This preview shows page 1. Sign up to view the full content.
Unformatted text preview: cylinder engine
was tested at McCook Field in 1923 w ith a mixture of water and ethylene
glycol at a high coolant temperature, probably near 300° F During 1 9281929 further tests were made at McCook Field with a Curtiss D -12 e ngine.
After considerable development work to avoid leaks and to overcome other
t roubles encountered, the use of this method of cooling was adopted for
Curtiss liquid-cooled engines by 1932, and used soon afterward by Allison
a nd Rolls-Royce. This change, which allowed operation of the coolant
55 a t 250° F, reduced the radiator area required by about 50 percent (fig.55).
T his improvement, together with better radiator design and radiator
cowling (fig. 56) brought the drag of liquid-cooled engines well below that
of air-cooled radials of equal power. Their installed weight, which had
b een greater than that of air-cooled radials, also came down to more
c omparable figures. Schlaifer gives the weight per horsepower of the best
liquid-cooled fighter installation in relation to a comparable air-cooled
i nstallation as 30 percent more at sea level and about the same at 25,000 ft.18
T he fact that the Battle of Britain was won by liquid-cooled engines
( the Rolls-Royce Merlin) gave a great impetus to the Army prejudice
in favor of water-cooled fighters.19 A ctually, both types were used, and it
was found that the air-cooled fighter was better at low altitude both because
of its lighter specific weight and its lesser vulnerability to small-arms fire.
F or commercial uses, however, the elimination of the weight, complication, and maintenance requirements that characterize liquid-cooling
has been a chief reason for the popularity of air-cooling for air-transport
purposes since about 1932; and with few exceptions, commercial air transports all over the world have used air-cooled engines, mostly of American
m anufacture, from the early beginnings in the late 1920s up to the present.
A lthough today (1969) jet and turbine engines are standard for large
m ilitary and commercial airplanes, there are still many more planes powered
by air-cooled piston engines, because of their use in planes of smaller size,
t han by all other types combined. 56 U nconventional Engines
H undreds of unconventional types of aircraft engines have been proposed,
b uilt, and tested. Among these the following may be mentioned.
I n this type the cylinders were
positioned around the crankshaft with their axes parallel to it. Its advantage
was its compactness, which provided a small frontal area and allowed
good s treamling. P erhaps the best known was the A lmen e ngine of 1921.
N one were successful—although d uring 1929 t here were brief demonstrations
of the Swiss Statex and British Redrup types, and an example of the latter,
t he Fury powered a Simmonds Spartan biplane in flight. The methods of
linking the pistons to the driveshaft caused lubrication and mechanical
p roblems that were never solved.
B ARREL- OR REVOLVER-TYPE ENGINES. T his was a 4-cylinder radial engine (fig. 57)
with rollers in the p...
View Full Document
- Winter '14
- The Land