THE TREND OF RACING-CAR DESIGN
THE TREND OF RACING-CAR DESIGN
BEING THE ANNUAL SURVEY OF PROGRESS MADE IN THE DESIGN AND CONSTRUCTION OF RACING CARS DURING THE PAST SEASON THIRTY-EIGHT has been a year of considerable interest in respect of racing-car design progress, because the change in the International Formula resulted in the construction of new road-racing cars of vastly differing type to those which suited the previous Formula. The new Formula was planned to encourage all sizes of engine but it soon became evident that only 3-litre supercharged and 4litre unblown engines would be of use, and even this assumed a boost of around
lb. per square inch for the smaller unit, which, as some 20 to 22 lb. was actually employed for the 3-litre German cars, left even the 41-litre unblown cars well out of the running. Nor did the 11-litre class of car become potent enough or sufficiently near to the permitted weightminimum to challenge 3-litre Formula cars, although continuing to exist as a very healthy separate entity. The German Mercedes-Benz and AutoUnion cars have been supreme amongst Formula cars and it is highly satisfactory that these 3-litre cars are only some 10 to 15 m.p.h. down in point of maximum speed over the previous 5 to 6-litre jobs and they are actually superior on the score of acceleration and road-holding, so that lap and race speeds have not materially diminished and have in some instances risen. This has been brought about because, although the German engineers had to build to a capacity reduction of 50 per cent, and a weight increase of over 10 per cent., they have managed a reduction of power of only 25 per cent., instead of 50 per cent., by reason of reducing individual cylinder capacity from 700 c.c. to 250 c.c., increasing peak revs. from 6,000 r.p.m. to 8,000 r.p.m. (a 83 per cent. increase) and bringing up the blower boost from the former 5 to 6 lb. per square inch and later 15 lb. to approximately 20 to 22 lb. per square
inch. High revving has been made possible by a short stroke in the region of 70 mm. In consequence, the b.h.p. per litre is approximately 140, compared to the 90 b.h.p. litre of last year’s Formula cars, and maximum speed is in the region of 170 to 180 m.p.h., while both MercedesBenz and Auto-Union develop over 400 b.h.p. by popularly accepted estimates. They weigh between 19 cwt. and 1 ton. Maserati claimed 850 b.h.p. for their new 8-litre and Alfa-Corse 306 b.h.p. for their Type 308 straight-eight. The V16 Alfa was first credited with 840 b.h.p. at 7,000 and later with 400 b.h.p. at 8,000 r.p.m. The use of higher-speed engines has not introduced any very vital new problems, but the 1938 cars were no longer completely reliable. Mercedes-Benz experienced valve failures, in spite of sodium cooling the exhaust valves, which, in any case, is difficult with small cylinders and liable to result in valve-sticking, and Auto-Union had carburation trouble, while both engines were harder on plugs and lost much oil, the latter trouble inconveniencing the drivers and, in the case of Auto-Union, of first causing repeated oiling of No. 3 plug on the near side, a trouble which Nuvolari again experienced at Donington. To cure oil loss Mercedes evolved an involved sump shape and pump layout. Another worry was that the V-type engines are harder to cool and Mercedes actually ran at the dangerously high oil temperature of 80°C. at Tripoli. This is partly due to lesser base chamber area and partly because more compact engines encourage lower bodywork and consequently reduced radiator area. Auto-Union have a better radiator position, which is estimated to he worth a 20 per cent. increase in cooling
element area. Sefac used an oil-cooler along the body side. Plug appetite was also evident on the new 1Hitre Alfas. Another problem with the new cars is that of fuel consumption, which has Increased from 5 to 21 m.p.g. Auto-Union retain a central tank, whereby weight distribution is unaffected by contents, and Mercedes now use two tanks, one in the tail and one as a saddle round the scuttle, of which the front one fills first. Both tanks are coupled by big-bore pipes and the latest design ensures that a lowering level shall not affect weight distribution, although driver-controlled rear shockabsorbers were previously used to com pensate for the change. Pressure refuelling is used at the pits, operating at the rate of about 5 gallons a second, and inspection windows indicate the tank
