B&O's 2-10-2 "Big Six" Locomotives: Specs, Roster, History

Last revised: November 2, 2024

The Baltimore & Ohio's fleet of Class S-1 2-10-2s were often referred to as "Santa Fe's" on most other lines, named after the railroad which first employed the wheel arrangement during the early 20th century.

However, on the B&O they were known as "Big Sixes" because of their incredible size and 6000 numbering series.

Most disliked the design in standard road service since they had counterbalancing issues. However, some, like the B&O and Santa Fe, found the locomotive more than sufficient, rostering more than 100 examples each.

The B&O normally assigned its fleet in heavy drag service along its West End main line. The railroad acquired its first 2-10-2s prior to World War I and with the coming of the diesel all were gone before 1960.

Before steam came to a close, numerous large wheel arrangements could be found all across Baltimore & Ohio's system, from the 0-8-8-0 and 2-8-8-0 to the 2-6-6-2 and 2-8-8-4.

However, none were as common in heavy drag service as the Big Six, a locomotive which worked the West End's stiff grades daily. Photographers like Bob Collins, Bill Price, and others caught the 2-10-2's often during the 1950's.

Photos

One of the Baltimore & Ohio's big 2-10-2 "Big Sixes" steams eastbound towards the railroad's shop complex at Cumberland, Maryland along the North Branch of the Potomac River with a massive Bethlehem Steel beam during a fall day in the 1950s. American-Rails.com collection.

History

The 2-10-2 wheel arrangement was first tested by the Santa Fe (hence its name) in 1903 when it requested a small batch of 2-10-0s be fitted with a trailing axle to enable back up moves when operating in pusher service over Raton Pass.

Soon, 2-10-2s built from the ground up were being ordered not only by the Santa Fe (which would roster more than 330) but also other railroads, which found its ten drivers and high tractive effort very appealing.

Unfortunately, it ran into some counterbalancing issues as according to SteamLocomotive.com there, "...was not enough room for counter weights on the relatively small driving wheels," an issue that was corrected in the later 2-10-4. Interestingly, despite this problem more than 2,000 were ultimately built for dozens of major railroads.

Diagram

Implementation

It was the Baltimore & Ohio's, however, that are often considered the very best 2-10-2s ever built; they were fast, powerful, reliable, and the railroad loved them.

Its first batch of Big Sixes arrived in 1914, manufactured by the Baldwin Locomotive Works numbered 6000-6030 and given Class S.

These sported the smallest drivers of any the B&O owned at just 58 inches. While this caused the locomotives to operate at slow speeds it provided more than 2,000 pounds of additional tractive effort (compared to later examples the railroad acquired) and one could regularly find the Class S's in heavy drag service.

A decade later the railroad went back to Baldwin for additional Big Sixes, purchasing 50 more that were designated as Class S-1 and numbered 6100-6149, which arrived between 1923 and 1924.

A Baltimore & Ohio 2-10-2 "Big Six" works a string of empty coal hoppers westbound over Sand Patch during the 1950s. A.C. Kalmbach photo. American-Rails.com collection.

This batch was part of an order that spanned 125 units in all, acquired through 1926; Class S-1's 6150-6174 were built by the Lima Locomotive Works (1923-1924), Class S-1a's numbered 6175-6199 also came from Lima in 1926, while the final S-1a's in 1926 numbered 6200-6224 were additional Baldwin products. It is these final 125 Big Sixes that are so often heralded as the best ever built.

The Class S-1's and S-1a's corrected some issues over the earlier Class S's that enabled more efficient operations such as increasing the drivers to 64 inches (allowing the locomotive's to operate much faster and at speeds over 30 mph they were the fastest 2-10-2s ever built) and the addition of more weight to the locomotives gave them a better factor of adhesion.

The S-1/a's also were equipped with a larger firebox and a wheelbase of nearly 90 feet (more than 14 feet longer than the original class).

Specifications

Builder	Baldwin Locomotive Works
Class	S
Date Built	4/1914 - 11/1914
Wheelbase (Engine)	40 Feet, 3 Inches
Wheelbase (Engine & Tender)	76 Feet, 5 13/16 Inches
Length (End-Of-Couplers)	87 Feet, 3 11/16 Inches
Height (Top-of-Rail to Top-of-Stack)	15 Feet, 5 ¾ Inches
Engine Weight	410,200 Lbs
Tender Weight	186,110 Lbs
Total Weight	596,310 Lbs
Weight on Drivers	332,400 Lbs
Tender Fuel Capacity	18.5 Tons
Tender Water Capacity	9,700 Gallons
Driver Diameter	56 Inches
Valve Gear	Walschaert
Driver Brake	American
Boiler Pressure	205 psi
High Pressure Cylinders (Diameter x Stroke)	30" x 32"
Maximum Tractive Effort	86,500 Lbs
Heating Surface/Superheating	1,308 Square Feet

