Pratt & Whitney R-2800 Double Wasp

https://en.wikipedia.org/wiki/Pratt_...00_Double_Wasp

The Pratt & Whitney R-2800 Double Wasp is a twin-row, 18-cylinder, air-cooled
radial aircraft engine with a displacement of 2,800 in³ (46 L), and is part of
the long-lived Wasp family.

The R-2800 is considered one of the premier radial piston engines ever designed
and is notable for its widespread use in many important American aircraft during
and after World War II. During the war years, Pratt & Whitney continued to
develop new ideas to upgrade this already powerful workhorse, most notably water
injection for takeoff in cargo and passenger planes and to give emergency power
in combat.

First run in 1937, the R-2800 was America's first 18-cylinder radial engine
design. The Double Wasp was more powerful than the world's only other modern
eighteen, the Gnome-Rhône 18L of 3,442 in³ (56.4 L). (The American Wright
Duplex-Cyclone radial of 3,347 in³ (54.86 L) was also under development at the
time,[2] and promised to be more powerful than either the P&W or Gnome-Rhone
radials. The Double Wasp was much smaller in displacement than either of the
other 18-cylinder designs, and heat dissipation was a greater problem. To enable
more efficient cooling, the usual practice of casting or forging the cylinder
head cooling fins that had been effective enough for other engine designs was
discarded, and instead, much thinner and closer-pitched cooling fins were
machined from the solid metal of the head forging. The fins were all cut at the
same time by a gang of milling saws, automatically guided as it fed across the
head in such a way that the bottom of the grooves rose and fell to make the
roots of the fins follow the contour of the head, with the elaborate process
substantially increasing the surface area of the fins.[4] The twin
distributors[5] on the Double Wasp were prominently mounted on the upper surface
of the forward gear reduction housing and almost always prominently visible
within a cowling, with the conduits for the spark plug wires emerging from the
distributors' cases either directly forward or directly behind them, or on the
later C-series R-2800s with the two-piece gear reduction housings, on the
"outboard" sides of the distributor casings.

When the R-2800 was introduced in 1939 it was capable of producing 2,000 hp
(1,500 kW), for a specific power value of 0.71 hp/in³ (32.6 kW/L). The design of
conventional air-cooled radial engines had become so scientific and systematic
by then, that the Double Wasp was introduced with a smaller incremental power
increase than was typical of earlier engines. Nevertheless, in 1941 the power
output of production models increased to 2,100 hp (1,600 kW), and to 2,400 hp
(1,800 kW) late in the war. Even more was coaxed from experimental models, with
fan-cooled subtypes producing 2,800 hp (2,100 kW), but in general the R-2800 was
a rather highly developed powerplant right from the beginning.


Type
Radial engine

National origin
United States

Manufacturer
Pratt & Whitney

First run
1937
First flown May 29, 1940

The following is a partial list of aircraft that were powered by the R-2800 (and
a few prototypes that utilized it at one point):

Brewster XA-32
Breguet Deux-Ponts
Canadair CL-215
Canadair C-5 North Star
Consolidated TBY Sea Wolf
Convair 240, 340, and 440
Curtiss P-60
Curtiss XF15C
Curtiss C-46 Commando
Douglas A-26 Invader
Douglas DC-6
Fairchild C-82 Packet
Fairchild C-123 Provider
Grumman AF Guardian
Grumman F6F Hellcat
Grumman F7F Tigercat
Grumman F8F Bearcat
Howard 500
Lockheed Ventura/B-34 Lexington/PV-1 Ventura/PV-2 Harpoon
Lockheed XC-69E Constellation
Martin B-26 Marauder
Martin 2-0-2
Martin 4-0-4
North American AJ Savage
North American XB-28
Northrop XP-56 Black Bullet
Northrop P-61 Black Widow
Northrop F-15 Reporter
Republic P-47 Thunderbolt
Sikorsky CH-37 Mojave
Sikorsky S-60
Vickers Warwick
Vought F4U Corsair
Vultee YA-19B

Specifications (R-2800-54)

General characteristics
Type: 18-cylinder air-cooled twin-row radial engine with water injection
Bo 5.75 in (146.05 mm)
Stroke: 6 in (152.4 mm)
Displacement: 2,804.5 in³ (45.96 L)
Diameter: 52.8 in (1,342 mm)
Dry weight: 2,360 lb (1,073 kg)

Components
Valvetrain: Poppet, two valves per cylinder
Supercharger: Variable-speed (in F8F-2, unified with throttle via AEC automatic
engine control), single-stage single-speed centrifugal type supercharger
Fuel system: One Stromberg injection carburetor
Fuel type: 100/130 octane gasoline
Cooling system: Air-cooled

Performance
Power output: 2,100 hp (1,567 kW) @ 2,700 rpm
Specific power: 0.75 hp/in³ (34.1 kW/L)
Power-to-weight ratio: 0.89 hp/lb (1.46 kW/kg)





*