In 1912, the Philadelphia & Reading Railroad built an experimental "Mikado" locomotive at the Reading shops. This locomotive had 61.5" diameter drivers, 24" x 32" cylinders, a 215 psi boiler pressure, it exerted 54,772 pounds of tractive effort and it weighed 329,310 pounds. The firebox was 326 square feet, the evaporative heating surface was 4,224 square feet and with the superheater the combined heating surface was 5,217 square feet. The design of this 2-8-2 which was given road number 1700 was deemed to be a success
In1917, the Baldwin Locomotive Works was given an order to build 56 locomotives based on this design in two subclasses. The first 26 of these "Mikados" had 61 ½" diameter drivers and were classified as Class M1-sa and assigned road numbers 1701-1726. The other 30 were built with 55 ½" diameter drivers and classified as Class M1-sb and assigned road numbers 1727-1756. All 56 of these 2-8-2s had 24" x 32" cylinders, they were delivered with a 215 psi boiler pressure and the M1-sa class exerted 54,772 pounds of tractive effort and the M1-sb class exerted 60,693 pounds of tractive effort.
These Class M1-sa and M1-sb locomotives used superheated steam and had Wootten boilers and a grate area of 108 square feet. The Wootten boiler was designed in 1877 to burn small sizes of cheap anthracite coal. Slow burning anthracite required a very large grate area to achieve the same heat as a much smaller one that burned bituminous coal. The firebox was extremely wide and shallow at the bottom and had a crown sheet curved with a large radius. The design permitted a thin fire and a light draft, which avoided blowing fuel out of the stack. The firebox was 298 square feet, the evaporative heating surface was 3,803 square feet and with the superheater the combined heating surface was 4,640 square feet.
There are no surviving Reading 2-8-2 .Mikado. type locomotives.
|Class||Qty.||Road Numbers||Year Built||Builder||Notes|
December 41029-41030, 41052
January 41089, 41094, 41106
November 42673-42686, December 42728-42733
Known as "Big Dutch Mikes", these had the enormous Wooten boiler in a conventional-cab arrangement. The first of the class was built in the Reading shops and had a saturated boiler with a heating surface area of 5,508 sq ft, of which 298 sq ft came from the firebox and combustion chamber. The remaining 2-8-2 were produced in two versions: this one, with the 61 1/2" drivers and the M1sb with smaller drivers and a lower boiler pressure (see Locobase 9548).
The M1s had a 36" high wall separating the firebox proper from the 81 sq ft combustion chamber and 14" piston valves. They burned a mixture of hard and soft coal.
In the mid-1920s, the Reading reworked the boilers considerably while increasing the cylinder volume; see Locobase 9547.
In the mid-1920s, the Reading rebuilt its stud of 61 1/2" Mikados, principally by removing 39 of the boiler tubes from the original layout. At the same time, the railroad increased cylinder volume by boring out the cylinder by 1". It's possible that the Reading determined that the original design had too much heating surface in the relatively underperforming tube bundle. Another flaw may have been lack of steaming space, which the deletion of 3 or 4 rows of tubes may have alleviated.
Connelly's Baldwin list shows that all of the M1s were rebuilt in 1924 and again (?) in 1943. The M1-sb that had 55 1/2" drivers were converted to M1-sa in two batches: the last 10 delivered were rebuillt by 1929, the first 20 were rebuilt in 1941-1943.
All of the M1s were scrapped in the late 1940s.
January 42799-42801, 42823-42825; February 42906-42908, 42939; October 44329-44330; November 44443-44445, 44474-44475; December 44577-44581, 44619-44621, 44674
January 44814-44816, 44870
After the first 26 Baldwin Big Dutch Mikes were delivered to the Reading (Locobase 9547), the railroad changed the specification by reducing the driver diameter by 6 1/2" and dropping the boiler pressure. Firebox heating surface area included 82 sq ft (7.6 sq m) in the combustion chamber; the latter was separated from the firebox by a brick half wall. Piston valves measured 14" (356 mm) in diameter. Apparently the Reading found the exhaust nozzle diameter a touch too large at 7" (178 mm); a handwritten "Hereafter" note states that exhaust nozzles were to measure 6 1/2" (165 mm).
Although the tractive effort remained about the same, the M1sb alosmst certainly proved sluggish. In any event, the last 10 were converted to M1sa (Locobase 9547) by 1929. The other 20 were converted to the M1sa standard in 1941-1943.
|Specifications by Steve Llanso|
|Railroad||Philadelphia & Reading||Philadelphia & Reading||Philadelphia & Reading|
|Road Numbers||1701-1726||1701-1726 (& 1727-1756)||1727-1756|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.47||0.47|
|Overall Wheelbase (engine & tender)||68.46'||50.32'||68.37'|
|Axle Loading (Maximum Weight per Axle)||65427 lbs||61580 lbs|
|Weight on Drivers||246600 lbs||249700 lbs||248734 lbs|
|Engine Weight||329300 lbs||334425 lbs||332225 lbs|
|Tender Light Weight||155700 lbs||162000 lbs||122000 lbs|
|Total Engine and Tender Weight||485000 lbs||496425 lbs||454225 lbs|
|Tender Water Capacity||8000 gals||8000 gals||8000 gals|
|Tender Fuel Capacity (oil/coal)||12.8 tons||12.9 tons||12 tons|
|Minimum weight of rail (calculated) on which locomotive could run||103 lb/yard||104 lb/yard||104 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||225 psi||220 psi||215 psi|
|Cylinders (dia x stroke)||24" x 32"||25" x 32"||24" x 32"|
|Tractive Effort||57319 lbs||60813 lbs||60693 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||4.30||4.11||4.10|
|Firebox Area||326 sq. ft||298 sq. ft||327 sq. ft|
|Grate Area||108 sq. ft||108 sq. ft||108 sq. ft|
|Evaporative Heating Surface||4224 sq. ft||3803 sq. ft||3803 sq. ft|
|Superheating Surface||993 sq. ft||993 sq. ft||837 sq. ft|
|Combined Heating Surface||5217 sq. ft||4796 sq. ft||4640 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||252.10||209.18||226.97|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||24300||23760||23220|
|Same as above plus superheater percentage||28917||28750||27400|
|Same as above but substitute firebox area for grate area||87287||79328||82960|