Yosemite Valley 2-6-0 "Mogul" Locomotives of the USA

Class Details by Steve Llanso of Sweat House Media

Class 27 (Locobase 5970)

Data from the Yosemite Valley website (http://www.yosemitevalleyrailroad.com/MOTIVE.POWER.HTML.DIR/YVRR.Blind.Photo.html -- 3 April 2004) and DeGolyer, Vol 53, p. 289. Works numbers were 39634 in April 1913 and 45130 in February 1917.

This railroad was built in the early 1900s to serve eastern Merced county in northern California from near Sacramento to the western entrance of the Yosemite National Park. Laid with 70 lb/yard (35 kg/metre) rail, the line had maximum grades of 2.4% and curves no sharper than 18 degrees (210 foot/64 metre radii)

This Mogul was a typical saturated-steam engine (Baldwin class 8 32-D) with balanced slide valve and wagon-top boiler. The YVRR paid $17,340.18. The builder's photo shows a very tall, thin stack; a later one shows a shorter one with a screen. With oil-firing there was much less chance of sparks starting wayside fires.)

Engine #28, delivered almost 4 years later, was a duplicate although its weight guarantees had climbed to 120,000 lb (54,431 kg) on the drivers and 143,000 lb (64,864 kg) overall. It was wrecked in 1920 but rebuilt and survived to be scrapped with 27 after the railroad closed in 1945.

Later Baldwins numbered 29 and 25 were similar in size, but had Walschaert gear and piston valves.

Class 29 (Locobase 5971)

Data from the Yosemite Valley website (http://www.yosemitevalleyrailroad.com/MotivePower.HTML.DIR/YVRR.Blind.Photo.html -- 3 April 2004). See also DeGolyer, Vol 65, pp. 343+ and Vol 76, pp. 394+. Works numbers were 55275 in January 1922 and 58685 in September 1925.

When the YVRR went back to Baldwin to buy another Mogul nine years after its first purchase (described in Locobase 5970), some things stayed the same. The locomotive had the same wheel base and the boiler diameter remained the same. But much was different: now the locomotive was superheated and had 10" (254 mm) piston valves serving long-stroke cylinders. The grate was smaller as was the oil-burning firebox overall and the total heating surface. Axle loading went up as did tender weight. And the price jumped more than $10,000 to $27,541.77.

To allow for track play on curves, the front and rear flanged driver sets were spaced 53 1/4" (1,352 mm) apart, while the middle set of plain-tire drivers, which were one inch wider at 6 1/2" (165 mm), had a gauge of 52 3/4" (1,339 mm).

#25 was bought in 1925 as a sister to 29 (go figure the numbering scheme!). After 20 years with the YVRR, both 25 and 29 were leased to the Southern Pacific during World War II. After the war and the YVRR's abandonment, 25 was scrapped but 29 was sold to a railroad in Northern Mexico.

Here, http://www.ferrocarriles.com/steam/indice/udey350/udey350.html (3 April 2004) picks up the 29's trail. At first used to construct the Sonora-Baja railroad, the engine soon transferred to Yucatan as SCyT's 7311-3. A long career in the Yucutan included adoption by the FC Unidos de Yucutan in 1960 and renumbering as 353 three years later. After going out of service in 1970 the locomotive idled in oblivion until it was rebuilt at the Merida shops by Jorge Gonzalez and friends.

Specifications by Steve Llanso of Sweat House Media
Locobase ID5970 5971
RailroadYosemite ValleyYosemite Valley
Number in Class22
Road Numbers27-2829, 25
Number Built22
Valve GearStephensonWalschaert
Locomotive Length and Weight
Driver Wheelbase (ft)14.1714.17
Engine Wheelbase (ft)22.7522.75
Ratio of driving wheelbase to overall engine wheebase 0.62 0.62
Overall Wheelbase (engine & tender) (ft)51.1651.17
Axle Loading (Maximum Weight per Axle) (lbs)
Weight on Drivers (lbs)113,750120,270
Engine Weight (lbs)134,600140,760
Tender Loaded Weight (lbs)90,400100,240
Total Engine and Tender Weight (lbs)225,000241,000
Tender Water Capacity (gals)45004500
Tender Fuel Capacity (oil/coal) (gals/tons)22402240
Minimum weight of rail (calculated) (lb/yd)6367
Geometry Relating to Tractive Effort
Driver Diameter (in)5757
Boiler Pressure (psi)190190
High Pressure Cylinders (dia x stroke) (in)19" x 28"19" x 28"
Tractive Effort (lbs)28,63928,639
Factor of Adhesion (Weight on Drivers/Tractive Effort) 3.97 4.20
Heating Ability
Firebox Area (sq ft)160148
Grate Area (sq ft)31.1026.80
Evaporative Heating Surface (sq ft)20911571
Superheating Surface (sq ft)342
Combined Heating Surface (sq ft)20911913
Evaporative Heating Surface/Cylinder Volume227.57170.98
Computations Relating to Power Output (More Information)
Robert LeMassena's Power Computation59095092
Same as above plus superheater percentage59096009
Same as above but substitute firebox area for grate area30,40033,182
Power L1567910,586
Power MT330.20582.14