ON THE TREND OF SPORTS-CAR DESIGN
ON THE TREND OF SPORTS-CAR DESIGN
Looking through some back issues of ” The Aeroplane” my attention was arrested by the following sentences in an obituary notice to the late Robert Loraine, actor and pioneer pilot ” Though he never went in for motor-racing he was a fine driver of sporting-cars in the days when driving a fast car was a man’s job. Bob’s Anstro-Daimler could do between eighty and ninety on the road, and did it. ‘ Now that reminds me that the sports-car has evolved along two distinct lines, at all events so far as the bigger engined examples are concerned. From the first appearance of those sporting Austro-Daimlers and AlphOnso Hispanos and Prince Henry Vauxhalls of pre-war days, performance alone mattered for quite a time and then refinement entered into it. Semi-sports cars strengthened the desire for really unassailable performance achieved without noise, without fuss and with complete and permanent protection from our diverse elements, until to-day driving even the most potent sports models is very different from driving fast motors in the days when the editor Of ” The Aeroplane ” went riding with Robert Loraine. This process of combining performance with refinement is still going on, and, apart from giving us very fast, essentially safe sports-cars which, even in this Belisha-infested world, will make decent average speeds and enable us to put 300 or even 400 miles into a day’s driving without fatigue, it has also added enormously to the well-being of the family car owner. Something of the acceleration, the responsiveness, the speed and the braking of the sports-chassis is embodied in the better modern utility ears, though things would be still happier if roadholding, steering and general controlability were developed to a corresponding degree Although we are concerned with cars of sporting mien, it may safely be written that to-day’s sports-car is tomorrow’s family coach, and even sportscar enthusiasts are sometimes confined to the jug-box, if only during business hours. So it behoves us to take a look at design tendencies as another year draws to a close. To-day the sportscar is in a very strong position because, apart from the small rather specialised sports models used primarily for trials work, and the essentially delicate thoroughbred cars appealing to skilful drivers with sufficient means to maintain expensive machinery, there is on the market a wide range of -sports-ears which can be used for ordinary high-speed travel and are, in fact, used regularly in this fashion, equipped as often as not with closed coachwork, albeit they have the stamina and performance required for serious competitive motoring. This latter type is especially popular in this
country. Alvis, Bentley, Autoyia, Talbot, Lagond a, M.G. , S. S. , Sidd eleySpecial, Crossley and Rover are examples of this class of high-performance ears. Overhead valves are operated without complication from a camshaft in the basechamber, via push-rods and rocking levers, which is productive of a good power curve and easy maintenance. Push-rod valve operation has proved suitable for extremely high-speed powerunits and overhead location of the camshaft is only desirable when combustion chambers are of hemispherical formation or in large or light-alloy built units where distortion is deemed likely to affect individual valve actuation. The o.h. camshaft System no longer necessitates elaborate drives, as the silent chain system has developed satisfactorily, nor need cam-noise stay the designer’s initiative. This more advanced type of engine still has adherents, notably Bug-atti and Alfa-Romeo on the Continent and Alta, British-Sahnson, Rapier, Squire and Frazer-Nash in this country, for which double o.h. camshafts are employed. The hemispherical head-shape has much to commend it, especially when high compression pressures are involved or high outputs are sought from unblown engines, though the scientists are now dubious of the part played by turbulence. Here Riley deserves special credit for contriving to employ push-rod actuation of inclined opposed o.h. valves, a feature also of the new V8 Autovia, and which used to figure on certain Dorman powerunits. But generally speaking the normal push-rod layout suffices for all ordinary purposes, which is probably the reason
why no one has of recent times challenged W. 0. Bentley and the late J. G. Parry Thomas in the matter of unique drives for the camshaft. It may be recalled that the six-cylinder Bentleys used to have a connecting rod and crankshaft drive and the Leyland eight a system of eccentricactuated rods ; nor must we overlook the work of M. Bignan as displayed at the Show, circa 1926. All M.G. models now have push-rod engines.
