San Pedro, Los Angeles & Salt Lake / Oregon-Washington RR & Navigation / Union Pacific 4-4-2 "Atlantic" Type Locomotives

Class A-2 (Locobase 8876)

These were Harriman Common Standard engines; see the description of the basic design at Locobase 5340. Works numbers were 23289-90, 23298-99, 23333-34, 23349-50, 23358, 23368 in December 1903 and 27383-27387, 27404, 27423-27426 in February 1906.

Locobase 4406 shows the locomotives delivered to the Oregon Short Line and the Oregon-Washington Railroad & Navigation Company subsidiaries.

The present examples have an entry to themselves because of their original road numbers. Clearly, marking a set of express passenger engines 1-20 suggests great expectations. Baldwin supplied the first group in December 1903 (to be followed by the OSL Atlantics) and picked up the work 2 years later in February 1906.

Like the other HCS Atlantics, these A-2s failed to meet those expectations, proving both slippery and underweight. They were withdrawn in the 1920s.

Class A-2/A-4 - OSL & OWR&N (Locobase 4406)

Like the A-3s of the Southern Pacific, these were Harriman Common Standard engines; see the description of the basic design at Locobase 5340. Built by Alco (Schenectady and Brooks) and Baldwin from 1904 to 1908. The 1904 and 1908 batches went to Oregon Short Line (3400-3411) while the 1911 Baldwins went to Oregon Western River & Navigation. They weren't entirely satisfactory, often being double-headed because of their slipperiness. Most were retired in the 1920s

Class A-3 (Locobase 5381)

Data confirmed by July 1908 table in American Engineer and Railroad Journal. See also "Atlantic Type Balanced Compound", Railway Master Mechanic, Vol XXX, #7 (July 1906), p. 336. Works numbers were 28336 in June 1906; 28616, 28625, 28639, 28655-28657, 28679-80 in July; and 28689, 28740-28743, 28929 in August.

These were the Vauclain compound version of the Harriman Common Standard engines. The design entered production 4 months after the last simple-expansion A-2s had left Baldwin's factory floor (see Locobase 8876).

An unusual component of the design were the slotted main rods coming from the inside LP cylinders and embracing the leading axle as they drove the rear axle. Like the simple Atlantics, they proved too slippery to last long on the Union Pacific. Moreover, their LP cylinders were out of proportion to the HP cylinders, yielding a ratio too high for the LP cans to be satisfactory in sharing the power load.

They were retired in 1921 and 1923 without being simpled or superheated.

Class A-81 - superheated (Locobase 7825)

These Harriman Common Standard engines (see Locobase 4406) were mostly scrapped in the 1920s. A few received a bit of a makeover that included a superheater and raising the boiler pressure to 200 psi. If they were slippery before, Locobase would suppose that increasing the tractive effort would worsen the condition. But the 4.55 factor of adhesion suggests otherwise.

By 1933, all of the OWRR&N Atlantics were out of service.

Class CT 70 / A-1 (Locobase 7260)

Data from SPLA&SL Locomotive Diagram book (the Salt Lake Route) supplied in May 2005 by Allen Stanley from his extensive collection.

This quartet of Atlantics had relatively small drivers, which suited the rail line over which they operated. Still, the design wasn't very satisfactory -- perhaps the small firebox limited steam-making -- and the class was retired in 1921.

See http://www.wemweb.com/arduous-road/build_railroad.html (accessed 5 Dec 2005) for details on constructing this railroad. The SP, LA & SL began building its line from Salt Lake City to Los Angeles via Las Vegas in 1901. In 1902, the UP acquired half of the stock from Utah Senator Williams Andrew Clark. Having shortened its name to the Los Angeles & Salt Lake (LASL) in 1916, Senator Clark sold the rest of its stock to the UP in 1921.

The LASL initials appeared on many UP-owned locomotives and rail cars for decades after.

Specifications
Class	A-2	A-2/A-4 - OSL & OWR&N	A-3	A-81 - superheated	CT 70 / A-1
Locobase ID	8876	4406	5381	7825	7260
Railroad	Union Pacific (UP)	Union Pacific (UP)	Union Pacific (UP)	Oregon-Washington RR & Navigation (UP)	San Pedro, Los Angeles & Salt Lake (UP)
Whyte	4-4-2	4-4-2	4-4-2	4-4-2	4-4-2
Road Numbers	1-20 / 3300-3319	3400-3411, 3500-3514	21-35 / 3320-3334	3503, 3505, 3510, 3513	3100-3103 / 3376-3379
Gauge	Std	Std	Std	Std	Std
Builder	Burnham, Williams & Co	several	Burnham, Williams & Co	shops	Alco
Year	1904	1904	1906	1910	1903
Valve Gear	Stephenson	Stephenson	Walschaert	Stephenson	Walschaert
	Locomotive Length and Weight
Driver Wheelbase	7'	7'	7'	7'	7.50'
Engine Wheelbase	27.58'	27.58'	27.83'	27.58'	26.17'
Ratio of driving wheelbase to overall engine wheebase	0.25	0.25	0.25	0.25	0.29
Overall Wheelbase (engine & tender)	58.17'	58.17'	58.72'	59.46'	59.08'
Axle Loading (Maximum Weight per Axle)	53500 lbs		56000 lbs	53450 lbs
Weight on Drivers	107000 lbs	105000 lbs	110000 lbs	106900 lbs	107000 lbs
Engine Weight	197000 lbs	196000 lbs	209000 lbs	199726 lbs	167000 lbs
Tender Light Weight	133050 lbs	162200 lbs	133050 lbs	147776 lbs	106635 lbs
Total Engine and Tender Weight	330050 lbs	358200 lbs	342050 lbs	347502 lbs	273635 lbs
Tender Water Capacity	7000 gals		7000 gals		5500 gals
Tender Fuel Capacity (oil/coal)	14 tons	tons	14 tons	tons	1748 gals
Minimum weight per yard of rail on which locomotive could run	89 lb rail	88 lb rail	92 lb rail	89 lb rail	89 lb rail
	Geometry Relating to Tractive Effort
Driver Diameter	81"	81"	81"	81"	70"
Boiler Pressure	190 psi	190 psi	200 psi	200 psi	200 psi
Cylinders (dia x stroke)	20" x 28"	20" x 28"	16" x 28"	20" x 28"	19" x 26"
Tractive Effort	22331 lbs	22331 lbs	22268 lbs	23506 lbs	22795 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort)	4.79	4.70	4.94	4.55	4.69
	Heating Ability
Firebox Area	180 sq. ft	174 sq. ft	180 sq. ft	174 sq. ft	135 sq. ft
Grate Area	49.50 sq. ft	49.50 sq. ft	49.50 sq. ft	49.50 sq. ft	42.20 sq. ft
Evaporative Heating Surface	2655	2649	2655	2196	2852
Superheating Surface				328
Combined Heating Surface	2655	2649	2655	2524	2852
Evaporative Heating Surface/Cylinder Volume	260.78	260.19	407.47	215.69	334.27
	Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation	9405	9405	9900	9900	8440
Same as above plus superheater percentage	9405	9405	9900	10890	8440
Same as above but substitute firebox area for grate area	34200	33060	36000	38280	27000
Power L1	8956	8866	5173	15960	9646
Power MT	369.06	372.31	207.35	658.29	397.49