Steam Locomotive Wheel Arrangements,
WHYTE System
Written by Bob Swanner

            As steam locomotive types became more numerous it became readily apparent that a better
system of locomotive identification was urgently needed. Specific locomotives were identified by individual
names “Prince of Wales”, “Devastator", “Intimidator”, or “Tom Thumb”, but trying to remember what type
engine the “Intimidator” was, got to be very confusing so a new system had to be devised.

            The new system is called the WHYTE System, named after Frederick Methvan Whyte a Dutch
New York Central mechanical engineer who designed it. This system identifies the locomotive by the
arrangement of its wheels, later most but not all wheel arrangements were named, usually by
the ones who first devised or bought that particular type.

            This system numbers the locomotive wheels starting with the front set at the headlight & working
back toward the rear set. . A steam engine might have two front guide wheels, six larger sized drive
wheels & zero rear (trailing) wheels, so it is designated: 2-6-0, read as two-six-oh

            The number of front guide wheels gives us an idea of the service for which  the locomotive was
intended.. Zero front wheels indicate slow speed where all adhesive weight is on drivers but there is no
guides front or rear to keep the large drivers centered so they won’t climb up & off the rail. Two front
wheels indicate medium speed like drag freight, but there are many fast exceptions.  Four wheels in
front indicate high speed service like passenger & priority freight. Additionally, the number of trailing
wheels indicates the steaming ability, the ability to run at sustained full throttle operation without loss
of steam pressure. Zero rear wheels indicate low power or low speed capability only, like switch
engines. Two rear guide wheels that were on the Atlantics, Pacifics, & Mikados indicate a moderate
improvement in steaming ability where a larger firebox, producing more steam, making higher steam
consumption possible. When the first four wheeled trailing truck was produced to support a truly
enlarged firebox was introduced on the 2-8-4 Berkshire, super power free steaming came into its’ own.
The trailing wheels also helped guide the locomotive in reverse.

            Remember this: The name is for the wheel arrangement, not a specific locomotive,
the “Tom Thumb” was a specific 0-4-0 locomotive.

            Listed are all the wheel arrangements with the types named.

            There will be a few types with more than one name, all that have been found are listed.

2-2-0 Vauxhall, Planet, Bury,
2-2-2 Adler, Firefly, Beuth,
2-4-0 John Bull,
4-2-0 Six Wheeler, Lafayette, Crampton,
4-2-2 Bicycle, Stirling 8 ft. single,
4-2-4 Pearson 9 ft. single,
6-2-0 John Stevens,
0-4-0 switcher,
0-4-2 Lion,
0-4-4 Forney 4-coupled,
2-4-2 Columbia,
4-4-0 American, Duke,
4-4-2 Atlantic,
4-4-4 Jubilee,
0-6-0 switcher,
0-6-4 Forney Six Coupled,
2-6-0 Mogul,
2-6-2 Prairie,
2-6-4 Adriatic,
4-6-0 Ten Wheeler,
4-6-2 Pacific,
4-6-4 Hudson, Baltic,
0-8-0 switcher,Monster 1830s,
2-8-0 Consolidation,
2-8-2 Mikado, MacArthur, Mud Hen, Bee,
2-8-4 Berkshire, Big Mike, Kanawha, Lima, Big Emma
4-8-0 Twelve Wheeler, Mastodon,
4-8-2 Mountain,
4-8-4 Northern, Dixie, Niagara, Greenbriar,
0-10-0 switcher,
2-10-0 Decapod,
2-10-2 Santa Fe, Central,
2-10-4 Texas, Selkirk, Colorado, A.T. & S.F # 5000 “Madam Queen”,
4-10-0   El Gobernador “The Governor” this is a specific name for one of a kind S.P. # 237,
4-10-2 Southern Pacific,
0-12-0 1863,
4-12-2 Union Pacific.

     The next group of locomotives is the Articulateds, which means hinged, where the
front engine can swivel, simple or compound notwithstanding.

0-4-4-0    First built by Fairly,
0-6-6-0   “Old Maude” type, first in U.S.A., Fairly,
2-6-6-4   The N & W “A” among others; not first of its’ type,
2-6-6-6   H-8 Allegheny, AG on the Virginian,
2-8-8-2   N & W  “Y” Series from Y1 to Y6b among many others, Chesapeake,
2-8-8-4   Yellowstone,  Cab Forward turned cab toward tender: AC-9,
4-8-8-2  Cab Forward which actually had three other wheel arrangements, this being the latest, the others were   2-6-6-2, 4-6-6-2 & 2-8-8-2.,
4-6-6-4   Challenger,
4-8-8-4   Big Boy,
2-10-10-2 used on Virginian & SantaFe,
2-8-8-8-2 & 2-8-8-8-4 Triplexes where the third set of drivers were under the tender, Erie & Virginian.

         Then we have the Beyer-Garret, Beyer-Peacock articulateds such as: 2-6-2 + 2-6-2,  4-6-2 + 2-6-4,
4-6-4 + 4-6-4,   2-8-2 +2-8-2,   4-8-2 + 2-8-4 etc.

        There are non-tender locomotives that are called tank engines, they are designated with a “T” after their wheel numbers like: 0-4-0T,  2-4-2T,  2-6-0T Etc.

       The next group of locomotives is the Duplexes: Most wearing the Pa. R.R. Keystone then the B & O: a Rigid Frame with two sets of drivers & cylinders.
2-2-2-0   Teutonic.

       The next set of wheel arrangements are the gear driven Shay, Heisler & Climax, that are numbered by the number of trucks:
2 truck [  8 wheels, all driven],
3 truck [12 wheels, all driven],
4 truck [16 wheels, all driven]

  Last & probably least are the rack engines of a few different types, 0-4-0T,  2-4-0T,  2-4-2T, 0-4-2T.

                  Nuts and Bolts
------------------------------------- April 9, 2009
 Questions?  Comments?