S-1, S-1a

Builder	Baldwin Locomotive Works, Lima Locomotive Works
Class	S-1, S-1a
Date Built	S-1 (1923-1924)
Date Built	S-1a (1926)
Wheelbase (Engine)	42 Feet, 11 Inches
Wheelbase (Engine & Tender)	89 Feet, 10 7/8 Inches
Length (End-Of-Couplers)	101 Feet, 3 3/8 Inches
Height (Top-of-Rail to Top-of-Stack)	15 Feet, 5 3/8 Inches
Engine Weight	436,510 Lbs
Tender Weight	298,400 Lbs
Total Weight	734,910 Lbs
Weight on Drivers	347,230 Lbs
Tender Fuel Capacity	23 Tons
Tender Water Capacity	15,800 Gallons
Driver Diameter	64 Inches
Valve Gear	Baker
Driver Brake	American
Boiler Pressure	220 psi
High Pressure Cylinders (Diameter x Stroke)	30" x 32"
Maximum Tractive Effort	84,300 Lbs
Heating Surface/Superheating	1,512 Square Feet

A Baltimore & Ohio 2-10-2 "Big Six" works a westbound freight upgrade over Sand Patch near Manila, Pennsylvania in the spring of 1955. American-Rails.com collection.

Of note were three 2-10-2s that were either slightly rebuilt or modified by the B&O over the years; according to David Mainey in his book "Baltimore & Ohio Steam In Color "...had a cast steel engine bed, light weight pistons, rods, and crossheads and cosmetic changes such as the placement of the air pumps on the pilot deck and centering of the headlight on the smoke box."

Due to this variation the B&O listed it as a Class S-1b. Additionally, #6105 and #6168 had similar changes as #6222 and both were listed as Class S-1c. In service the Big Sixes put on quite a show along the West End where they were normally assigned most of the time.

Mr. Mainey's book, for instance, offers some incredible color photography of these beasts working hard in helper service shoving freights up the stiff 2%+ grades over Sand Patch at locations such as Manila, Mance, and passing SA Tower at Sand Patch, Pennsylvania.

Roster

S

Class	Builder	Road Numbers	Serial Numbers	Date Built
S	Baldwin	6000-6030	41309, 41631-41632, 41644-41645, 41663, 41681-41683, 41701-41705, 41711-41717, 41757-41761, 41792-41794, 41799-41800	4/1914 - 11/1914

S-1

Road Number	1956 Renumbering	Serial Number	Builder	Date Built
6100	-	57214	Baldwin	10/1923
6101	-	57215	Baldwin	10/1923
6102	-	57216	Baldwin	10/1923
6103	-	57232	Baldwin	10/1923
6104	-	57330	Baldwin	10/1923
6105	500	57331	Baldwin	10/1923
6106	501	57332	Baldwin	10/1923
6107	-	57333	Baldwin	10/1923
6108	-	57334	Baldwin	10/1923
6109	-	57335	Baldwin	10/1923
6110	-	57336	Baldwin	10/1923
6111	-	57337	Baldwin	10/1923
6112	-	57338	Baldwin	10/1923
6113	502	57439	Baldwin	11/1923
6114	503	57440	Baldwin	11/1923
6115	504	57447	Baldwin	11/1923
6116	-	57448	Baldwin	11/1923
6117	505	57449	Baldwin	11/1923
6118	-	57450	Baldwin	11/1923
6119	506	57451	Baldwin	11/1923
6120	507	57452	Baldwin	11/1923
6121	-	57453	Baldwin	11/1923
6122	508	57454	Baldwin	11/1923
6123	-	57455	Baldwin	11/1923
6124	-	57456	Baldwin	11/1923
6125	-	57457	Baldwin	11/1923
6126	-	57458	Baldwin	11/1923
6127	-	57459	Baldwin	11/1923
6128	-	57460	Baldwin	11/1923
6129	-	57461	Baldwin	11/1923
6130	-	57460	Baldwin	11/1923
6131	509	57463	Baldwin	11/1923
6132	510	57464	Baldwin	11/1923
6133	-	57465	Baldwin	11/1923
6134	511	57466	Baldwin	11/1923
6135	-	57467	Baldwin	11/1923
6136	-	57468	Baldwin	11/1923
6137	512	57469	Baldwin	11/1923
6138	-	57470	Baldwin	11/1923
6139	-	57471	Baldwin	11/1923
6140	-	57569	Baldwin	12/1923
6141	-	57570	Baldwin	12/1923
6142	-	57571	Baldwin	12/1923
6143	-	57572	Baldwin	12/1923
6144	-	57573	Baldwin	12/1923
6145	514	57574	Baldwin	12/1923
6146	-	57575	Baldwin	12/1923
6147	515	57576	Baldwin	12/1923
6148	-	57594	Baldwin	1/1924
6149	-	57595	Baldwin	1/1924
6150	516	6700	Lima	3/1924
6151	-	6701	Lima	3/1924
6152	517	6702	Lima	3/1924
6153	-	6703	Lima	3/1924
6154	-	6704	Lima	3/1924
6155	-	6705	Lima	3/1924
6156	-	6706	Lima	3/1924
6157	518	6707	Lima	3/1924
6159	519	6709	Lima	4/1924
6160	-	6710	Lima	4/1924
6161	-	6711	Lima	4/1924
6162	-	6712	Lima	4/1924
6163	-	6713	Lima	4/1924
6164	-	6714	Lima	4/1924
6165	-	6715	Lima	4/1924
6166	-	6716	Lima	4/1924
6167	-	6717	Lima	4/1924
6168	520	6718	Lima	4/1924
6169	-	6719	Lima	4/1924
6170	-	6720	Lima	4/1924
6171	-	6721	Lima	4/1924
6172	521	6722	Lima	4/1924
6173	-	6723	Lima	4/1924
6174	522	6724	Lima	4/1924

