By

AMINE LAKHDARI

Preface

Throughout the semester, this course has helped me develop not only my

knowledge but has given me and idea about how an aero piston engines is

developed through the last century.

The following is specific assignment that shows my knowledge and my

progression throughout the course.

TABLE OF CONTENTS

SECTION TITLE

1.0 Introduction

1.1 Design and development

2.0 Peacetime

3.0 Variants

3.1 Military

4.0 Applications

5.0 Specifications (R-2800-54)

6.0 Crankshaft Development

6.1 Connecting Rod Evolution

6.2 Clamp-type Crankshaft

6.3 Face-splined Crankshaft

7.0 Conclusion

1.0 Introduction

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

1.1 Design and development

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); which itself was even larger than the contemporary American Wright Duplex-Cyclone radial of 3,347 in³ (54.86 L) then

under development (and promising to be more powerful than either the P&W or Gnome-Rhone radials), but 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. Cylinder cooling was effected by aluminum

cooling muffs that were shrunk onto the steel alloy forged barrels. In addition to requiring a new cylinder head design, the Double Wasp was probably the most

difficult to effectively direct a flow of cooling air around. The twin ignition magnetos 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 driveshafts for the magnetos emerging from the gear reduction

case either directly forward or directly behind the magneto's cases, or on the later C-series R-2800s with the two-piece gear reduction housings, on the "outboard"

sides of the magneto 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 designing

of conventional air-cooled radial engines had become so scientific and systematic by then that the Double Wasp was introduced at a power rating that was not

amenable to anything like the developmental power increases that had been common with 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. However, 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.

The first prototype F4U Corsair, the earliest aircraft to use the Double Wasp

The R-2800 was used to power several types of fighters and medium bombers during the war, notably the US Navy's Vought F4U Corsair, with the XF4U-1 first prototype Corsair becoming the first-ever airframe to fly with the Double Wasp on

May 29, 1940, and the first single-engine US fighter plane to exceed 400 mph (640 km/h) in level flight during October 1940. The R-2800 also powered the

Corsair's naval rival, the Grumman F6F Hellcat, the US Army Air Forces' Republic P-47 Thunderbolt, the twin-engined Martin B-26 Marauder and Douglas A-26

Invader, as well as the first purpose-built twin-engined radar-equipped night fighter, the Northrop P-61 Black Widow. When the US entered the war in

December 1941, some major changes in American military aviation engine design and manufacturing philosophy rapidly emerged, with such long-established

engines as the Wright Cyclone and Double Wasp being re-rated on fuel of much higher octane rating (anti-knock value) to give considerably more power. By 1944, versions of the R-2800 powering late-model P-47s (and other aircraft) had a rating

(experimental) of 2,800 hp on 115-grade fuel with water injection.

After World War II, the engine was used in the Korean War, and surplus World

War II aircraft powered by the Double Wasp served with other countries well past the Korean War, some being retired as late as the latter part of the 1960s when the aircraft were replaced.

2.0 Peacetime

Engines naturally grow in power with development, but a major war demands the

utmost performance from engines fitted to aircraft whose life in front-line service was unlikely to exceed 50 hours' flying, over a period of only a month or two. In

peacetime however, the call was for reliability over a period of perhaps a dozen years, and the R-2800's reliability commended its use for long-range patrol aircraft

and for the Douglas DC-6, Martin 4-0-4, and Convair 240 transports. This last application is noteworthy, since these were twin-engined aircraft of size, passenger capacity, and high wing loading comparable with the DC-4 and the first

Constellations.

Today, three-quarters of a century after the first prototype Double Wasp was built

and run, it is still used in many restored vintage warbird aircraft displayed at air shows — such as the over two dozen airworthy examples of the first airframe design it powered, and sees frequent service worldwide on aircraft such as the

Canadair CL-215 water-bomber. In addition, many R-2800s continue to power DC-6 cargo and fuel-carrying aircraft in locations such as Alaska. A total of

125,334 R-2800 engines were produced between 1939 and 1960.

3.0 Variants

This is a list of representative R-2800 variants, describing some of the mechanical

changes made during development of the Double-Wasp. Power ratings quoted are usually maximum "military" power that the engine could generate on takeoff and at

altitude: 100 Octane fuel was used, unless otherwise noted.

