Early 20th century aircraft engine
The
Pratt & Whitney R-1860 Hornet B
was a relatively uncommon
aircraft engine
. It was a development of
Pratt & Whitney
's earlier
R-1690 Hornet
and was basically similar, but enlarged in capacity from 1,690 to 1,860 cubic inches (30.5 L).
[1]
[2]
Cylinder bore was increased by 1/8" and the
crankshaft
stroke
by 3/8". Both engines were
air-cooled
radial engines
, with a single row of nine cylinders.
Design and development
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The cylinder and valve design was typical for Pratt & Whitney, a simple design with two large valves driven by
pushrods
. The enlarged engine was designed by George Willgoos and was first available in 1929.
[3]
The Hornet series of engines was similar to the
Wasp
, but larger. In both series a nine-cylinder single-row engine was later supplemented by an enlarged fourteen cylinder engine, with two rows of the same cylinders, but reduced in number to seven per row to aid cooling to the rear row (it was never made into a larger, 18 cylinder radial like the related Wasp was).
Two of these engines, the enlarged single-row Hornet B described here and the
R-1830 Twin Wasp
, were of near-identical displacement (1860 vs. 1830), although the fourteen-cylinder Twin Wasp was more complex and costly than the nine-cylinder, single-row Hornet B. The Twin Wasp was by far the more powerful engine though, even in its early versions it produced 800
bhp
to the Hornet B's 575 bhp. Having more cylinders per the same displacement also creates a smoother engine, since the individual pistons are smaller and lighter, and the
stroke
is shorter, which reduces the vibration of reciprocation, and therefore crew and mechanical fatigue. The reduced stroke also allows for a higher maximum RPM limit, since the mean
piston speed
is reduced, the distance the piston has to cover per each engine revolution being shorter. Having a shorter stroke but a higher rpm limit for the same displacement reduces the
peak torque
levels, but allows for a higher maximum
horsepower
rating. A further advantage was the reduced diameter of the Wasp: 48 inches compared to 57. This reduced drag, and the relatively large diameter of the Hornet would also have been a serious drawback for visibility if used in a small single-engined aircraft.
Although a technically competent design, the enlarged Hornet B engine was not a commercial success. Customers preferred to buy the R-1830 Twin Wasp instead, which in time became the most numerous aircraft engine ever produced.
Applications
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Specifications
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Data from
"Pratt & Whitney Hornet R-1860-B"
. Smithsonian
National Air and Space Museum
.
and
Aircraft Piston Engines by Herschel Smith
General characteristics
Components
Performance
- Power output:
575 hp (429 kW) at 1,950 rpm
See also
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Related development
Comparable engines
Related lists
References
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- Notes
- ^
Gunston, p.163
- ^
Connors, p.79
- ^
Smithsonian
- Bibliography
External links
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