GLOSSARY OF TECHNICAL TERMS
adhesive weight
Weight carried by the driving wheels.
articulated locomotive
Locomotive with two engines (the unit comprising cylinders, valve gear, and wheels) pivoted under a single frame: for example, Mallets and Beyer Garratts.
ash-pan
Steel receptacle below the fire-grate designed to collect ash and regulate the flow of air, normally through damper doors controlled by the fireman, into the grate.
Atlantic
Popular name for 4-4-2 locomotives, derived from their early use on the Atlantic Coast Line Railroad and the Philadelphia and Reading Railway, which ran the type to Atlantic City, New Jersey.
Baltic
Popular name for 4-6-4 locomotives in Europe, derived from the Nord railway 4-6-4s of 1911 designed to work Paris to St Petersburg expresses – from the Seine, that is, to the Baltic. The type was known as the Hudson in the USA. The first American 4-6-4s were built for the New York Central Railroad in 1927, its principal main line running north from New York up the Hudson Valley.
bar frame
Locomotive frames constructed from steel bars, square in section; first used in England, by Edward Bury in 1830, it was a common feature of the majority of US locomotives from 1840.
Belpaire boiler
Type of boiler developed by Belgian locomotive engineer Alfred Belpaire between 1860 and 1864, characterized by a flat-topped fire-box.
big end
The crank-pin end of the connecting rod, where stresses are higher (or ‘bigger’) than at the cross-head end – the Achilles heel of many steam locomotives.
blast-pipe
Pipe carrying exhaust steam from the cylinders into the centre of the smoke-box; the gap between the blast-pipe and the chimney above it creates a vacuum which draughts the boiler, drawing heat from the fire-box through the boiler tubes and thus raising steam.
blower
Device providing a draught for a locomotive’s fire, through jets of live steam, when steam to the cylinders is shut off. A safety device, too, it ensures that fire is not blown back through the fire-box door by draughts from the chimney back through the boiler tubes.
Boxpok wheels
Disc driving wheels, as opposed to the usual spoked wheels, patented by General Steel Castings of Granite City, Illinois, and popular in the USA in late steam locomotive design. They were easier to cast and easier to balance than spoked wheels. Variations included the lighter Bulleid Firth Brown wheels fitted to Bulleid’s steam locomotives for the Southern Railway.
brick arch
Constructed from firebricks or concrete inside the fire-box, this is designed to direct air from the fire-hole to the hot gases, ensuring complete combustion before they reach the boiler fire-tubes. It also helps prevent particles of fuel from being drawn into the fire-tubes and helps maintain even heat within the fire-box.
Caprotti valve gear
Camshaft-operated valve gear using poppet valves invented by Italian engineer and architect Dr Arturo Caprotti in 1921. More costly to make and to fit than conventional piston valves, this was a more efficient option.
chimney
Known as a ‘stack’ in the USA, the chimney exhausts steam from the blast-pipe, ejects hot gases, as well as smoke and poorly combusted fuel particles, from the smoke-box, and is a key element in the draughting and steam process. Its shape was raised to something of a fine art in Great Britain.
compound
System using steam twice in high- and then low-pressure cylinders, increasing the work done by expanded steam. Compound locomotives were often highly efficient.
connecting rod
Steel rod connecting the piston rod with the crank on the driving axle or driving wheel, and converting the to-and-fro motion of the piston into the rotary action necessary to turn the driving wheels.
cut-off
Point at which steam is cut off from entering cylinders. Controlled by the driver through a reverser screw gear or a ratchet lever in the cab, the cut-off can be set anywhere, but is normally between 10 and 75 per cent of the piston stroke. When starting, the driver will work the locomotive at a high percentage cut-off to maximize the flow and force of steam in the cylinders, reducing this as the locomotive gets into its stride.
dome
Fitting, usually in the shape of a dome or a bowler hat on top of the boiler, designed to collect steam and housing the regulator valve – the valve, operated by the regulator (or ‘throttle’), that admits steam to the cylinders – and, sometimes, safety valves. It was originally designed to raise the entry to the main steam-pipe above the boiler to stop boiling water from flowing into the cylinders. Domeless boilers were a feature of late-generation steam locomotives.
drawbar horsepower (dbhp)
The net power a locomotive has to pull its train. In practice, this was measured by dynamometer cars equipped with the necessary measuring and recording instruments. Calculated as: dbhp = tractive effort × speed ÷ 375.
grate
Grill of fire-bars at the bottom of the fire-box on which the fire rests. Gaps between the bars create currents of air to assist combustion.
