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 of correspondence from 'The Autocar' magazine featuring reader letters on technical terms, fuel efficiency, driving techniques, and sports car performance.
| Identifier | ExFiles\Box 160\5\ scan0092 | |
| Date | 27th December 1940 | |
| 652 The Autocar December 27th, 1940. CORRESPONDENCE Winter or summer, a scene such as this scarcely “dates” with the season. The photograph was taken from the famous Horseshoe Pass, near Llangollen, in Wales, a testing ground as well as a noted viewpoint. OPINIONS EXPRESSED ARE THOSE OF OUR CORRESPONDENTS, WITH WHICH “THE AUTOCAR” DOES NOT NECESSARILY AGREE. LETTERS INTENDED FOR PUBLICATION SHOULD BE ADDRESSED TO THE EDITOR, “THE AUTOCAR,” DORSET HOUSE, STAMFORD STREET, LONDON, S.E.1 “DUMB-IRON AND DOG-CLUTCH” Derivations Suggested [49901.]—Your contributor, “S. R.{Sir Henry Royce} S.” (The Autocar December 6th, page 581) asks “Why dumb-iron, why dog-clutch?” Two guesses: In the days of horse-drawn vehicles, to distinguish the “iron” supporting one end of a three-quarter elliptic spring, as distinct from the more lively piece of spring occupying a similar position in the full-elliptic spring, the word “dumb” would not be too bad. Vide “dumb-waiter.” Dog-clutch? Well, all the best dogs have teeth, and it’s the teeth that distinguish dog-clutches from other clutches. London, S.W.1. GREEN INK. 64 M.P.G.! On a Two-year-old Fiat 500 [49902.]—It may interest you to know that my Fiat 500 has just attained 64 m.p.g. on Pool petrol with normal running. It is two years old, and has done 33,000 miles. Home Forces. R.{Sir Henry Royce} R.{Sir Henry Royce} S. CLARKE, 2nd Lt. COASTING TECHNIQUE Methods Which Have Been Found Satisfactory [49903.]—The subject of a “Query and Reply” in your December 13th issue is a matter I have given much attention to, and I should like to offer a few remarks. (1) If you switch off the ignition with the car in gear, assuming the carburettor is adjusted for slow running, you will be passing unexploded petrol through the cylinders and thereby not only washing them clean of all lubricant, but diluting the oil in the sump. (2) If your hand throttle is so adjusted as to cut off the petrol entirely when closed, then you will be sucking oil up into the cylinders and probably oiling up the plugs. (3) If you are in a hilly country and run down in neutral, and do this continually, you will soon be wearing out the brakes. Twice I have been run into in the Alps by people who had followed this method until their brakes were practically useless. My own methods, which have proved satisfactory, are as follows. My hand throttle is adjusted to cut off the petrol supply altogether when closed. I have an extra air arrangement fitted. I find that, in my case, for free-wheeling a slope of about 1 in 30 is best. If you then cross the crest at, say, 30 m.p.h., you will maintain that speed throughout the slope, as the internal friction and air resistance just about balance the pull of gravity. If the slope is steeper, say 1 in 20, the car will gather speed rapidly and the brakes will have to come into play. In such a case I run down in top gear, with petrol and ignition off and the extra air opened. If still steeper slopes are encountered the same methods are adopted, but a lower gear is used. Telegraph Hill, on the Exeter-Torquay road, is labelled “Steep hill, 1 in 6.” I have never, in scores of journeys, been able to read anything steeper than 1 in 7¾ on my Tapley (an almost indispensable fitment for mountainous country). Most of it is 1 in 10 to 1 in 12. I can ascend it on top, if the road is clear; when coming down, I go into third, switch off the ignition and petrol and open the extra air, and, as a rule, have no need to employ even one touch of the brakes. Let me take a rather extreme case which illustrates these principles. You ascend the Stelvio from the Bormio side. You then have 18¾ miles descent to Gomagoi at an almost uniform slope of 1 in 11, with 48 (not 44 as usually stated) acute hairpin bends. If you free-wheel down you will have to ease your brakes continuously, but going down in gear you have no trouble at all, waste no petrol, and oil up no plugs if you have adopted the simple measures described. If one knows the road, or can see it for a good distance ahead, free-wheeling is economical and pleasant. But with a twisty road, and possibly very steep gradients ahead, it is more prudent to descend in gear. Torquay. W. MALLESON. “TALKING OF SPORTS CARS” Considering Acceleration in the Higher Realms of Performance [49904.]—And now a “last word” from the owner of the Bentley (loud and prolonged cheering, presumably !) Clearly, Mr. W. Boddy [49891] regards my Bentley as in need of a champion, and small wonder; but grateful as I am to him for his timely intervention, I protest there is not, nor has there ever been, an “8-litre Bentley versus Type 57S Bugatti discussion.” Despite all Mr. C. W. P. Hampton’s smoke-screens and red-herrings, for the most part ignored by me, the sole point at issue has always been: Is acceleration from 0-100 m.p.h. in 40 sec. by a car said to be capable of 112-115 m.p.h. “good,” | ||