Beginner's Glossary

Beginner's Glossary


Note: Almost all of the words in this list are taken directly from the Beginners pages (yes, I actually read through the entire thing!). I have also thrown in a few words that I think you will need to know (or be able to find a definition for). I have assumed that nothing RR related is too obvious to be defined.

I have followed the convention of only capitalizing words that are proper names, trade-marks and certain abbreviations. However, my computer seems to have a mind of its own and keeps trying to re-capitalize things that I have left lower case. - Ross


AAR — Association of American Railroads. The AAR is responsible for the rules which facilitate the interchange of cars between RRs. It originally established many of the safety rules now in place, most of which have been taken over by the Federal Government (see FRA). . It is also the umbrella organization that looks after political and public relations affairs for the nation's railroads.
AC (alternating current) — electric current which changes its direction of flow or movement back and forth through a wire.
accessories — Any of a number of electrically operated items on the layout, other than the locomotives and track. Includes switch machines, lighting for buildings, small motors for animation, etc.
air brush — an air powered system for applying paint from a miniature spray gun. It allows extremely thin, smooth layers of paint to be applied to a model and can also be used for special effects such as weathering.
alternating current — (see AC)
auto carrier — a type of railroad car designed to carry automobiles and light trucks. Modern auto carriers usually are enclosed to protect their cargo from vandalism while in transit.

backdrop — a photo, painting or relief model on a wall or partition continuing the background scenery to or above the horizon line; or sometimes the wall or partition behind a modeled scene upon which the photo, painting or relief model is or is to be applied.
baggage car — a car for the carriage of passenger's baggage or express shipments in passenger trains. Usually with one to three large side doors and few if any windows.
ballast — material placed under the track structure to facilitate drainage of water while supporting and cushioning the track on the prototype. Usually made of crushed rock, but can also be of any cheap locally available material such as oyster shells, burned clay, or locomotive cinders. Mostly for show on the model, but can also help to hold the track in position and cut down on noise transmission when used properly.
benchwork — the structure which holds up the track and scenery of a layout.
block (electrical) — a section of track that is electrically isolated from the rest of the layout for control purposes.
block (signal) — on the prototype, a section of track into which only one train may be allowed to enter at a time.
box car — an enclosed railroad car for the carriage of commodities that require shelter from the weather. Early boxcars were simply that — a box on wheels with doors in the sides. Modern boxcars often have extra equipment for the safe carriage of specific commodities (ie: racks for certain types of auto parts, movable bulkheads to secure cargo while in transit, etc.).
branch line — a secondary track leading off the main line which proceeds to towns of lesser importance.
brush (electrical) — a short, usually carbon based rod in a motor used to transfer electricity from the static wires to the moving commutator.
brush (paint) — a tool used to apply paint to a model consisting of a long round handle with bristles at one end. Generally speaking you should buy the best brushes you can afford as they will last a life-time when properly taken care of. Good quality brushes will also do a better job.

