The Fairbanks-Morse Model 38D-8-1/8
is a two stroke cycle opposed piston diesel engine. As the name
implies, it is an 8-1/8 inch bore engine that went into production
in 1938 using a design based on German technology. Fairbanks-Morse
also built a smaller 5-1/4 inch bore opposed piston engine with
very similar design and features. The engine featured a welded crankcase
and an unusual cylinder liner arrangement with two pistons per cylinder
and no cylinder head. The cylinders have no intake or exhaust valves,
the air is admitted and the exhaust is expelled through ports in
the liner wall, with the opening controlled by the travel of the
pistons in the cylinder. There are two fuel injection nozzles per
cylinder, directly across from each other on the liner wall, that
inject fuel into a firing chamber formed by the heads of the two
The Fairbanks-Morse OP engine was
one of the engines able to pass the mid-1930s U. S. Navy submarine
qualification tests, and was approved for application to fleet submarines.
The GM-owned Winton Engine Company, which became the Cleveland Diesel
Engine Division of GM in 1937, was another builder whose products
passed the submarine qualification tests, and they split the business
for new construction fleet submarines about equally with FM during
the late 1930s and through World War Two.
The Fairbanks Morse OP engine achieved
an enviable record for reliability in submarine service, and this
made Fairbanks-Morse a strong contender for postwar diesel marine
engine sales. They also entered the diesel locomotive market, compenting
with Electro-Motive, ALCO, Baldwin, Lima, and later General Electric.
Despite the success of the OP engine in submarine service, it was
treated rather indifferently under railroad maintenance, and suffered
as a result. The FM product tended to be regarded as an oddity on
railroads, and this led to a retreat from the US railroad market
in 1953 and a complete exit by 1960. Throughout this period, FM
continued to build and sell OP engines for marine and industrial
use, and the engine remained in widespread use in new construction
for the U. S. Navy for many decades. Today the Navy continues to
run many OP engines and is the largest remaining marine customer
for the Fairbanks-Morse 38D-8-1/8.
Article and page design by Preston Cook, ©2009
Above: The 12 cylinder Fairbanks Morse 38D-8-1/8
engine was an extremely powerful prime mover at the time of its
introduction, typically rated at 2400 horsepower in the Roots blower
version. The same engine with series turbocharging was rated at
up to 3600 horsepower.
Above: This diagram shows the unusual arrangement
of the pistons and connecting rods in the Fairbanks Morse Opposed
Piston diesel engine. Two pistons share the cylinder, one connected
to the upper crankshaft and the other to the lower crankshaft. Timing
between the two crankshafts is coordinated by a vertical drive with
a spring cushion pack.
Above: Fairbanks Morse advertising in the marine
trade press took full advantage of the excellent record of their
engines in World War Two U. S. Navy Fleet Submarines. This wartime
FM ad tells of the missions of the USS Wahoo.
Images courtesy of Fairbanks-Morse Company