Denver & Rio Grande Western 4-8-2 "Mountain" Type Locomotives

Introduction

The Denver & Rio Grande Western Railroad took delivery of its first ten "Mountains" (road numbers 1501 through 1510) from the American Locomotive Company in 1922. These Class M-67 locomotives had 28 x 30 cylinders, 63" drivers, a boiler pressure of 210 psi, a tractive effort of 66,640 lbs and a weight of 377,000 pounds.

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.

Roster by Richard Duley

ClassRoad NumberYear BuiltBuilder
M-671501-15101922ALCO
M-781511-15201923ALCO
M-671521-15301923ALCO
M-751600-16001926Baldwin

Class Details by Steve Llanso

Class 14-34 1/4 E (Locobase 6822)

Data from D&RGW 12 - 1937 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

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.

Class 14-36 1/4 E (Locobase 6821)

Data from D&RGW 12 - 1937 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection.

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

Class M-67 (Locobase 1344)

Data from 1937 D & RGW locomotive diagram book supplied in May 2005 by Allen Stanley from his extensive collection. Works numbers were 63307-63316 in June 1922 and 64288-

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.

Class M-75 (Locobase 204)

Dat afrom D&RGW 12 - 1937 FOLIO 10 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive collection. Works numbers were 59240-59244 in May 1925 and 59293-59295, 59336-59337 in July.

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
Class14-34 1/4 E14-36 1/4 EM-67M-75
Locobase ID6822 6821 1344 204
RailroadDenver & Rio Grande Western (D&RGW)Denver & Rio Grande Western (D&RGW)Denver & Rio Grande Western (D&RGW)Denver & Rio Grande Western (D&RGW)
CountryUSAUSAUSAUSA
Whyte4-8-24-8-24-8-24-8-2
Road Numbers1501-15301600-1609
Gauge3'3'StdStd
BuilderBaldwinBaldwinAlco-BrooksBaldwin
Year19221925
Valve GearWalschaertWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase13'13.75'17.25'18.25'
Engine Wheelbase31.17'31.92'39.83'41.50'
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 lbs73130 lbs
Weight on Drivers138000 lbs142000 lbs257500 lbs290530 lbs
Engine Weight181000 lbs199000 lbs377000 lbs419310 lbs
Tender Light Weight106000 lbs106000 lbs277600 lbs291000 lbs
Total Engine and Tender Weight287000 lbs305000 lbs654600 lbs710310 lbs
Tender Water Capacity5000 gals5000 gals14000 gals15000 gals
Tender Fuel Capacity (oil/coal)8 tons8 tons25 tons25 tons
Minimum weight of rail (calculated) on which locomotive could run58 lb/yard59 lb/yard107 lb/yard121 lb/yard
Geometry Relating to Tractive Effort
Driver Diameter44"48"67"67"
Boiler Pressure190 psi190 psi210 psi210 psi
Cylinders (dia x stroke)20" x 24"21" x 24"28" x 30"25" x 30" (3)
Tractive Effort35236 lbs35611 lbs62661 lbs74930 lbs
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.92 3.99 4.11 3.88
Heating Ability
Firebox Area144 sq. ft154 sq. ft425 sq. ft512 sq. ft
Grate Area40.20 sq. ft42.70 sq. ft80.20 sq. ft95 sq. ft
Evaporative Heating Surface2155 sq. ft2495 sq. ft4667 sq. ft5093 sq. ft
Superheating Surface505 sq. ft707 sq. ft1333 sq. ft1495 sq. ft
Combined Heating Surface2660 sq. ft3202 sq. ft6000 sq. ft6588 sq. ft
Evaporative Heating Surface/Cylinder Volume246.94259.33218.29199.21
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation763881131684219950
Same as above plus superheater percentage908998982054724539
Same as above but substitute firebox area for grate area3255835697108885132250
Power L111847152112060819361
Power MT757.05944.63705.75587.67

Photos

Reference

Credits

Introduction and roster provided by Richard Duley. Class details and specifications provided by Steve Llanso of Sweat House Media.