cab (locomotive) - the enclosed area from which a locomotive is controlled
cab (electrical) — the electric equipment necessary for one operator to control one train.
cab control — a system whereby any one of two or more cabs can be connected, one at a time, to any block of track for electrical control purposes.
caboose — a rolling office usually placed at the end of a train for the use of the conductor and train crew. Now rarely used. Most have been replaced by "FREDs"
Campbell kit — an older well known brand of wood structure kits.
can motor — a small precision electrical motor used in more expensive model locomotives. So called because they are usually enclosed in a metal covering resembling a can. Can motors require very little electric current to operate.
carpenter's glue — see yellow glue
chair car — a passenger car which does not provide lounge, dining or sleeping accommodations. Usually used to refer to coach, but may be used by some when referring to parlor cars.
Chopper — a brand of tool manufactured by Northwest Shortline used to cut stripwood into pieces of the same exact length.
circuit breaker — a device used to halt the flow of electricity in a circuit in the event of an overload or short circuit.
clearance gauge — a tool used to determine that there is sufficient space around the track to clear the equipment in a moving train. The NMRA makes clearance gauges in most scales that also test for a number of track and wheel relationships.
closure rail — the rail in a turnout or switch that stretches between the frog and the moving points.
coach — a railroad car providing for the transportation of passengers in one large compartment. Usually in less luxurious accommodations and without provision for sleeping. Seats are normally arranged in pairs across the width of the car with a central aisle running the length of the car.
code (rail) — the height of a rail measured in one thousandths of an inch without the decimal point. The same code rail may be used in different scales to represent rail of different weights. For instance, code 100 rail represents the very heaviest weight of rail used only on the mainlines of a very few railroads in HO scale, while it can represent the light rail used on a branch line in O scale.
combine — a passenger car with more than one section used for different purposes. The most common combine had both baggage and coach sections, but there have also been postal-baggage combines, postal-coach combines, etc.
command control — a system for controlling trains on a model railroad where a constant voltage (usually ac) is placed on the track with a control signal impressed the ac power. A special receiver or decoder is required to be mounted in each locomotive to read the signal. Command control allows more than one locomotive to operate in an electrical block at different speeds and in different directions. DCC is the most common command control system at this time.
common rail wiring — track wiring in which only one rail is divided into blocks. The other rail is used as a common return from all blocks. This system greatly simplifies conventional wiring and can result in a significant saving in money for electrical switches and wire. It may not work with certain types of power packs having controls for more than one loco or with some electronic control systems.
commutator — the rotating part of a motor to which the drive shaft is attached which converts electric current to motion.
contact cement — an adhesive which is applied to both surfaces to be joined and then allowed to dry completely. When the surfaces are bought into contact the adhesive grabs instantly forming a strong and tight bond. May be water-based or solvent-based. Solvent based adhesives should be used with care as their fumes can be harmful.
container — a box of standard dimensions used to transport freight from shipper to consignee without having to "break bulk" (load and unload) at each change of transport method. Most containers are designed to be carried by rail, truck and water (intermodal).
container car — a car used to carry intermodal containers.
cookie cutter benchwork — a flat table top that is cut alongside the roadbed so that the track may be raised or lowered.
cork roadbed — a cork product placed under the track to (1) represent the shape of the ballast roadbed and (2) cushion and deaden the sound generated by the trains and their motors.
couplers — the hardware which is used to join the cars in a train. The couplers transmit the pulling force of the locomotive between the cars and through the train.
craftsman kit — a kit which provides all of the materials necessary to build a structure or piece or rolling stock together with the necessary plans and instructions, but which requires a greater degree of skill to assemble.

DC current — electrical current that flows continuously in one direction only
DCC — Digital Command Control — the NMRA sponsored command control system that has become the most commonly used command control system in model railroading world-wide. An alternating current of constant voltage is placed on the track with a control signal of varying frequency impressed upon it. The DCC signal is actually an alternating DC waveform, containing the digital information. The basic system is required to produce results as set forth in the NMRA Standard so that equipment produced by different manufacturers can be operated together.
dining car — a restaurant car providing tables and chairs for patrons and usually a full kitchen in the same car.
direct current (see DC current)
DPDT switch — double pole-double throw switch — an electrical switch allowing the current from two circuits to be simultaneously switched back and forth from one set of wires to another set. May be provided with a center off position in which case it is abbreviated DPDT(CO). May also be wired to serve as a reversing switch.
DPM — Design Preservation Models — a manufacturer of mostly brick structure kits.
draft gear — the box which holds the couplers on a car and transmits the pulling forces between the couplers and the car's frame.
dual cab control — (see cab control)
Duplicutter — A tool manufactured by Northwest Shortline used to cut sheets of wood or plastic into strips
of an exact width.

easement — a curve of decreasing radius introduced before a regular curve to ease a train into the curve providing a gradual transition from straight track to curved. On the real railroads a very precise hyperbolic curve is calculated. On the model it is sufficient to introduce a larger curve first before your regular curve. Easements make trains look better when entering and leaving the curve and cut down on derailments.
engineer — the train crew member who actually drives the engine.
express car — a baggage car or box car assigned to express company service. The express companies were the UPS of the pre-1970 world.