S-1a

Road Number	1956 Renumbering	Serial Number	Builder	Date Built
6175	523	7060	Lima	5/1926
6176	-	7051	Lima	5/1926
6177	524	7052	Lima	5/1926
6178	525	7053	Lima	5/1926
6179	-	7054	Lima	5/1926
6180	-	7055	Lima	5/1926
6181	-	7056	Lima	5/1926
6182	-	7057	Lima	5/1926
6183	-	7058	Lima	5/1926
6184	-	7059	Lima	5/1926
6185	526	7060	Lima	5/1926
6186	-	7061	Lima	5/1926
6187	527	7062	Lima	5/1926
6188	-	7063	Lima	5/1926
6189	-	7064	Lima	5/1926
6190	528	7065	Lima	5/1926
6191	-	7066	Lima	7/1926
6192	-	7067	Lima	7/1926
6193	-	7068	Lima	7/1926
6194	-	7069	Lima	7/1926
6195	-	7070	Lima	7/1926
6196	-	7071	Lima	7/1926
6197	529	7072	Lima	7/1926
6198	-	7073	Lima	7/1926
6199	530	7074	Lima	7/1926
6200	531	59062	Baldwin	3/1926
6201	532	59063	Baldwin	3/1926
6202	533	59064	Baldwin	3/1926
6203	-	59114	Baldwin	4/1926
6204	-	59115	Baldwin	4/1926
6205	-	59116	Baldwin	4/1926
6206	-	59117	Baldwin	4/1926
6207	534	59118	Baldwin	4/1926
6208	535	59119	Baldwin	4/1926
6209	-	59120	Baldwin	4/1926
6210	-	59121	Baldwin	4/1926
6211	-	59178	Baldwin	5/1926
6212	-	59179	Baldwin	5/1926
6213	-	59180	Baldwin	5/1926
6214	-	59181	Baldwin	5/1926
6215	-	59182	Baldwin	5/1926
6216	-	59183	Baldwin	5/1926
6217	536	59184	Baldwin	5/1926
6218	-	59185	Baldwin	5/1926
6219	537	59186	Baldwin	5/1926
6220	-	59228	Baldwin	5/1926
6221	-	59229	Baldwin	5/1926
6222	538	59230	Baldwin	5/1926
6223	-	59231	Baldwin	5/1926
6224	-	59232	Baldwin	5/1926

Baltimore & Ohio 2-10-2 "Big Six" #6112 (S-1) is seen here entering the Cumberland Narrows (Maryland) as it heads westbound, circa 1950s.

Retirement

The Baltimore & Ohio's original Big Sixes were early victims of retirement; two were dismantled in 1925 to construct new 4-8-2 Mountains and fifteen others were scrapped in 1938. Most were gone by the mid-1950s. The Class S-1's could still be found working heavy freights until virtually the end of the B&O's steam era.

As diesels gradually replaced steam on the railroad's fabled mountain grades in the east (most were gone from this region by 1956) the Big Sixes were sent west to work in drag service along the relatively flat Toledo, Akron, and Chicago Divisions during their final few years where those remaining could be found at the terminal in Willard, Ohio.

Finally, all were pulled from service by 1959 and scrapped. Normally, the B&O was very astute to preserve its history. However, by the late 1950s the railroad was having serious financial issues, which most likely explains why no Big Sixes were saved for preservation.

Sources

Edson, William D. Steam Locomotives Of The Baltimore & Ohio: An All-Time Roster. Potomac: William D. Edson, 1992.

Mainey, David. Baltimore & Ohio Steam In Color. Scotch Plains: Morning Sun Books, 2001.

Reynolds, Kirk and Oroszi, David. Baltimore & Ohio Railroad. Osceola: MBI Publishing, 2000.

Schafer, Mike. Classic American Railroads. Osceola: MBI Publishing, 1996.