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") Wootten firebox. According to Tratman, the Reading gave as a key reason for adopting a tank-locomotive layout the need for the fastest possible turnarounds at the downtown Philadelphia terminal.
Tratman continued with the key requirements: "A powerful but flexible engine was required, with good acceleration, as there are numerous sharp curves and heavy grades, and there are ten stops in the first ten miles. The engines are designed to haul trains of six cars" After experimenting with one of the Central of New Jersey's tanks, the Reading had this class built. " To tackle the sharp curves, Baldwin's front truck had a swing of 7 ins. [178 mm] to each side of its normal eentral position. This was an unusual amount of play.
"The road has had ten of these new tank engines in suburban service for a little more than a year," added Tratman,"and Mr. H. D. Taylor, Superintendent of Motive Power and Rolling Equipment, states that their use is still an open question and that he is not yet prepared to furnish information as to their performance."
Baldwin's weight estimates for the first batch--108,000 lb (48,988 kg) on the drivers, 178,000 lb (80,740 kg) for the engine--proved to have fallen way short. Actual adhesion weight came in six short tons higher and engine weight exceeded expectations by eleven tons. The "estimates" for the second batch not quite a year later were, not surprisingly, much more accurate. Chris Hohl's "catch" of the 6" (152 mm) increase in the later batch's wheelbase to 31 ft 3 in (9.52 m), combined with his observation that weight went up slightly to 204,000 lb (92,533 kg), highlighted his further finding that coal capacity in the bunker increased by 1 1/2 tons (1,361 kg). So high a capacity rarely appeared in a tank locomotive.
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 ten more years, being retired and scrapped once the Reading finished electrifying that part of its system.
|Principal Dimensions 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|
|Driver Wheelbase (ft / m)||12.50 / 3.81||12.50 / 3.81|
|Engine Wheelbase (ft / m)||30.75 / 9.37||30.75 / 9.37|
|Ratio of driving wheelbase to overall engine wheebase||0.41||0.41|
|Overall Wheelbase (engine & tender) (ft / m)||30.75 / 9.37|
|Axle Loading (Maximum Weight per Axle) (lbs / kg)||51,167 / 23,209|
|Weight on Drivers (lbs / kg)||120,860 / 54,821||115,925 / 52,583|
|Engine Weight (lbs / kg)||201,700 / 91,490||211,625 / 95,992|
|Tender Loaded Weight (lbs / kg)|
|Total Engine and Tender Weight (lbs / kg)||201,700||211,625|
|Tender Water Capacity (gals / ML)||3000 / 11.36||3000 / 11.36|
|Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)||3.75 / 3.40||6.30 / 5.70|
|Minimum weight of rail (calculated) (lb/yd / kg/m)||67 / 33.50||64 / 32|
|Geometry Relating to Tractive Effort|
|Driver Diameter (in / mm)||61.50 / 1562||61.50 / 1562|
|Boiler Pressure (psi / kPa)||200 / 13.80||200 / 13.80|
|High Pressure Cylinders (dia x stroke) (in / mm)||20" x 24" / 508x610||20" x 24" / 508x610|
|Tractive Effort (lbs / kg)||26,537 / 12037.00||26,537 / 12037.00|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.55||4.37|
|Firebox Area (sq ft / m2)||156.20 / 14.51||164.80 / 15.32|
|Grate Area (sq ft / m2)||68.54 / 6.37||68.54 / 6.37|
|Evaporative Heating Surface (sq ft / m2)||1982 / 184.13||1788 / 166.17|
|Superheating Surface (sq ft / m2)|
|Combined Heating Surface (sq ft / m2)||1982 / 184.13||1788 / 166.17|
|Evaporative Heating Surface/Cylinder Volume||227.12||204.89|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||13,708||13,708|
|Same as above plus superheater percentage||13,708||13,708|
|Same as above but substitute firebox area for grate area||31,240||32,960|