level. The capacity is approximately 7Q gallons, entailing one stop in the course of the usual road race. 11-litre cars do about 61 m.p.g., and the 2-litre Alta 5 m.p.g., so that they just go through a 200 mile race without a stop, though this involves having 40 gallons of fuel in the tail at the commencement. The unblown 41-litre cars scored in earlier races by reason of a fuel consumption of 7 m.p.g. So far as Formula cars are concerned, rumours of alternative types and newcomer marques came to naught. MercedesBenz changed from straight-eight to V12, having built a V12 record car previously, Auto-Union from V16 to V12, and AlfaRomeo used straight-eight, V12 and a new V16. Maserati had a straight-eight based on the earlier 11-litre four-cylinder, Bugatti a straight-eight and Sefac a VR. All these were blown 3-litres. Delahaye ran an unblown 41-litre V12. The Maserati proved faster than the Mercs. on isolated occasions, the Delahaye grabbed two victories before the blown motors got potent, and Auto-Unions found more speed and acceleration than Mercs. for the Italian and British Grands Prix and seemed to have caught up on
road-holding as well. Bugatti did 147 m.p.h. on the straight at Cork but, like Alfa, ran intermittently, and was not durable. In other spheres, the E.R.A is still a “six,” with no prospect of the rumoured V12 materialising, Maserati ran 11-litre ” sixes ” hut is going back to the four-cylinder, and Alfa introduced very successful new 11–litre straighteights. The Alta remains a ” four ” in both 1 and 2-litre forms and the 750 c.c. Austins are ” fours.” Major Gardner’s
astonishing M.G. is a ” six.” America is said to have a six-cylinder Formula Miller on the stocks. Particulars of power output are hard to come by, but in comparison with the 140 b.p.h. per litre of the 8-litre Formula cars, 200 b.h.p. at 8,000 r.p.m is claimed for the 1Hitre Alfa (130 b.p.h. per litre) and the Zoller E.R.A.
cannot be far behind. Major Gardner’s M.G. gave 193.5 b.h.p. at 6,800 r.p.m. (nearly 179 b.h.p. per litre) and the 750 c.c. Austin is said to give the same efficiency, or 134 b.h.p. at 8,500 r.p.m. Alta claims 325 b.h.p. at 5,800 r.p.m. from the 2-litre, or 160 b.h.p. per litre. The 41-litre tmblown Delahaye gives about 230 b.h.p. at 5,600 r.p.m. (54 b.h.p. per litre) with a prospect of getting the peak speed up to 6,000 r.p.m. next year. E.R.A. uses a stroke of 95.2 mm., the M.G. a stroke of 71 mm., the 11-litre Alfa one of 70 mm. and Alta a stroke of 100 mm. Supercharging is universal, apart from the uublown Formula jobs, for road racing. Mercedes-Benz still sucks from the carburetters in conventional manner, using twin Roots blowers at the front and double carburetters. Auto-Union has a single Roots blower at the rear, drawing from twin carburetters. AlfaRomeo continued to use their double Roots blower beside the block, the 8litre Maserati had twin Roots blowers, one above the other, and Bugatti a Roots blower. E.R.A. now use the huge Zoller vane-type compressor in the cockpit, drawing from two S.U.s, the new 11-litre Maserati will have two Roots blowers, and the Alta has a Roots blower turning at one-and-a-half times engine speed. Major Gardner’s M.G. has a Centric vane compressor. Pressures are notably high. Metes. and Auto-Union are believed to blow at 20 to 22 lb., with a possibility that Mercs. went higher for Donington. E.R.A. uses 25 lb. for racing and 40 lb. for sprint work, in place of the former 15 lb., Alta uses 17 lb., and 24 lb., Gardner’s M.G. 26 lb. and Harvey-Noble’s Brooklands 750 c.c. M.G. 28 lb. The If litre Alfa has a Roots blower beside the block on the near side, with single car buretter beneath. Normally the vane compressor gives better low speed acceleration than a Roots blower and can function at a lower speed. In the case of the E.R.A. this is not so, because the speed of the big Zoller is kept down to two-thirds engine speed, resulting in low torque below 3,500 r.p.m., whereas the Murray-Jamieson Roots blower on earlier cars was run at three times engine speed and gave high torque down to 2,000 r.p.m.—which is why ” Bira ” uses ” Romulus” at the Crystal Palace. Faulty metal has been a worry with the E.R.A. supercharger this year and higher speed may be used in due course. Abecassis’s 11-litre Alta is blown at 12
lb. Compression ratios remain around 6 to 1 to 8 to 1 for blown engines and up to 10.5 to 1 unblown. Fully inclined valves in hemispherical combustion chambers remain common,