fine scale — Modelers in the far distant past sometimes made their models for practical reasons with some of the dimensions of certain parts of a model to a coarser scale than an exact reduction would require. These parts are therefor not to exact scale. Therefore some of the dimensions in the NMRA Standards are coarser than may be absolutely necessary with today's state-of- the-art modeling. Fine scale modelers tighten up those dimensions, though they do not necessarily use exact measure. (see also Proto87)
flat car — a freight car with an unenclosed flat deck.
flextrack — track which may be laid straight or custom curved by the modeler to virtually any radius. The track comes with rails fastened to realistic ties. Usually sold in three foot or meter lengths.
flywheel — a round metal weight that is attached to the drive shaft of a motor so that its inertia will smooth out the motor's stops and starts.
FRA — Federal Railroad Administration — the main Federal Government railroad regulatory agency in modern times.
FRED — flashing rear end device — equipment which has been used to eliminate the caboose. FREDs not only flash a warning light to the rear of the train, they also transmit the brake pipe air pressure at the end of the train to the engineer so that he knows that his train remains together.
freight car — any of a number of types of railroad cars designed for the carriage of freight. Freight cars include: box cars, flat cars, tank cars, hopper cars, gondola cars, container cars, etc.
freight container — see container
frog — The casting used in the angle where the rails cross and diverge in a turnout or switch.

G Gauge — a system operating model trains on rails 64 mm (2.519") apart. There are several different scales representing real track gauges of from 24" to 4-8-1/2" that use G Gauge. The most common scale used with G gauge track is 1:22.5 or .533" to the foot.
gap (rail) — a cut made through a piece of rail to isolate two electrical blocks from each other. Gaps are best filled with a bit of plastic when in the middle of a piece of track or an insulated rail joiner can be used at the end of a piece of piece of track. In either case this will keep the rails from accidentally closing the space and causing a short circuit.
gauge — The distance between the rails. The most common US gauges are standard gauge of 4 feet 8 and a half inches and (more rarely) 3 foot narrow gauge. Internationally, the British colonial gauges of 42 inches and meter gauge are also popular as narrow gauges.
glad hand — the metal fitting on the brake hose on the end of a car which is used to connect the air brake system from one car to the next. The curved metal wires that hang down from model couplers to activate magnetic uncoupling are sometimes also referred to as "glad hands."
gondola — a low sided open top railroad car for the carriage of bulk commodities such as coal or stone, for the carriage of steel shapes, or commodities that are too big to fit into a boxcar. May have doors in the bottom for dumping the commodity carried.
ground foam — foam rubber that has been dyed and then ground for use in simulating various kinds of foliage in model scenery.
grade — trackage which rises from one level to another. In this country, usually expressed as a percentage of rise — that is a rise of 1" in every 100" (or any other unit) is equal to a 1% grade; 2 in 100 = 2%, and so forth. In many foreign countries, rise is expressed in rise of one per a number of units: that is a 1 in 100 rise is the same as a 1% grade; a 1 in 50 is equivalent to a 2% grade, and so forth.
ground throw — a manual apparatus used to change the position of a switch or turnout.
guard rail — bridge — rails laid across a bridge between the regular running rails to restrain the wheels of a derailed car so that it does not go completely off the track while on the bridge.
guard rail — turnout — the short pieces of rail located across from the switch frog which pull the wheels away from the frog and guide them through the switch or turnout.

