A SUPERCHARGED ROLLS-ROYCE

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36

A SUPERCHARGED ROLLS-ROYCE DETAILS OF D. FITZPATRICK’S BLOWN 1926 “PHANTOM I”

MENTION amongst enthusiasts of supercharging a Rolls-Royce always arouses interest and discussion, because the Rolls-Royce Company has never listed a blown car, although it is no secret that such engines have been assembhd for experimental purposes in the Derby factory before new models have been finally decided upon—the performance and reliability of the present ” Phantom III ” Rolls-Royce is adequate recommendation to the policy of not making a supercharged engine. So far as we know the only supercharged car of this world-renowned marque in use Is the 1926 “Phantom I ” saloon which

D. Fitzpatrick had Centric-supercharged under the supervision of L. C. McKenzie some time ago, more or less for “fun.” It finished fourth in the Vintage S.C.C. Welsh week-end event this year, and definitely merits a brief description. Students of motoring history may suggest that we have forgotten the remarkable car which Amherst Villiers, who is nowadays busy with the Villiers-Mays light aero motor, produced some thirteen years ago. Actually, our reply is that this car, although still in use, is no longer supercharged. It was actually one of the first of the ” Phantom 1″ cars and had a succession of Barker bodies. Villiers made a big Roots blower for it, very much like the famous superchargers he later evolved for the 4i-litre Bentley engine, and we believe that it blew at about 8 lb per square inch. Be also designed a very nice little fourcylinder engine, of, we believe, 8.6 h.p. and some 900 c.c., which had o.h. valves actuated by an o.h. camshaft. He arranged this engine to drive the blower and mounted the whole layout in a cradle on the off side of the chassis, suspending the cradle on a series of hydraulicallydamped links which transmitted the weight to the opposite chassis sidenumbers to that on which the cradle was mounted. The carburetter was arranged to act normally or under pressure at will, as on a Merceas-Benz, the blower

blowing through it. When the driver wished to use the blower he pressed a separate starter button, started the small engine, and so brought in the blower. We understand that this complicated layout was really beautifully made, that the engine was properly modified in respect of connecting-rods, pistons, etc., to withstand supercharging, and, in fact, that some 00,000 was spent on the car, irrespective of bodywork changes. Villiers, so rumour says, even went so far as to rig up a most complicated set of electrical facia indicators relating to the behaviour of every part of the installation, though we believe he never found time to couple everything up. No wonder he was wrathful when he discovered a reference to the car as making more noise than anything else, of being unreliable, and of having an Austin Seven engine to drive its blower, in a weekly motoring journal, after an experimental visit to Brooklands. At the time Villiers argued that motoring papers had no right to casually report happenings at the Track on non-race days, when it was in use for research, rather than for publicity, purposes—an argument with which we are in complete agreement. Actually, Villiers’ separate engine was supercharged by the blower it drove and thus contrived to retrieve some of the power absorbed in driving the blower, while the Rolls-Royce engine in any case gave away none of its output for rotating the blower—surely a very sound idea. The car was built for Capt. Kruse and was later owned by Lady Dorothy Paget and is still in service, but it is no longer blown, so we can claim to be describing the only supercharged Rolls-Royce in the notes which follow. Fitzpatrick’s car is a 1026″ Phantom I “which he has modernised and supercharged just as a bobby, after having the car put into really good order mechanically. The body is a particularly handsome two-door drophead, with a low, single-pane screen, which started life as a Weyrnann fabric body on a 20 h.p. Rolls-Royce, and which was converted to metal panelling and given a new rear-truck by Cooper Motor Bodies,

