Recently we were able to inspect two promising Smith Specials. One of them had, only the day before, won one of the 500-c.c. car races at Brough, in the hands of D. Parker, who found the course loose and dusty. This car is one which C. F. Smith ran at Silverstone last year, and it will be seen at this venue again, in Parker’s hands, on May 14th. The other car is Smith’s new 1,000-c.c. mount. It has a tubular rear-engined chassis and transverse-leaf spring-and-wishbone independent suspension front and rear on the Cooper formula, but a slightly shorter wheelbase than a Cooper. The rear axle is de Dion type, and on each side a long tubular locating member runs from it to a pivot on the chassis side-member. A V-twin J.A.P. engine will drive by chain to a Norton gearbox, and a Z.N. differential unit, made in Smith’s workshops, will be incorporated in the final drive. Centre-lock wire wheels are used which weigh less than Cooper aluminium-alloy wheels, although they do not, of course, incorporate the brake drums. The latter are, however, of light-alloy, with very deep cooling ribs and the liners bonded to the alloy. Actuation is hydraulic, with the hand brake acting on a sprocket-drum to comply with regulations. Fuel will be carried in two saddle tanks, one on each side of the chassis, each with a capacity of five gallons. The body is being made by Cooper’s Garage and rather smaller air-scoops will be used than those favoured by Cooper himself. Newton shock-absorbers neatly mounted at 45 degrees are incorporated in the suspension system. This car is too heavy for serious 500-c.c. racing, but will be run in this form at Silverstone.
Reverting to Parker’s J.A.P.-engined car, it has normal, not de Dion, independent rear suspension, but is otherwise of similar design. It will be towed to race meetings on its trailer behind Parker’s well-known 1939 competition 3 1/2-litre Jaguar two-seater which constitutes his hack-transport as well as his sprint car and which gives yeoman service. One of its non-standard features comprises neatly-mounted, vertical hydraulic-strut shock-absorbers outboard of the front springs.
It should, perhaps, be explained that C. F. Smith specialises in sidecar racing, using his machines for testing the special bearings that he manufactures for J.A.P. engines. Last year he broke the sidecar record at Shelsley Walsh.
A feature of post-war trials has been the success of the small car in a sphere once dominated by Ford V8 engined cars. This has been due largely because enthusiasts have achieved trials-cars of good power/weight ratio by installing Ford Ten-engine units in Austin Seven or other ultra-light chassis. If this trend is disturbing to the big-car owner who craves the trials limelight, it cannot but be heartening to the Ford Motor Company to find that what their V8 engine did before the war their Dagenham-built “Ten” is doing to-day.
Most people who seek to motor in a stirring fashion are fully aware that a good power/weight ratio is the answer. The Allard provides a useful yardstick, because the two-seater weighs about 21 cwt. and develops about 85 b.h.p. and certainly possesses an enviable degree of acceleration. So, says your special-builder, if I can build a car which weighs 10 1/2 cwt. I shall need less than 45 horse-power to make it perform like an Allard. And, broadly, that is correct, although such matters as engine torque and gear-ratios, etc., may enter into this simple equation with disappointing results, on occasion. That, however, is not to gainsay the excellence of almost any car which weighs very little and has a sufficiency of horses under the bonnet. Reducing weight is certainly easier than increasing the horses, and weight removed stays removed (except for an accumulation of mud and road dirt which no enthusiast will allow), whereas the added horses are apt to grow disconcertingly tired, if they do not escape altogether.
Now the Ford Ten-engined lightweight vehicle, 80 b.h.p. and 10 cwt. or thereabouts, has proved potent in trials, brisk on the road, and eminently practical. However, special-builders never rest for long and it seems possible that another form of approach may materialise ere long — doing without water!
In a recent Bristol M.C. & L.C.C. trial there appeared an Austin Seven chassis endowed with an air-cooled flat-twin A.B.C. engine. One appreciates at once that such engines may not be a practical proposition, at all events for trials. They may overheat, tear out the transmission or burst. But are they worth while, purely from the view point of weight reduction? On paper, definitely they are.