To revert to present-day designs, valve-bounce still limits engine speeds in certain designs, though some people assert that this is another application of the masked valve ports that humoured the model T Ford. Alvis apparently has no leanings in this direction, as the cluster of nine springs round each valve stem still figures on the 1937 engines. The side-valve power-unit is not nearly so backward these days, for high-octane pump fuels and the research struggles between followers of Whatmough and Ricardo have hastened its progress. If the predications of the futurists come true it may again come into its own, when engines are tucked horizontally into funny places with a premium on compactness. The Railton has shown British sportsmen what the big, yankee-type of L-head motor can do, and this year it is joined by the English version of the supercharged side-valve Graham and the Ford V8-engined Jensen, while the Brough-Superior falls within this category. And on the Continent Mercies-Benz and Renault make use Of side-by-side valves. Compression-ratios of 6 to 1 or higher are permissible by using aluminium heads, whereas with o.h. valves hardened seats are then necessary, which is costly, though the one-time nightmare of a seat coming adrift has been largely dispersed. The super-imposed valve layout, which intrigues those who keep slide-rules where you carry your Watermans, is now used only on certain Crossley and Triumph models and the proprietary engine of the Morgan 414. Just to remind you how slowly we progress and how far off is stagnation I would emphasise that D.K.W. is the sole representative of the two-stroke cycle, Minerva alone employs sleeve-valves, and standard diesel
engined cars are completely absent from the British market. In connection with the last-named development, MercedesBent should be watched closely.
Two very prominent features of 1937 programmes are the widespread adoption of engines of increased capacity, from M,G.’S new Midget to the lig Mercedes straight-eight, and a growing interest in multi-cylinders.
The use of larger engines is proof that designers are quickly taking advantage of the concession that demands only 15:1in taxation for each horse in our possession, either to provide better performance or to maintain existing performance in conjunction with more luxurious coachwork or more rigid frames.
The multi-cvliniler trend, emphasised by the new V12 Lagonda, straighteight Sunbeam, V8 Autovia, and V8 Standard engines, backed up by the inane Daimler eights, the Riley V8 and the Rolls-Royce V12 amongst British makes alone, indicates a serious attempt to obtain high performance with the maximum of refinement and smoothness, to provide improved torque at low rates of crankshaft rotation, .and in the case of large capacity engines, to reduce bearing loadings and keep within reasonable bounds the volume of _combustion spaces. Here let us remember that this seeking after perfection has led British engineers to express themselves in terms of -many cylinders in the past. the V eight-cylinders by Rolls-Royce, Guy, and Talbot-Darraeq, and the in-line eights of Sunbeam. Leyland, BeverleyBarnes, Wolselev, Hillman and Triumph, for instance, still lingering in the memory..
The problem is not an elementary one, for those technicians who avoid the complexities of distribution, firing order, rigidity and balance, telling themselves that long bonnets are dangerous anyway, discover that the V formation cherishes difficulties all its own, involving inaccessibility big-end design, and synchronisation of ignition and valve-timing. Daimler, Hispano-Sniza and Lincoln list V12 engines and on the Continent .and in America the in-line eight is well established Although our cars are all lunch too heavy, with isolated exceptions. little interest is displayed in lightweight engine • construction, although the fascinating
Siddeley-Special unit is constructed on aero-engine principles of light alloys, with inserted aluminium-bronze valve seats, the six-cylinder A.C.s retain the alloy block with ” wet ” cylinder liners and the new V4 Lancia Aprilia has separate cylinder liners. As weight is difficult to conserve structurally, things seem unlikely to improve, especially as we are worse off nowadays, when independent suspension or rubber-floated power calls for rigid chassis frames and fabric bodywork has gone out of fashion. But engine construction generally reaches a very high .standard, crankshafts being properly balanced both statically and dynamically and carried in bearings adequate in size and proportions, supported in rigid alloy crankcases. New roller bearing liners and aluminium, bronze and silver cadmium alloy bearings are coming into use. The fully counter-balanced crank Shaft of the Lammas-Graham runs in bearings lined with cadmium-silver alloy, while the eight-in-line Sunbeam, Georges Roesch’s beautiful production, has ten white-metal lined bearings supporting a counter-balanced steel crankshaft. The new twelve-cylinder Lagouda has alloy con-rods 1-tinning direct on a nitrohardened crankshaft, which is progress
