The V12 in production
There is something definitely intriguing about the V-twelve, and in this article Cecil Clutton traces the history of production examples of the type, from the Packard of 1915 to the 4.3-litre Alfa-Romeo of immediate pre-war days. – Ed.
Six cylinders we accept as a matter of course, and Eights are in fairly common parlance, but there is something rare and exciting about a twelve-cylinder motor, even though it has been brought into the mass production market by the Lincoln Zephyr. It is, however, quite interesting to glance at the outstanding points of the very few twelves which have made good in production, and one or two others besides.
The first serious competitor was the V12 Packard, introduced in the early part of 1915. Like all its successors, it had a 60˚ V-engine and the dimensions were 76.2 x 127 mm., giving a capacity of 6,950 c.c. The blocks were staggered to each other, and each opposite pair of rods (rather long and flimsy H-section) shared a journal. The crankshaft was supported in only three main bearings and was only 2" in diameter. Despite this it was described as being perfectly smooth up to its maximum of 3,000 r.p.m., although one cannot help wondering. Ignition was by coil and power was transmitted to a three-speed unit gearbox via a multi-plate clutch. With a 4.36 to 1 axle ratio it presumably had a maximum of not more than 70 m.p.h., but it must be remembered that American roads at that time were not conducive to high speeds. The car was certainly an innovation and its turbine-like torque must have been a revelation in those days, because the next year no fewer than six American manufacturers were offering a V12. Although not much seen in this country, the V12 Packard was still in production shortly before the war, with independent front suspension, and was capable of over 100 m.p.h. with ordinary coachwork. Many American V-engines have had side-valve engines with valves inside the V, and until the invention of the hydraulic tappet, adjustment was a most formidable undertaking.
In 1931 Packard's tried an experimental front wheel drive V12, but it does not seem to have gone into serious production.
The immediately post-war period produced one or two interesting examples, and the 1919 Salon contained twelves by Lancia, Lorraine Dietrich and Voisin. The Lancia was an 80 x 100-mm., 22˚ V, o.h.v., single carburetter affair; the Lorraine measured 70 x 140 mm., with o.h.v. and dual ignition; and the Voisin was a 7,238-c.c., 80 x 120-mm. unit with two aluminium blocks bolted together and cast-iron sleeve valves working direct in the aluminium blocks. The inside of the water jackets was enamelled under pressure and stoved to prevent porosity – quite a point, as some Bentley owners may care to recollect of their aluminium side plates. Half of the induction manifold was cast with each block and machined smooth, with a Zenith carburetter bolted to the back end. The crankcase, too, was aluminium and carried the crankshaft in three roller main bearings. The crankshaft was in two parts, bolted and keyed together. In fact, everything about the engine seems to have been as difficult as possible. The transmission was no less unusual, incorporating hydraulically operated front brakes. Two-thirds of the semi-elliptic rear springs were in front of the axle and the rear shackles were attached to swinging levers, pivoted on the side of the rear dumb-irons and with the other end connected to horizontal coil springs. One feels instinctively that the machine must have bristled with snags!
In 1921 came a 6.8-litre, 85 x 100-mm., V12 Fiat, which was notable for its exceptional cleanness of outline. The starter and dynamo were concealed inside the V and the induction manifolds were cast integral with the water outlet pipes and fed by a single carburetter. The cylinder heads were detachable and the overhead valves push-rod operated. The three-speed gearbox had a silent second speed and was in unit with the engine, which gave off 100 b.h.p. Four-wheel brakes were again a feature.
Probably none of the above four cars was produced in any numbers.
