#4165 passing near Mt. Shasta in Northern California, 1943.

# 4294 Cab-In-Front Articulated Locomotive

A National Historic MechanicalEngineering Landmark

The American Society of MechanicalEngineers � May 7, 1981

California State Railroad MuseumSacramento, California

Southern Pacific #4294 as photographed in 1944.

Southern Pacific #4294, a4-8-8-2 cab-in-front articulatedlocomotive, is the sole survivingsteam locomotive of its type.This engine is the culmination ofa series of steam locomotivedesigns and developments thatgrew out of the ever expandingneed for power, speed andtractive effort.

The 4-8-8-2Some people called the 4-8-8-2s

“back-up” locomotives; others calledthem “cab-in-front.” However, their cor-rect designation was “Articulated-Con-solidation” or “A-C” for short. Theywere numbered from 4100 to 4294.

Southern Pacific was the only majorrailroad in this country to use steamlocomotives with the cab in front. Thisdesign concept allowed the engineer andfireman to see further down the track andcontributed to greater safety aroundcurves, and through tunnels and snow-sheds in the mountains. It also eliminatedsmoke and heat entering the cab of theengine.

The 4-8-8-2 locomotives were reallytwo engines combined into one. Theyhad one boiler which served two sets ofcylinders driving independent groups ofwheels. “Consolidation” was the namegiven the older type of freight locomotivehaving eight driving wheels.

The 4-8-8-2 locomotives were long,heavy, and the largest, most powerful

Facts About the #4294 LocomotiveLength of engine and tender: 125 feet, 6 inches.

Weight of engine and tender loaded: 1,046,900 pounds.

Horse power: 6,000. Tractive power: 124,300 pounds.

Size of 4 cylinders: diameter 24 inches; stroke 32 inches.

Boiler pressure: 250 pounds. Diameter of drivers: 63 inches.

locomotives on the Southern Pacific dur-ing their time. They were fast—capableof attaining speeds of 70 miles per hour.These locomotives were used to haulheavy freight and passenger trains overthe steep grades in the Sierra and Cas-cade Mountains. On the Overland Routethey pulled the Overland Limited, SanFrancisco Challenger and Pacific Limitedup the Sierra.

The Southern Pacific’s Roseville—Sparks Sierra Crossing, built initially as asingle track railroad in 1869, reached fullcapacity in 1908. At that time seriousconsideration had to be given to increas-ing that capacity.

The 2.3 percent maximum grade in the87 miles from Roseville to Summit madeslow going for both passenger andfreight trains. As many as six 2-8-0 or4-8-0 type locomotives were needed tomove a train at 10 mph over the district.These trains had to stop frequently forfuel and water. Upon reaching the sum-mit, the helper locomotives wereremoved from the train and returned light(without cars attached) to Roseville. Thisincreased the number of individual move-ments and filled the district to capacity.

A partial solution was to double trackthe line. Another was to find morepowerful locomotives and eliminate thenumber of helpers needed.

Improving on the design of AnatoleMallet of France, the Baldwin LocomotiveWorks had improved steam generationand distribution in articulated compoundlocomotives. Samuel Vauclain of Baldwindeveloped the compound principle to sin-gle coupled locomotives and adaptedmany of his improvements to the articu-lated design.

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Baldwin suggested using 2-8-8-2 com-pound articulated locomotive weighing394, 150 pounds on 57-inch drivingwheels to help meet the SouthernPacific’s need. Two 26-inch H.P. (highpressure) cylinders would receive steamdirectly from the throttle and exhaust intotwo L.P. (low pressure) 40-inch with 30-inch stroke. Boiler pressure was 200pounds and the locomotives would exert94,880 pounds tractive effort.

Physical conditions of the original con-struction of the railroad restricted thedimensional freedom of the design. Thiswas to plague the designers of the sub-sequent articulated locomotives throughthe end of steam.

Two locomotives, delivered in 1909(Numbers 4000 and 4001), were classedMC 1. Four sisters were delivered to

Union Pacific properties in Oregon andldaho.

Functionally the new locomotives livedup to, and in many cases exceeded, ex-pectations. They handled 1,200 tons at10 mph with substantial savings in fueland water.

Problems arose, however, from ex-tended operation in tunnels and the near-ly 30 miles of snowsheds. Exhausttemperatures, which approached 750degrees, combined with combustiongases to make the cabs all butuninhabitable. To aid breathing underthese conditions, aspirators were in-stalled in the cabs to draw air from theair brake system. While furnishing a formof air to assist breathing, this did nothingto relieve the intense heat. Engine crewsbegan to resist assignment to trains

powered by the two mallets.

Many legends and secondhand storiesabound regarding the solution of theproblem. Several tests were made back-ing the locomotives with the tender run-ning first. This proved to be unsatisfac-tory, so the daring decision was made toturn the locomotive around and run withthe cab in front. The tender was trailedfrom the L.P. engine.

Fifteen locomotives of the new designwere ordered from Baldwin for deliverylate in 1909. They followed the basicspecifications of the original locomotives,but were slightly heavier. They solved thehabitability problem with the additionalbenefit of an unobstructed view of thetrack. Some problems were experiencedin the delivery of fuel to the firebox.Southern Pacific was a pioneer in the use

Locomotive Shop at Sparks, Nevada in 1944.