but it is extremely interesting that Mercede.s-Benz have gone back to four valves per cylinder, while the new 11-litre Maserati will also have this arrangement. Delahaye use four valves to fill each big unblown pot, and the M.G. has a twovalve pent-roof head with single o.h. camshaft. Otherwise twin o.h. camshafts per block are universal, with geardrives, although Alta uses a chain-drive. Why multi-valves should be employed in high-temperature small-bore easily fed engines is something of a poser. Rotary valves make no real headway, but Breyer is building a Cross rotary valve J .A.P. engine for 1939 sprint events. Sodium cooling of exhaust valves is used by Mercedes and by Robin Jackson for the 186 m.p.h. M.G., though then it is not easy to keep valve stern diameters small. Auto-Union dropped the central single camshaft operating via rockers and push-rods, in favour of three o.h. camshafts, of which the outer pair actuate the exhaust valves and the central one both rows of inlet valves via
rocking levers. E.R.A. has high set camshafts operating via short push-rods and rockers. Lightweight engine construction is still the vogue. Mercedes-Benz use cylinders machined from solid steel billets and welded in blocks of three, with light welded sheet water jackets. AutoUnion use light alloy blocks and detachable heads. Metes. have a fixed head. Alta uses alloy block, crankcase and sump, wet cylinder liners, and an alloy head with aluminium-bronze valve seats. E.R.A. has combined block and crankcase in iron and an alloy head and sump. The eight cylinder Maserati has its cylinders in two blocks of four. So far as head design is concerned, 12 or 14 mm. centrally located plugs are usual, and Mere. and Auto-Union both have twin
magnetos. Delahaye has two plugs per cylinder. Mercedes-Benz and Auto-Union have ball and roller bearing engines, Mercedes with a solid crankshaft running in split roller bearings. One British authority is at a loss to explain the durability of such bearings and suggests re-rollering between each race, but from Germany comes a statement that these bearings
give no cause for anxiety. They are lubricated at a pressure as low as 4 lb. per square inch and no oil gauge is used. Delahaye also has a roller-bearing crankshaft, running in seven bearings. E.R.A. uses a four-bearing crankshaft with roller centre bearing and graphited-bronze plain-end bearings and plain lead-bronze big-ends, fed at 110 lb. oil pressure. Lead-bronze stands a higher shock loading than the older white metals, but is not necessarily better as a bearing surface. Alta has a four-bearing crankshaft running in water-cooled plain bearings.
Dry sump lubrication comes into its own on the racing engine, though Alta has no use for it and does not even rib the sump to any extent. Mercedes use a big oil reservoir beneath the engine and E.R.A. a chassis-frame oil tank. Mercedes and Auto-Union have gone back to five-speed gearboxes, in which the highest ratio is an overdrive for use on 170 m.p.h. straights. It is said that top was not used at Donington, where 7,800 r.p.m. was reached on the indirect ratios. Alta, M.G. and E.R.A. have E.N.V. epicyclic transmission. The if litre Alfa has a four-speed gearbox in the rear axle, where Me/vs. and Auto-Union also locate their ratio-chests. To overcome wheelspin the Germans employ the Porsche self-locking differential and E.R.A. also use it, the slip factor before locking being 15 per cent. in the latter case. More gear-changing is done on the new Formula cars. Mercedes use a single dry-plate clutch and the E.R.A. has no
clutch. E.R.A. use torque-tube transmission and straight-bevel final drive, the axle having steel tubes and an alloy central housing. Tubular frame construction is general. Mercedes have frail, oval-shape 4 inch side members in light alloy, tied by four tubular cross-members. They used a lighter frame after the first 1938 races but found it too whippy and went back to the earlier pattern for Donington. AutoUnion retain their tubular frame with the side members formed as water tubes. The latest E.R.A. has box-section side members united by tubular cross-members and braced by drilled transverse stays. The eight-cylinder Type 308 AlfaRomeo has a box-section frame and the If Alfa a tubular frame with tubular bracing. Alta employs simple channel
side members very rigidly united by tubular members. To gain a lower seating position Mercedes introduced on the road-racing car the off-set transmission formerly used, for the twelve-cylinder record-car, and the 186 m.p.h. M.G. had a similar transmission layout and, the latest 2-litre Alta a double-drive rear axle, for the same reason. Auto-Union, with rearmounted engine, can sit the driver as they wish, but placed the seat further back this year and shortened the wheelbase. The E.R.A. has a comparatively high seating position. The Mere. wheelbase is about 10 ft. 6 in., and that of the Ii-litre E.R.A. 8 ft. The E.R.A. has a track of 4 ft. 4+ in. front and 4 ft. rear. So far as weight is concerned, the Mercs. weigh about 19 to 20 cwt. (the Formula permits 16,69 cwt.), Auto-Union just over 19 cwt., the 3-litre Maserati 17 cwt., the Delahaye single-seater 17 cwt., the Bugatti 18 cwt. 1 qr. and the record