of Putney, about six years ago. The floor was appreciably lowered, giving a seating position that is not unlike that of a modern Rolls-Royce, and the wheel comes absolutely in the driver’s lap. The instruments are now all grouped in a big, oval centre panel and include a blower-pressure gauge, while disc wheels further modernise the car. The original 33″ x 5′ covers have been replaced by 19″ x 7″ tyres, and Houdaille hydraulic shock-absorbers replace the R-R dampers. Following a crash a deeper radiator with flush-fitting ” Phantom II” shutters was substituted for the original and the exposed dumb-iron cross-tube was replaced by a neat dumb-iron apron, two under apron cross members being used in its place, one of which Mackenzie made up from an old crankshaft. The honeycomb went back 1″ to take the shutters. These modifications not only resulted in an extremely handsome car, but brought the road-holding up to quite “Phantom II” standards. Now as to the supercharger. It is a huge Centric vane-type compressor, Type 6400., with a special extension to accommodate the long drive-spindle. It is driven from the crankshaft by twin belts, and the new cross-member in the chassis was arranged to permit easy withdrawal of the crank shaft pulley. The blower is driven at 1.8 times engine speed and gives a maximum boost of 6 lb per square inch. It is very like the unit on Major Gardner’s 186 m.p.h. M.G. and, was tacked on to the Rolls in August 1938. It originally drew from two Solex carburetters set beneath the casing, their flanges as a wide ” V,” but acceleration faded at over 60 m.p.h., so two very large l I” S.U. carburetters were fitted, Mackenzie doing an excellent job of work in accommodating them, also in ” V ” formation, without alteration of the bonnet—the car carries only R.A.C. and Vintage S.C.C. badges, and Fitzpatrick did not wish to advertise the

blower’s presence. To do this bit of stowage McKenzie uses slightly different angles for the pipes, as between the front and rear carbs. The delivery pipe goes right up, over the block, and joins an inverted R.. R. inlet manifold on the near side at a flange joint. The exhaust branches have been cut off at the ends and re-welded up to make this juggling possible. At first the blower pipe went through rather involved contortions so as to join the standard manifold where the R-R carburetter used to tack on—until Fitzpatrick suddenly thought of inverting the manifold. There are two blow-off valves immediately on to the blower casing. To humour the engine it was given new valves, dome-headed, and special Mackenzie pistons with crowns 2 mm. thicker than usual, but weighing 3f oz. less. The head had formerly been machined by about ih in. and was now copperised, the latter a great improvement. So, instead of lowering the compression-ratio, it went up, as the old Phantom I” had quite a moderate ratio. The rear-axle, originally 3.4 to 1, was replaced by an axle of 3.2 to 1, which Rolls-Royce Ltd. used to supply in isolated cases to “Phantom I” owners who fitted two-seater bodywork. The alterations in behaviour are very instruc tive. The car now cruises at 75 m.p.h., which was about its former maximum, and is much silkier at this speed. At really low speeds the engine feels a shade harsher, but there is no trace of pinking and very little blower noise, while top-gear running is improved, it being possible to crawl at almost zero m.p.h. in the highest ratio and build strongly away. Warming-up and starting are unaffected and you cannot hear the engine at all when. idling. We are told that the pick-up beats a 4+-litre Bentley and in town, only going up to 3 lb boost, it certainly is bomb-like. Disco’ fuel is used, but National Benzole is possible, and the car is giving 10 m.p.g. against 13 m.p.g. with the Solex layout and 10-12 m.p.g. unblown—and the final needle combination is still being sought. We believe that in spite of its excellent construction it is impossible to make a “Phantom I” rev, very willingly because of the camshaft shape, and for this reason a 1935 “Phantom II” camshaft may ultimately be em ployed. At present an improvement in torque has been effected, and the performance increase would be greater if an axle ratio even higher than 8.2 to 1

could be used. One very interesting point is that, after supercharging, the autovac, which is over the rear exhaust pipe, began to boil, a trouble never previously experienced and due solely to the increase in heat-flow—which may explain a whole lot to those who have tacked boost on to expensive engines and found that standard bits and pieces have objected in an expensive way. In conclusion, Fitzpatrick has a very unusual car, albeit one of quietly handsome external appearance, pleasantly

disguising its increased potency. The car is a credit not only to McKenzie’s Garages, but to the Rolls-Royce Company, who put such excellent workmanship and materials into the ” Phantom I ” as to permit of this drastic experimentation with a thirteen-year-old-example.

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