Santa Fe 4-6-4 "Hudson" Locomotives

The Atchison, Topeka & Santa Fe bought ten 4-6-4s (road number 3450 through 3459) from the Baldwin Locomotive Works in 1927. Curiously, Santa Fe did not refer to these locomotives as Hudsons. Instead, the Santa Fe classified them as an extension of the 3400 class of Pacifics. They were built as Duplex Stoker fired coal burners and converted to oil burners in 1932. During the 1930s these ten locomotives were overhauled and reworked to have 79" drivers and the boiler pressure was raised to 230 psi which changed the tractive effort to 43,300 pounds.

Six more 4-6-4s were designed by the Santa Fe in 1936 and ordered and received from Baldwin in 1937 (road numbers 3460 through 3465). They were oil burners and of a larger and more robust design then the earlier ten. One of this last group, number 3460, was built as a streamlined locomotive and called the "Blue Goose", the only one the road would have. These last six had 23.5 x 29.5 cylinders, 84" drivers, a boiler pressure of 300 psi and a tractive effort of 49,300 pounds.

In December of 1937, number 3461 led a train from Los Angeles all the way to Chicago a distance of 2,227 miles to set a world's distance record for a steam locomotive.

There are two surviving AT&SF 4-6-4s, number 3450, at the LA County Fairplex in Pomona, CA and number 3463, at the Expocenter in Topeka, KS.

Class Details by Steve Llanso of Sweat House Media

Class 3450 (Locobase 406)

Data from diagram presented at . See also DeGolyer, Vol 77, pp. 152-185. Works numbers were 59993-59997 in April 1927 and 60033-60037 in May. Cost set at $73,735.60 each.

Coal burners had 15,000 US gal (65,775 litres) water, 20 tons coal in their tenders.

This first series of 10 Hudsons had the same boiler as the 3400-series Pacifics, but a much bigger grate. The cylinders got their steam through 15" (381 mm) piston valves that had a maximum travel of 9" (227 mm).

Retrofitted in the late 1930s with redesigned tube layout and larger, 79-in drivers; see Locobase 11102.

Class 3450 (Locobase 11102)

Data from diagram presented at . See also

About 10 years after the AT & SF took delivery of its first Hudsons (Locobase 406), they substantially modified their boilers by cutting 34 tubes out of the boiler and adding 28" (711 mm) combustion chamber to the firebox. Further supplementing the direct heating surface by adding 108 sq ft (10 sq m) of thermic syphons changed the ratio of direct to total heating surface to truly superpower proportions.

Overshadowed by the world-class 3460 Hudsons and the series of 4-8-4 in Santa Fe passenger work, the 3450s operated in the Midwest between Chicago and Colorado. Later on, they connected San Francisco with Bakersfield down the San Joaquin Valley.

Class 3460 (Locobase 449)

See also "Atchison, Topeka and Santa Fe steam engine diagrams and blueprints," Kansas Memory, a website of the Kansas Historical Society, diagram at . (Thanks to Chris Hohl for the valve gear ID.) Works numbers were 62083-62088

Firebox had combustion chamber, two thermic syphons, Worthington feedwater heater.

Built 10 years later than the 3450 series (Locobase 406), these engines show the impact of the superpower revolution. Relatively high-drivered type on S.K.F. roller bearings but, unlike the Northwestern and Milwaukee Road engines, Five of the six were never streamlined. The firebox sported 95 sq ft (8.8 sq m) of thermic syphons and arch tubes, tube and flue ratios are reversed, the boiler is much larger and has a much larger superheater area. Boiler pressure increased by 36%. Steam was admitted to the cylinders through 13" (340 mm) diameter valves with 7" (179 mm) travel.

Although tractive effort is only 10% higher, the drier steam must have given the engines disproportionately more power. 3461 showed the class's long legs when it ran the full 2,227 miles from Los Angeles to Chicago in December 1937, making five fuel stops along the way. The average speed was 45.4 mph with top speeds of 90.

A thread in Yahoo's steam_tech forum includes a post by Kurt Greske, (, who notes that S Kip Farrington, in his book "Santa Fe's Big Three", quotes extensively from a highly critical engineering report of 3461's many defects after two months of running in October-December 1937.