half wave current — alternating current that has had one half or side of the alterations removed so that what remains are a series of humps all of the same polarity. Used to help break the inertia of a direct current motor and get a model locomotive moving smoothly from stop.
hard shell — a system for building very thin but extremely strong plaster scenery base using a proprietary gypsum plaster called Hydrocal.
hi-cube — a box car with a higher than normal inside height providing more cubic capacity for the carriage of light weight, high volume freight.
hi-rail — the use of scale locomotive and car bodies on tinplate (usually O gauge 3-rail) track.
HO scale — a reduction of size of 1:87.1 in the model which is equal to 3.5 mm to one foot. HO standard gauge uses a track gauge of 16.5 mm (.649"). When the scale for HO was set many years ago, O scale models were built to a scale of 7 mm to the foot. So HO was "Half O" or 3.5 mm to the foot.
Homabed — a proprietary system of track bed consisting of Homosote which has been cut to the outline of the ballast cross-section of track and milled to an exact thickness. See also Homosote.
Homosote — a brand name of paper based sound deadening and insulating board intended for house construction, usually sold in 4'x8' sheets in various thicknesses. Used by model railroaders as a base for track because of its sound deadening properties and because it is both soft enough to make it easy to drive spikes into it while being hard enough to hold them.
hopper car — a railroad car arranged so that its contents will easily slide down and out through doors in bottom located "hoppers." Originally an open topped car, but now many are covered to protect cargoes as varied as grains, ground clays, and chemicals.
horn-hook coupler — a type of coupler sometimes erroneously referred to as an "NMRA coupler" that is used on the cars in most train sets as well as on cars intended for sale to beginners. They were designed by an NMRA committee, but were never adopted by the NMRA as a Standard.
Hydrocal — a proprietary brand of gypsum plaster noted for its quick drying and high strength. Used by model railroaders as a strong, thin scenery base.

interchange — one or more tracks used to exchange cars between railroads. On a model this is an easy way to generate traffic as well as to provide a connection from the model to the rest of the world.
intermodal — equipment designed to be used by more than one mode of transportation, most commonly rail, water and road.

Kadee couplers — a proprietary system of couplers in several scales allowing automatic coupling by pushing cars together and magnetic uncoupling. Micro Trains produces the same couplers in N scale. These have been the couplers of choice of most serious modelers for many years. Since Kadee's patents ran out recently, there have been a number of imitators or clones on the market.
kitbash — altering the parts of a kit to produce a car or structure that is unique, or combining parts from two or more kits to produce the same result.

layout — the sum of the track, scenery, buildings, locomotives and cars of a model railroad.
left hand turnout (or switch) — a turnout which directs a train to the left of the straight line of travel.
Liquid Nails — a proprietary brand of panel adhesive sold in tubes to be used with a caulking gun.

main line — the primary route or most heavily used tracks of a railroad.
meter — electric — a gauge used to measure the flow of electric current. Most commonly found on a model railroad are volt meters and ampere (or amp) meters.
MMR — Master Model Railroader. One who has completed the requirements established by the NMRA by obtaining certificates in the Achievement Program as a "Master" of at least seven areas of model railroading.
MOW — maintenance of way. Used to maintain the track and track structure of a railroad.

N scale — models built to a scale of 1:160. The letter "N" was chosen because N standard gauge track has the rails laid 9 mm apart and since the scale originated in Germany, the N signifies "nine" in German, English and several other languages. The gauge has since been changed to 8.97 mm or .353". One foot in N scale = 1.90 mm (.075").
narrow gauge — track whose rails are laid to a gauge of less than that of "standard gauge" or 4 feet 8 and one half inches. The most common narrow gauges in this country have been 3 foot gauge and 24 inch gauge. In the rest of the world, the British colonial gauge of 42 inches and meter (39.34") gauge have also been popular.
NMRA — the National Model Railroad Association
NMRA Gauge — a track gauge that also has a number of other uses for checking wheel and track relationships. In most gauges it can also serve as a clearance gauge.
non-revenue equipment — railroad rolling stock that is not directly used to earn money. This includes cabooses and work equipment of all kinds.

O scale — models built to a scale of 1:48 or ¼"=1'0. At one time O scale was the most popular size for modelers, but it was surpassed by HO scale during World War II. It has a rather small, but fiercely partisan group of followers who sometimes refer to it as the "King of Gauges." O standard gauge is set at 1.250".
O-27 gauge, O-72 gauge — tinplate track and the models built to operate on it by such manufacturers as the Lionel Corporation. The numbers refer to the diameter of a circle of this type of track. These tinplate trains are not strictly speaking O scale, although they are often referred to as such.
OO scale — models built to a scale of 1:76.2 or 4mm to the foot. At one time this scale was in contention with HO for a place as the most popular among modelers, but now it is a minority scale with very few (but very devoted) fans. Track gauge is .750" or 19.0 mm.
open frame motor — an older style motor still found on many less expensive models. Its main disadvantage as opposed to the newer can motors is that it draws more electric current. Older style open frame motors also tend to "cog" when they first try to move from stop as each segment of their commutator hangs up briefly as the motor's brushes pass over it providing a rather jerky and uneven start.
open framework benchwork — benchwork that is completely open except in level areas so that scenery may be built both above and below track level.

