Railroad Terms

S

• Scale – The size of things on a model railroad relative to a real railroad. For example, in the most popular scale, HO, models are 1/87th full size.
• Scenic Break – A scenic break is a deliberate barrier to disguise the fact that the main line links two sections of a layout which either clash or should, be widely separated. An example might be a rural landscape and a heavily populated city.
• Scissor Crossing – Junction between two parallel railway tracks enabling trains to cross over from one to the other in either direction.
• Scratchbuilding – Making a model from raw materials and parts and not using kits.
• Section Hand – A track worker.
• Selective Compression – A modeling technique that gives the impression that there are more buildings in a scene than are really possible. This is accomplished by making the buildings in the background smaller to give the impression that they are further away.
• Semaphore – A type of fixed signal with a pivoted arm that can be raised or lowered as required.
• Semi-Conductor – Material used in electric traction rectifiers, whose electrical resistance depends on the direction of the applied voltage. Silicon and Germanium are typical examples.
• Seniority – Length of service relative to others.
• Service Track – Track which engines take on coal and water.
• Shaker Bar– A tool carried in steam locomotive cabs that would be placed on the grate levers mounted in the cab deck to allow the fireman to shake the grates in the firebox, dumping ashes into the ash pan below the firebox.
• Shanty– A caboose, also a small building.
• Shay– A type of steam locomotive using a gear drive in place of a side rod drive, designed by Ephraim Shay in the late 1800′s, and produced by what became the Lima Locomotive Works. This locomotive was designed for logging and other operations where heavy grades and sharp curves existed and prevented the use of side rod-type locomotives.
• Shoo-fly Track – Temporary track used primarily for mainline service.
• Shuffle – To switch cars.
• Shunt – To switch to another path.
• Shunting Movements–Movements inside of stations and yards for making up trains, moving cars between different tracks, and similar purposes. Shunting movements are done under simplified conditions with restricted speed and in viewing range.
• Shuttle – Train which gives a frequent return service over a short route.
• Siding – A passing siding or temporary storage area, An auxiliary track turning out from the mainline and rejoining at another point along the main; can be used as a holding track; Sidings can also be used in the form of a branch or short line to service a small town and rejoin the mainline at a distant point.
• Signal – This means of controlling the movement of trains by warning or advising the engineer of the occupational state of the line ahead or the intention to divert to another line.
• Signal Box – Tower or building housing equipment for the operation of points and signals in a particular section of a route.
• Silo – Sand storage tower for filling locomotive sandboxes.
• Single Track System – Consists of a single track between two terminals.
• Six-Footway – Area between parallel railway tracks.
• Skew – Bridge spans obliquely and is, therefore longer than the square gap.
• Slab – Track rails laid on a continuous concrete or asphalt base instead of conventional sleepers and ballast to minimize settlement and changes in alignment; this helps to reduce maintenance costs.
• Slack– The motion, forward or back, that one or more cars, locomotives, or parts of a train has without moving other coupled cars, locomotives, or parts of the train. Loose slack is the free movement or lost motion between parts of a train. Spring slack is the movement beyond the free or lost motion brought about through compressing the draft gear springs. Slack is necessary so as to start one car at a time and so that the train may be operated around curves and over high and low places.
• Slack Action– Movement of part of a coupled train at a different speed than another part of the same train.
• Sleeper – Steel, wood, or precast concrete beam for holding the rails to correct gauge and distribute the load imposed by passing trains. The sleepers are usually set in crushed rock or ballast.
• Slippery Track –A highly greased track near the roundhouse or back shop where a newly rebuilt locomotive could be run in without going anywhere and without calling an engine crew or pilot.
• Slug – A locomotive that receives its electrical current to run the traction motors from another locomotive. They are not equipped with their own diesel and therefore must be operated with another locomotive.
• Smoke Box – The section of a steam locomotive boiler at the forward end which houses the main steam pipes to the cylinders, exhaust pipe, and stack.
• Smoking a Meet – Sending a column of black smoke to signal any approaching train that another is present.
• Snow Plough – A special vehicle propelled by, or attachment to, the front of a locomotive to remove snow from the track. The snow plow may be of a simple wedge shape or rotary type.
• Snow Shed – Substantially built shed along the side of a mountain with a sloping roof erected over the railway to provide a path for avalanches without blocking the line.
• Solebar –Longitudinal main frame, outer member of carriage or wagon under-frame, usually of channel section.
