The De Havilland-M.G. Sprint Special

Interest has been lent to this season's sprint contests by the appearance in some of them of T. Dryver's remarkable De Havilland-M.G. —  remarkable because this car has a D.H. Gipsy aeroplane engine in a surprisingly small chassis.

During the war Cecil Clutton had an article in Motor Sport discussing the possibility of such an engine in a road car, the conclusion being that if adequate cooling could be arranged and sufficiently high gear ratios installed, a 100-m.p.h. car needing major overhauls once every 100,000 miles would result. The feeling was that something like a 3-litre Bentley chassis would be required, with special gearbox, and even this might need strengthening.

What Dryver has done is to get a Gipsy aeroplane, engine into a Q-type M.G. Midget chassis, a quite outstanding accomplishment, although, as his car is a sprint special, the cooling problem is reduced.

The car was built in the owner's home garage and on the kitchen table, assisted by his 19-year-old son, in, as he says,"the old Shelsley tradition." An absolute minimum of machining and welding was "farmed out,” yet construction occupied only about six months, working evenings and weekends.

Dryver's aim was to have a lot of fun without spending a fortune and he reckons that his D.H.-M.G. cost him only £135 to prepare for this year's Prescott Testing Weekend, and about £150 to date, inclusive of modifications and repairs after "blow-ups."

The engine is the faithful D.H. Gipsy Major air-cooled, in-line, 118 by 140-mm. four-cylinder, normally of 6,124 c.c., but this one has been rebored to a slightly greater size. It normally gives 130 b.h.p. at 2,350 r.p.m. on a compression ratio of 5.25 to 1. It weighs complete about 3½ cwt., including flywheel and clutch.

In the chassis the engine is upside down, as it would be mounted in an aircraft, and also back-to-front, rotating anti-clockwise, so that the flywheel can be mounted on the propeller boss.

The engine is virtually standard, but a simple tubular inlet manifold has been made up, in the home workshop, to take two 1 7/8-in.-bore horizontal S.U. carburetters A simple wet sump was also made up, which holds 1½ gallons of oil, to replace the dry-sump lubrication system used in the air. Basil Davenport advised the use of 2-in. diameter in place of 1¾-in. diameter inlet valves and these, together with an advance in ignition timing of the magnetos, is thought to have put the speed above 3,000 r.p.m. and the power output in the region of 150 b.h.p. Incidentally, plastic oil pipes are used, so that there is visible evidence of oil flow without the need for a gauge.

Originally the clutch was modified Vauxhall Fourteen, but this couldn't quite cope with the power, so a 30-h.p. Ford V8 flywheel and clutch were adapted, retaining the Vauxhall bell-housing and toggle arms but using the Ford thrust-race. A simple clutch shaft was made up, incorporating a steel disc and rubber universal joint, to convey the drive to a separate gearbox.

The gearbox is from an Alvis Silver Eagle of about 1931 vintage, mounted back-to-front to provide upward instead of downward gearing! The gearbox ratios are thus 3.75. 2.33, 1.5 and 1.0 to 1, giving, in conjunction with the 5.0 to 1 back axle, overall ratios of 5, 3.33, 2.15 and 1.33 to 1. Dryver uses first (ex-top) and second (ex-third) on full throttle without qualms, but third (ex-second) is reserved for long straights and top (ex-first) will never be used as there appears to be a possibility of the gearbox bursting and the driver does not, in any case, fancy the speed at which the propeller-shaft, immediately beneath his seat, would then be turning. This shaft is a short, home-modified Hardy Spicer, taking the drive to the Q-type M.G. back axle, in which the differential assembly has been turned upside down to counteract the anti-clockwise rotation of the crankshaft.

The chassis and body are monoposto Q-type M.G., strengthened where necessary but modified as little as possible to preserve a decent appearance. The total weight is 11½-12 cwt.

The engine and chassis were purchased from E. Lloyd-Jones, who had already commenced work on it, and this was completed by Dryver, his young son, and the young son's friend, Tony Smith.

The De Havilland-M.G. clocked 53 sec. on its very first appearance, at the B.O.C. Prescott Testing Weekend.

It was entered for the Nottingham S.C.C. sprint at Whitsun but snow and rain on a winding, undulating, narrow course resulted in a risky but satisfactory run, the driver then making fastest saloon-car time in a Daimler Conquest.

At the Cheltenham M.C. Staverton sprint meeting the Vauxhall clutch only permitted half-throttle in third gear, and when the flywheel sheared its pins the next day, luckily with little other damage, the Ford V8 assembly was fitted.

At Shelsley Walsh in June the car was motoring very well in practice when coming out of the S-bend the clutch sheared the pins of the pressure-plate housing, bending the clutch shaft, chewing-up the thrust mechanism, and even loosening the flywheel. The bell-housing split into many pieces and nearly removed Dryver's feet. In the best Shelsley Walsh tradition, with the kind co-operation of a Great Whitley garage, the three enthusiasts toiled most of the night, the next morning and late into the afternoon, returning to the hill in time for the second runs, when an exhausted driver did a disappointing 54 sec. in heavy rain, getting wheelspin most of the way.

An all-night tow behind a Ford Zephyr took the D.H.-M.G. to Rest and Be Thankful, where it made four runs, including practice, entirely devoid of trouble. The second run, which seemed the fastest, was missed by the timekeepers, but the third, accomplished in 69 sec., was deemed quite pleasing in view of the pot-holes and many bends. The car was running better than ever before.

Its owner finds the rear ½-elliptic suspension satisfactory, the brakes very fair, but finds the steering uncertain, largely because the front wheels have a saucy habit of leaving the ground after a slow corner! Alteration of the very stiff front springs and stiffening of the chassis frame will probably effect a cure. At present it is neither a drive nor a ride on dry roads but a fight, and being near-suicide in the wet it puts the "S” back into sport, says Dryver.

The whole point of creating a "special” such as this is that you make it yourself instead of buying it, and cars of this kind are certainly welcomed by spectators and make those sprints which are still organised well worth while to the clubs concerned with them. — W. B.