The R-2800 was developed and modified into a basic sequence of subtypes, "A" through "E" series, each of which indicated major internal and external

modifications and improvements, such that the "E" series engines had very few parts in common with the "A".

3.1 Military

Notes

The dash number for each military type (e.g.: -21) was allocated to identify the complete engine model in accordance with the specification under which the engine was manufactured, thus it did not necessarily indicate the sequence in

which the engines were manufactured; for example: the -18W was a "C" series engine, built from 1945, whereas the -21 was a "B" series engine, built from 1943.

Until 1940 the armed forces adhered strictly to the convention that engines built for the Army Air Force used odd numeric suffixes (e.g.: -5), while those built for the

US Navy used even (e.g.: -8). After 1940, however, in the interests of standardization, engines were sometimes built to a joint Army-Navy contract, in

which case the engines used a common numeric suffix (e.g.: the -10 was used by both Army and Naval aircraft.)

The suffix W e.g.: -10W denotes a sub-series modified to use A.D.I Anti-Detonate

Injection or water injection equipment, using various mixes of water and methyl alcohol (CH3OH) injected into the carburetor to increase power for short periods:

several models of R-2800s were fitted as standard with A.D.I and did not use the W suffix. Few commercial aircraft used water injection.

"A" Series:

R-2800-1

1,500 hp (1,118 kW) at 2,400 rpm at 7,500 ft (2,286 m). Production prototype of "A" series engines with the first flight test July 29, 1939.

Single-speed two-stage supercharger. Production = 2 (P&W). Tested in Vultee YA-19B.

R-2800-5

1,850 hp (1,379 kW) at 2,600 rpm at 2,700 ft (823 m). Main production "A"

series engine used in Martin B-26A, early B series and XB-26D and Curtiss C-55/XC-46. Production = 1,429 (P&W 475, Ford 954.)

"B" Series:

A preserved "B Series" R-2800-21 or -59. The A and B series can be most readily identified by their smooth, single piece nose casings. This photo shows the simplified, tubular ignition harness fitted to some R-2800 subtypes.

R-2800-8

2,000 hp (1,491 kW) at 2,700 rpm at 1,000 ft (305 m); 1,800 (1,342 kW) at

2,700 rpm at 15,500 ft (4,724 m). First series production "B" Series engine using a two-stage, two-speed supercharger and with internal engineering

changes resulting in increased power and reliability. Updraft Bendix-Stromberg PT-13D-4 pressure carburetor. First production engines delivered to U.S.N November 11, 1941. Used in Brewster F3A-1, Goodyear FG-1,

Vought F4U-1 and F4U-2. Production = 3,903 (P&W 2,194; Nash 1,709.)

R-2800-8W

2,250 hp (1,677 kW) WEP with water injection. First production engine

using ADI equipment, major production version of -8 and used in same versions of F4U Corsair. Production = 8,668 (P&W 5,574; Nash 3,094.)

R-2800-10 and R-2800-10W

2,000 hp (1,491 kW) at 2,700 rpm at 1,000 ft (305 m); 1,800 (1,342 kW) at

2,700 rpm at 15,500 ft (4,724 m); up to 2,250 hp (1,677 kW) WEP with water injection. Similar to -8 series apart from downdraft PT-13G2-10 and

PT-13G6-10 (-10W) carburetor. Used in Curtiss XP-60E, Grumman F6F-3 (-10; late production -10W) and F6F-5 (-10W) series and Northrop XP-61,

YP-61, and P-61A-1. Production = 4,621 -10 (P&W 2,931; Nash 1,690) and 12,940 -10W (P&W 3,040; Nash 9,900); Total = 17,561.

R-2800-21

2,000 hp (1,491 kW) at 2,700 rpm at 2,500 ft (762 m); 2,000 hp (1,491 kW)

at 2,700 rpm at 25,000 ft (7,620 m). First production variant fed by a General Electric C-1 turbosupercharger. Designed for use in the Republic P-

47B, C, D, G and XP-47F and K. Production = 5,720 (P&W 1,049; Ford 4,671.)

