfect curve because that would make it impracticable long, slender, and fragle. For any standard turnout there is an equivalent substitution radius, as shown in the diagram, which can be substituted for the actual rail location in fitting the turnout into a section of curve. Approximate values for substitution radii are given in the table above.

Q. What is guage?

Gauge is the distance between the inside faces of the two rails. Standard gauge in the United States and most of the British Commonwealth is 4'8.5", with 3' and 2' as fairly common narrow gauges. Note that this standardization did not exist when railroads were first being built, causing excessive delays when people and freight had to transfer between railroads with incompatible gauges.

Q. Whats the " glad hand " ?

The glad hand he is referring to is the trip pin as referred in the Kadee instructions. It is the piece of "wire" that comes out of the bottom of the coupler and is used in automatic uncoupling operations.

On the prototype, the 'glad hand' is the cast iron end of the hose(s) on the end of the freight/passenger car. Which mates with the similar piece on the next car in the train. They got the name 'Glad hand', because of the resemblance to the 'handshake' of people when meeting. When the two hoses are mated, and there is an angle of 70 to 90 degrees between the hoses, they stay 'hooked up'. Tension, from pulling on the hoses, car uncoupling (intentional), coupler knuckle breaking (unintentional), will straighten out the connection between the two hoses, When they are 'straight', they no longer hook together, and the air pressure in the line (hose) "blows" the connection apart. (AUTOMATIC Emergency Brake Application)

The Kadee uncoupler pin, sorta resembles the air hose glad-hand connection between cars.

Q. What is hydrocal?

This a plaster product commonly used for creating terrain. The easiest sources seem to be model railroad stores, since I've yet to find a building supply store that has any idea what I want. The advantage of hydrocal is that it is very strong once it sets up, as opposed to plaster which needs something underneath it to support it even after it dries. Hydrocal needs support while setting but cardboard strips do just fine. Regular plaster requires chicken wire and wood supports for shaping -- it's a lot more work, and a lot more weight.

Q. What does kitbashed mean?

Kitbashing refers to starting with one or more commercial kits but assembling the pieces in a different fashion, often adding other material or recutting the original pieces.

Q. What is a "moving frog"?

There are several types of frogs that "move". Some model (and some real) frogs have moving wing rails that actually close the gap for the opposite route, reducing wheel "bounce" and thus reducing frog wear. In model railroading, the old "Tru-Sclae" turnouts have this type of frog.

The slim switches by M"arklin for the K track system (H0 central conductor, AC) also have moving frogs. And from Fleischmann there are switches with moving frogs coming in 1993 (for Profi track, H0 2-rail DC).

At all the high speed railroads (at least TGV and ICE, I don't know about Japan) there are switches with moving frogs used. But they are very long, and they have concrete sleepers. The type used on DB high speed lines allows 250 km/h on the straight track and 160 km/h on the curved track. The model switches described above have wood sleepers and are still too short to be used on a scaled high speed line.

Q. What is a Maintenance of Way (MOW) car?

These are "non-revenue" cars (so-called because they are not used to service paying customers) used by the railroad for upkeep on the track, roadbed, and surrounding infrastructure. These are typically older or damaged cars no longer suitable for high-speed work. They include things such as cranes, ballast cars (converted hoppers used to spread gravel between the ties), tie cars, rail cars, etc. Since they are usually fabricated by the shop crew out of whatever is available they come in a wider range of styles than ordinary cars.

Q. What does prototype mean?

It has several meanings, but typically refers to real-world trains (in contrast to scale models of them). Also called 12"-to-the-foot. However, it can also mean the first item in a series, which meaning is often applied to equipment built as tests by real railroads.

Q. What is a rerail frog?

A rerail-frog is a kind of a metal ramp thing that is used to help re-rail a car or engine that has gone off the track but not wandered too far away or overturned. It is temporarily spiked, wedged or clamped next to the rail at the wheel that needs to be lifted back over the rail and then the car is pushed or pulled by the engine to get the wheel to ride up over the ramp and back onto the track.

Typically in branch line service you would see these dangling from the sides of the tender along with some chains or cables. More tools including jacks, levers, wrenches for splice bolts and so on might be kept in the caboose or stashed on the engine.

Q. What does RTR mean?

Abbreviation for "ready to run," indicating that the model can be removed from the box and placed directly on the tracks without any assembly, and usually without painting or lettering.

Q. What is scale?

Scale is the ratio between the model and the prototype; for example, N scale is 1/160th of the size of the real world.

The standard scales, listed in approximate order of popularity, are:

HO 1/87 (actually 3.5mm to the foot, or 1/87.1)
N 1/160 (1/152, 2mm per foot in the UK)
O 1/48 (but see below)
G 1/22.5 or 1/24, or whatever the manufacturer decides
S 1/64
OO 1/76.2 (4 mm to the foot, mostly used in the UK)
Z 1/220
No.1 1/32
TT 1/120 (common scale in the former GDR, only produced by Zeuke in Berlin)

Q. What does scratchbuilt mean?

Scratchbuilt usually means starting with wood, cardboard, plastic, or other basic materials and then designing and cutting all of the necessary pieces.

Q. What are "shake the box" kits?

"Shake the box" is a slightly derogatory term describing a kit so simple to assemble that all you need to do is shake the box and it is finished. (Actual assembly usually takes 30-60 minutes and requires only a knife, plastic glue, tweezers and a small screwdriver.) This ease of assembly usually indicates that there is a lower level of detail, but also makes the kits less expensive and allow you to build up a large fleet in a reasonable amount of time. Athearn freight cars are an example of a good quality kit of this type.

Q. What is a traction layout?

The term as used in model railroading refers to streetcars, trolleys, and electric-powered interurban lines. They usually contain very tight curves and overhead wiring (functional in some cases) in an urban setting.

Q. What is a turnout?

From "Railway Track and Maintenance: A Manual of Maintenance-of-Way and Structures" by E.E.R. Tratman, McGraw-Hill Book Company, Inc., 1926, p. 342 [formerly published under the title of "Railway Track and Track Work"], quoted here without permission:

Turnouts -- Where a train is to be diverted from one track to another, a turnout is installed, which is essentially a curve connecting two parallel or diverging tracks. This curve, however, is composed of three principal parts: (1) a switch, consisting of two movable rails to direct the train onto one track or the other, as desired; (2) a frog to allow the wheel flanges to pass the intersection of the rails; and (3) rails, known as lead rails, connecting the frog with the switch rails.

Q. What is a winterization hatch?

A hatch or cover used to cover up or close off the normal ventilation for oil-coolers, air-coolers or excess fan/radiator area for exterme cold weather.

Q. What's a "Zulu outfit"?

A freight car carrying people. Living rough, in the car. Could be emigrants heading west, opr ranch hands accompanying a shipment of cattle, or....In first case, could have animals in the car with them.