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.
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|
|Railroad||Philadelphia & Reading||Philadelphia & Reading|
|Number in Class||10||10|
|Builder||Burnham, Williams & Co||Reading|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.41||0.41|
|Overall Wheelbase (engine & tender)||30.75'|
|Axle Loading (Maximum Weight per Axle)||51167 lbs|
|Weight on Drivers||120860 lbs||115925 lbs|
|Engine Weight||201700 lbs||211625 lbs|
|Tender Light Weight|
|Total Engine and Tender Weight||201700 lbs||211625 lbs|
|Tender Water Capacity||3000 gals||3000 gals|
|Tender Fuel Capacity (oil/coal)||3.5 tons||6.3 tons|
|Minimum weight of rail (calculated)||67 lb/yard||64 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||200 psi||200 psi|
|Cylinders (dia x stroke)||20" x 24"||20" x 24"|
|Tractive Effort||26537 lbs||26537 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.55||4.37|
|Firebox Area||156.30 sq. ft||164.80 sq. ft|
|Grate Area||68.54 sq. ft||68.54 sq. ft|
|Evaporative Heating Surface||1982 sq. ft||1788 sq. ft|
|Combined Heating Surface||1982 sq. ft||1788 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||227.12||204.89|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||13708||13708|
|Same as above plus superheater percentage||13708||13708|
|Same as above but substitute firebox area for grate area||31260||32960|