Ten more "Mountains" (road numbers 1511 through 1520) came in 1923. They were designated Class M-78 and were equipped with boosters which increased their tractive effort to 78,967 pounds. They were identical to the Class M-67 locomotives except for the boosters and an increase in total weight of 7,200 pounds. A second batch of ten Class M-67s (road numbers 1521 through 1530) came from ALCO in 1923 and were similar to the 1922 Class M-67s except for an increase of 1,600 lbs in total weight.
A final ten (road numbers 1600 through 1609) came from the Baldwin Locomotive Works in 1926 and were designated as Class M-75. These M-75s had three 25" dia. x 30" stroke cylinders, 67" dia. drivers, a boiler pressure of 210 psi, a tractive effort of 74,970 lbs and weighed 419,300 pounds. All forty of these D&RGW "Mountains" were dismantled between 1948 and 1955.
|Class||Road Number||Year Built||Builder|
Locobase doesn't know for sure, but believes this, like Locobase 6820, is a proposal submitted to the D&RGW in the 1920s in response to an inquiry about a narrow-gauge Mountain engine; Neither was built, probably because the railway was phasing out narrow-gauge operations.
Locobase doesn't know for sure, but believes this is a proposal submitted to the D&RGW in the 1920s in response to an inquiry about a narrow-gauge Mountain engine; Locobase 6822 shows a smaller version. Neither was built, probably because the railway was phasing out narrow-gauge operations. This design compares well to other narrow-gauge Mountain designs in Locobase (most of which were sized to the Cape Gauge of 42"). It has a lot of boiler for the cylinder volume, a useful degree of superheat, and reasonably tall drivers
64696 in June 1923.
When built, firebox heating surface totallled 368 sq ft (34.2 sq m) , and included 33 sq ft (3.05 sq m) of arch tubes.. As later modified, the fhs now included the combustion chamber (63 sq ft/5.85 sq m) and 92 sq ft (8.55 sq m) of thermic syphons in both the firebox proper and in the combustion chamber.
First Mountains built for the Rio Grande, these engines came in three batches, all running on unusually small 63" drivers. 1501-1510 and 1521-1530 were identical; 1511-1520 had a booster engine mounted on the trailing truck and were designated M-78; these ran Grand Junction to Denver.
These dual-service locomotives used three cylinders. Drury (1993) comments: "Their construction by Baldwin is something of a curiosity. They constitute five-sixths of Baldwin's three-cylinder production; and Brooks, which had built D&RGW's two-cylinder Mountains, was the chief advocate of three-cylinder power."
The firebox had combustion chamber, 17 sq ft of arch tubes, and 90 sq ft of thermic syphons. The boiler had feedwater heater. Each of the cylinders was supplied through a 12" piston valve.
The railway would later modify the firebox by deleting the arch tubes and increasing the thermic syphon area to 96 sq ft. At that point, the combustion chamber accounted for 100 sq ft of direct heating surface. Also, the boiler gained three heating tubes and somehow added 75 sq ft of superheater area even though the flue count and length remained the same.
Using 3 cylinders on a locomotive burning low-calorie, semi-bituminous Rosebud coal seems an odd choice. Even though each cylinder was smaller the total cylinder volume was greater than a comparable two-cylinder locomotive. Apparently the firebox and boiler were big enough and the railway was apparently satisfied enough to maintain the design's 3-cylinder layout until retirement in the late 1940s.
1601 was dismantled in December 1941 for some reason; the next to go was 1604 in March 1948 and the last was 1607 in November 1949.
|Specifications by Steve Llanso|
|Class||14-34 1/4 E||14-36 1/4 E||M-67||M-75|
|Railroad||Denver & Rio Grande Western (D&RGW)||Denver & Rio Grande Western (D&RGW)||Denver & Rio Grande Western (D&RGW)||Denver & Rio Grande Western (D&RGW)|
|Locomotive Length and Weight|
|Ratio of driving wheelbase to overall engine wheebase||0.42||0.43||0.43||0.44|
|Overall Wheelbase (engine & tender)||60.25'||61.17'||82.23'||86.41'|
|Axle Loading (Maximum Weight per Axle)||64500 lbs||73130 lbs|
|Weight on Drivers||138000 lbs||142000 lbs||257500 lbs||290530 lbs|
|Engine Weight||181000 lbs||199000 lbs||377000 lbs||419310 lbs|
|Tender Light Weight||106000 lbs||106000 lbs||277600 lbs||291000 lbs|
|Total Engine and Tender Weight||287000 lbs||305000 lbs||654600 lbs||710310 lbs|
|Tender Water Capacity||5000 gals||5000 gals||14000 gals||15000 gals|
|Tender Fuel Capacity (oil/coal)||8 tons||8 tons||25 tons||25 tons|
|Minimum weight of rail (calculated) on which locomotive could run||58 lb/yard||59 lb/yard||107 lb/yard||121 lb/yard|
|Geometry Relating to Tractive Effort|
|Boiler Pressure||190 psi||190 psi||210 psi||210 psi|
|Cylinders (dia x stroke)||20" x 24"||21" x 24"||28" x 30"||25" x 30" (3)|
|Tractive Effort||35236 lbs||35611 lbs||62661 lbs||74930 lbs|
|Factor of Adhesion (Weight on Drivers/Tractive Effort)||3.92||3.99||4.11||3.88|
|Firebox Area||144 sq. ft||154 sq. ft||425 sq. ft||512 sq. ft|
|Grate Area||40.20 sq. ft||42.70 sq. ft||80.20 sq. ft||95 sq. ft|
|Evaporative Heating Surface||2155 sq. ft||2495 sq. ft||4667 sq. ft||5093 sq. ft|
|Superheating Surface||505 sq. ft||707 sq. ft||1333 sq. ft||1495 sq. ft|
|Combined Heating Surface||2660 sq. ft||3202 sq. ft||6000 sq. ft||6588 sq. ft|
|Evaporative Heating Surface/Cylinder Volume||246.94||259.33||218.29||199.21|
|Computations Relating to Power Output (More Information)|
|Robert LeMassena's Power Computation||7638||8113||16842||19950|
|Same as above plus superheater percentage||9089||9898||20547||24539|
|Same as above but substitute firebox area for grate area||32558||35697||108885||132250|