passing siding — trackage used to allow two trains to pass each other on a single track line or to allow an engine to run around its train. Usually has turnouts at each end in model railroad practice but may be stub ended in the prototype.
passenger car — a railroad car designed for the carriage of passengers, or for service to passengers (such as a dining car or lounge car), or for use in a passenger train (such as baggage or postal car).
percent (grade) — see grade
piano wire — a very strong, stiff, flexible wire intended for the strings in a piano but usable for many purposes in model railroading.
pin vice — a handheld device used to hold very small drill bits, files and other very small tools while working on a model.
points — the movable rails of a turnout or switch.
postal car — a railroad car designed for the carriage of the U.S. Mails. Until the mid-1970s, there was usually a provision for picking up mail bags from smaller stations while the train was in motion, sorting the mail enroute by Railway Postal Clerks, and dropping bags of mail off at stations along the train's route.
power pack — a commercially manufactured, usually sealed, complete unit for powering model trains consisting of a transformer to reduce house voltage to that required for operating the trains, a rectifier to change alternating current to direct current, a rheostat to vary the voltage applied to the track, and a reversing switch. May also have additional switches, indicator lamps, etc.
PROTO87 — a group that models track and wheels to exact scale in HO. NMRA Standards are somewhat oversized to allow for more reliable operation of model trains on track that is built to less exacting standards.
prototype — the real thing. That from which we are making our model.
pulse power — see half wave

radio control — any of a number of systems using a wireless hand held device to control the speed and direction of a train. May use constant voltage on the track with a device on the engine receiving a radio signal from the controller telling it how much voltage to use and which direction to go. Or it may use a conventional cab system and just control the voltage produced by a fixed power pack through signals transmitted by radio.
rail — a "T" shaped steel shape designed to be laid end-to-end in two parallel lines on cross ties or similar supporting materials to form track to support railway cars. In the prototype, rail size is measured in pounds per yard. In the model in 1/1000's of an inch (see "code")
rail joiner — a metal or plastic piece folded into a flattened "C" shape which slides onto the web of each of two pieces of model rail to join and hold them in end to end alignment.
rail code — see Code rail
railway post office (RPO) — a car built by the railroad to standard postal designs and leased to the United States Post Office in which one or more postal clerks picked up, sorted and delivered mail while the car was enroute between two cities.
Rapido couplers — the original couplers used on N-scale cars named for the company that first produced them. From the top they look like the letter "C". Many N-scale cars are still produced with these couplers.
razor saw — a very thin metal cutting saw useful for cutting track among other things.
ready-to-run — rolling stock that can be taken from the box and placed directly on the track with minimal (if any) assembly by the modeler.
Recommended Practice — a practice not absolutely essential to interchange of models between modelers and their layouts which is recommended by the NMRA for use by all modelers and manufacturers.
rerailer — a usually plastic device built into a piece of track that will cause a derailed truck to run back onto the rails. Most are disguised as a RR crossing.
rheostat — a device used to add resistance to an electric circuit with the result of reducing the voltage applied to the track.
right hand turnout (or switch) — a turnout which directs a train to the right of the straight line of travel.
riser — a wood piece extending from the benchwork to the underside of the track to support it at a specific height.
roadbed — in model railroading the material laid under the track to support it, deaden sound, and represent the contour of the ballast. Most often made of cork, but may also be made of paper (Homosote) or rubber.
rolling stock — freight, passenger and MOW cars. Equipment designed to roll on the track.
RP — see Recommended Practice
RPO — see railway post office
rubber cement — a glue formed of rubber dissolved in a solvent to form a cement most useful for joining light porous materials such as paper and wood. Can also be used as a contact cement by applying to both surfaces to be joined and allowing to dry to the touch before joining the materials.

