THE NEW FORMULA
THE chief interest prevalent amongst followers of International Grands Prix concerns the new formula that will remain in force from ]938-40; what new cars it will originate and how it will govern the trend of design. As long ago as August, 1936, MOTOR SPORT discussed the possibilities of the Formula at some length, and that article might profitably be re-read at the present time. It was originally proposed that the new formula should come into force this year but the existing maximum-weight ruling remained for the 1937 season and we start racing under the new formula next season. This new formula limits the capacity of supercharged cars to 3-litres and that of unsupercharged cars to 41-litres, and it imposes a scale of minimum weights for various engine size classifications, as follows :—
These weights relate to cars without fuel, engine-oil and tyres. Whereas the existing formula, introduced with a view to reducing the maximum speeds of the cars, stipulated a maximum weight of 750 kg. (approximately 3.4i cwt.) for cars of any capacity, the new Formula involves a scale of minimum weights. Now the old ruling not only failed to reduce speed, but it did not, as we at first imagined it must, limit designers to engine capacities of around 3-litres and thereby encourage fast-revving engines blown at high pressures. Auto-Union contrive to install 6-litre, and Mercedes 5i-1itre powerunits and still get within the 750 kg. limit and naturally crankshaft speeds and blower boosts are limited automatically in very large engine sizes by reason of inertia stresses and heat-flow, apart from the desire to court complete reliability when some 400 to 500 b.h.p. is already realised, without going to extremes. Now the new formula imposes 1;2 ivimum weights, which is an attempt to prevent the construction of super-fast dangerously light cars, as well as to even things up amongst cars of varying engine capacity, but it also limits engine size. The Auto-Union, Mercedes-Benz, AlfaRomeo, Maserati and Bugatti G.P. cars, built for 1934 to 1937 formula racing, are no. longer eligible. Had the existing formula merely been modified by substituting a minimum weight limit in place of the 750 kg. maximum, designers would almost certainly have made use of even larger engine sizes, and would not have made use of the extra weight ” allowance” to use more rigid frames or better faired bodies, etc. (if there can be anything better streamlined than a G.P. Mere.). In this connection it will be recalled that last year Mercedes employed a 5.6-litre engine for record work, but could not at first get within the 750 kg. limit. If, on the other hand, engine size had been limited, but the 750 kg. ruling retained, valuable engine developments would have been encouraged, and experiments in weight reduction would probably have continued, but the cars would have tended to be as dangerous as before, because equivalent power/weight ratios would -be realised. And although the road-holding of the present 750 kg. 5to 6-litre cars is so remarkable that the present G.P. cars are not, in fact, as dangerous as everyone feared at first, this happy state of affairs might not hold true of a 3litre car, developing some 350 b.h.p. and weighing under 13 cwt. So, taken all round, the new formula seems a very Good Thing. Especially as engine design should benefit, as was the case under the q-litre capacity limit of a decade ago, in view of the sliding weight scale rendering it practically equivalent to a fixed
capacity limit. Indeed, there will be more incentive to increase crankshaft speeds and improve volumetric efficiency under the new Formula than wider one which specified a fixed capacity limit but allowed designers a free hand as regards minimum weights, because startling things can now be done as regards weight conservation, whereas highly-boosted or tuned engines are likely to be unreliable, so that engine development would tend to be superseded by weight cutting under such a ruling. That this question of reliability is not stressed too highly is indicated by the use of very big powerunits, developing around 90 b.h.p. per litre, in existing cars, rather than the use of smaller, more efficient engines that would reduce the total weight appreciably below the 750 kg. limit for an equivalent power-output. Another way of looking at it is that Auto-Union and Mercede.sBenz are building unblown 41-litre cars as well as blown 3-litre jobs for the new Formula contests, deeming the unblown cars to have certain advantages over certain circuits. The blown racing engine develops far and away so much more power than its unblown brethren that, even on courses with