‘hammer blow’
Force exerted by the thrust of the connecting rod on the crank and transmitted through the driving wheels to the rails.
horsepower (hp)
Measurement of power, equivalent to 550 ft-lb per second, or the equivalent of 745.7 W. The true maximum output of a horse is about 15 hp. A healthy human can manage up to about 1.2 hp and an Olympic athlete can double that.
indicated horsepower (ihp)
Power developed in the cylinders of a locomotive, calculated from a measurement of the pressure in the cylinders using an ‘engine indicator’. This equipment was housed in a timber shelter erected around the front end of a locomotive – an interesting place for engineers to spend up to several hours as the engine was worked up to maximum power.
injectors
Operated by the fireman, these feed water into the boiler from a tank or tender using live steam from the boiler or exhaust steam from the cylinders. Anyone who has made a cappuccino with a traditional espresso machine will be familiar with the concept.
Mallet
Type of locomotive with two sets of engines mounted on bogie frames and set below a single boiler, designed by the Swiss engineer Anatole Mallet in 1884. Mallets grew to prodigious size in the United States. With the front engine unit articulated, American Mallets were able to negotiate tight bends despite their immense length.
Mikado
Locomotive with 2-8-2 wheel arrangement. The name was given to the Bt4/6 class 2-8-2s built by Baldwin of Philadelphia for the Japanese Nippon Railway in 1893. After the Japanese attack on Pearl Harbor on 7 December 1941, some US railroads, including the Chesapeake and Ohio and Union Pacific, adopted the name MacArthur for the type, after General Douglas MacArthur, chief of staff of the US Army in the 1930s who was recalled to active duty in 1941.
Mogul
Name for locomotives with 2-6-0 wheel arrangement, from the first British 2-6-0 type, the Great Eastern Railway’s No. 527 Mogul, designed by William Adams and built by Neilson and Company in Glasgow, in 1878.
motion
The sequence of piston rods, connecting rods, and valve gear that power and turn the driving wheels of a locomotive.
Mountain
Name for locomotives with 4-8-2 wheel arrangement. Named after the first locomotives of this type, the Alco-built 4-8-2s of 1911, designed to work heavy passenger trains single-handed over steeply inclined mountain sections of the Chesapeake and Ohio Railway in the Alleghenies.
Pacific
Name for locomotives with 4-6-2 wheel arrangement. The first true Pacifics were the thirteen Q class 4-6-2s built by Baldwin to designs by Alfred Luther Beattie, chief mechanical engineer of the New Zealand railways in 1901. The locomotives were shipped across the Pacific. The last was withdrawn in 1957. None was preserved.
pannier tank
A tank locomotive with water tanks carried on either side of the boiler and raised clear of the running board. An apt name for locomotives that were very often the mules of the steam railway world.
poppet valves
Steam-chest valves opened and closed by rotary or oscillating cams. Theoretically, but not always, more efficient than conventional piston valves. The best known poppet valve set-ups were designed and manufactured by Caprotti, Franklin, Lentz, and Redlinger.
regulator
The throttle on a steam locomotive, opening a valve at the top of the boiler to admit steam to the cylinders, operated by the driver through a number of different types of levers mounted in the cab.
reverser
Forward and reverse control also used to ‘cut off’ steam entering valves and cylinders. The equivalent of gears in a car and used in tandem with the regulator.
saturated steam
Steam that has not been superheated.
