On a steam locomotive, a driving wheel is a powered wheel which is
driven by the locomotive's pistons (or turbine, in the case of a steam
turbine locomotive). On a conventional, non-articulated locomotive,
the driving wheels are all coupled together with side rods (also known
as coupling rods); normally one pair is directly driven by the main
rod (or connecting rod) which is connected to the end of the piston
rod; power is transmitted to the others through the side
On diesel and electric locomotives, the driving wheels may be directly
driven by the traction motors. Coupling rods are not usually used, and
it is quite common for each axle to have its own motor. Jackshaft
drive and coupling rods were used in the past (e.g. in the Swiss
Crocodile locomotive) but their use is now confined to shunting
On an articulated locomotive or a duplex locomotive, driving wheels
are grouped into sets which are linked together within the set.
3 Whyte notation
4 Other uses of the term driving wheel
5 In popular culture
6 See also
The four driving wheels on one side of a
One of six 6 ft 8 in (2.03 m) driving wheels belonging
to 60163 Tornado
Driving wheels are generally larger than leading or trailing wheels.
Since a conventional steam locomotive is directly driven, one of the
few ways to 'gear' a locomotive for a particular performance goal is
to size the driving wheels appropriately. Freight locomotives
generally had driving wheels between 40 and 60 inches (1,016 and
1,524 mm) in diameter; dual-purpose locomotives generally between
60 and 70 inches (1,524 and 1,778 mm), and passenger locomotives
between 70 and 100 inches (1,778 and 2,540 mm) or so. Some long
wheelbase locomotives (four or more coupled axles) were equipped with
blind drivers. These were driving wheels without the usual flanges,
which allowed them to negotiate tighter curves without binding.
The driving wheels on express passenger locomotives have come down in
diameter over the years, e.g. from 8 ft 1 in (2,464 mm)
GNR Stirling 4-2-2
GNR Stirling 4-2-2 of 1870 to 6 ft 2 in
(1,880 mm) on the
SR Merchant Navy Class
SR Merchant Navy Class of 1941. This is because
improvements in valve design allowed for higher piston speeds.
Main article: Engine balance
A driving wheel on a steam locomotive.
On locomotives with side rods, including most steam and jackshaft
locomotives, the driving wheels have weights to balance the weight of
the coupling and connecting rods. The crescent-shaped balance
weight is clearly visible in the picture on the right.
In the Whyte notation, driving wheels are designated by the middle
number or numbers in the set. The
UIC classification system
counts the number of axles rather than the number of wheels and
driving wheels are designated by letters rather than numbers. The
suffix 'o' is used to indicate independently powered axles.
The number of driving wheels on locomotives varied quite a bit. Some
early locomotives had as few as two driving wheels (one axle). The
largest number of total driving wheels was 24 (twelve axles) on the
2-8-8-8-4 locomotives. The largest number of coupled
driving wheels was 14 (seven axles) on the ill-fated AA20 4-14-4
Other uses of the term driving wheel
The term driving wheel is sometimes used to denote the drive sprocket
which moves the track on tracked vehicles such as tanks and
In popular culture
Many American roots artists, such as The Byrds, Tom Rush, The Black
Crowes and the Canadian band
Cowboy Junkies have performed a song
David Wiffen called "Driving Wheel", with the lyrics "I
feel like some old engine/ That's lost my driving wheel."
These lyrics are a reference to the traditional blues song "Broke Down
Engine Blues" by Blind Willie McTell, 1931. It was later directly
Bob Dylan and Johnny Winter.
Many versions of the American folk song "In the Pines" performed by
artists such as Leadbelly,
Mark Lanegan (on The Winding Sheet), and
Nirvana (On MTV Unplugged In New York) reference a decapitated man's
head found in a driving wheel. In addition, it is likely that
Chuck Berry references the locomotive driving wheel in "Johnny B.
Goode" when he sings, "the engineers would see him sitting in the
shade / Strumming with the rhythm that the drivers made."
There is a band named Driving Wheel, featuring former Shaman's Harvest
members Ryan Tomlinson and Craig Wingate.
AAR wheel arrangement
Drive axles in the article Axle
^ Fowler, George L. (1909).
Locomotive Dictionary (1909 ed.). New
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^ "Another Balancing Scheme".
Locomotive Engineering. New York: Angus
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^ Herr, E.M.; Bush, S.P.; Lewis, W.H.; Quereau, C.H. (September 3,
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^ Ransome-Wallis 2001, p. 505.
^ Inkster, Ian, ed. (2017). History of Technology. Vol. 33. London and
New York: Bloomsbury Academic. pp. 55–56.
ISBN 978-1-4742-3725-3 – via Google Books.
^ Holland, Julian (2011). "Know your Engine: Main line diesel and
electric locomotive wheel arrangements". More Amazing and
Extraordinary Railway Facts. Newton Abbot: David & Charles – via
^ Boscawen, Robert (2010) . Armoured Guardsmen. Barnsley,
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^ Simons, Lisa M. Bolt (2010). The Kids' Guide to Military Vehicles.
Mankato, MN: Edge Books. p. 7. ISBN 978-1-4296-3370-3 –
via Google Books.
^ "Lyrics: Driving Wheel". MusixMatch. Retrieved July 8, 2017.
^ "Broke Down Engine Blues". Genius. Retrieved July 8, 2017.
^ "Lead Belly - In the Pines". Song Meanings. Retrieved July 8,
Ransome-Wallis, P., ed. (2001) . Illustrated Encyclopedia of
World Railway Locomotives. Mineola, NY: Dover Publications.
ISBN 0-486-41247-4 – via Google Books.
Locomotive running and valve gear
Valve gear types
AAR type A switcher truck
Radial steering truck
Schwartzkopff-Eckhardt II bogie
Other running gear elements