Firebox fitted with combustion chamber that supplied 78 sq ft and 103 sq ft of thermic syphons contributing to the firebox heating surface, boiler had feedwater heater. Known on the D & RGW as Westerns.
More frankly passenger haulers than their 14 predecessor M-64s, these five Westerns had roller bearings on axles carrying larger drivers. Laid out as a superpower locomotive in all respects, the firebox heating surface included 139 sq ft of combustion chamber and 122 sq ft of thermic syphons (located in both the firebox and the combustion chamber).
They ran from Denver to Salt Lake City -- 745 miles through the Royal Gorge and Tennessee Passes hitting 80 mph in some spots -- until retirement in 1952-1954.
| Specifications | ||
|---|---|---|
| Class | M64 | M68 |
| Locobase ID | 257 | 258 |
| Railroad | Denver & Rio Grande Western (D&RGW) | Denver & Rio Grande Western (D&RGW) |
| Whyte | 4-8-4 | 4-8-4 |
| Road Numbers | 1700-1713 | 1800-1804 |
| Gauge | Std | Std |
| Builder | Baldwin | Baldwin |
| Year | 1929 | 1938 |
| Valve Gear | Walschaert | Baker |
| Locomotive Length and Weight | ||
| Driver Wheelbase | 18.75' | 19.25' |
| Engine Wheelbase | 44.42' | 47' |
| Ratio of driving wheelbase to overall engine wheebase | 0.42 | 0.41 |
| Overall Wheelbase (engine & tender) | 89.75' | 95.29' |
| Axle Loading (Maximum Weight per Axle) | 70448 lbs | |
| Weight on Drivers | 252000 lbs | 279172 lbs |
| Engine Weight | 408500 lbs | 479360 lbs |
| Tender Light Weight | 269500 lbs | 394000 lbs |
| Total Engine and Tender Weight | 678000 lbs | 873360 lbs |
| Tender Water Capacity | 14000 gals | 20000 gals |
| Tender Fuel Capacity (oil/coal) | 20 tons | 26 tons |
| Minimum weight per yard of rail on which locomotive could run | 105 lb rail | 116.32 lb rail |
| Geometry Relating to Tractive Effort | ||
| Driver Diameter | 70" | 73" |
| Boiler Pressure | 240 psi | 290.10 psi |
| Cylinders (dia x stroke) | 27" x 30" | 26" x 30" |
| Tractive Effort | 63735 lbs | 68503 lbs |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.95 | 4.08 |
| Heating Ability | ||
| Firebox Area | 446 sq. ft | 555 sq. ft |
| Grate Area | 88 sq. ft | 106 sq. ft |
| Evaporative Heating Surface | 4917 | 5506 |
| Superheating Surface | 2229 | 2336 |
| Combined Heating Surface | 7146 | 7842 |
| Evaporative Heating Surface/Cylinder Volume | 247.33 | 298.67 |
| Computations Relating to Power Output (More Information) | ||
| Robert LeMassena's Power Computation | 21120 | 30750.60 |
| Same as above plus superheater percentage | 27707.81 | 39910.69 |
| Same as above but substitute firebox area for grate area | 140428.21 | 208966.33 |
| Power L1 | 38320.37 | 56106.99 |
| Power MT | 1340.98 | 1772.31 |
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