From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specification sheet for the Wraith 25/30 chassis, detailing the engine.
| Identifier | ExFiles\Box 139\3\ scan0167 | |
| Date | 3rd June 1938 | |
| 600 To Bkl. from Rm{William Robotham - Chief Engineer}/Cr.{Mr Cra???ster / Mr Chichester} Rm{William Robotham - Chief Engineer}/Cr.{Mr Cra???ster / Mr Chichester}1/MH.{M. Huckerby}3.6.38. SPECIFICATION WRAITH 25/30 ROLLS-ROYCE CHASSIS. Engine. A six cylinder overhead valve engine is used, having a bore of 3 1/2" and a stroke of 4 1/2", capacity 4257 cc., R.A.C. rating 29.4 H.P. The cylinder block is a monobloc casting with a detachable cylinder head, the crankcase sump and clutch casing being made of a special Rolls-Royce aluminium alloy to ensure lightness, in compatability with strength. The valves are push rod operated from the camshaft which runs in seven bearings in the crankcase. There are two valves per cylinder. The seven bearing crankshaft is balanced statically and dynamically to within very fine limits, further, a spring loaded damper is fitted to the front of the shaft, ensuring great smoothness of running, and reduced wear of crankshaft journals and bearings. The big end bearings are in a new R.R. bearing alloy which has a much bigger load capacity than ordinary whitemetal. An important point in the suppression of noise is the Rolls-Royce patent design of piston - a product of years of research. Ignition by battery and coil is provided, the ignition timing being controlled automatically by a centrifugal governor incorporated beneath the distributor head. A carburetter of the downdraught type with fixed jet is mounted on the induction pipe. An idle system with adjustable needle is embodied, ensuring reliable slow running of the engine, whilst an accelerating pump connected directly to the throttle gives rapid acceleration and flexibility at all speeds. The air intake and silencer of exclusive R.R. design which is fitted to this carburetter is of large proportions and has been specially developed with a view to reducing to a minimum the sound made by the air entering the carburetter. | ||