indeed. Engines in touring cats now run up to 4,000 r.p.m., Or more, and it is not unusual for sports-car units to safely exceed 5,000 r.p.m. The cylinder-wear bogy has not yet been banished, but it is hoped that hi-metal pistons may help matters, and Sports-car enthusiasts can be relied upon to give warming-up operations the thought they merit. Ignition, cooling and lubrication we are now able to take very largely for
granted. Coil ignition systems are universal, where the magneto is used it is nearly always in the form of Scintilla Vertex equipment, and 14 min. plugs having come very quickly into the ken of the ordinary motorist., the 12 mm. has made its appearance. The call for automatic advance and retard mechanism governed by conditions in the inlet manifold as well as by engine speed has to some extent been answered, and it is a subject for congratulation that high-compression engines generally behave so well under automatic control, for which modern pump fuels share much of the praise. Cooling on high-output engines is usually by pump or its modern offsprinF, the belt-driven impeller, and thermostatic control of warming-up, on the by-pass system, is largely used, the controlled radiator shutters pioneered by Straker-Squire having fallen sadly lrom grace. The elimination of steam-pockets
has received attention, and the outstanding problem is that of making engines that operate at around the economic temperature of 100°C refrain from overheating dangerously during spells of full-throttle work around Brooklands or up trials hills. Is it streamlining that has banished filler caps to under bonnet positions, where they have assumed the proportions and awkwardness of hot-water-bottle stoppers ? In spite of greater bearing loadings and interference with the flow of air past the sump, modem lubrication systems are well-nigh foolproof. Yet it is not so many moons ago since even sports engines of repute could get away with splash feed to the bearings and a wick-feed to overhead valve-gear. Although bearing loads and rubbing speeds have increased, failure of the lubrication system to cope with normal conditions is extremely rare. The amount of oil passed through a bearing, rather than the pressure at which it is introduced, is now cons,dered important. Oil cooling radiators have yet to become common, but will not become essential until light alloy construction raises sump temperatures to a dangerous level. Dry-sump systems are the watertight solution, though only Aston-Martin thus safeguards those of us v?ho extend our throttle foot for prolonged periods. The system is not compatible to quan tity produced engines. The Sunbeam Company used it for the 3-litre they marketed from 1925 to 1930, but. come to that, the very first 3-litre Bentley had a semi-dry arrangement, though an isolated sump was used in place of a separate tank. Renault uses a novel oil-cooler located in a water-iacket extension, and the eight-in-line Sunbeam has provision for the cooling water to first warm and then regulate the heat of
the lubricant. Aluminium sumps are general, those of Bugatti, Riley, Standard V8 and Sunbeam being especially wellribbed, while big filters, externally placed for cleaning, are common. The V12 Lagonda sump holds 3 gallons of lubricant and increased sump capacity is a popular, if indirect, method of keeping temperature under control The next part of the lubrication system due tor improvement is the filler, dip-stick, and sump-draining department. But before our engineers get industrious, let them remember the case of the easy-drain system which let all the oil out of the engine while indicating ” sump-full” to the irate owner on a patent level indicator . . Carburetion should be thoroughly understood by now, and certainly hotspotting and manifold formation show some tendency towards comparative standardisation. Multi-carturetters to “maintain power-curves and whip up responsiveness are still popular, which, if it does not increase consumption, certainly puts up first cost and can impose some unpleasant moments during maintenance, Some designers would do well to remember Robert Brewer, and his experiments at Brooklands with corks in inlet tracts, conducted before be wrote his book” Economics of Carburetting and Manifolding.” The