Allison V-3420 implementation

[wuzak]

Further reading reveals that the X engine based on teh Liberty was in fact a design of the AAC, which Allison built. It was the X-4520.

Though the name plate says otherwise:

Pictures of the engine itself:
http://www.enginehistory.org/Allison/X-4520/Allison_45201.jpg
http://www.enginehistory.org/Allison/X-4520/Allison_45202.jpg

From Allison Serial Numbers, by Dan Whitney, AEHS.

 

[wuzak]

From Allison Early Engines, pdf presentation:

X-4520
Crankshaft with Roller Bearings and Wide Throws, Upper and Lower Cylinder Banks Are Offset to Facilitate Two Sets of Connecting Rods on Each Crankshaft Throw

Bore: 5.75in/146.05mm
Stroke: 7.25in/184.15mm
Capacity: 4518cu.in/74l
Power: 1320hp/984kW

Quite a massive engine for the power, but what would match it in the mid 1920s?

 

[Shortround6]

Possibly a development of the Napier Cub: Napier Cub - Wikipedia, the free encyclopedia

Or a Packard engine: http://www.enginehistory.org/Packard/jpgs/1A-2775 supercharged.jpg

 

[wuzak]

The Packard X-2775 or 1A-2775 is an interesting engine:

1A-2775 - Supercharged (1928 )
Bore: 5.375in/136.525mm
Stroke: 5in/127mm
Capacity: 2723cu.in/44.6l
Weight: 1635lb/742kg
Rated power: 1400hp/1044kW @2600rpm
Maximum power: 1500hp/1119kW @ 2700rpm

2A-2775 - Supercharged (1935)
Weight: 1722lb/781kg
Rated power: 1900hp/1417kW @2800rpm

An interesting engine. Undersquare dimensions (stroke smaller than bore) and quite light for its capacity. 1900hp in 1935 is impressive - wonder what was wrong with it?

It is possibly a little lightweight for further development. 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.

It also appears to have angles of 60°/120°/60°/120° rather than the 90°/90°/90°/90° of the X-4520 and later Vulture and DB604. So it will be taller, but narrower.

The 2A-2775 has a power rating of about what the AAC wanted for their XBLR (the XB-15 and XB-16), but couldn't get.

http://www.enginehistory.org/Packard/StatsAllPackardAero.pdf

 

[wuzak]

This site has a drawing of the 1A-2775 with some dimensions, but you have to be a memeber to download.