S scale — a scale of 1:64 or 3/16" (.188"/4.76 mm) to the foot. S standard gauge is .875" (22.2 mm).
SPST — single pole single throw switch. A simple on/off switch to be located in one line of an electric circuit.
scale — the ratio of size of a model to the size of the real thing. Usually expressed as the number of units of measure in the prototype that one of the same units of measure equals in the model.
scale rule - a special ruler showing scale feet and inches for one or more modeling scales.
scale mile — a real mile scaled down in the same proportion as the model. Some common scale miles equal: N = 33.0 feet; HO = 60.7 feet; S = 82.5 feet; and O = 110.0 feet.
scenery — material used on the model layout to represent the land, trees, crops, grass, weeds, water, etc of real life. Structures are also considered scenery.
scratch build — a model that is completely builder constructed without the use of any commercial parts except for motor, gears, couplers, light bulbs, and wood and metal shapes.
sectional track — track usually sold to beginners in fairly short standardized lengths and curves of fixed diameter.
shake-the-box kit — a kit designed for the beginner that has relatively little for the modeler to do. Hence "shake the box" and it is assembled.
siding — the prototype railroads consider a siding to be a track auxiliary to the main track where trains can meet or pass. A siding may be either single ended with a turnout at one end only, or double ended with turnouts at both ends. Modelers extend the meaning to also include the track at industries used for the storage of freight cars while being loaded and discharged.
signal — a device used to tell an engineer the condition of the track ahead of his train. Information communicated includes whether the track is clear or occupied by another train, and often also the route over which his train will travel.
sleeping car — a passenger car equipped with sleeping accommodations. The beds are usually arranged to fold away during daylight hours.
Snap Saw — a proprietary brand of razor saw specifically designed for cutting track
Snap Switch — a proprietary brand of turnout designed to work well with sectional track
Snap Track — a proprietary brand of sectional track.
solid state — term for electronic relays and circuits provided on or in a solid chip or other such device.
spike — an "L" shaped nail used to secure track
staging — trackage — usually hidden — used to store complete trains out of or away from the layout, from which they can be run into the operating area and to which they can be returned and stored when they are no longer needed. Staging usually represents places well outside of the layout's depicted area so that trains may be considered to run from some place well beyond the basement onto the layout and then to continue on to someplace else beyond the basement.
Standard — a measurement, ratio, value or relationship that is required in order to allow the interchange of cars and locomotives between track of different manufacturers and layouts of different modelers.
stock rail — the continuous rails of a turnout — that is an extension of the original two rails in front of and continuing down the outside on either side of the turnout.
stripwood —basswood or another very fine-grained wood cut into strips usually of scale dimensions for use in the construction of fine scale models.
switch (track) - a device allowing the rails to split or diverge into two or more routes. Model railroaders usually refer to these as "turnouts."
Switch (electrical) - a device used to turn on and off or divert electrical current.
switch machine - an electrical device used to change the position of a switch or turnout.

