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).
Defining supercharged and un-supercharged 2-cycle engines and outlining regulations for race competitors.
| Identifier | ExFiles\Box 160\3\ scan0306 | |
| Date | 20th May 1939 guessed | |
| (4) Supercharged 2 cycle engine : A 2 cycle engine is said to be supercharged when the introduction into the cylinder (or cylinders) of the air or gaseous mixture intended for combustion is caused by means other than the travel of a driving piston of uniform diameter. Un-supercharged 2 cycle engine : A 2 cycle engine is said to be un-supercharged when only the travel of the piston of uniform diameter causes the introduction into the cylinder (or cylinders) of the air or gaseous mixture intended for consumption. N.B.- Supercharged or un-supercharged 2 cycle engines are admitted within the scope of the formula of the " Le Mans 24 hour race " on the same lines as 4 cycle engines. In the present regulations, the normal cylinder capacity is that set out in the Catalogue; the geometrical cylinder capacity is that corresponding to the dimensions of the stroke and bore. The corrected cylinder capacity is the cylinder capacity increased, in case of need, on account of the use of a compressor. The basic cylinder capacity, serving to determine the mileage and the distribution into categories, is the geometrical cylinder capacity for vehicles with an engine not fitted with a compressor, and the corrected cylinder capacity if a compressor is used (refer to art. 15). Competitors (manufacturers or private individuals) must comply with the following obligations : I. - Cars entered must correspond with the description of a commercial catalogue in normal use. The decisions of the race stewards as to whether the vehicles presented may or may not be admitted shall be final. 2. - Cars must have a minimum of two comfortable seats facing forward in front; the rear seats are optional. Doors are not compulsory. 3. - Cars entered must be fitted with a bona fide touring body and comprise, throughout the duration of the 24 hours, in a perfect condition of fixing and efficiency regarding which the decisions of the race stewards shall be final at any time during the event : windscreen, wings, bonnet, lamps, headlamps, horns, automatic starter, rear vision device and an efficient silencer. At the start, cars must be fitted with tyres in a new condition. The same shall apply to the spare wheels. 4. - Cars must correspond to a catalogue in current use, but as this does not generally specify the compression ratio of the engine, its setting, the weights, shapes or composition of the connecting rods and pistons, the diameter and lift of the valves, the transmissions ratios, the make and number of carburetters, the make of the electric equipment, the capacity of the fuel and lubricant tanks and the nature of the cooling liquid, it is admitted that, on the points above enumerated only, competitors enjoy absolute freedom. 5. - Discrepancies in the cylinder capacity compared with the normal cylinder capacity, as defined by the manufacturer's catalogue, will be limited as follows : a) Plus tolerance. - The cylinder capacity shall not exceed the normal catalogue cylinder capacity by more than " three per cent ". ... | ||