Southern Pacific 4294

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Southern Pacific 4294
SP4294 Neil916.JPG
Type and origin
Power type Steam
Builder Baldwin Locomotive Works
Serial number 70101
Build date March 1944
Configuration 4-8-8-2 Articulated Consolidation
Gauge 4 ft 8 12 in (1,435 mm)
Driver diameter 63 in (1,600 mm)
Minimum curve 320 ft. radius (18 degrees per 100 ft. chord)
Wheelbase 112 ft. 2 in. (engine 67 ft. .25 in.)(driver 44 ft. 7 in.)
Length 123 ft. 8 in. (loco 78 ft. 11 in.)
Width 10 ft.
Height 16 ft. 4 in.
Weight on drivers 531,700 lb (241.2 t)
Locomotive weight 657,900 lb (298.4 t) [1] (boiler empty 576,800 lb) [2]
Tender weight 393,330 lb (empty 160,000 lb)
Locomotive and tender
combined weight
1,048,000 lb.
Tender type Rectangular Model 220-R-6
Fuel type Bunker C (#6 fuel oil)
Water capacity Boiler 10,935 / Nathan 4000-C Non-Lifting Injector 12,000 Gals/Hr
Tender capacity 6,100 Gal. Oil / 22,000 Gal. Water
Sandbox capacity 2 Ton to front 3 drivers of both engines
Boiler Diameter 108.125 in.
Boiler pressure 250 psi (1.7 MPa)
Feedwater heater Worthington Type A6
Firegrate area 139 ft.
Heating surface:
– Tubes
3,456 square feet
– Flues 1,834 square feet
– Tubes and flues 240 tubes / 91 flues
– Firebox 1700 Degrees
Superheater type Elesco Type E
Cylinder size 24 in × 32 in (610 mm × 810 mm) (bore × stroke)
Valve gear Walschaerts
Valve type dual piston "spool"
Performance figures
Maximum speed 63 mph.
Power output 6,000 hp at 40 mph
Tractive effort 124,300 lbf (553 kN) Towage Capacity 9,000 Ton
Operator(s) Southern Pacific Railroad
Class AC-12
Number in class 20
Number(s) 4294
Nicknames Cab Forward
First run March 19, 1944
Retired March 5, 1956
Preserved one
Restored May 1981, Cosmetic
Current owner the city of Sacramento, California
Disposition indoor static display at the California State Railroad Museum

Southern Pacific 4294 was the last steam locomotive ordered new by Southern Pacific Railroad (SP). It was built by Baldwin Locomotive Works in March 1944, and was used hauling SP's trains over the Sierra Nevada, often working on Donner Pass in California.

Construction and use[edit]

SP4294 was the last of 256 Southern Pacific articulated cab forwards starting with class AC-1. 4294 was the last in a group of 20 locomotives that comprised SP's AC-12 class of 4-8-8-2 cab forward locomotives.

Its most distinguishing feature was that the cab and firebox were at the front of the locomotive instead of the traditional rear. This was done essentially by running a 2-8-8-4 machine backwards with myriad modifications. The engineer and fireman swapped sides and faced away from the firebox. The tender was moved to behind the "new" locomotive back to improve forward vision. The smoke box end coupling was strengthened. The power reverse lever (Johnson Bar) and the steam throttle motion direction was reversed. The left side Walschaerts return (fly) cranks are mounted 36 degrees left of the drive crank radial, when the drive pin is at bottom-dead-center. The right side return cranks are mounted 36 degrees right of the drive crank radial, when the drive pin is at bottom-dead-center, to reverse the expansion link timing on both sides. [3]

Conventional Walschaerts return crank position in red

This specific SP design was a necessity in the long tunnels and snow sheds of Donner Pass and other mountainous regions where it kept smoke, heat, and soot away from the operating crew and offered them clean, cool air to breathe. It also provided the crew a superb view. It entered service on March 19, 1944, and was retired from active service on March 5, 1956.


SP was convinced to preserve one of the class and donated 4294 to the city of Sacramento, California, where it was put on outdoor display October 19, 1958, at the SP station next to the C. P. Huntington, the railroad's first locomotive. Construction for Interstate 5 necessitated a move for the locomotive, and it was stored in the SP shops until May 1981. At that time it was moved again, this time to its current location, the California State Railroad Museum, where it remains on static display.

Had it not been for the negotiating efforts of the Railway and Locomotive Historical Society in the 1950s, 4294 likely would have been scrapped along with all of the other SP cab forward locomotives. As a result, 4294 is the only SP cab forward that has been preserved.

At one time, it was hoped that 4294 could be restored to operating condition. According to CSRM personnel, the biggest impediments toward such a project are the estimated costs and the current policies of both Union Pacific Railroad and BNSF Railway in regards to operations. The cost of such a restoration is estimated between $1 million and $1.5 million, an amount that the museum feels would be prohibitive given the current prospects for its eventual operation.[4]


  • Diebert, Timothy S. and Strapac, Joseph A. (1987). Southern Pacific Company Steam Locomotive Conpendium. Shade Tree Books. ISBN 0-930742-12-5. 
  1. ^
  2. ^ Andersonn, David (17 July 2013). Cab-Forward. Russell O'Day. 
  3. ^ Church, Robert (1982). Cab-Forward. The Story of Southern Pacific Articulated Locomotives. Wilton, California: Central Valley Railroad Publications. 
  4. ^ Wyatt, Kyle K., Curator of History and Technology, CSRM, 2007-08-21