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Front view of SP 4294.

By Marcin Wichary (originally posted to Flickr as [1]) [CC BY 2.0 (], via Wikimedia Commons

Front view of SP 4294.
SP herald.
Southern Pacific 4294 cab-forward steam locomotive on display at the California State Railroad Museum in Sacramento, California.

Southern Pacific 4294 cab-forward steam locomotive on display at the California State Railroad Museum in Sacramento, California.

By Neil916 (Talk) - I (Neil916 (Talk)) created this work entirely by myself., CC BY-SA 3.0,

Baldwin logo.

Southern Pacific 4294
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
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. It is essentially two locomotives, linked together, sharing fire box, boiler and crew. Only the front locomotive has its cranks quartered 90 degrees apart. The front and back drive axles are free to roll out of phase with respect to each other. If unloaded, the locomotive has a vertical oscillation, near 50 mph, that can lift the tires above the rails.

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 drive wheel axles are reversed, end for end without rekeying the return "fly" cranks, to reverse the expansion link timing on both sides.

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.

Southern Pacific 4294 Overview
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 1⁄2 in (1,435 mm) standard gauge
Driver diameter: 63 in (1,600 mm)
Minimum curve: 319.62 ft (97.42 m) radius or 18°
Wheelbase: 112 ft 2 in (34.19 m) (engine 67 ft 0.25 in or 20.43 m)(driver 44 ft 7 in or 13.59 m)
Length: 123 ft 8 in (37.69 m) (loco 78 ft 11 in or 24.05 m)
Width: 10 ft 0 in (3.05 m)
Height: 16 ft 4 in (4.98 m)
Adhesive weight: 531,700 lb (241,200 kg; 241.2 t)
Locomotive weight: 657,900 lb (298,400 kg; 298.4 t)[1] (boiler empty 576,800 lb) [2][page needed]
Tender weight: 393,330 lb (178,410 kg) (empty 160,000 lb or 73,000 kg)
Total weight: 1,048,000 lb (475,000 kg)
Tender type: Rectangular Model 220-R-6
Fuel type: Bunker C (#6 fuel oil)
Water capacity: Boiler 10,935 US gal (41,390 l; 9,105 imp gal) / Nathan 4000-C Non-Lifting Injector 12,000 gal/h (45 m3/h; 10,000 imp gal/h)
Tender capacity Oil: 6,100 US gal (23,000 l; 5,100 imp gal)
Tender capacity Water: 22,000 US gal (83,000 l; 18,000 imp gal)
Sandbox capacity: 2 tons (1.8 t; 1.8 long tons) to front 3 drivers of both engines
 • Firegrate area: 139 sq ft (12.9 m2)
Boiler Diameter: 108.125 in (2,746 mm)
Boiler pressure: 250 psi (1.7 MPa)
Feedwater heater: Worthington Type A6
Heating surface:
 • Tubes: 3,456 sq ft (321.1 m2)
 • Flues: 1,834 sq ft (170.4 m2)
 • Tubes and flues: 240 tubes / 91 flues
 • Firebox: 1,700 °F (930 °C)
Superheater: Elesco Type E
Cylinder size: 24 in × 32 in (610 mm × 810 mm) diameter × stroke
Valve gear: Walschaerts
Valve type: dual piston "spool"
Performance figures
Maximum speed: 63 mph (101 km/h)
Power output: 6,000 hp (4,500 kW) at 40 mph (64 km/h)
Tractive effort: 124,300 lbf (553 kN)
Towage Capacity: 9,000 tons (8,200 t; 8,000 long tons)
Factor of adhesion: 4.28
Operator: Southern Pacific Railroad
Class: AC-12
Number in class: 20
Number: 4294
Nickname: 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

See also:


Cab Forward Locomotives

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