Napier L48 modifications 1904-1908

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Bill Boddy

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As designed, F-head engine had inlet-valves with flat seats, sealing against three concentric circular areas. with holes through each valve-head (Benz and Mercedes persisted with what Bob Chamberlain calls “this piece of nonsense” until after 1909, Ignition was by patented Napier “synchronised system”. A single water-heated Napier carburettor was used. 0.3in thick copper water jackets were electro-deposited, a process taking four weeks in 1904! Valve timing; inlet opens at TDC, closes 30deg after BDC; Exhaust 50deg before TDC, closes 10deg after TDC.

As first shown in June 1904. L48 did not have its separate reverse lever. and the front springs’ top leaves were too short. This was corrected, and normal radiator replaced by side cooling-tubes. Speedometer fitted driven first by friction-wheel. then by spur-gear from offside front wheel. About March 1905. wood-spoke wheels replaced with Dunlop detachable wire wheels. After steering problems at Daytona. radius-arms replaced back-axle torgue-tube for Gordon Bennett race. Brake-operating geometry seriously at fault, causing car to hit a wall in 1905 GB when handbrake locked on, as had happened to 1905 GB Napier. Pawl and ratchet removed for Daytona runs. Camber of springs reduced during 1906.

For high speed at Brooklands in 1907, new Rudge wheels and stronger front axIe fitted. plus drum-type friction-dampers: the latter necessitated steering alterations, geometry being impaired by lowered drag-link and by shorter Pitman-arm used later to increase leverage (Chamberlain has made no alterations. believing dead steering action to be in keeping with a car of this age — the correct sentiment! Flat spring-leaves were now used, chassis-height being maintained by longer shackles. At this time rear radius-rods were removed, and it is believed back shackles were eventually locked-up.

New cooling header-tank fitted in 1908 permitted simpler bonnet and improved car’s appearance: this later replaced by crude tank of similar shape. perhaps due to an accident. 15-litre, 61/4 x 5in engine replaced in 1908 by larger one of 61/8 x 6in. For the Match Race, stroke was increased to 7in, when top-speed eas in the region of 130mph. Geometry of the brake gear has been improved by Chamberlain so that rachet can be safely used for parking, which seems reasonable. The Napier was known as L48 but in its final form at Brooklands it was chassis No 599, with engine No 5019.

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