The "Colorados" were designated Class M-4 and were assigned road numbers 6310 through 6327. They were built with 64" diameter drivers, 31" x 32" cylinders, a 250 psi boiler pressure, they had a rated with a tractive effort of 90,000 pounds and each weighed 512,110 pounds.
The boiler had feedwater heater, the valve gear had limited cutoff with 1/4-in lead, 3/8-in lap opening relatively and a 15" piston valves. The firebox heating surface included 43 sq ft of arch tubes and 107 square feet of combustion chamber. The firebox area was 492 square feet. The evaporative heating surface was 5914 square feet and with the superheater the combined heating surface was 8,401 square feet.
All eighteen of the Class M-4 locomotives were rebuilt by the CB&Q in the late 1930s and early 1940s. The cylinder diameter was reduced to 28" with a resultant change in tractive effort to 83,300 pounds and the piston valve was changed to 14". Several other changes were made including substitution of lighter materials, which reduced the total weight of each locomotive to 504,570 pounds. These changes allowed the rebuilt Class M-4a "Colorados" to achieve higher speeds.
There are no surviving CB&Q 2-10-4 "Colorado" type locomotives.
| Class | Qty. | Road Number | Year Built | Builder | Notes |
|---|---|---|---|---|---|
| M-4 | 12 | 6310-6321 | 1927 | Baldwin | 1 |
| M-4 | 6 | 6322-6327 | 1929 | Baldwin | 2 |
Data from tables and diagram in 1930 Locomotive Cyclopedia and from CB&Q 3 - 1953 Locomotive Diagrams 2 supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. See also DeGolyer, Volume 81, pp. 386+. (Thanks to Chris Hohl for his 9 September 2016 email reporting the tender's original coal capacity and for his 22 September 2017 email reporting unlikely boiler pressure values for 177 entries. A Locobase macro caused the error .) Baldwin works numbers were 60210-60211, 60252-60255 in October 1927; 60262, 60281-60283, 60291-60292 in November; 60767-60770 in April 1929; 60805-60806 in May.
Boiler had a feed water heater,: Elesco Type K-50 in the first six, Worthington Type BL in the last 12. Valve gear had limited cutoff with 1/4-in (6.3 mm) lead, 3/8-in (9.5 mm) lap opening relatively generous 15" (381 mm) piston valves. B4 Power reverse gear from Barco. Duplex stoker moved the coal.
Data for 1927 (6312); tractive effort is usually given as 90,000 lb because in the late 1930s the Burlington reduced the cylinder size to 28" in diameter when they rebuilt ten of the 18 as M-4A; see Locobase 5475.
Firebox heating surface included 43 sq ft (3.99 sq m) of arch tubes and 107 sq ft (9.94 sq m) of combustion chamber.
The Burlington called these Texas-type locomotives "Colorados".
Data from Corbin & Kerka (1960), p. 133 and from CB&Q 3 - 1953 Locomotive Diagrams 2 supplied in May 2005 by Allen Stanley from his extensive Rail Data Exchange. (Thanks to Chris Hohl for his 21 September 2019 email reporting the tender's correct coal capacity.)
These are the 10 M-4 Colorados (first described in Locobase 96) that were modified in the late 1930s-early 1940s to improve reliability. The big change was to drop the cylinder diameter to 28"/ 711 mm (and the piston valve diameters to 14"/356 mm), which lowered tractive effort to 83,000 lb (37,648 kg or 369.2 kN) and reduced all the demand factors commensurately while raising the factor of adhesion to 4.00. At the same time the railroad fitted disk drivers with better counterbalancing and installed Timken roller bearings on all driving axles, the main rod, and the leading truck bearings.
