Packard X-2775: Difference between revisions

Packard 1A-2775
Type	24-cylinder liquid cooled X-configured piston engine
National origin	USA
Manufacturer	Packard Motor Car Company
First run	1927
Produced	1927-1935
Number built	3
Developed from	1A-1500

Often called the Packard X-2775, Packard's official designation for this engine was 1A-2775 in 1927 and 1928, and 2A-2775 in 1935. The engine was constructed as a single crankcase with four banks of six cylinders in what is close to an X-configuration. The engine was an upright 60 degree vee-12 and an inverted 60 degree vee-12 sharing a common crankcase. Although technically incorrect, the engine has been characterized as two Packard 1A-1500 V-12 engines coupled with a mutual crankcase.

Design and development

The engine was taller than it was wide due to the 60 degree angle at the top and bottom vees. angles of 60°/120°/60°/120° with Undersquare dimensions (stroke smaller than bore) and light for its capacity.

The 2A-2775's 1900 hp was impressive in 1935, and is rated at about what the USAAC wanted for their XBLR (the XB-15 and XB-16) Long Range Bomber project.

Packard supplied a new and very powerful liquid-cooled engine for this project: the Packard X-2775 engine of 1250 hp. In fact this engine consisted of two 625 hp Packard V-1500 V-12 engines coupled with a mutual crankcase with one part upright and the other one inverted to form a 24-cylinder X-type engine with four rows of six cylinders. In this form, the new Kirkham-William racer as it was called was the most powerful biplane racer ever built for the Schneider Cup event. The racing team was, however, not very lucky with the new racer since it only accumulated a very flew flying hours before the race in Venice. They asked the organizing committee for a time extension, but because this was not granted the entry for the race had to be withdrawn. It was later converted to a landplane with a fixed wheel undercarriage and managed to set a new world-speed record of 519 km/h but this record was never officially recognized.

After the failure of the Kirkham-Williams biplane racer to perform in the 1927 Schneider Cup race, the Americans made a last attempt for the 1929 race at Calshot, U.K. The original biplane racer was totally redesigned into a mid-wing monoplane racer with an even more powerful Packard X- 2775 engine producing 1500 hp. It was named Mercury I. The work was done by the Naval Aircraft Factory at Philadelphia under great secrecy. Racing Pilot Al Williams was again a leading individual in this project. Great care was taken for aerodynamic shaping of the racer using wind-tunnel data from tests with scale models and the result was an extremely good-looking racer.

Upon completion, Al Williams did the initial flight- testing with the lower rated engine from the biplane racer near the Santee Wharf of the Annapolis Military Academy. Because the both floats were buried very deep in the water, and the torque of the big Packard engine produced a tendency for the left wing to dig into the water he hardly managed to become airborne in the plane because the use of full rudder and ailerons to keep the plane on a straight course produced too much drag. He was also troubled by water spray hitting the propeller and fuselage. He finally managed to make a short hop with the Mercury but because of a fuel pressure drop he had to land on the water again, resulting in bending the propeller. In spite of these problems, the Mercury was a very promising type and the disappointment of Williams’s group must have been great when the U.S. Navy declined a request to transport the Mercury by vessel to the U.K!

Compare Buzzard/R with later Griffon in terms of weight. 1140lb/517kg for the Buzzard, 1640lb/744kg for the R (including that massive supercharger with double sided impeller) and the Griffon 65 at 1980lb/900kg.

Variants

• 1A-2775 rated at 1200 hp (894 kw) at 2600 rpm and max of 1250 hp (932nbsp;kw)at 2700 rpm Weight 1513 lb (691 kg)
• 1A-2775 rated at 1400 hp (1044 kW) at 2600 rpm and max of 1500 hp (1119 kW) at 2700 rpm - Weight: 1635lb (742 kg) - Supercharged (1928)
• 2A-2775 rated at 1900 hp (1417 kW) at 2800 rpm-Weight: 1722lb/781kg- Supercharged (1935)

Specifications (variant)

General characteristics

• Type: 24-cylinder, liquid-cooled, X-configured, piston engine
• Bore: 5 3/8 in 136.525 mm
• Stroke: 4 in 127 mm
• Displacement: 2723 in³ 44.6 L
• Dry weight: 1635 lb/742 kg

Components

• Valvetrain: 4-valve, overhead-cam
• Supercharger: Gear-driven supercharger

Performance

• Power output: 1400 hp 1044 kW at 2600 rpm
• Specific power: .50 hp/in³
• Power-to-weight ratio: .85 hp/lb