breaking M.G. about 16 cwt. Ii-litre cars do not appear to approach the 11 cwt. Formula minimum, the latest E.R.A. turning the scales at about 14+ cwt., against the 13 cwt. of the earlier Rootsblower cars. Tyres are usually changed once at least on one or both pairs of wheels during a Formula race, which tallies nicely with the refuelling stop, refuelling, by the way, taking longer with the increased tankage. Mercedes and Auto-Union used 7 in. x 22 in. rear covers at Rheims (actual section about 91 in.), where Auto-Union had 5.50 in. x 19 in, front covers and Mercs. 6 in. x 19 in. covers on the front wheels. At Donington both used 7 in. x 19 in. rear covers. For record work light treads are the vogue and Gardner’s M.G. had rear Dunlops of 5.35 in. x 19 in. with 3 mm. treads, designed for 170 m.p.h., while Eysion’s
tyres had an outside film of thin rubber over the ply in lieu of tread, a very heavy casing, strongly reinforced beads, and special rubber compounds of low heatgeneration. Every credit is due to Dunlop for safely carrying the record-breakers at over 350 m.p.h. Suspension now plays a more important part in road-racing than engine efficiency. Stiff cord-bound half-elliptic no longer rule the roost ; indeed, racingcar springing now displays remarkable Mercedes, Auto-Union, Maserati, Alfa-Corse, E.R.A., Alta and Riley all employ independent front suspension and Alfa and Alta use independent rear suspension, as did Mercs. and Auto-Union last year. Taking front springing first, Mercedes use pressedsteel transverse wish-bones and four-coil coil springs controlled by hydraulic shock
absorbers. Auto-Union use two 2 in. swinging arms and transverse torsion bars and were said to have used an improved shock-absorber after Rheims. Shortening the swing arms last year materially reduced steering kick-back. At Donington. they used Pischtel and. Sachs double-piston hydraulic shockabsorbers at the front. The big Maserati has double wish-bones and parallel torsion bars ; Alfa Dubonnet coil springs enclosed on a normal stub-axle assembly ; Delahaye a transverse leaf spring, conventional stub axle and. rearwards extending torque member ; E.R.A. transverse torsion bars on the Porsche system with Luvax hydraulic shock-absorber and. trailing links ; Alta vertically rising wheels controlled by coil springs, and the 111litre Alfa a transverse leaf spring. The Alfa Dubonnet system has very low unsprung weight, the .Maserati and Mere. layout amply resists side stresses, and the E.R.A. and Alfa designs have good resistance to brake torque. Brooke has used Daimler type independent front suspension with coil springs on his BrookeSpecial, Maclure a system with heavy transverse swinging arms and coil springs on his Riley, and Parnell a Lancia coil system for his M.G., while the Morgan coil layout, which originated in pre-war times, is popular for sprint cyclecars. Bugatti remains faithful to a normal front axle and half-elliptic springs. Bugatti has had excellent results from De Ram shock-absorbers, likewise E.R.A. on their all-half-elliptic chassis. E.R.A. modified their i.f.s. for 1938 by using a much larger flange to take the side thrust from the links. Delahaye also use Fischtel and Sachs front shock-absorbers. Turning to rear suspension, in 1936-7 it seemed that independent springing of the rear wheels would become essential to secure the required wheel adhesion, for Formula cars could spin their wheels at over 100 m.p.h. in top cog. In passenger cars increased comfort derived from elimination of lateral relationship is another consideration, but, though this was of no moment for racing, neither was tyre wear on account of scrub. So Mercs. and Auto-Union used swinging half-axles. Alas, this layout resulted in rolling and, in snaking at high speeds. Moreover, the trunnions at the inner end of the halfshaft casings had to take all the torque and brake stresses, and soft springs allowed the frame to roll round the axles. Mere. introduced torque arms running back from the brake back-plate, but breakages occurred at this point of anchorage. So i.r.s. had to go. As additional unsprung weight could not be tolerated, the De Dion axle was introduced, in which a light beam ties the wheels but the drive is