few bends and long straights, or, alternatively with corner following corner in such close succession that full acceleration could not be used, one would expect the blown motor to score heavily and to hold the fort, were it not for the reliability factor. In this argument the sliding weight scale does not enter, as 3-litre blown and 41-litre unblown cars are allotted the same minimum weight of 15 cwt., and in neither case should the leading designers have the slightest difficulty in getting both types down to it. In theory, at any rate, a ruling which allows 750 c.c. cars weighing 880 lb. to compete with 3-litre blown and 4i-litre unblown cars weighing 1,700 lb. should encourage designers to seek high outputs from all sizes of engines, which will mean high-pressure supercharging or high compression-ratios in unblown engines, and increased crankshaft peak speeds, -While in the case of cars which are now below the set weight minimums, beneficial advantage will doubtless be taken of the opportunity to strengthen frames and suspension units, to completely fair off protuberances and, perhaps, to use bigger fuel tanks with a view to reducing the number of pit-stops in the Course of a race—for the minimum limits take no heed of the weight of fuel carried, but petrol tank size does put up weight, even when forming part of the bodywork, and has in the past undoubtedly been limited in G.P. cars to get them within the 750 kg, limit (the Auto-Unions apparently fill tanks to a capacity of around 20 gallons, necessitating two stops in a 250 mile race)* and in 1 fare cars to preserve a good power-weight ratio. There is, however, one curious aspect of the new formula. Whereas the 750 kg. maximum. limitation resulted in remarkable weight paring to make cars eligible and was only possible for the leading racing-car constructors, who could afford to experiment with, and use, very expensive light alloys (remember the very big engines, the use of which might seem to contradict this statement, only came as knowledge of lightweight construction increased-141 cwt. is astonishingly light for even a 4-litre racing-car), the new sliding scale of minimum weights will, as we have just emphasised, give designers something to play with. But this only applies to the larger engined cars. Having built 51 to 6-litre cars weighing under 141 ewt., Auto-Union and Mercedes, for instance, will not be embarrassed by making blown 3-litre and unblown litre cars turn the scrutineers’ scales at 151 cwt. Indeed, having done what they have with relatively huge power-units, they should be able happily to get unblown 4-litre cars within the 131 cwt. limit or blown 21-litres to turn the scales at the same figure, if so inclined. But when we come to the smaller engined cars the opposite rules. Although cars well outside the minimum limits will naturally be eligible to start, they will not draw more than starting-money, and probably not that for long., for they will be up against a weight maximum imposed not by the A.I.A.C.R. but by their rivals. So we shall have the curious state of affairs that while some constructors are adding weight, in a beneficial manner we hope, in order to comply with the Formula, other constructors will be fighting as hard as before the complex battle of weight-paring, that they may put up a show against rivals in the same capacity classes, or, indeed, in the races as a whole. Fortunately no one maker is likely to gain such a lead in this weight conservation as to be able to overlook the need to develop engine design as well. Fortunately again, small engines lend themselves better than large ones to high peak speeds and high-pressure boosting, which will even up to some extent these power-weight ratio discrepancies. But this is really where the 1938-40 Formula weakens, at all events in the eyes of impartial observers of designprogress as exemplified by G.P. racing and of those particularly associated with the smaller-engined cars, which include