superheater
The first superheaters, designed by Wilhelm ‘Hot Steam Willy’ Schmidt, were fitted to locomotives of the Prussian State Railways in 1898. The equipment, formed of coils of pipes inside large boiler flues, re-heats and ‘dries’ saturated steam produced in the boiler. The thermal efficiency of superheated locomotives was up to 50 per cent greater than that of saturated steam locomotives.
thermic siphon
Heat-exchanging device comprising flattened funnels directing water from the tender or tank to the hottest areas in and around the fire-box so as to speed up and increase steam production. Patented by US engineer, John L. Nicholson, in 1928.
tractive effort
The force exerted by a locomotive at the point of contact between wheel rim and rail, and a measure of the locomotive’s ability to pull or push a train away from rest. Not the same thing as horsepower, which is a determinant of speed. A high tractive effort is essential for heavy freight locomotives, but not for high-speed locomotives designed to haul light passenger trains. Tractive effort falls with speed, while power rises. Calculated as: TE = piston diameter squared × piston stroke × 85 per cent of boiler pressure ÷ diameter of driving wheels. A three-cylinder engine has 50 per cent greater tractive effort than a two-cylinder engine; a four-cylinder engine has 100 per cent greater tractive effort than a two-cylinder engine.
Walschaerts valve gear
Form of valve gear patented by Belgian engineer Egide Walschaerts in 1844. Gradually it became the most popular, reliable, and easy to maintain steam railway locomotive valve gear and was adopted worldwide.
SELECT BIBLIOGRAPHY
Allen, Cecil J.
Locomotive Practice and Performance in the Twentieth Century (W. Heffer & Sons, 1949)
British Pacific Locomotives (Ian Allan, 1962)
Two Million Miles of Train Travel (Ian Allan, 1965)
Atkins, Philip
Dropping the Fire: The Decline and Fall of the Steam Locomotive (Irwell Press, 1999)
Ball, Don, Jr, and Whitaker, Rogers E. M.
Decade of the Trains: The 1940s (New York Graphic Society, 1977)
Barnes, Robin
Some 20th Century British Locomotives That Never Were (Jane’s Publishing, 1985)
Bellwood, John, and Jenkins, David
Gresley and Stanier: A Centenary Tribute (NRM York, 1976)
Blakemore, Michael, and Rutherford, Michael
Duchess of Hamilton: Ultimate in Pacific Power (NRM York, 1990)
Bond, Roland
A Lifetime with Locomotives (Goose & Son, 1975)
Broncard, Yves, and Fenino, Felix
French Steam (Ian Allan, 1970)
Brown, William
Hush-Hush: The story of LNER 10000 (Kestrel Railway Books, 2010)
Bruce, Alfred W.
The Steam Locomotive in America – Its Development in the Twentieth Century (W. W. Norton, 1952)
Bulleid, H. A. V.
Master Builders of Steam (Ian Allan, 1963)
Bulleid of the Southern (Ian Allan, 1977)
Carter, Ernest F.
Unusual Locomotives (Frederick Muller Ltd, 1960)
Catchpole, Paul
The Steam Locomotives of Czechoslovakia (published by the author, 1995)
Chacksfield, J. E.
Sir Henry Fowler: A Versatile Life (The Oakwood Press, 2000)
Sir William Stanier: A New Biography (The Oakwood Press, 2001)
Chapelon, André
La Locomotive à Vapeur, 2nd edn 1952, trans. by George W. Carpenter (Camden Miniature Steam Services, 2000)
Chester, Keith R. (ed.)
Russian and Soviet Steam Locomotives, 2 vols (Trackside Publications, 2000)
Clay, John F.
The Stanier Black Fives (Ian Allan, 1972)
Clay, John F. (ed.)
Essays in Steam (Ian Allan, 1970)
Clay, John F., and Cliffe, J.
The West Coast Pacifics (Ian Allan, 1976)
Cox, E. S.
Locomotive Panorama, 2 vols (Ian Allan, 1965–6)
Chronicles of Steam (Ian Allan, 1967)
World Steam in the Twentieth Century (Ian Allan, 1969)
Day-Lewis, Sean
Bulleid: Last Giant of Steam (George Allen & Unwin, 1964)
Drury, George H.