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Southern Pacific’s first cab-in-front (top) shows the original compound articu-lated engine after cylinder conversion to single expansion H.P. #4034(above) was one of the first Mallet consolidated (double expansion) cab-in-front engines. #4272 (below) shows the latest configuration.

of oil for fuel and did not have to solveburner problems having used the flatburners since the conversion to oil for theentire locomotive fleet in 1907. To helpsolve the problem, a pump was placed inthe fuel Iine to the burner. Later it wasfound by pressurizing the oil compart-ment to 5 pounds psi in the tender, thepump could be eliminated. The successof the 15 MC 2 class locomotivesprompted orders to be placed for 12more in 1912 which were classed MC 4.Additionally, 12 locomotives of the2-6-6-2 wheel arrangement wereordered for use on passenger trains.Like the MC 1 and 2 classes, they alsowere equipped with separable boilers,walshaert valve gear, and 25-inch and38-inch cylinders with 28-inch stroke.The weight was 320,000 pounds on 63-inch drivers. Boiler pressure was 200pounds and they developed 65,920pounds of tractive effort. Equipped withwhale back tenders of Southern Pacificdesign, they had greater fuel and watercapacity than the square tenders on theMCs.

Tracking problems and excessiveoverhang in the front of the locomotivesbrought about their conversion to 4-6-6-2wheel arrangement by placement of afour wheel truck under the fire box andredesigning the front frame structure.Their performance eliminated the use ofhelpers on the average passenger trainand expedited schedules.

Twenty more 2-8-8-2s were ordered in1912. Classed MC 6 they were similar tothe original locomotives and brought thetotal units in service at Roseville to 46.The two original conventional locomo-tives had been sent to SouthernCalifornia for use on Beaumont Hill.

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#4170, being used as a mid-train helper near Colfax, California, was one of the first series built for H.P. only.

By 1917 competitive pressures dictat-ed faster freight schedules that could notbe met with the slow moving compoundarticulated locomotives. Eleven 2-10-2type single expansion locomotives wereordered from American LocomotiveCompany and placed in service inRoseville. So successful were theselocomotives that 159 more units wereordered through 1924 and in 1925 the4-10-2 type was added. The rigid wheelbase of these units increased rail wearand general track maintenance costs.

A reappraisal of articulated locomo-tives was made. In 1922 BaldwinLocomotive Works delivered a series ofsimple H.P. 2-8-8-2 conventional cablocomotives to the Chesapeake andOhio Railroad which proved that in-creased speeds and tractive effort couldbe obtained with articulated locomotives.

Southern Paciffc’s Motive PowerDepartment studied the possibility ofconverting the Mallets to simple locomo-tives with the additional benefit of theirflexibility and short fixed wheelbase.(Simple locomotives had high pressurecylinders only.)

Locomotive 4041 was taken into theshops at Sacramento in 1927 for theconversion. The L.P. cylinders werereplaced with 22-inch cylinders and theoriginal H.P. 26-inch cylinders werebushed to 22 inches. The boiler pressurewas increased to 210 pounds; tractiveeffort to 90,940 pounds. Tests showedthe 4041 could handle the same tonnageas the 4-10-2s at 15 mph—an increase

of 50 percent. Plans were then made toconvert all the Mallets to simple. Thisthen led to the ultimate design of the4-8-8-2 types.

State-of-the-art techniques and appli-ances were incorporated in the design ofthe new locomotives. Assembled caststeel frames, cast steel cylinder blocks,front end throttles, E type superheaters,BL feedwater heaters, Nathan forcedfeed lubricators and many other devicesproved in use on the 2-10-2, 4-10-2 and4-8-2 types designed, built and placed inservice during the 1920s. Lateral motionboxes were applied to the fourth and fifthaxles, flange lubricators, water tirecoolers and clips were applied for useduring periods of heavy braking.

The redesigned boiler was to becomethe standard for the subsequent 195locomotives in eight classes. The firsttwo classes, AC 4 and AC 5 (numbered4100-4109, 4110-4125), carried 235pounds boiler pressure. Beginning withthe AC 6 class, the boiler pressure wasraised to 250 pounds and allowed thetractive effort to be raised to 124,300pounds from 116,900 pounds.

With the AC 6 class in service by1931, the 10 coupled locomotives werereassigned to other parts of the system.Although the new locomotives werelarger and heavier, their flexibilityreduced track wear and the ACs were toreign supreme in the Sierra until dis-placed by diesels in the 1950s.

Beginning with the AC 7 class in 1937,integral cast steel frames were used. The

cylinders and end beams were cast inone piece with the frame, thus reducingframe maintenance costs. The use ofBox-Pok disc driver allowed crossbalancing and made the top speed of thelocomotives around 65 mph. Earliersome of the AC 4 and 5 classes wereassigned to dual service between LosAngeles and Bakersfield. The greaterspeed allowed the locomotives to beused in both passenger and freight ser-vice throughout the lines west of El Paso,although the heaviest concentration wasalways at Roseville.

