Denver & Salt Lake / Denver, Northwestern & Pacific Other Articulated Locomotives in the USA


Class Details by Steve Llanso of Sweat House Media

Class 200/Class 76 (Locobase 11471)

Data from "Locomotive Building," The Railway Age Gazette, Vol XLVIII, No 13 (1 April 1910), p. 923. See also "Mallet Engine for the DNW&P," Railway and Locomotive Engineering, Volume 22, No 2 (February 1909), p. 83. (Thanks to Chris Hohl for his Excel spreadsheet prepared by Chris Hohl and supplied in a 7 March 2015 email and a 5 August 2018 follow-up pointing out an incorrect LP cylinder diameter.) Works numbers were 46560-46561 in November 1909 and 48230-48235 in July 1910.

In the long, detailed article on the first engine of this class, the RAG says the DNW&P would be opening a "new field for the Mallet locomotive", a duty that allows the magazine to describe at some length an essential feature of mountain railroading in the winter:

"The engine here illustrated will be used principally as helper and pusher with the rotary snow plows in use on this road ...One of the most essential things in the operation of the rotary snow plow is that it should be handled by as few engines as possible in order that starting and stopping may be done quickly, so as to avoid danger of bucking the plow into a hard packed mass of snow or ice. Heretofore it has been necessary to use as many as five consolidation engines in pushing the rotary during the most severe weather."

So what could the single 200 do that the five smaller engines couldn't?

"It is expected, however, that this Mallet engine, being able to work as slow as four or five miles per hour without danger of stalling. and at its maximum of power, and in fact at an increased power, if necessary, by working it simple, will greatly reduce the number of engines necessary in this kind of service, and so increase the efficiency of the plow."

And an additional benefit: "It must be understood, however, that this engine will also be used in regular road service."

These Mallets didn't remain all-adhesion engines for long. In 1912, the railway added a leading truck for better tracking. At the same time, they added a mechanical stoker. See Locobase 6819.

So modified, they served in a helper-engine role until 1947-1952.


Class 210/Class 76/L-77 (Locobase 5407)

Data from table in Railway Mechanical Engineer, Volume 90, No 5 (May 1916), p236 and . See also "Train Wrecks-Miles from East Starting Point", The Moffat Road-Former 'Hill' Route) A Self-Guiding Auto Tour, Arapaho and Roosevelt National Forests brochure, United States Forest Service, 1962, archived at [], last accessed 17 March 2019; and Edward T. Bollinger and Frederick Bauer, The Moffat Road (Denver: Sage Books, 1962), p. 137. Works numbers were 53292-53293 in 1913, 55986-56296 in October 1916.

Drury (1993) says that these locomotives were the beneficiaries of two updates to the Mallet design the railroad was already operating -- a leading truck to make it a better road engine and a mechanical stoker. A third and perhaps most important addition was the superheater delivered with the engines. Like most other compound Mallets of the time, their HP cylinders were served by piston valves, the LP cylinders by slide valves.

Class leader 210 never operated on the Rio Grande as it was destroyed in a wreck on 5 December 1924. Bollinger and Bauer recounted the sequence of events that began when "a drive rod broke and cleaned off all the air pipes so there were no air brakes or air reverse gear to control the monster." Engineer Tom Carr and his fireman leaped off the locomotive while it was still going only 10 mph (16 kph).

George Schreyer, running the 206 farther up the line saw the 210 closing in on his train although it was supposed to keep a ten-minute distance. He sped up his train and eventually stopped at Ranch Creek. After waiting for the speeding 210, he called the dispatcher to check her status and Tom Carr told him about 210's runaway. Schreyer believed that 210's leap off the upper level must have just cleared his engine, although he didn't actually hear her make the "broad jump". Carr ran up to the spot and saw that the 210 had "bounced on the right of way at the lower level, and then gone on over the cliff to her final resting place."

Opinions differed on whether the 210's boiler actually blew up. "In any event," wrote Bollinger and Bauer"a mass of wreckage lay below track level near the Rifle Sight Notch tunnel." Although the boiler and engines [i.e., the running gear] were salvaged, the rest was left to rust.

The rest of the class was substantially updated beginning in 1926 with a Standard Type B stoker,. All but two (210 and 216) received Nicholson thermic syphons in the firebox and Sellers exhaust steam injectors. They went to the Denver & Rio Grande Western in 1947, from which they retired a few years later (1949-1951) as 3370-3375.


Class Class 76/ L-77 (Locobase 6819)

Data from D&RGW 1956 Locomotive Diagrams supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also Edward T. Bollinger and Frederick Bauer, The Moffat Road (Denver: Sage Books, 1962), p. 137.

