Texas & Pacific 4-6-2 "Pacific" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class P-1-R (Locobase 8512)

Data from T&P 1 -1950ca Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. (Thanks to Chris Hohl for his query on the modification dates that led to a revision to 1940 for the first.)

Most of the original P-1 stud (Locobase 170) remained relatively unchanged during its service life. In at least two instances, however, the railroad put the locomotives through a substantial upgrade. The three locomotives shown in this entry were modified in February 1940 (700), April 1944 (704), and February 1945 (706).

In addition to installing two thermic syphons that contributed 74 sq ft to the firebox heating surface, the shops thoroughly reconfigured the boiler and firebox. In place of the 242 2" tubes and 34 5 3/8" flues, the boiler now held 160 2 1/4" tubes and 35 5 1/2" flues, all cut down by 30 inches. Twenty-seven of those inches went into a combustion chamber ahead of the firebox.

The result was a substantial drop in combined heating surface, but significant increases in direct heating surface (almost 50%) and superheater area (22%) combined with a 15-psi increase in boiler pressure. All things considered, and granting that the small boiler put an upper limit on steam supply, this revised design was now one of the most efficient and powerful examples in Pacificdom, particularly when compared to those with similar driver diameters.

[NB: Engine 700 received a similar boiler, but instead of thermic syphons, the firebox housed three security circulators that added 46 sq ft of heating surface. Total evaporative heating surface came to 2,904 sq ft - 28 sq ft less than the thermic-syphon mod.]

Class P-1/P-1a/P-1b (Locobase 170)

Firebox data from T&P 1 -1950ca Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection. (The T&P 1 - 1922 diagram book shows slightly different values for the Baldwin firebox, including 28 sq ft of arch tubes. They were removed in 1933.) See also DeGolyer, Volume 61, pp. 402+. (Thanks to Chris Hohl for his 11 March 2016 for noting the tender capacities and weight.)

The oil-burning Pacifics P-1 (600-606, built by Baldwin-works numbers 51574, 51606, 51632-51633 in March 1919; 51666, 51744-51745 in April) and P-1a (707-713, built by Brooks--works numbers 61286-61292 in December 1919) . The Brooks engines were slightly heavier and had other small differences. Richmond supplied eight more locomotives (works numbers 64057-64064) based on the Brooks engines in 1923. Described in Railway Age Gazette in 1926.

The Baldwins were ordered with Southern valve gear, but that specification was changed before the locomotives were built. In any case, 14" (356 mm) piston valves served steam to the cylinders.They were delivered with tenders weighing 175,000 lb ( 79,379 kg) and carrying 9,000 US gallons (34,065 litres) of water and 3,200 (12,112 litres) of oil.

At least two of the class were fitted with thermic syphons and a modified superheater layout; see Locobase 8512.

Specifications by Steve Llanso of Sweat House Media
Locobase ID8512 170
RailroadTexas & Pacific (T&P)Texas & Pacific (T&P)
Number in Class322
Road Numbers700*, 704, 706600-606/701-721
Number Built22
BuilderTexas & Pacificseveral
Valve GearWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)1313
Engine Wheelbase (ft)34.5834.58
Ratio of driving wheelbase to overall engine wheebase 0.38 0.38
Overall Wheelbase (engine & tender) (ft)74.1574.15
Axle Loading (Maximum Weight per Axle) (lbs)56,80052,876
Weight on Drivers (lbs)170,400173,357
Engine Weight (lbs)270,000275,080
Tender Loaded Weight (lbs)242,260242,260
Total Engine and Tender Weight (lbs)512,260517,340
Tender Water Capacity (gals)12,00012,000
Tender Fuel Capacity (oil/coal) (gals/tons)50085008
Minimum weight of rail (calculated) (lb/yd)9596
Geometry Relating to Tractive Effort
Driver Diameter (in)7373
Boiler Pressure (psi)200185
High Pressure Cylinders (dia x stroke) (in)26" x 28"26" x 28"
Tractive Effort (lbs)44,07940,773
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.87 4.25
Heating Ability
Firebox Area (sq ft)329216
Grate Area (sq ft)59.6059.60
Evaporative Heating Surface (sq ft)29323780
Superheating Surface (sq ft)1036844
Combined Heating Surface (sq ft)39684624
Evaporative Heating Surface/Cylinder Volume170.41219.69
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation11,92011,026
Same as above plus superheater percentage15,01913,011
Same as above but substitute firebox area for grate area82,90847,153
Power L119,65916,295
Power MT763.04621.68


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