R-2800-59

2,000 hp (1,491 kW) at 2,700 rpm at 2,500 ft (762 m); 2,000 hp (1,491 kW) at 2,500 rpm at 25,000 ft (7,620 m); 2,300 hp (1,700 kW) WEP with water injection. Main production variant used in P-47 series, fed by an improved

C-23 turbosupercharger. Differed from -21 in being fitted with A.D.I and a General Electric ignition system with a simplified, tubular ignition harness

developed by the Scinitilla Company in partnership with Bendix. Used in P-47C and D, XP-47L. Production = 11,391 (P&W 592; Ford 10,799).

"C" Series

A "C Series" R-2800, with the two section nose casing incorporating torque-monitoring equipment and a Spark Advance unit, with the "outboard" driveshaft

location for each of the twin ignition magnetos.

R-2800-18W

2,100 hp (1,566 kW) at 2,800 rpm at 1,000 ft (305 m); 1,800 hp (1,342 kW)

at 2,800 rpm at 25,500 ft (7,772 m). First series production variant of the "C" Series, which was a complete redesign of the R-2800. Some of the main changes were forged, rather than cast cylinders, allowing an increased

compression ratio (from 6.65:1 to 6.75:1), a redesigned crankshaft, a single piece, rather than split crankcase center section, and a two section nose

casing, incorporating hydraulically operated torque-monitoring equipment and an automatic, vacuum operated spark-advance unit. The supercharger

used fluid coupling for the second stage. Updraft Bendix-Stromberg PT-13G2-10 carburetor. Used in Vought F4U-4 and -4 variants. Production =

3,257 (P&W).

4.0 Applications

Martin B-26 Marauder

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

5.0 Specifications (R-2800-54)

Pratt & Whitney R-2800

Data from FAA TCDS

General characteristics

Type: 18-cylinder air-cooled twin-row radial engine with water injection Bore: 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)

6.0 Crankshaft Development One of the things that made the original Pratt & Whitney “Wasp” so successful in 1926 when it first passed its type test was the

ability to make its power at a higher RPM and a lighter weight than its competition.

Key to this accomplishment was the use of a one-piece master rod and two-piece

crankshaft. Though twopiece crankshafts had been built before, George Mead and

Andy Willgoos chose a new construction consisting of a split crankpin splined to its

mating crankpin, the whole assembly being held together with a bolt through the center

of the crankpin. "Wasp" Crankshaft (Pratt & Whitney)

This construction was used in many, but not all, Pratt & Whitney designs preceding the R-2800. It is therefore no surprise that the designers chose this same type of construction for two-throw R-2800 crankshaft. The original R-2800

crankshaft compensated for the weight of the master rod and link rods in the usual fashion, by providing a counterweight that balanced all of the rotating mass and

one-half of the reciprocating mass. Initially, no vibration dampers of any kind were provided. It is unclear whether this was wistful thinking on the part of the

designers, or merely acknowledgement that no one could predict the vibration behavior anyway, so they may as well start testing to uncover the problems as early

as possible. One thing the designers did consider was placement of the master rods as close as possible to 90 degrees to one another so that second-order inertia

torques could cancel as nearly as possible, reducing 2X torsional excitation of the crankshaft.

George E. Meloy was heavily involved in R-2800 crankshaft development almost from the start. One of his first jobs at Pratt & Whitney was to write a report on the history of R-2800 development, which included many details on the successes and

failures of the crankshaft. Meloy was later responsible for sorting out problems with the “C” engine crankshaft and getting it into successful production in the

Kansas City, Missouri plant. Some of the people who worked for Meloy remember him for being the only person they know who could walk into a test cell and not

get oil on his clean white shirt. Meloy was born in Chicago in 1916, but at the age of four moved east to New York. He eventually settled in Teaneck, New Jersey

where he graduated from Teaneck High School. Meloy received a Bachelor of Aeronautical Engineering from New York University. Despite the scarcity of jobs

brought about by the Depression, Meloy started work at Pratt & Whitney one week after graduation in 1938. Initially a test engineer, Meloy advanced rapidly through

project engineering and finally into management. While his real love was in

development, like many capable technical people, he had the management role forced upon him. However, he did not despair. Says Meloy, “Every moment spent

at Pratt, to me, was worthwhile. I didn’t watch the clock, didn’t have to. During the war years, we worked 54-hour weeks. There were no perks back in that time,

understandably. We were just happy to do it. It gave us a feeling we were doing something worthwhile for the defense of the nation.”