Visually, the remaining classes werethe same with a few minor differences.The wedge-shaped cab gave a semi-streamlined look as opposed to the flatfaces of the previous classes. Continuedimprovement of appliances were madeto all classes as they became availableincluding continued improvement in oilburner design. All of these locomotiveswere equipped with friction bearings andlubricated by the patented spring padlubricators. Large rectangular tenderswere fitted to these locomotives having acapacity of 6,100 gallons of oil and22,000 gallons of water. The AC 12s( # 4294) weighed 658,000 pounds inworking order. The tenders weighed198,000 pounds (388,900 pounds fullyloaded).

The last year of operation for thesegiants was 1956. The last cab-in-front tooperate was the # 4274 during theweekend of November 30, andDecember 1. A farewell excursion over

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#4172 on the turntable at Roseville, 1937.

the Sierra was sponsored by a railenthusiast group.

The #4294 had been removed fromservice prior to this time. Fred A. Stindt ofthe Pacific Coast Chapter, Railway &Locomotive Historical Society solicitedsupport from Southern Pacifie and civicgroups to save the last of these uniquemachines.

On October 19, 1958, #4294 waspresented to the City of Sacramento and

placed on display next to Southern The foregoing historic developmentPacific’s first locomotive, “C. P. Hunt- was made possible through the ef-ington.” Freeway construction forced the fort of many dedicated mechanicalremoval of # 4294 to storage at engineers who designed, calculat-Southern Pacific shop facilities at Sacra- ed and documented the myriadmento. The locomotive was later given to details that are involved in the con-the State of California by the City for struction and manufacture of smallrestoration and display in the California and large machinery. The AmericanState Railroad Museum where it again Society of Mechanical Engineers isjoins the “C. P. Huntington” in an impres- proud to acknowledge this silentsive display of the development of the partnership in the success of thesesteam locomotive in the West. behemoths of the rails.

Cab-in-fronts at the roundhouse in Roseville, 1937.

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The California State Railroad Museum occupies a block-long site along the Sacramento River in Old Sacramento.#4294 is displayed in the Museum of Railroad History (upper left). The Central Pacific passenger station is shownat the lower right.

The California State Railroad Museum:The #4294’s New Home

The new Museum of Railroad Histo-ry is the largest and most complexphase of the California State RailroadMuseum. Located in Old SacramentoState Historic Park, it was built underthe direction of the California Depart-ment of Parks and Recreation.

The Museum is the largest of itskind in the world. It houses 22 piecesof historic railroad rolling stock, hun-dreds of authentic artifacts of railroadhistory and folklore, and many thrillingexhibits and displays.

The first phase of the Museum,opened four years ago, was thereconstruction of the Central Pacificpassenger station on a block-long sitealong the Sacramento River.

Second phase was the completionof the Big Four Building—formerly theHuntington-Hopkins Hardware Storeand the Stanford Brothers Dry Goods

Store. The building houses the Muse-um’s administrative offices, flexible ex-hibit space and one of the most ex-tensive reference libraries ofrailroadiana in existence. The buildingalso contains the Big Four conferenceroom and the office of the CentralPacific Railroad where the idea of thetranscontinental railroad wasproposed.

Largest phase, just completed, isthe three-story Museum of RailroadHistory, built on a five acre site thathouses restored locomotives andcars, and 40 interpretive exhibits deal-ing with railroads and their impactupon the nation

John H. White, Jr., chairman of theDepartment of Industries at the Smith-sonian Institution, has described theMuseum’s railroad equipment as “oneof the great collections in the UnitedStates.”

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ACKNOWLEDGEMENTS

The Rail Transportation Division of The American Society of Mechanical Engineers gratefullyacknowledges the efforts of all who cooperated on the landmark designation of the #4294Cab-in-Front locomotive. A special thank you is extended to the California State RailroadMuseum, Southern Pacific Transportation Company, and the Pacific Coast Chapter of theRailroad & Locomotive Historical Society for their assistance.

The American Society of Mechanical EngineersDr. Charles E. Jones, presidentDr. Robert Gaither, president electCharles O. Velzy, vice president, industry departmentRichard K. Pefley, vice president, Region IXDr. Peter Chiarulli, deputy executive director

The National History and Heritage Committee, ASMEProf. J. J. Ermenc, chairmanDr. R. Carson DalzellProf. R. S. HartenbergDr. Paul HartmanRobert M. Vogel, Smithsonian InstitutionCarron Garvin-Donohue, staff director of operationsJill Birghenthal, administrator

The Rail Transportation Division, ASMED. G. Blaine, chairmanH. M. JonesM. F. HengelB. J. EckR. H. BrodeurJ. P. Van Overveen, History and Technology

The #4294 Cab-In-Front Locomotive is the 59th National Landmark designated by theSociety. For a complete listing of Landmarks, please contact the Public Information Depart-ment, ASME, 345 E. 47th St., New York, NY 10017 212/644-7740.

This brochure was produced with the assistance of Mr. Brian Thompson,author-historian and vice chairman, Pacific Coast Chapter of the Railway &Locomotive Historical Society.

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