Mounted on the frame as Sprung weight—some fine examples appeared on the Brighton Road on November 20th last! Mere., AutoUnion, and Delahaye use this layout, Mercedes with parallel torsion bars, Auto-Union with torsion bars, and Delahaye with a transverse leaf spring. E.R.A. are believed to have experimented with fully independent rear suspension, having parallel torsion bars, but roadholding was poor and the off-set engine seriously affected weight distribution. It seems they will use half-elliptic springs and a rigid axle for 1939, with De Ram damping in some cases. The V12 Alfa and eight-cylinder Alfa are believed to have full the former with an underslung transverse leaf spring. Bugatti and Maserati (3-litre) use normal axles with
reversed quarter-elliptic springs. Alta has the vertical coil spring system of full i.r.s., and the iflitre Maserati now uses normal quarter-elliptic springs and normal _axle, with torque members running forward to the frame, after reversed quarter-elliptics had effected improvement over the old half-elliptic layout. Early in the season Mercedes had superior road-holding to the Auto-Unions, while the eight-cylinder Type 308 Alfa-Corse was notably excellent in this respect. The increased weight of the 1938 cars has been of material benefit in point of stability. Hydraulic braking is general, though Bugatti uses cables. E.R.A. changed from a combined Lockheed-Girling actuation to full Lockheed hydraulic operation and also used a two-leadingshoe design to obviate the need for adjust ment. This is important for a 1-A-litre car which can run non-stop through a 200-mile race, because one stop for brake adjustment may entail a loss of time equivalent to one or two seconds per lap for the entire race. The Maserati falls into line with hydraulic actuation, but has the hand-brake operating the
rear shoes only via cables. Its back plates are in three parts, of which the centre one carries all the operating gear. Mere. and Auto-Union used new brake drum layouts later in the season. Bodywork design does not undergo much change, apart from lowering, though more compact size has its problems, as Men’s. had to bring the exhaust pipes outside the bodies after their drivers
had experienced overheating. Mercs. used two lengths of tail and Auto-Union two types of nose cowl. The Auto-Union rear engine position puts about 69 per cent. of the maximum weight over the rear .axle. They sat the driver further back for this year and experienced some float at the front end. Steering remains lower geared for the Formula cars than
for the 1A-litre jobs. America talks Of a Formula Miller for 1939, with blown six-cylinder 3-litre rear-placed engine, four-wheel drive and all round independent suspension by transverse leaf springs. Otherwise, four-wheel-drive makes no headway. In other spheres than road-racing, high spots have been the speeds of 186 m.p.h. from the 1,100 c.c. M.G., 286 m.p.h. from the 5.6-litre Mercedes-Benz and the 350 m.p.b. runs of Cobb’s and Eyston’s twin aero-engined cars. Bodywork enclosing the wheels is now employed for these short record runs, but Major Gardner and Caracciola did not have entirely enclosed cockpits, though Cobb sat forwards in total enclosure and Eyston adopted a closed cockpit this year. Cobb’s car alone was four-wheel-driven—it is astonishing for how long rear drive and open cockpits have persisted for over 200 m.p.h. work. Eyston overcame the fume-difficulty with a far nicer gas mask than those doled out to you and me during the recent Crisis. It is interesting that Eyston again found the tail-fin of no value but air-flap brakes now seem more effective. Cobb’s R.ailton had, ice-water cooling, as did the unsuccessful “Silver Bullet ” some years ago, and Eyston dispensed with a radiator for his 357 m.p.h. record run. ” Thunderbolt ” changed from leaf to coil suspension this year and its triple-axle chassis is quite unique. The Railton used some 2,600 Napier horses to do 353 m.p.h. and ” Thunderbolt ” approximately 6,000 Rolls-Royce horses to do 358 m.p.h.. The respective weights and top gear ratios are : :i tons and 1.35 to 1 ; 6 tons
17 cwt. and 1.23 to 1. The respective power/weight ratios are : 2.8 lb. per lt.p. and 2.55 lb. per h.p. It seems unlikely that smaller engined cars will .take this record in the near future, but do not imagine that the aeroplav.e motors are unbooste.d—the Napier ” Lion,” one of the most efficient ttero motors ever, has risen from 900 to 1,300 b.h.p. without going above the former speed of 3,300 r.p.m., and the Wills-Royce ” R ” has gone up from 2,300 Ish,p. at 3,200 r.p.m.