normal 3.8 litre I3ugatti engine has but a single itsstrumerit .ind the in-line Sunbeam has a carburetter at each end of its lengthy manifold. On the other hand, I suppose there is some excuse for using a cluster of ” gas-works” on small sports engines, when the slight loss of volumetric efficiency consequent upon hot-spotting and the use of a manifold spells the slaughter of so many ?,’s of a second on acceleration times. A.C. and Alvis have three instruments for some of their sixcylinder models, twins are widely used on ” fours ” and Frazer-Nash has two instruments, each with two float chambers, on their new Ulster 100 four-cylinder. Downdraught carburetters are still popular, and their especial fads are now fairly well understood. This type is used to feef? a ta)oster on the Graham and LammasGraham engines. The divers methods Of modern fuel feed are foolproof for all
practical purposes, but a simple system ot reserve storage and twin filler caps on the tank should be universal. The headway made by supercharging
is really disappointing. For years experts have predicted the application of forced induction to touring engines built to suit the supert.harger but to-day, some fifteen years since Merc6ds-Benz adopted this component for production engines, we have only the racing highpressure system to boost up power at peak crankshaft speeds and proprietary sNstems operating ineiiitiently at pressures of a few lb. per sq. in. The unique air-through-the-carburetter, clutch controlled Merc6des system has been applied to four, six, and eightcylinder engines of widely varying sizes and the more one examines the method the greater admiration it arouses. AlfaRomeo, Frazer-Nash with twin centries, and Rapier use built-in fairly highpressure systems, and Graham, Lammas, Brough and Auburn prefer a gentle draught through the induction tra,-1, inspired by big-velocity centrifugal boosters. The difficulty with tacked-on supercharge, which several firms foster, seems to be that either the pressure has to be kept too low to do much good in terms of performance, or else valves, pistons and gaskets need to be changed, when fuel consumption becomes prohibitive unless further expense is entailed in raising the axle ratio. A consumption of under 23 m.p.g. from 850-1,100 c.c. engines will not suit many of us. In fairness, I must say that I know of a Centricblown M.G. Midget that is blown well enough to be potent in trials tests, yet which gives its 30 m.p.g. at a cruising
speed of around 45 m.p.h. Perhaps Messrs. Pomeroy and McEvoy have the elusive solution in their new Velox supercharger. So to the chassis. The craze for low build is retarded, but some very neat work in this direction is seen, even amongst family cars of low price. Chassis frames tend to become more rigid, and will need to be stiffer still when all-round independent suspension becomes general, all of which spells a very unwelcome increase in weight. Box section side-members are assisting cruciform cross-bracing in this stiffening-up process, excellent examples of this form of side-member being found on Talbot, Riley, Alvis, S.S., Morris, Daimler, Renault and Lanchester chassis, amongst others. The forward-mounting of the powerunit, inspired by the Wolseley-Hornet, is deplorable, not only because it ruins appearance, but because on fast chassis the weight distribution is not then all it might be, though if a purchaser made a rule that he would consider only those cars having radiators above or behind the front axle, choice would be decidedly limited. Quoting without reference to the book, Frazer-Nash, Bentley, Merl MksBenz, Bugatti and Lagonda were amongst the few cars retaining good ” chassis
lines ” of the cars at Olympia. The opposite line of attack to making frames very rigid is still met occasionally. One hesitates to advocate it, although Railton has proved it to work exceptionally well and there is no gainsaying the improvement in performance which results from the saving in avoirdupois, while in the past we have had plenty of forms of body construction that will humour a flexing frame. Moreover, the present tendency seems to be to take road-holding for what it is, bothering very little about the” feel” of the car as a whole, provided it corners fast and does not waltz under heavy braking or a racing-start. Albeit there will always be a demand for rigid ” allin-one-piece” motor-cars amongst those who can pay for this quality, and it is found to a great extent in the better sports models of the past, which is one reason why the second-hand dealers who advertise in the back of this paper still do good business in these days of easy payments and inexpensive new cars.