6.1 Connecting Rod Evolution The first one-piece master rod assembly featured a locked silver-plated bearing and locked knuckle pins. A silver-plated flange on the forward face of the master rod

bearing carried thrust loads on the master rod. This design was discarded because of weaknesses that became apparent during testing. By strengthening portions of

the master rod and link rods that were highly stressed, as well as increasing the fillets and radii at stress concentration points, master and link rod structural failures

were eliminated. Aiding this process was moving knuckle pin oil delivery passages to the knuckle pin retaining plates. Much of the master rod development was done

using brittle lacquers. These coatings were the only instrumentation available at that time for internal engine parts. Brittle lacquers have the characteristic of cracking when the material to which they have been applied flexes. By analyzing

the concentration and orientation of cracks in the lacquers, highly stressed engine components could be improved by adding metal in the right places Master rod

bearing failures prompted a series of experiments into bearing construction and materials. The original copper-bronze and bronze bearings were replaced with

silver lead bearings in April of 1938, eliminating the material problems. The question of how to retain the bearings got more attention. These were originally a

press-fit. Use of set screws to lock the bearings was tried but not successful

Master Rod Evolution

The Figure shows the evolution of R-2800 master rods. The two left-most rods,

P/N 27967 and P/N 32830 are early experimental designs that never saw production. The center rod, P/N 34405 was used in the “A” and “B” series of

engines. The fourth one, P/N 87017, was used in the “C” series of engines. The one on the right, P/N 86132, was used in early “E”, “CA”, “CB”, and “CE” series

engines. Compare the sharp edges and tight radii on the early rods with the generous fillets and large radii of the later ones. Note the progressively larger cross

section of the rods, and center rib in the web of the later design. Extremely high quality of fit and finish is evident in all the examples.

6.2 Clamp-type Crankshaft

Despite difficulties with crankshaft development, it was this crankshaft design that

was used in the R- 2800 “A” and “B” series engines that saw the majority of the action and contributed so much to the winning of World War II. See Figure

One solution to the weakness of the splined crankshaft was a clamp-type crankshaft. This took the form of a two-counterweight crankshaft without 4.5X

torsional vibration dampers that received considerable attention and testing from May through October of 1939. This crankshaft design had slightly better 4.5X propeller blade tip stress characteristics than the four-counterweight crankshaft, but

otherwise had identical vibration characteristics with the two counterweight splined-crankpin crankshaft.8 But it was also harder to assemble, requiring special

alignment fixtures and assembly techniques, and prone to slippage. Considerable experimentation went into finding the correct amount of clamp bolt stretch. Each

experiment involved engine teardown, inspection, and reassembly. The frequent tightening of the clamp bolt caused galling of the clamp surfaces and necessitated

re-drilling of the cotter pin hole in the clamp bolt with each assembly.9 Refinement of the clamp-type crankshaft continued. Dynamic counterweights were added,

along with other improvements. Planners intended this type of crankshaft for the production “C” engine to be built in Kansas City, Missouri. Much of the

experimental development of the “C” engine, which began on September 1, 1940,

was done with the clamp-type crankshaft.10 but this crankshaft design never saw production

Clamp-type Crankshaft Representative Of Those Tested By Pratt & Whitney (Navy)

6.3 Face-splined Crankshaft Instead, a face-splined crankshaft construction was developed and used in the “C”

and all subsequent R-2800 engines.