‘These are rough calculations based on the Donington G. P. British constructors. In the first place, even if the specified minimums could be exactly realised all down the scale, the new Formula is not based on a ” straightline ” graph. Thus, the 3-litre blown cars are allotted 850 kg minimum, or a capacity/weight ratio of 3.53 c.c. per kg., whereas a 2-litre car is set 3.04 c.c. per kg. and a 1-litre, 2.15 c.c. per kg. While we do not entirely agree with Humphrey Cook’s recent statement that it is easier to obtain b.h.p. from a large-bore engine than one with a small bore, certainly engines below 14-litres, or, conversely, over 3f-litres, in our opinion, are hardly likely to be on level terms in respect of b.h.p. output per litre, with those coming within these limits, at all events for the first season to which the new Formula applies and applying this consideration especially to British cars. Consequently, it is apparent that the Formula does not treat various-sized cars on an equality, either in respect of power/weight ratio pure and simple or from the viewpoint of possible power output per litre allied to capacity/weight ratio. But things are even worse in practice, for so few cars are likely to get down even to the set minimums. As MOTOR SPORT pointed out in August 1936, neither the Austin Seven nor the then existing if-litre E.R.A.s came very near to the set minimums (the scale has been slightly modified since that article was written), weighing 1,092 lb. and 1,500 lb. respectively. The Ma.serati Six 1 flitre was appreciably nearer and we suggested at the time a four-cylinder engine as a modification to realise the rock-bottom minimum, which is now used. The 2litre E.R.A., although handicapped, is in a promising position, and E.R.A. will race, but amongst blown cars the 3-litre class seems to have most advantage. Merades-Benz and Auto-Unions are pre paring cars of this size, probably straighteights, and Delage, Alfa, Bugatti and Fiat may follow suit. Also, we believe that E.R.A. Ltd. will make a brave stand with a 3-litre E.R.A., though we
do not think a team of such cars will be raced during 1938. We agree with Mr. Cook that the 3-litre looks like being in an unassailable position, at all events for the first season, basing one’s outlook on the fact that as engine outputs are at present, and having regard to the weight scale and difficulties of realising the minimums in the smaller classes, a 1-litre car would need to develop 64 per cent. b.h.p. per litre, a lf-litre 32 per cent. b.h.p. per litre and a 2-litre 16 per cent. b.h.p. per litre above that of a blown 3-litre developing 300 b.h.p. (a not unattainable figure) to hope to start on an equality. The 2.9-litre Alfa-Romeo is in a very enviable position, as the 1936 two-seater Mille Miglia cars actually came within the 750 kg. limit. So Kenneth Evans will be able adequately to represent Britain as a driver and we wonder if he will merely add. ballast to comply with the
new Formula. Staniland and Martin have 2.9 Alfas and Ashby’s 3.2-litre Alfa-Romeo should liner down suitably if its owner contemplates racing abroad. Darracq is said to be building a blown sixteen-cylinder 3-litre, and the use of multi-cylinders implies our predicted rise in peak revs, and volumetric efficiency generally. Coming to the tmblown cars, AutoUnion are using rear-engined twenty-fourcylinder 4f-litres, according to rumour, on short, twisty courses, and Mercedes 12cylinder, 4f-litre cars. Bugatti is developing his new straight-eight 41-litre. Delahaye will run the recently-introduced 12-cyl 4f-litre, which took the big prize at Montlhery road-circuit, and Darracq
probably their sports-type 4-litre which won the T.T. Only on certain circuits would one expect present unblown cars to hold the blown jobs.
Experience in modern sports-car racing should enable 4f-litre unblown cars like Bugatti, Darracq and Delahaye to get down to their set minimums fairly easily and in some cases they may even be lighter than the 3-litre blown contingent by reason of not needing to carry so much fuel with which to run through a race or run until a routine stop. Our 41-litre Bentleys and 4f-litre Lagondas are appreciably heavier, but a lot of weight could no doubt be pared. There is another aspect in which the new Formula tends to handicap the smaller cars, and that is that bodywork size has to conform to measurements that represent building the car within a rectangle of 850 mm. x 250 mm. The result will be that the smaller car will have a frontal area of almost the same as that of the bigger cars, which will limit maximum speed and acceleration to high speeds and not assist the very vital weight-paring process. A pity the sliding scale was
forgotten here. Bodies will be wider than hitherto, which should best suit the converted unblown sports-cars and Ettore Bugatti.
Finally, there is the aspect of speed reduction. Certainly the new Formula cars will be less spectacular to watch, even the best of the blown 3-litres, next year, but even so they will probably be giving off something like 460 to 480 b.h.p. quite soon, and possibly 600 b.h.p. eventually, which will go a long way towards washing out that extra cut of avoirdupois, as well as fostering engine efficiency in a commercially widely-used capacity division. The new Formula is not ideal, but it is very, very interesting.