table top benchwork — a flat table-like top fastened to a stiffening framework upon which the track is laid all at one level.
tangent — track that is straight, not curved.
tank car — a car for the carriage of liquids. Modern tank cars usually have a horizontal tank but early ones had one or more vertical tubs mounted on a flat car. Tank cars may be insulated or uninsulated, lined for the carriage of various chemicals, or designed to carry commodities under pressure. The tank may be divided into discrete sections to allow the carriage of several different liquids in the same car.
terminal block — an electrical device used to easily connect a circuit's wires together. A simple terminal block will have two screws joined by a brass plate. One or more wires can be fastened under each screw. Solder lugs can be substituted for the screws. Several of these simple terminal blocks can be ganged together to allow wires from several different circuits to each have their own connections. Barriers may be set between the screws to keep wires from different circuits from accidentally touching.
throttle — an electrical device used to control the speed of a train. Most often this is a rheostat which wastes electric current by turning it into heat in order to vary the voltage applied to the track. The lower the voltage, the slower the train will run.
throw bar — the narrow bar which joins the rails at the points of a turnout which allows the switch to be "thrown" from one side to the other. Normally has an extension which allows a ground throw or switch machine to be attached at the side and a hole at the middle for an under-table mounted switch machine.
tie — the cross members to which the rails are fastened. Ties keep the rails in gauge, cushion the rails and transmit the forces of a moving train to the ballast. Traditionally, ties were made of wood — in modern times creosoted wood. In the most modern installations on high speed track, concrete ties are being substituted for wood.
tin plate — equipment once designed to be sold to children, most often running on 3 rail track. Cars and locomotives are often shortened to allow them to negotiate sharp curves. Originally pressed from thin sheet steel (ie: tinplate). Detail is usually coarser than scale and often exaggerated. In modern times most often sold to collectors.
track — the structure of parallel rails and cross ties that support the train while transmitting its forces to the ballast and roadbed.
track gauge — a device used to set and maintain the proper distance or gauge between the rails.
track nail — small nails provided to fasten sectional track to its base.
traction - general term for electrically propelled street cars (trolley cars) and interurban cars.
train set — a set provided (usually by a single manufacturer) for beginners that contains an engine, an assortment of cars of various types, track and usually a power pack. Although some train sets are quite inexpensive, caution should be used when buying them as often the components are of poor quality.
trolley — the wheel at the end of a "trolley poll" which rides on the wire which provides power to a street car.
trucks — the assembly of wheels, axles, bolster and side frames that provides the rolling portion of a car or diesel locomotive.
TT scale — a scale of 1:120 or 1/10" to the foot. TT from "table top." The track gauge is .471" (12.0 mm).
turnout — model railroad term for a track switch. This was adopted to avoid confusion with electric switches.
turnout number — the ratio of the number of units along the center line of a switch frog traversed for each unit the frog spreads to the sides. A No. 4 frog diverges 1 unit for every 4 it moves ahead; a No. 6, 1 for every 6 units. Although we usually refer to a turnout or switch number, in reality the measurement is for the frog.

vertical curve — the curve assumed by the track as it changes from level to a grade or vice versa. For good operation, this needs to be a very large radius.
volt — a unit of electrical pressure.

weathering — the operation of simulating the action of time, sun, rain, dirt and dust on the appearance of a model. Properly weathered models look more realistic than unweathered models.

white glue — any of a number of water based casine glues, almost all of which are white (hence the name). White glues are used for joining porous materials such as paper and wood. The original and best known brand is Elmer's Glue. They are inexpensive and reasonably strong but when dry they are not waterproof.
wing rail — the portion of the closure rail which is bent to extend past the frog.
wye — a triangular arrangement of track such that engines or trains may be turned around. Wye tracks need special wiring to prevent short circuits.

X-acto knife — a popular brand of hobby knife using interchangeable knife blades of different shapes.

yard — an assembly of tracks within defined limits used for the purpose of breaking down arriving trains, storing cars, and making up departing trains. There may also be tracks for special purposes such as cleaning cars, repairing them, and servicing locomotives.

yellow glue — any of a number of water based resin glues useful for joining porous materials such as paper and wood. These glues are water proof when dry and are generally yellow in color (hence the name). Their joint is stronger than that obtained from white glues but they cost more. Also called Carpenter's Glue.

Z scale — models built to a scale of 1:220. These are the smallest practical models in mass production at the time of this writing. .055" (1.39 mm) = one foot and the track gauge is approximately ¼".
Zona saw — a brand name of a modeler's saw designed for very thin straight cuts in metals.

Some sources for further reading
courtesy of Jennifer Eble at the Kalmbach Library

Dictionary of Railway Track Terms - Simmons-Boardman Books, 1990
Glossary - NMRA Data Sheets, 1999
The Railroad Dictionary of Car and Locomotive Terms - Simmons-Boardman Publishing, 1980
Railway Age's Comprehensive Railroad Dictionary - Simmons-Boardman, 1984
"What Does That Mean?" - Melanie Buellesbach, Model Railroader December 1997 p. 90
Walther's Catalog (any scale) Glossary

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Page last updated December 4, 2014