B&O
Class Q-4 Mikado Locomotives
The Baltimore & Ohio Railroad was among the first trunk lines in
this country to recognize the advantages of the Mikado type for heavy
freight service and
in 1911 ordered 40 locomotives of this type from the Baldwiin
Locomotive Works. . These locomotives used saturated steam with a
working pressure of
205 pounds and the cylinders were 24 inches in diameter by 32 inches
stroke. With drivers 64 inches in diameter the maximum tractive force
was 50,200
pounds.
Using this original design as a base, a large number of additional
Mikados were subsequently bnilt; improvements being introduced wherever
it was' possible to better fit the locomotives for the special
conditions existing on this
railroad system. Including fifty Mikados now being built, the total
number of this type thus far constructed by the Baldwin Locomotive
Works for the Baltimore and
Ohio, is 420. This includes 100 standard light Mikados ordered by the
United States Railroad Administration. The new locomotives are
designated as Class
Q-4, and have cylinders 25- 3/4 inched in diameter by 32 inches stroke.
The steam distribution is controlled by 14 inch piston valves.
Forty-five of these locomotives are equipped with Baker valve motion
and five with Young valve motion. Both types of gears are controlled by
the Ragonnet type B power
reverse mechanism.
In the locomotives equipped with Baker gear, the valve travel is 7
inches, the steam lap 1 inch and the lead 14 inch. The locomotives with
the Young gear
have the same lead, but the travel is increased to 9 inches and the
steam lap to l>e inches.
The boiler is of the extended wagon top type, equipped with a
superheater and brick arch and carrying a steam pressure of 220 pounds.
Its general dimensions are closely similar to those of the boilers used
in the first Mikados
built for this road. The installation of a superheater has necessarily
changed the arrangement ot the tubes and caused a reduction in thetube
length of from 21 feet
to 20 feet 5 inches. The new locomotives are fired with Duplex stokers
and are equipped with one piece cast-steel ash pans having single
hoppers with swing
bottoms. The pans are designed to give sufficient clearance for a
"booster" should it be decided to install this device at any time in
the future.
(from a 1921 magazine,
in the public domain)