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).
Page from 'The Autocar' magazine featuring reader correspondence on various topics, including technical advice on Bentley valve clearances and rotary engines.
| Identifier | ExFiles\Box 160\5\ scan0169 | |
| Date | 18th October 1940 | |
| October 18th, 1940. 194 Publics Campaign 1378 The Autocar 491 Correspondence parallel drive is more efficient and easily maintained than that of a 90 degree, whether by worm or bevel; and (2) torque reaction does not impose variable additional loading on the springs. A free wheel is an obvious benefit and has no attendant disadvantages. TRUBIE MOORE (Capt.). Leeds. [As will surely be obvious, anyone such as the contributor of the Everyman article in question, who has a wide and intimate knowledge of different designs, is likely to draw upon his experience and knowledge in putting forward suggestions for a new design. We repeat, however, that the D.K.W. design was not drawn upon consciously. Also, the type of body differs from that car's. As to our correspondent's accusation of discrimination in the past on this journal's part against Continental and unorthodox designs, we feel that sufficient answer is given by study of the pages of The Autocar over, say, the past five years, wherein every type of car has received its share of attention and praise or criticism, irrespective of country of origin. In particular, regarding one make of front wheel drive car of French origin mentioned by this reader, The Autocar has always recognised, and duly drawn attention to, its exceptional merits.—ED.{J. L. Edwards}] its direction at the end of a stroke. Of course it does, in relation to the actual cylinder it is working in, and the forces acting on it are exactly the same as in other types of engine (considering each cylinder separately). Now “The Scribe” says that in a radial engine the pistons go up and down, i.e., in relation to the engine mounting or chassis; but they might just as easily go from side to side, which, in fact, they do in some of the cylinders. Bearing this in mind, let us consider the rotary engine. Suppose the crankpin is fixed so that t.d.c. is at the top of the engine. The piston will then be at the top of the cylinder. Now if the cylinder is rotated half a turn the piston will be at the bottom of the cylinder, and as the cylinder rotates on a fixed point in the chassis the piston must have altered its position in relation to the chassis to get to the bottom of the cylinder. Therefore it goes up and down, as the piston in any other type of engine does. The trouble with “The Scribe’s” argument is that in one sentence he talks about the piston going up and down, and in another about its changing direction, which does not mean the same thing. In any case, it is horrible to picture all those cylinders flying round and round and trying to capture a piston on the way. D.{John DeLooze - Company Secretary} F.{Mr Friese} ARNOLD. Brockley, London, S.E.4. THE 3-LITRE BENTLEY Correct Valve Clearances [49812.]—The information given in letter [49787] is not all correct. The following are the correct Bentley valve clearances:— Chassis 1 to 222, all 15 thous. All long chassis, inlet 4 thous., exhaust 6 thous.; but some of these have later camshafts. Short chassis models up to 1926 are generally the same, but these have usually been changed. All after 1926, 19 thous. Very old 3-litres have caps on the end of the valve stems. These usually have the 15 clearance. It is always wise to ask Bentley's, quoting the engine number. It is very unlikely that any 3-litres sold to the public ever did 100 m.p.h. Changing from 8/20 by 120 to 5.25-21 tyres will not affect the speedometer reading; indeed, I have driven 3-litres with wheels between 6.00-16 and 7.00-21, and the mileage recorded on a given run varies very little. In any case, A.T. speedometers read fast as old age creeps on, and the needle wags so much that the “exactly five per cent. slow, old boy,” is all nonsense. It's always slow, note! If Mr. Thwaites fits a 4J engine in his dream 3-litre, he will find he has terrific performance with good fuel consumption, and it is easy to do. Do not be tempted by too high a gear; 3.78 is the best. I have used as high as 3 to 1, but don't recommend it. W. G.{Mr Griffiths - Chief Accountant / Mr Gnapp} S. WIKE. Manchester, 20. ROADS DAMAGED IN RAIDS Flexibility of the System, but Need for Reducing Delay to a Minimum [49814.]—The appointment by the Minister of Home Security of Sir Warren Fisher as a Special Commissioner to co-ordinate and facilitate the work of the authorities responsible for the restoration of roads damaged by enemy action is welcomed. The British Road Federation would urge upon the authorities concerned, and upon Sir Warren Fisher, the need of carrying out such repairs as will make any damaged roads usable at the very earliest possible moment. Happily, due to the flexibility of road transport, diversions can be made at will, but diversions for any longer than is absolutely necessary are serious additions to the time of journeys and the fuel consumption of vehicles. The delays are increased and the costs enhanced. No doubt the Ministry of Supply would help local authorities to build up a reasonable stock of materials against such calls as may be made on them, and the Minister of Labour would enable them to find the men when necessary. The rapid restoration of traffic routes is an affair of more than local importance, and the Federation hopes that proper steps will be taken to ensure that the dislocation of road traffic is reduced to the minimum. F.{Mr Friese} G.{Mr Griffiths - Chief Accountant / Mr Gnapp} BRISTOW, Hõn. Secretary, British Road Federation. London, S.W.1. SUMMARY of CORRESPONDENCE INSTRUCTION BOOKS FOR NOTABLE CARS.—Mr. J.{Mr Johnson W.M.} R.{Sir Henry Royce} Brooks, of North Walsham Wood, Norfolk, has an instruction book for each of the following cars: 3-litre Blue and Red Label Bentleys, six-cylinder Bentley, six-cylinder 1929 Lagonda, and six-cylinder 1933 Talbot. On receipt of 10s. subscription to be given to the local hospital, Mr. Brooks will be pleased to forward any one of these instruction books to an interested present owner. “THE PISTONS GO ROUND AND ROUND” Forces in a Rotary Engine Exactly the same as in Other Types [49813.]—I do not often break into print, but when anyone comes forward with a theory like “The Scribe's” in your issue of October 4th—well! The whole thing hangs on his last sentence, maintaining that the pistons of a rotary do not reverse their direction. Taken on its face value it is absolutely correct. However, he starts off by asking if the piston of a rotary engine reverses BOOKS for MOTORISTS Issued in conjunction with “THE AUTOCAR” Net Price. By Post. 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