Philadelphia & Reading 2-6-4 "Adriatic" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class Q1-b (Locobase 2808)

Data from Oct 1903 American Engineer & Railroad Journal. Works numbers were 22591, 22613, 22617, 22627, 22636, 22673 in August 1903 and 24175, 24176, 24226-24227 in May 1904.

These very unusual tank engines hauled commuter trains between Reading Terminal in Philadelphia and Chestnut Hill. Note the very short tube length, relatively low drivers, and very wide (105") firebox.

Beginning in 1920, the Reading reconfigured the boiler; see Locobase 9460.

Class Q1-c/Q1-d (Locobase 9460)

Data from RDG 11 - 1926 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Raildata collection.

A decade and half after the Reading introduced the 2-6-4T Q1-a and Q1-b locomotives to commuter service (Locobase 2808), it rebuilt eight of the boilers in 1920-1922 with almost four dozen fewer tubes. Locobase suspects that the railroad wanted to increase the spacing between tubes for better circulation at the cost of about 200 sq ft of tube heating surface. The shops also replaced the original Stephenson link motion with outside Walschaert valve gear.

In 1924, all of the rebuilds were reclassified Q1-d, in which the weight was redistributed by adding more coal bunkerage, raising the total from 3 3/4 tons to 6 1/4 tons. Adhesion weight dropped from 127,900 lb to 115, 925 lb. The Q1-ds served for about 10 more years, being retired and scrapped once the Reading finished electrifying that part of its system.

Specifications by Steve Llanso of Sweat House Media
Locobase ID2808 9460
RailroadPhiladelphia & ReadingPhiladelphia & Reading
Number in Class1010
Road Numbers376-385376-385
Number Built10
BuilderBurnham, Williams & CoReading
Valve GearStephensonWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)12.5012.50
Engine Wheelbase (ft)30.7530.75
Ratio of driving wheelbase to overall engine wheebase 0.41 0.41
Overall Wheelbase (engine & tender) (ft)30.75
Axle Loading (Maximum Weight per Axle) (lbs)51,167
Weight on Drivers (lbs)120,860115,925
Engine Weight (lbs)201,700211,625
Tender Loaded Weight (lbs)
Total Engine and Tender Weight (lbs)201,700211,625
Tender Water Capacity (gals)30003000
Tender Fuel Capacity (oil/coal) (gals/tons) 3.50 6.30
Minimum weight of rail (calculated) (lb/yd)6764
Geometry Relating to Tractive Effort
Driver Diameter (in)61.5061.50
Boiler Pressure (psi)200200
High Pressure Cylinders (dia x stroke) (in)20" x 24"20" x 24"
Tractive Effort (lbs)26,53726,537
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.55 4.37
Heating Ability
Firebox Area (sq ft)156.30164.80
Grate Area (sq ft)68.5468.54
Evaporative Heating Surface (sq ft)19821788
Superheating Surface (sq ft)
Combined Heating Surface (sq ft)19821788
Evaporative Heating Surface/Cylinder Volume227.12204.89
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation13,70813,708
Same as above plus superheater percentage13,70813,708
Same as above but substitute firebox area for grate area31,26032,960
Power L164926136
Power MT355.26350.08


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