| S | T |
"SAFTY VALVE" - A valve on a boiler which lets steam escape when it exceeds a certain predetermined pressure.
"SAMSON" class -Designed by George & Robert Stephenson, England's premier locomotive builders in the 1830s, a number of these engines were bought by American railroads, principally those serving New England.
SAND DOME - A bin filled with sand, straddling a boiler top, for the purpose of sanding the rails to achieve more traction.
SANDER - A mechanism attached to a locomotive for the purpose of sanding the track in front of the driving wheels for added traction. Its origin in 1836 is attributed to an unidentified Pennsylvania engineer, inspired by a placque of grasshoppers whose crushed bodies greased the rails. Not until 1840s, however, was a commercial sander used. On later locomotives sand was also applied to the rails behind the drivers for backup movements.
SATURATED STEAM - Steam that contains liquid droplets.
SCHMIDT SUPERHEATER -A superheater consisting of a two-compartment resevoir and numerous external tubes. Saturated steam entered one compartment and passed through the tubes, where it was heated, to the second compartment, from which the super heatedsteam passed to the throttle valve. The design wrote an end to balanced compound engines by providing comparable fuel economy witout the need for extra cylinders or moving parts.
SETSCREW - A screw by which a valve opening can be regulated.
"Shay" type - A logging locomotive, Ephraim Shay in 1880, which adjusted itself to the irregularities of hastily laid track by the flexible linkage and beveled gears connecting its longitudinal crankshaft and the wheels of two trucks. Nicknamed a "side-winder," it evolved over a period of sixty five yearsinto husky twelve- and sixteened-wheeled locomotives.
SIDE ROD A steel rod that connects the crankpins to any two adjoining driving wheels on the same side of a locomotive to distribute the power from the main rod to the driving wheels.
SIMPLE ARTICULATED LOCOMOTIVE - A locomotive in which the cylinders receive steam at full boiler pressure, as opposed to a compound articulated locomotive.
SINGLE ACTION PISTON - A piston the exerts a thrust in only one direction, relying on a counterbalancing weight, accumulated momentum, or the action of another piston, or pistons, for its unpowered return strokes.
SLIDE VALVE - A valve that admits steam to and exhausts it from a cylinder.
SLIDING AXLE - See lateral-play axle.
SMOKE BOX - A forward portion of a boiler ahead of the water section.
SMOKE STACK - An iron or steel chimney attached to the top of a smoke box, through which smoke and gases are dischared.
SPUR GEAR - A flat gear with broad transverse teeth on its periphery.
STACK - See smokestack.
STATIONARY ENGINE - A steam engine placed in a permanent position.
STAYBOLT - A bolt threaded at both ends, screwed through the inner and outer plates of a firebox to hold the plates several inches apart.
STEAM BRAKING - Reversing the valve gear in order to decelerate the engine. This type of braking risked blowing out the cylinder heads, but engine men used to it for many years in emergencies. Mounting boiler pressures and heavy train tonnages eventually put an end to the practice.
STEAM DOME - A vertical chamber on top of a steam boiler in which steam accumulated.
STEAM PUMP - See injector
STEPHENSON GEAR - A valve gear that enabled an engineer to run an engine forward or backward, and to regulate the time during which steam was admitted to the cylinder. Used extensively by Robert Stephenson, one of who's employees designed it in 1842, the gear had actually been invented ten years earlier by William James, who had sent drawings of it to an English company where they had been filed and forgotten.
STOKER - A device for adding fuel to the firebox.Although mechanical stokers had been tried as early as 1850, all were failures until the early 1900s, when Arachimedes' screws were applied to conveyers. By 1910 stokers were efficient enough to replace extra firemen on big engines.
STRAIGHT AIR BRAKe - See atmospheric brake.
STRAP IRON - In railroad service, a flat iron bar mounted on a wooden stringer and used as a running rail.
STRINGER - A timber laid in thearth or on stone ties, whose upper surface iron plates, or running rails were applied.
STROKE - Recipricating movement such as that as a piston rod. ( See the "CRAB" in the Depot).
SUNFLOWER STACK - A smokestack with a wide mouth shaped like an inverted cone.
SUPERHEATED STEAM - Steam directed through auxiliary coils in the flues to increase its temperature. This gave it greater volume and fluidity, enabling it to do more work in relation to the fuel consumed. The advantage to using super heated steam was recognized soon after the turn of the present century.
SUPERHEATER - An auxiliary heater that produces superheated steam.
Back To Top
T
"TALLOW POT< - A nickname still in use for fireman. In the mid nineteenth century during non stop journrys of any distance, the fireman had to make his way forward on the running-board to replenish the lubricating tallow in the valve chamber.
TANDEM COMPOUND TYPE - A steam locomotive with a high- and low pressure cylinder set end to end on each side, with the pistons mounted on one rod. In 1893, ten years after the failure of the system in a test the first of eighty-six tandem compounds was constructed for the Atchison, Topeka ans Santa Fe Railroad. See alsocompound type.
TANK ENGINE - A locomotive wwith compartments for carring its own fuel and water. Although small tank engines were used in Europe in the md-nineteenth century, their tractive effort decreased as the water and fuel were consumed. Matthias Forney improved on them in the 1860s with his 0-4-4T (Tank) type which imposed the variable load on the trailing truck.
TENDER - A railroad car stocked with fuel or water for running of the engine.
"TEXAS" TYPE - A 2-10-4 locomotive, first used on the Texas & Pacific in 1926. The originating firm -Lima-built a total of 141 of them for thr T&P, Chesepeake & Ohio, Chicago Great Western, and Kansas City Southern.
THREE CYLINDER COMPOUND Type - A steam locomotive in which the third cylinder either received steam from a pair of cylinders outside the frames, or fed its own exhaust into them. The first kind originated in England in 1878 and the second in France. Neither was popular in the United States.
THROTTLE - The combination of equipment by which the amount of steam admitted to the cylinders is controlled.
THROTTLE VALVE -A device for regulating the supply of steam from the boiler to the cylinders.
TONNAGE RATING - The number of tons of train weight a locomotive of a certain class could handle a particular division.
TORQUE - The turning power of a shaft or wheel.