The next V12 of any importance seems to have been the Double Six Daimler, which first appeared with double sleeve valves in 1926. It had a seven-bearing crankshaft, and 81.5 x 114-mm. cylinders gave a capacity of 7,136 c.c. With a final ratio of 4.37 to 1 it had a top gear performance of 2-82 m.p.h. Daimler's continued to produce V12s with various modifications for several years, and the Royal Family had a number. In 1935 the V12 Daimler had an 81.5 x 104-mm. motor (6,511 c.c.), developing 142 b.h.p. at 3,400 r.p.m., but they were eventually dropped from the range. Next comes another sleeve-valve Voisin of 1929. This had a much smaller engine, of only 3,860 c.c. (64 x 100 mm.) and it had two cast-iron sleeves per cylinder. The sleeves were driven from a central "camshaft" and there was a safety device to prevent them from falling into the works in ease of a seizure. The hollow crankshaft had the record diameter of 4" and the engine developed 115 b.h.p. at 3,900 r.p.m. Some performance particulars would be interesting, but I have not been able to discover any. Later, M. Voisin excelled himself, in 1936, by producing a twelve-cylinder in line! At least, he threatened to do so, but whether it ever materialised is not entirely clear.
Although not a twelve-cylinder, it is worthy to record that in 1930 Cadillacs produced a V16 of 7-litre capacity (77 x 102 mm.). In order to get even torque it is necessary that a V16 should be disposed at either of the rather inconvenient angles of 45° or 135°. Cadillacs chose the narrower angle and were, therefore, almost obliged to use overhead valves. There were two carburetters, on the outer sides of the blocks. This machine displayed very fine workmanship and the chassis price was £1,500. In 1938 Cadillacs changed to the 135° engine, with side valves on the inside of the V. Marmons also produced a V16.
In 1931 a truly remarkable 8-litre V12 was marketed by the Mayback Company, at a chassis price of £1,900. It had a maximum speed of 105-110 m.p.h. and a five-speed gearbox, later increased to six. The gears were in constant mesh and engaged by dog clutches. The operation, however, was pre-selective, the actual engaging of the dogs being vacuum operated, while another vacuum control synchronised the engine speed before the dogs could be engaged. The ratios in six-speed form were 14, 10.4, 5.7, 4.2, 3.2 and 2.5 to 1, but in an engine which, of all others, should be best able to do with a minimum of ratios, the complication seems rather overdone.
Also in 1931 came what may perhaps be regarded as the king of production cars, the V12 Hispano Suiza. This was a square engine, 100 mm. both ways, giving a capacity of 9,424 c.c. and an R.A.C. rating of 75 h.p. The cylinder blocks were aluminium castings with screwed-in, nitralloy steel liners. Unlike the famous 37.2 six-cylinder model, which had an overhead camshaft, the V12 had pushrod operated valves, worked by a single camshaft in the centre of the V. The banks were, as usual, offset to each other and the rods were tubular with heavily finned big-end caps. The crankshaft was carried in seven main bearings and transmitted the drive via a multi-plate clutch to a unit three-speed synchro-mesh gearbox, the final ratios being the remarkable ones of 2.72, 4.10 and 5.44 to 1. The maxima in the gears were 50, 80 and 100 m.p.h., from which it appears that nothing like peak revs, could be attained in top gear. Maximum revs, are not known to me, but were presumably around 3,300 per minute. The model was described as the 54-220 h.p., and, assuming the engine peaked at 3,000 r.p.m., it was certainly an efficient unit, as this would indicate a b.m.e.p. of 100 lb. per sq. in. at a piston speed of only 2,000 f.p.m. To some extent these figures must be conjectural, but they cannot be far out. Despite the high axle ratio, the model tested by The Autocar in 1934 accelerated from 10-80 m.p.h. in top gear in 6 4/5 secs., while the acceleration through the gears to 50 m.p.h. took 9 2/5, secs., to 60 m.p.h. 12 secs., and to 70 m.p.h. 15 secs. This car (which, incidentally, was surely one of the most handsome ever made) weighed 39 cwt. and cost £3,500, the chassis price being £2,750; 100 m.p.h. could be exceeded under favourable circumstances, but an indication of the cruising speed is given by a Brooklands lap at 95 m.p.h. The brakes were quite up to the performance and stopped the car from 30 m.p.h. in 26 ft. – a remarkable feat for any machine, but quite staggering for a 2-ton motor-car. In the matter of brakes, Hispano's were very much pioneers, and as early as 1919 their cars were fitted with a very efficient servo-assisted outfit, operating on all four wheels.
