USRA Designs

USRA Mikado Steam Engine








One of the high priories of the USRA when designing its locomotives was standardization--the fewer variations in parts, the lower the cost and the ease of maintenance. No where was this better seen than in the locomotive tender.


The USRA settled on a single basic design for its tenders, with three variations for water capacity. All were designed for a 16 ton coal load. The two switchers held 8,000 gallons; the light and medium engines held 10,000 gallons and the largest engines having the largest boilers (the heavy Santa Fe and the two Mallet designs) held 12,000 gallons.


All the water-bottom rectangular tenders had a Commonwealth cast-steel frame that included the front drawbar pocket, the rear draft sills and the truck center plates.


The freight and switching engines (which included the Mikado design) used Andrews type trucks with cast steel side frames made by American Steel Foundries or Buckeye Steel Casting carrying 33" diameter, 2 1/2" wide rolled steel wheels with a 70" wheel base mounted on axles having 6" by 11" journals.. The truck bolsters were fitted with triplet elliptic springs made by Standard Steel Works. Side bolsters were specified for both the front and back trucks. The passenger engine tenders used built-up trucks with 6' wheel base and 36" wheels of either the Barber or the Commonwealth type.


About the tender body, Railway Mechanical Engineer, August 1918 said "The tank is the usual type of construction, the corners being formed by 2-1/2" by 2-1/2 angles. The bottom and top plates are 5/16" in thickness, while the sides and ends are 1/4" thick. The tank manhole is 18" wide by 8' in length across the tank. The great length materially facilitates spotting of the locomotive at water plugs."


A Franklin radial buffer wedge type was specified between engine and tender. The drawbar between engine and tender was to be straight and a Franklin Unit safety bar was included. The coupler release rigging at the back of tender was specified as Imperial Type "B", Imperial Appliance Co, Chicago Ill.


The Westinghouse ET-6 brakes consisted of a 14"x12" Type L tender brake cylinder with JM type expander and #4 brake pipe vent valve with the following flexible joint connections (Franklin Ball joints) between the engine and tender:

--One 1 1/4" for train line

--One 3/4" for independent brake


The USRA specified the uses of Creco Third-Point Brake Beam Support and Safety Device by Chicago Railway Equipment Company for all its tenders and freight cars.



Continue to the 10,000 gallon 16 ton tender->




August 22, 2012