in 1931 to about 3,000 b.h.p. The respective capacities are 23.4 and 36.6 litres. In sprint circles racing cyclecars giving over 200 b.h.p. for a weight of 10 cwt. sometimes beat multi-cylinder cars. In this sphere Appleton is experimenting
with an Arnott blower giving a boost of 30 lb. per square inch, after dropping his Appleton-Special’s blow from 25 lb. to 16 to 18 lb. Air-cooled motor-cycle engines are used alone Or in multiples, Waddy using two single-cylinder engines and a driving axle for each in ” Fuzzi,” John Bolster four V-twin J.A.P.s driving the rear-axle by chains, Richard Bolster four single-cylinder engines and Charlie Martin four blown “singles.” Sumner has a blown V-twin in a shaft-driven frame. High mechanical efficiency and elimination of cooling jacket weight explains this apparent insanity. Maclure has had another good season with his unblown Riley Six, aided. by varied engine size and a carburetter per
pot. Enclosure of wheels extends to sports-car bodywork and probably accounted for some of the brake failure in the T.T. Discussion on the association between weight distribution and over and under steering in .a side-wind took place following Rosemeyer s fatal accident with the record-breaking enclosed AutoUnion on a gusty day.
At Brooklands outer-circuit racing seems to have gained an improved following, and the 8-litre Baimato-Hassan nearly beat the absolute lap record, other typical track cars being the 61-litre Bentley-Jackson, the 44-litre PaceyHassan, the Bowler-Hofman, the Duesenberg, Dunham’s Alvis, the old Hotchkiss and Brettel’s Talbot, etc. The Dunlop balloon-sided tyres are still popular for fast outer-circuit lappery. In the field of individual design development, Staniland’s much modified 3-litre Alfa-Romeo, now called the MultiUnion, beat the 3-litre lap record at over 133 m.p.h. and also proved very fast on road circuits and A. F. Ashby applied personal theories relating to port area, head design and con-rod stiffening, etc., to an ex-Ferarri 2.9-litre Alfa-Romeo and gained a convincing win in a short Brooklands road handicap. Sir Herbert Austin’s twin o.h.c. 750 c.c. Austins have again run very Well and some praiseworthy individual tuning of elderly
M.G.s has been seen. The Alta has gained greater reliability and beaten E.R.A. in short races on occasions. France has rather shown us how in sportscar races, with 3 and 44-litre unblowu motors, and the blown Alfa is potent here. As to the doodlebug, it no longer seems to have anywhere at which to ” doodledice.” In conclusion, racing-car design has never been more imbibed with engineering stimulus than to-day and we can look forward to another year of the existing Formula—and to new 200 b.h.p. 14-litres—with great interest and no small excitement. THE M.C.C. ” EXETER ” The 1939 INI.C.C.’s first classic goes over to standard tyres. The date is January 6th-7th and entries close on December 12th—the day this issue is due. Fingle Bridge will not be used, and SIMMS is an optional climb, success here washing out one failure elsewhere. A special award goes to those who ascend every thing, Simms included. Details of the
first big trial under the new regime from : J. A. Masters, Bloomsbury Mansions, 26, Bloomsbury Way, W.C.1. THE E.R.A. CLUB We are now selling little E.R.A. pin badges at 1/0 each, post free. The profits made on these badges will be added into the fund going to the works each year. Postal orders should be made payable to the E.R.A. club and sent to me at the club address. Remittances to C. N. S. PRINcax,
Hon. Assistant Secretary. The E.R.A. Club, 10 Park Place,