It is surprising to find that Lincoln's did not produce a V12 until 1932. The price of the complete car was £1,895, and it was certainly a very fine machine. When first produced the engine had a capacity of 7,238 c.c. (82 x 114 mm.) and the maximum speed was 95.74 m.p.h. on the highest of the alternative final ratios, which was 4.23 to 1; second gear, 7.56 to 1, was good for 54 m.p.h. The cruising speed was up to 80 m.p.h. Later, the engine was reduced to 79.38 x 114.3 mm., giving a capacity of 6,900 c.c., and in 1935 this unit gave 150 b.h.p. at 3,400 r.p.m. In the same year that very excellent car, the Lincoln Zephyr, was produced at a price of £550. This had a 70 x 95-mm., 4,378-c.c. engine developing 110 b.h.p. at 3,900 r.p.m., which gave a maximum speed of 90 m.p.h. on the 4.44 to 1 top gear, while acceleration from 0-50 m.p.h. through the gears took 10.3 secs.
Of the several other American V12s which have appeared on the market from time to time the Auburn was probably the most prominent after the Packard and Lincoln.
The year 1935 saw the introduction of two very important English V12s, by Rolls Royce and Lagonda.
The "Phantom III" Rolls Royce, marketed at a chassis price of £1,850, had a 7,340-c.c., 82.5 x 114-mm. engine of light construction, with aluminium cylinder blocks. It would carry an enormous 2 1/2-ton motor-car at over 90 m.p.h. and accelerate from 0-50 m.p.h. in 12.6 secs. The final ratios were 4.25, 5.59, 8.45 and 12.71 to 1, giving a maximum in third gear of 73 m.p.h. This indicates a top speed of around 4,000 r.p.m., and as the engine speed, in production form, is probably limited by the weight of the hydraulic tappet valve gear, one wonders whether a "Phantom III" engine slightly bored out (for which there is room) and suitably developed might not become an exceedingly potent unit.
Also very remarkable was the V12 Lagonda of 4,480-c.c. capacity and cylinders measuring 75 x 85 mm. With a 2-ton saloon body this machine comfortably exceeds 100 m.p.h., while, owing to the short stroke and exceptional smoothness of the engine, it will hold the magic three figures for considerable periods without any sign of stress. The staggering smoothness and silence with which the engine climbs to 5,500 r.p.m. can lead an unaccustomed driver into quite nasty situations if he does not keep an eye on the speedometer; but as against that it must be confessed that the torque below 3,000 r.p.m. is disappointing by comparison. For this reason, the Lagonda seems to be a car which should have carried a Cotal gearbox, as this would have eased the strain of driving tremendously. The valve operation on the Lagonda is interesting, consisting, to all intents and purposes, of a side-valve layout put upside down on top of the engine and operated by an overhead camshaft! With the improved four-carburetter layout, which was about to be produced when the war started, there is little doubt that the low speed torque would have been much improved. The power output in touring form was some 170 h.p., but in Le Mans form it went up to the excellent figure of 220 b.h.p. at 6,000 r.p.m.
Delahayes raced an unblown 4 1/2-litre V12 under the 1937 G.P. formula, though its only success was at the Pau Grand Prix in 1938. The cylinder dimensions were 75 x 84.7 mm., and there were two plugs and two push-rod operated valves per cylinder. The power output was upwards of 250 h.p. at less than 5,000 r.p.m. Delahaye later marketed a variety of this machine and performance figures would be most interesting. Probably the total number sold was very small, but at least one came to this country.
Last of all came a V12 4.3-litre unblown Alfa-Romeo. It had two o.h.c. per bank and three down-draught carburetters in the V. A maximum speed of 140 m.p.h. was mentioned. The car appeared at Liège in 1939 and ran in practice, but the actual race was cancelled on the eve of the outbreak of war. Whether it was intended to market this car is not entirely clear, but it carried quite a production looking 2-seater body at Liège and must be a very high-powered motor-car.