Northwestern Pacific / El Paso & Northeastern 2-6-2 "Prairie" Type Locomotives

Class PR-3 (Locobase 8173)

Data from the NWP 10 - 1950 Locomotive Diagram book supplied in May 2005 by Allen Stanley from his extensive collection. See the excellent roster on http://ncespee.railfan.net/rosters/oldnwptxtros.html, access 9 February 2007.Works numbers were 22446 and 22474 in July 1903.

Although often described as "Prairie Tanks", this pair can lay only a small claim to that characterisation. The diagram's outline suggests that this was a Mogul tank with a trailing axle added to hold up the bunker. Baldwin delivered them separately to the California Northwestern as 33-34.

Class Pr-1 (Locobase 10785)

Data from Baldwin Locomotive Works, Record of Recent Construction ((1903), No. 39, p. 256-257. Works numbers were 20999, 21024, and 21036-21037 in September 1902.

The only set of Prairies to operate for an Espee line, this quartet was produced for the EP & NE in single units. The EP & NE added two more (24657-24648, road #24-25) in September 1904 as class Pr-2; Locobase suspects they were very similar.

The class soon came under the El Paso & Southwestern when that railroad bought the EP & NE in 1905 and were renumbered 134-139. At some later date, the quartet was superheated; see Locobase 8671.

Class Pr-1 - superheated (Locobase 8671)

Data from SP 7 - 1951 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

Entering service on the El Paso & Northeastern with saturated boilers (Locobase 10785), this quartet was superheated relatively early, receiving the units between February 1912 and June 1913. In the process, they acquired outside radial valve gear, cylinders with 2" greater diameter, but less heating surface and lower boiler pressure.

They wore the EP & SW herald until the Southern Pacific bought the EP & SW in 1925. At that point they were assigned to the Southern Pacific de Mexico as 700-703, where, except for the 703, they ran until scrapping in 1934-1935. 703 had one more stop to make. Modified for oil-burning and re-re-numbered 1903, this engine operated on Bay Area commuter lines until 1934.

Specifications
Class	PR-3	Pr-1	Pr-1 - superheated
Locobase ID	8173	10785	8671
Railroad	Northwestern Pacific (SP)	El Paso & Northeastern (SP)	El Paso & Northeastern (SP)
Whyte	2-6-2T	2-6-2	2-6-2
Road Numbers	33-34 / 201-202	20-23	20-23 /134-37/ 1900-1903
Gauge	Std	Std	Std
Builder	Burnham, Williams & Co	Burnham, Williams & Co	Burnham, Williams & Co
Year	1903	1902	1912
Valve Gear	Stephenson	Stephenson	Walschaert
	Locomotive Length and Weight
Driver Wheelbase	8.50'	13.33'	13.33'
Engine Wheelbase	22.50'	31.50'	31.50'
Ratio of driving wheelbase to overall engine wheebase	0.38	0.42	0.42
Overall Wheelbase (engine & tender)	22.50'	58.96'
Axle Loading (Maximum Weight per Axle)
Weight on Drivers	84000 lbs	125190 lbs	136800 lbs
Engine Weight	117100 lbs	183865 lbs	200500 lbs
Tender Light Weight		116135 lbs
Total Engine and Tender Weight	117100 lbs	300000 lbs	0
Tender Water Capacity		6000 gals
Tender Fuel Capacity (oil/coal)
Minimum weight per yard of rail on which locomotive could run	47 lb rail	70 lb rail	76 lb rail
	Geometry Relating to Tractive Effort
Driver Diameter	47"	69"	70"
Boiler Pressure	160 psi	180 psi	170 psi
Cylinders (dia x stroke)	17" x 22"	21" x 28"	23" x 28"
Tractive Effort	18398 lbs	27380 lbs	30576 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort)	4.57	4.57	4.47
	Heating Ability
Firebox Area	91.60 sq. ft	188.30 sq. ft	188 sq. ft
Grate Area	14.20 sq. ft	53.50 sq. ft	53.90 sq. ft
Evaporative Heating Surface	1099	3520	2669
Superheating Surface			494
Combined Heating Surface	1099	3520	3163
Evaporative Heating Surface/Cylinder Volume	190.15	313.60	198.23
	Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation	2272	9630	9163
Same as above plus superheater percentage	2272	9630	10629
Same as above but substitute firebox area for grate area	14656	33894	37074
Power L1	3376	8228	11865
Power MT	265.81	434.69	573.64