Locobase has not been able to determine if the other locomotives in the class fell victim to so many leaks, misalignments, and overheated bearings and bushings. Certainly the design's use of such high steam pressures was likely to strain any weak point in the design or manufacture of the engine. Baldwin's response to such a string of calamities is also not reported and would make very interesting reading.

See Locobase 125 for the 1945 rebuild into possibly the most powerful express passenger locomotive ever. Retired in 1956.

Class 3460 (Locobase 125)

Data from tables in 1947 Locomotive Cyclopedia and 1945 diagram at "Atchison, Topeka and Santa Fe steam engine diagrams and blueprints," Kansas Memory, a website of the Kansas Historical Society, diagram at . (Thanks to Chris Hohl for persuading me that the rebuild did not include changing the valve gear.)

Santa Fe rebuilt the 3460-series Hudsons described in Locobase 449 in 1945, installing a new arrangement of tubes and flues. The engine had 90 sq ft (8.35 sq m) of thermic duplex syphons in the firebox and security water circulators in the 25-in combustion chamber.

Specifications by Steve Llanso of Sweat House Media
Class 3450 3450 3460 3460
Locobase ID 406 11102 449 125
Railroad Santa Fe (ATSF) Santa Fe (ATSF) Santa Fe (ATSF) Santa Fe (ATSF)
Whyte 4-6-4 4-6-4 4-6-4 4-6-4
Road Numbers 3450-3459 3450-3459 3460-3465 3460
Gauge Std Std Std Std
Builder Baldwin Santa Fe Baldwin Santa Fe
Year 1927 1937 1937 1945
Valve Gear Walschaert Walschaert Walschaert Walschaert
Locomotive Length and Weight
Driver Wheelbase 13.67' 13.67' 14.50' 14.50'
Engine Wheelbase 38.58' 36.67' 41.10' 41.10'
Ratio of driving wheelbase to overall engine wheebase 0.35 0.37 0.35 0.35
Overall Wheelbase (engine & tender) 81.38' 61.36' 88.67' 88.67'
Axle Loading (Maximum Weight per Axle) 68300 lbs 70000 lbs 71570 lbs 71600 lbs
Weight on Drivers 198300 lbs 206000 lbs 213440 lbs 210800 lbs
Engine Weight 343500 lbs 352000 lbs 412330 lbs 417300 lbs
Tender Light Weight 287000 lbs 298900 lbs 396340 lbs 396246 lbs
Total Engine and Tender Weight 630500 lbs 650900 lbs 808670 lbs 813546 lbs
Tender Water Capacity 15000 gals 15000 gals 20000 gals 20000 gals
Tender Fuel Capacity (oil/coal) 5000 gals 5000 gals 7000 gals 7108 gals
Minimum weight of rail (calculated) 110 lb/yard 114 lb/yard 119 lb/yard 117 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter 74" 79" 84" 84"
Boiler Pressure 220 psi 230 psi 300 psi 300 psi
Cylinders (dia x stroke) 25" x 28" 25" x 28" 23.5" x 29" 23.5" x 29.5"
Tractive Effort 44223 lbs 43307 lbs 48618 lbs 49456 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.48 4.76 4.39 4.26
Heating Ability
Firebox Area 314 sq. ft 338 sq. ft 375 sq. ft 433 sq. ft
Grate Area 88 sq. ft 88 sq. ft 98.50 sq. ft 99 sq. ft
Evaporative Heating Surface 4156 sq. ft 3397 sq. ft 4770 sq. ft 4303 sq. ft
Superheating Surface 980 sq. ft 952 sq. ft 2080 sq. ft 2020 sq. ft
Combined Heating Surface 5136 sq. ft 4349 sq. ft 6850 sq. ft 6323 sq. ft
Evaporative Heating Surface/Cylinder Volume 261.25 213.54 327.65 290.56
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation 19360 20240 29550 29700
Same as above plus superheater percentage 23038 24693 38415 39204
Same as above but substitute firebox area for grate area 82205 94843 146250 171468
Power L1 24810 25994 73177 69903
Power MT 827.48 834.57 2267.53 2193.21



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