Guide to North American Steam Locomotives: History and Development of Steam Power since 1900 (Kalmach Books, 1993)
Durrant, A. E.
The Steam Locomotives of Eastern Europe, 2nd edn (David & Charles, 1972 )
Durrant, A. E., Lewis, C. P., and Jorgensen, A. A.
Steam in Africa (Hamlyn, 1981)
Fryer, Charles
Experiments with Steam (Patrick Stephens, 1990)
Giesl-Gieslingen, A.
Anatomie der Dampflokomotive (Verlag Josef Otto Stezak, 1986)
Glancey, Jonathan
The Train: An Illustrated History (Carlton Books, 2004)
Tornado: 21st Century Steam (Books on Track, 2010)
Gottwaldt, Alfred B.
Baureihe 05: Schnellste Dampflok der Welt (Franckh’sche Verlagshandlung, 1981)
Gruber, John, and Solomon, Brian
The Milwaukee Road Hiawathas (Voyageur Press, 2006)
Heywood, A. J., and Button, I. D. C.
Soviet Locomotive Types (Frank Stenvalls Forlag, 1995)
Hirsimaki, Eric
Lima: The History, 2nd edn (Hundsman Publishing, 2004)
Hollingsworth, Brian
An Illustrated Guide to Modern Trains (Salamander Books, 1985)
Huddleston, Eugene L., and Dixon, Thomas W.
The Allegheny: Lima’s Finest (Huddleston Dixon, 1984)
Kiefer, P. W.
A Practical Evaluation of Railroad Motive Power (Steam Locomotive Research Inc., 1947)
Klein, Maury
Union Pacific, vol. 2: The Rebirth 1894–1969 (Doubleday, 1990)
Kratville, William W.
The Challenger Locomotives (Kratville Publications, 1980)
Lamb, J. Parker
Perfecting the American Steam Locomotive (Indiana University Press, 2003)
Le Fleming, H. M., and Price, J. H.
Russian Steam Locomotives (David & Charles, 1960)
Maillet, M.
L’Oeuvre d’André Chapelon à la SNCF et son Influence Mondiale (Les Editions du Cabri, 1983)
Mierzejewski, Alfred C.
Hitler’s Trains: The German National Railway and The Third Reich (Tempus, 2005)
Miller, Kenneth L.
Norfolk and Western Class J: The Finest Steam Passenger Locomotive (Roanoke Chapter National Railway Historical Society, 2000)
Mullay, A. J.
Streamlined Steam: Britain’s 1930s Luxury Expresses (David & Charles, 1994)
Nock, O. S.
William Stanier: A Biography (Ian Allan, 1964)
British Locomotives at Work (George Allen & Unwin, 1967)
Railways of the USA (A. & C. Black, 1979)
British
Locomotives of the 20th Century, vol. 2: 1930–60 (Book Club Associates, 1984)
Locomotive Practice & Performance, vol. 1: The Age of Steam, 1959–68 (Ian Allan, 1989)
Péroche, Marcel
Pacific Senator, trans. by Roland Wilson (Argyll Publishing, 1984)
Powell, A. J.
Living with London Midland Locomotives (Ian Allan, 1967)
Ransome-Wallis, P.
On Railways at Home and Abroad (Batchworth, 1951)
Engines in Britain and France (Ian Allan, 1957)
Ransome-Wallis, P. (ed.)
The Concise Encyclopaedia of World Railway Locomotives (Hutchinson, 1959)
Reed, Brian (ed.)
Locomotives in Profile, 4 vols (Profile Publications, 1971–4)
Riemsdijk, Van J. T.
Compound Locomotives: An International Survey (Pendragon Books, 1994)
Robertson, Kevin
Leader: Steam’s Last Chance (Alan Sutton, 1988)
Rogers, Col. H. C. B.
Chapelon: Genius of French Steam (Ian Allan, 1972)
G. J. Churchward (George Allen & Unwin, 1975)
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