• Soleplate – Longitudinal main frame member of a built-up carriage bogie, usually of standard rolled steel section of pressings. Also, a plate was inserted between the chairs and the sleeper at a pair of points to maintain the correct gauge and prevent any spreading of the gauge that might occur from the gradual enlargement of the spike holes in the wooden sleepers.
• Spar – The wooden rod used in poling operations.
• Spark Arrester - A device, usually in the form of a mesh or baffle plate fitted in the smoke box to prevent the emission of live coals and sparks from the chimney or smoke stack.
• SPDT – Single pole double through. A type of electrical switch used in model railroading.
• Special – A train not shown in the working timetable or pre-planned.
• Spike – Square section heavy steel nail driven into the wooden sleeper to affix flanged rail in position.
• Split Switch – A term referring to the condition that exists at a switch when one pair of wheels under a car follows a course different from all other wheels under the car, generally resulting in a derailment.
• Spring Switch– A switch equipped with a spring mechanism to restore the switch points to their original position after having been trailed through.
• Spot –To marshall or shunt. To move a car to the desired location.
• Spur – A divergent track having only one entry, a branch line over which irregular service is offered.
• Stabling – Accommodation for a short period of time.
• Staff – Wooden stick which must be carried by each train traveling on a single line section of a railway branch line to maintain absolute block working and prevent the possibility of a head-on collision.
• Staging Yard- several lengths of track on a layout used for storing or putting trains together before an operating session.
• Stagger – Interlacing of sleepers at switches and crossing or making rail joints in one running rail not to coincide with those in another rail.
• Standard Gauge – The most common distance between rails in a country. Also, a three-rail tin plate train was manufactured by Lionel and others.
• Starter Signal – A signal in British practice that gives authority to a train to proceed into a block section.
• Station – Any stop along the mainline.
• Station Way – A small station with a passing track only.
• Steam Chest – A box containing the valve mechanism for the cylinders of a steam locomotive.
• Step On- A train moving at a relatively slow speed that never stopped while changing crews.
• Stephenson Valve Gear – The mechanism that controls the movement of the steam distribution valve of a steam locomotive. Stephenson Valve Gear (link motion) – A valve gear in which the steam lead is greatest at mid-gear and greatest at full forward.
• Walschaert Valve Gear – A valve gear in which the lead is constant at any position of the reversing gear.
• Stock Car – American term for a vehicle used for the conveyance of cattle.
• Stub – A short diverging track ending in a bumper; it has a switch only at one end
• Stub Axle – Short non-revolving axle which supports only one wheel.
• Stub Terminal – A dead-end track with a bumping post; used in yards, industrial spurs, mining, and logging areas.
• Stud Contact – Similar to the 3-rail, the conductor rail is replaced by a row of energized studs along the center of the track. A long collector skates on the locomotive and picks up the current. Used by Marklin and in O gauge.
• Styrene – Short for polystyrene, a plastic commonly used for modeling. Comes in sheets, blocks, and rods of many different thicknesses and sizes.
• Sub-roadbed–The base supporting platform on which your layout will be built. Usually, plywood and other material are on top, such as homosote or extruded foam sheets.
• Superheater – A device for raising the temperature and volume of the steam after it leaves the boiler through the application of additional heat.
• Superelevation – Amount by which one rail of a curved track is raised above the other.
• Superelevation is ‘positive’ when the outer rail is higher than the inner rail and ‘negative’ when the inner rail is higher than the outer. Also called Cant. Superelevation allows the train to maintain a faster speed.
• Suspension – Connecting system, including springs, between vehicle wheel and body, designed to give the best possible riding qualities by keeping unsprung weights to a minimum and reducing shock loadings on track. Switch device for opening and closing an electrical circuit.
• Switch – American term for points. Also called Turnout. A track section allows the train to move from one track to another. The switch is also a term used to describe the sorting of freight cars.
• Switchback – A method of climbing a steep grade in a confined area. This is accomplished with a series of switches requiring the train to change direction as it climbs up the side of a mountain on a series of switchbacks.
• Switch Machine – A mechanical device that will change the position of a turnout; it can be used manually or by remote control from a control panel.
• Switch stand – A mechanical device (usually done manually) that will change the position of a turnout and simultaneously change the position of the signal mounted on top of the switch stand.
• Switching District – An area where shippers have access to many railroads through a terminal.
• Switching railroad – Also called a terminal railroad. These railroads move freight in a limited area between shippers and a terminal where freight is transferred to long-haul railroads.
• Synchronous – Electric motor whose speed varies in direct proportion to the frequency of the supply.

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