Boiler had feedwater heater, valve gear had limited cutoff with 1/4-in lead, 3/8-in lap. Firebox heating surface included 43 sq ft (4.00 sq m) of arch tubes and 107 sq ft (9.94 sq m) of combustion chamber.
| Principal Dimensions by Steve Llanso of Middle Run Media | ||
|---|---|---|
| Class | M-4 | M-4A |
| Locobase ID | 96 | 5475 |
| Railroad | Chicago, Burlington & Quincy (CB&Q) | Chicago, Burlington & Quincy (CB&Q) |
| Country | USA | USA |
| Whyte | 2-10-4 | 2-10-4 |
| Number in Class | 18 | 10 |
| Road Numbers | 6310-6327 | 6311-6313, 6315-6320, 6322 |
| Gauge | Std | Std |
| Number Built | 18 | |
| Builder | Baldwin | CB&Q |
| Year | 1927 | 1935 |
| Valve Gear | Baker | Baker |
| Locomotive Length and Weight | ||
| Driver Wheelbase (ft / m) | 22.33 / 6.81 | 22.33 / 6.81 |
| Engine Wheelbase (ft / m) | 45 / 13.72 | 45 / 13.72 |
| Ratio of driving wheelbase to overall engine wheelbase | 0.50 | 0.50 |
| Overall Wheelbase (engine & tender) (ft / m) | 95.96 / 29.25 | 95.96 / 29.25 |
| Axle Loading (Maximum Weight per Axle) (lbs / kg) | 72,800 / 33,022 | |
| Weight on Drivers (lbs / kg) | 353,000 / 160,118 | 333,430 / 151,241 |
| Engine Weight (lbs / kg) | 512,440 / 232,439 | 504,570 / 228,869 |
| Tender Loaded Weight (lbs / kg) | 385,700 / 174,951 | 385,700 / 174,951 |
| Total Engine and Tender Weight (lbs / kg) | 898,140 / 407,390 | 890,270 / 403,820 |
| Tender Water Capacity (gals / ML) | 21,500 / 81.44 | 21,500 / 81.44 |
| Tender Fuel Capacity (oil/coal) (gals/tons / Liters/MT) | 24 / 22 | 24 / 22 |
| Minimum weight of rail (calculated) (lb/yd / kg/m) | 118 / 59 | 111 / 55.50 |
| Geometry Relating to Tractive Effort | ||
| Driver Diameter (in / mm) | 64 / 1626 | 64 / 1626 |
| Boiler Pressure (psi / kPa) | 250 / 1720 | 250 / 1720 |
| High Pressure Cylinders (dia x stroke) (in / mm) | 31" x 32" / 787x813 | 28" x 32" / 711x813 |
| Tractive Effort (lbs / kg) | 102,106 / 46314.56 | 83,300 / 37784.29 |
| Factor of Adhesion (Weight on Drivers/Tractive Effort) | 3.46 | 4.00 |
| Heating Ability | ||
| Tubes (number - dia) (in / mm) | 87 - 2.25" / 57 | 87 - 2.25" / 57 |
| Flues (number - dia) (in / mm) | 222 - 3.5" / 89 | 222 - 3.5" / 89 |
| Flue/Tube length (ft / m) | 21.50 / 6.55 | 21.50 / 6.55 |
| Firebox Area (sq ft / m2) | 492 / 45.71 | 492 / 45.71 |
| Grate Area (sq ft / m2) | 106.50 / 9.89 | 106.50 / 9.89 |
| Evaporative Heating Surface (sq ft / m2) | 5914 / 549.42 | 5907 / 548.77 |
| Superheating Surface (sq ft / m2) | 2487 / 231.05 | 2487 / 231.05 |
| Combined Heating Surface (sq ft / m2) | 8401 / 780.47 | 8394 / 779.82 |
| Evaporative Heating Surface/Cylinder Volume | 211.59 | 258.97 |
| Computations Relating to Power Output (More Information) | ||
| Robert LeMassena's Power Computation | 26,625 | 26,625 |
| Same as above plus superheater percentage | 34,613 | 34,613 |
| Same as above but substitute firebox area for grate area | 159,900 | 159,900 |
| Power L1 | 29,345 | 35,949 |
| Power MT | 916.35 | 1188.46 |