"C" series Crankshaft (Pratt & Whitney)

It is the opinion of the author, and this opinion is shared by retired Pratt & Whitney engineers Elton Sceggel11 and Gordon Beckwith12, that improvements in gear

cutting technology at the Gleason Works of Rochester, N.Y. made possible the machining of complex involute splines necessary for this new joint. The face

splined crankshaft is first mentioned in a report on the bending behavior of various crankshaft joints. In this report, six joint designs were tested: the traditional

internal spline; the clamp-type; the face splined with an internal tension bolt torqued to a stretch of 0.0018”; a hollow one-piece pin (to simulate a one-piece

crankshaft; a face-splined with plug; and a face-splined with an internal tension bolt stretched to 0.0068”

Detail of Face Splines (Pratt & Whitney)

The results are presented in Figure 5.7, which strongly supports the argument that the face-splined construction with proper tension bolt torque is far superior to other

designs.13 the face-splined crankshaft construction was not without its development troubles. A large bolt centered in each crankpin held the face splines

in close contact. It took considerable experimentation and cost George Meloy a lot of sleep before suitable locking pins for this bolt were produced.14 By October 29,

1942, the first examples of the face splined two-counterweight cranks with 4.5X bifilar dampers on the rear counterweight were undergoing torsional and linear vibration testing. It is noteworthy that in this test, master rods were installed twenty

degrees apart in cylinders 8 and 9. This arrangement was ideal for eliminating 1X torsional vibration at the expense of 2X torsional vibration.15 Later addition of a

2X bifilar torsional vibration damper to the front counterweight eliminated the 2X torsional vibration problem inherent to this master rod orientation. While the

crankshaft would undergo continued improvement during its service life, these changes were minor, consisting of things like silver-plating the face spline mating

surfaces and use of lighter weight bifilar damper construction. The face-splined joint concept proved itself in service and remains in use in R-2800 “C” and later

engines in use today

Crankshaft Bending Studies (Pratt & Whitney)

7.0 Conclusion Despite the problematical development of the R-2800, it became a fine engine. In

World War II, it powered numerous fighters and medium bombers, and secured a reputation for ruggedness that was unsurpassed. Howard Camp, a fighter pilot

friend, flew both P-51s and P-47s in World War II. I once asked him which airplane he preferred. “It depends”, he replied without hesitation, “on whether you

are shooting or being shot at. You want the Mustang if you are shooting and the Thunderbolt if you are being shot at!” The R-2800 also had a reputation for being

robust. While the Wright R-3350 was a great engine, it required considerable care from its operators. On the other hand, the Pratt & Whitney R-2800 could take a lot

of abuse and keep right on going. Just prior to World War II, Frank Walker was responsible for the development of anti-detonation injection (ADI) for the R-2800.

ADI forces a water-alcohol mix into the induction system to cool the supercharged fuel-air mixture, thereby allowing a much higher manifold pressures and power

outputs. Using ADI, Walker was able to coax 3800 HP from an experimental “C” engine at manifold pressures up to 150 in Hg!1 This is nearly twice the power the engine was designed to produce. In addition to its reputation for ruggedness in

aircraft like the P-47, the R-2800 developed a reputation for reliability in airline service after World War II. It had a recommended time between overhauls of 2000

hours on twin-engine aircraft, and 3000 hours on 4-engine aircraft.2 The Douglas DC-6 was powered by four R- 2800s. When Douglas designed the newer, larger

DC- 7, it chose the more powerful R-3350, and instructed pilots to run them at high power settings in order to achieve promised performance. There is more than a

grain of truth in the old joke “What’s the difference between a DC-6 and a DC-7? The DC-6 is a four engine airplane with three-bladed props; the DC-7 is a three-

engine airplane with four-bladed props.” The fact that many R-2800s are still in use today nearly sixty years after they were built is testimony to the quality of the

vibration solution and crankshaft construction. It is also testimony to the dedication of the engine designers and test engineers. It is no doubt satisfying to Gordon

Beckwith, as well as the other test engineers who did not know when to go home, that all of that time spent after hours in the test house was worthwhile.

Sources:

http://www.ww2aircraft.net/forum/engines/terminology-engine-data-36560-

3.html#post1006503

http://neam.org/index.php?option=com_content&view=article&layout=edit

&id=1093 "Pratt & Whitney R-2800-39 Double Wasp"

Pratt & Whitney R-2800 Double Wasp From Wikipedia

No Short Days: The Struggle to Develop the R-2800 "Double Wasp"

Crankshaft By Kimble D. McCutcheon

AMINE LAKHDARI

2013.07.0041

Mark of distribution

Mark obtained

Sequences of topic

3 to 5

Depth of topic 5 to 7 Importance of topic

5 to 7

Total marks 15