The Napier Sabre Engine
Part 1: Shop Layout, Work Flow, Production Sequence, Machining the Crankcase and Cylinder Block
by J. A. Oates, A.M.I.E.I., M.Inst.Met.
This article first appeared in the Volume 6, Number 66 (April, 1944) issue of Aircraft Production magazine, and is presented here through the kind permission of Flight International. Thanks also to Bruce Vander Mark for furnishing volumes of Aircraft Production for scanning.
Fitted to the Typhoon and other aircraft, the Napier Sabre weighs 2,360 lb and develops 2,200 bhp at 3,700 rpm. It measures approximately 80” by 40” by 43” and is a compact 24-cylinder horizontal H-type sleeve-valve engine with a bore and stroke of 5.000” and 4.750” respectively, giving a total swept volume of 36.69 litres. The short stroke enables the overall width to be kept to a minimum. For a liquid-cooled twin crankshaft engine, the specific weight of 1.07 lb per brake horse power is highly creditable. To ensure efficient operation under arduous conditions, high-quality workmanship and materials are essential. That this is the case with the Sabre will be seen from the description below of the manufacture o f the crankcase and cylinder block, and from subsequent articles dealing with other major components.
|Fig. 1. Views of the Sabre showing the double-entry type supercharger. These illustrations gives some idea of the compactness of the installation.|
|2,200 HP Napier Sabre Engine
Four of the upper row of cylinders have been removed to show the pair of crankshafts mounted one above the other in the crankcase. Each crankpin has a pair of connecting rods operating in cylinders opposite to the crankshaft concerned and the twenty-four cylinders are arranged in two flat rows of twelve cylinders apiece. On each side of the two crankshafts and between the upper and lower sets of cylinders is a torsion shaft that operates the sleeve valves through skew gears. These shafts, driven by the airscrew gearing, are extended at the rear of the cylinder blocks to drive the two-speed supercharger.
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