Drury (1993) shows that these started out on the DNW&P as 0-6-6-0 Mallets (Locobase 11471) that acquired a leading truck in 1912 to improve their over-the-road qualities. The result was a very uncommon Mallet wheel arrangement in the US. At the same time they were fitted with mechanical stokers. A photo of 200 in 1947 (Drury, p. 162) underscores the odd look of a short boiler over the engines, even if one mentally deducts the leading truck.

They were, wrote Moffat Road authors Bollinger and Bauer, "a legend of slow-moving bull-dog type power that rarely slipped their drive wheels. [They] were built to run twenty miles per hour [32 kph] and could do thirty five [56 kph]" and "were not excessive in repair work".

The design served its purpose for decades and was updated beginning in 1926 with Sellers exhaust steam injectors, Nicholson thermic syphons, and Standard Type B stokers.

Except for the 202, which fell under the torch in early 1947, the rest of the class was renumbered by the Denver & Rio Grande Western when it took over the D&SL in April 1947 as 3361, 3363-3369. The eight locomotives lasted a little longer before going to the ferro-knacker in 1949-1951.

See the as-built 2-6-6-0s also supplied to the D&SL in 1913 and 1916 at Locobase 5407.

Principal Dimensions by Steve Llanso of Sweat House Media
Class200/Class 76210/Class 76/L-77Class 76/ L-77
Locobase ID11,471 5407 6819
RailroadDenver, Northwestern & Pacific (D&SL)Denver & Salt Lake (D&SL)Denver, Northwestern & Pacific (D&SL)
CountryUSAUSAUSA
Whyte0-6-6-02-6-6-02-6-6-0
Number in Class779
Road Numbers200-209/3363-3369210-216200-209
GaugeStdStdStd
Number Built77
BuilderAlco-SchenectadyAlco-SchenectadyAlco-Schenectady
Year190919131926
Valve GearWalschaertWalschaertWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft / m)10.83 / 3.3010 / 3.0510 / 3.05
Engine Wheelbase (ft / m)30.67 / 9.3539.08 / 11.9139.17 / 11.94
Ratio of driving wheelbase to overall engine wheebase 0.35 0.26 0.26
Overall Wheelbase (engine & tender) (ft / m)64.33 / 19.6172.75 / 22.1772.75 / 22.17
Axle Loading (Maximum Weight per Axle) (lbs / kg)55,583 / 25,21255,683 / 25,257
Weight on Drivers (lbs / kg)327,500 / 148,552331,500 / 150,366332,000 / 150,593
Engine Weight (lbs / kg)327,500 / 148,552359,000 / 162,840362,000 / 164,201
Tender Loaded Weight (lbs / kg)160,000 / 72,575160,500 / 72,802176,000 / 79,832
Total Engine and Tender Weight (lbs / kg)487,500 / 221,127519,500 / 235,642538,000 / 244,033
Tender Water Capacity (gals / ML)9000 / 34.099000 / 34.099000 / 34.09
Tender Fuel Capacity (oil/coal) (gals/tons / ML/MT)12 / 10.9012 / 10.9012 / 10.90
Minimum weight of rail (calculated) (lb/yd / kg/m)91 / 45.5092 / 4692 / 46
Geometry Relating to Tractive Effort
Driver Diameter (in / mm)55 / 139755 / 139755 / 1397
Boiler Pressure (psi / kPa)225 / 15.50225 / 15.50225 / 15.50
High Pressure Cylinders (dia x stroke) (in / mm)20.5" x 32" / 521x81321" x 32" / 533x81321" x 32" / 533x813
Low Pressure Cylinders (dia x stroke) (in / mm)33" x 32" / 838x81333.5" x 32" / 851x81333.5" x 32" / 851x813
Tractive Effort (lbs / kg)67,483 / 30609.8170,456 / 31958.3470,456 / 31958.34
Factor of Adhesion (Weight on Drivers/Tractive Effort) 4.85 4.71 4.71
Heating Ability
Firebox Area (sq ft / m2)206 / 19.14229 / 21.27229 / 21.27
Grate Area (sq ft / m2)72.20 / 6.7172.20 / 6.7172.20 / 6.71
Evaporative Heating Surface (sq ft / m2)5241 / 486.904111 / 381.924118 / 382.57
Superheating Surface (sq ft / m2)879 / 81.661249 / 116.03
Combined Heating Surface (sq ft / m2)5241 / 486.904990 / 463.585367 / 498.60
Evaporative Heating Surface/Cylinder Volume428.73320.47321.01
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation16,24516,24516,245
Same as above plus superheater percentage16,24519,16919,981
Same as above but substitute firebox area for grate area46,35060,80063,376
Power L14083831910,427
Power MT164.91331.95415.44

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