The original air-cooled A.B.C. small-car engine, introduced in 1917, was claimed to weigh 65 lb. and to give 25 b.h.p. at 3,000 r.p.m. Later versions of this Grenville Bradshaw creation developed appreciably more power, presumably without much increase in weight. The thought of installing one in an 8 1/2-cwt. car is attractive! We received recently a letter relating to a Douglas water-cooled flat-twin car raced at Brooklands in 1921. The amusing thing was that its power/weight ratio was just about that of the present-day Ford Ten-engined special such as the Buckler or a Dellow. The engine was bench-tested at 31 b.h.p. at 3,250 r.p.m., the car weighed about 10 cwt. with 28-in, wide plywood-panelled, wooden-frame two-seater body and the half-mile was covered at 75 m.p.h., pulling a 4.0 to 1 top gear on 710 by 85 covers. Before this causes sneering at modern specials, it can be added that this Douglas engine, pretty hotly tuned, didn’t give so very much more power than a standard bread-and-butter Ford Ten unit, for which Ford’s claim 30.1 b.h.p. at 4,000 r.p.m. on a 6.2 to 1 compression-ratio. Moreover, the weight of the Douglas applied with a body that wouldn’t, one imagines, survive one present-day trial, and with very tiny-section tyres and the flimsy lamps, wheels, etc., of its day, whereas to-day’s specials usually have battery, starter and dynamo, comparatively large-section tyres, heavier wheels and more substantial lamps, etc. Nevertheless, the thought of doing 75 m.p.h. at 3,600 r.p.m. and accelerating as briskly as a modern 30-h.p./10 cwt. special is alluring.
Perhaps, then, the air-cooled engine for trials may yet stage a return. Indeed, there are rumours afloat of a J.A.P.-engined Austin Seven as we write.
What saving can the “without water” exponents claim? Well, the Ford Ten engine unit weighs approximately 275 lb. with starter and all components, added to which there is the weight of an adequate radiator and another 25 lb. for the 2 1/2 gallons of water that the manufacturers deem necessary to keep it cool; say an all-on total of 320 lb. Now the sort of 1,100-c.c. air-cooled V-twin J.A.P. engine that graced pre-war Morgan three-wheelers weighed, again with all components, but with a handle in place of an electric starter, a mere matter of 135 lb. Moreover, it developed 39.4 b.h.p. at 4,500 r.p.m. in normal trim. Further comment would seem superfluous! Except, perhaps, to remark that John Bolster’s o.h.v. J.A.P.s give over 50 b.h.p. each.
Do not run away with the idea that Ford makes heavy engines. We have taken the Ford Ten for comparison with the J.A.P. because it figures in many highly-successful and potent present-day trials specials. It is actually notably light for this class of water-cooled engine and the famous 30-h.p. Ford V8 unit, indeed, weighs only 534 lb., or 150 lb./litre. Racing engines rather make one gasp in this respect, the weight claimed for the original 6-litre Auto-Union engine being quoted, for example, at 620 lb.
Reducing the weight of the complete vehicle isn’t so easy, even if “doing without water” seems to be the answer so far as the engine is concerned. In 1916, when keeping down the weight of small cars was a matter of making them go at all rather than go briskly, a now-defunct paper took a census of the weights of readers’ light-cars. The lightest proved to be the then distinctly-spidery 7-h.p. Jowett and even these, notwithstanding the sparse equipment of those times, turned the scales at over 8 cwt. Most of the flimsy four-cylinder small cars weighed more than 12 cwt. Our own experience suggests 10-12 cwt. for vintage small cars and 8 1/2 cwt. for a certain 1928 touring Austin Seven docked of its hood, spare wheel, front wings, etc., and with 8.50 by 19 tyres. So that to get even a 1,100-c.c. trials-special carrying road equipment, starter, battery and dynamo down to 10 or 10 1/2 cwt. is a very reasonable effort.
To close on the optimistic note with which this discourse opened, i.e., that 45 horse-power and 10 1/2 cwt. spell the equivalent of Allard performance, let us remember that the figure for litres-per-ton-mile is a surer guide to what will happen when you put your throttle-foot down. The figure for the Allard two-seater is 5,250 and the formula by which you can discover the figure for your own car is: – 5,025 VG/WR, where V = capacity in litres, G = top-gear ratio, W = weight of car in tons and R = rolling radius of the rear tyres. The last-named figure can be obtained from the tyre manufacturer if the size is quoted.