Synchro-mesh gear-change has engulfed us and may engulf the service stations in a few years’ time. This, and the E.N.V. box, have not ruined the fun of driving to the extent some of us feared, but it would be pleasant if all sports-car designers would bear in mind that quite good remote control rigid levers can be used even with unit construction synchro boxes. It is interesting that if occasionally your sportsman does make use full of synchro-mesh when it is available, feeling he just for once really hadn’t time to double-declutch, yet when he gets back to a plain box he invariably uses it just as fully without crashing the pinions. Which goes to show . . . I like plain boxes and I have a weakness for girdertype levers in visible gates after recently driving an elderly Austin Twelve and a Big Six Bentley, but modernity has ended all that and we must bow to progress. Alvis have taken a pride in gearboxes since the” 12-50 “days and now have allsilent all-synchro four-speed boxes while the Talbot Ten is an inexpensive car with an excellent all-synchro box.
The modern clutch takes a mighty lot of punishment and can be forgotten, and transmission systems continue to improve in details of construction. Braking, likewise, is very very good, though methods of adjustment while driving seem to have disappeared, and we have heard of unpleasant happenings on very rare occasions when a master Pipeline of a hydraulic system has snapped—though owners of early-type Buguttis never listen to this story. Austin, Autovia, the long-base Aston-Martins, Lagonda, Morgan, Rapier. Riley, and S.S. have adopted the proprietary Girling direct-pull operation which has helped F.R.A. racing-cars to victory. Bendix servo-shoes are popular and HispanoSuiza, Bentley and Rolls-Royce favour gearbox-driven servos. When vacuum servo operation is used, reservoirs are usually added, which we can appreciate after feeling the brakes go solid when we stalled the engine of an unfamiliar and very large automobile in heavy traffic. Torque members on the front axle are coming into use, Aston-Martin and M.G. using steel-wire linkages. Suspension deserves an article to itself. Suffice it to say that in spite of all that is written about improved road-holding with independently suspended wheels, certain cars like the 5-litre and 3.3-litre Bugattis and all models of the Frazer-Nash go round corners with ” carriage springs ” as quickly and as safely as anything. And automatic
and driver-controlled damping of rigid axles provides a tricky answer to exponents of individual wheel movement, as those who have ridden in recent Bentley, Rolls-Royce, Lagonda and other cars will testify Unquestionably independent suspension is desirable on the score of accurate steering, better braking, increased comfort and even longer tyre life, but at present there are important problems to solve in connection with wear of moving parts, geometry of linkage and weight of unsprung sections. As with front-wheel brakes in 1924-26, many lines of attack are seen, and different systems fight for recognition, and it will be a few years before the position is clarified, after which the rigid axle will join the transmission brake and the beaded-edge tyre. Mentioning tyres,
let us pay a little homage to the makers of modern tyres, and to racing-men who have spurred on their researches. Tyre life is really astonishing, considering how hard we accelerate and how Hore Belisha makes us brake—and how certain forms of knee-action scrub our covers. Steering makes steady headway, and independent suspension, while it will present problems of its own, must ultimately make cars still more controllable. Higher gearing is now possible without loss of finger-tip action. I believe the B.M.W. . led the way in this connection and I still have not experienced quite its equal. Is it too much to expect the Minister of Transport to ban cars with steering-wheel ratios of 5 to 1 lock-to-lock, for which a certain enterprising American accessory maker has produced small sub-handles, steam-wagon pattern Rear
view mirrors and carburetion flat-spots and crankshaft periods, coinciding 14 ith a speed of 29 m.p.h. in top gear, seem desirable items of sports-car specifications, judging by the number of my friends, known to be reasonable experienced drivers, who acquired their first endorsements this year.
We have some very fast cars for 1937. The new 4.3-litre Alvis, the 4+-litre Bentley, the Bugatti, the Competition Dela.haye, the Ulster 100 and Shelsley Frazer-Nashes, the T.T. B.M.W., the V12 Hispano-Suiza, the latest ” Rapide ” 41-litre Lagonda. and the blower MercedesBenz, should each exceed 100 m.p.h. quite happily. And 90 m.p.h. is a pace that is far more common than a year or so ago. I have been writing for hours and have covered very little of this subject.