MOTOR SPORT
A NEW SUPERCHARGED SPORTS CAR.
THE 12 h.p. Invicta first appeared at Olympia last year, and attracted much favourable comment, and Messrs. Invicta now announce the introduction of a supercharged model. ‘ The car is a welcome departure from the policy of unimaginative cutting-down which seems to be prevalent in some parts of the industry, and evidently the designer has been given a free hand to embody all the refinements which he considered desirable. The car was first built to give a good performance with an engine of low horse
power rating, the power being obtained by the highefficiency methods brought to light by racing. Now, by the expediency of fitting a ” Powerplus ” supercharger to the engine, the car takes its place among high-grade sports cars as a machine of distinctly brisk performance.
The six-cylinder engine has a bore and stroke of 57 mm. and 97.9 mm. respectively, giving a capacity of just under 1500 c.c., with a tax of £12. Overhead valves are
fitted, operated by an overhead camshaft and set at 90° in a hemispherical head. The camshaft is driven by double roller chain, and the head can be removed for decarbonising without disturbing the valve timing. The chain sprocket drives the camshaft through a dog and a positioning peg. When the nut on the end of the shaft is slacked off, it allows the sprocket to be moved sideways sufficiently to clear the dog, and the head comes off on. removing the holding-down nuts. A stirrup fitted about Finch under the sprocket prevents this from coming out of mesh with the chain, so that there is no chance of the timing being disturbed. Four standards and three intermediates carry the hollow camshaft and rocker shafts, and oil is fed into them through one of the standards, and thence to all moving parts. The rockers
move on floating bushes, while the cam rollers are really roller bearings, since needle rollers run between the pins and the outer shells. Steeply domed aluminium pistons are fitted, giving a compression of 6 to 1. The connecting rods are steel,
the bearing metal being poured in. direct. The crankshaft is a very massive affair, with triangular webs, and with the neat torque-damper fitted in front, the engine ought to be extremely smooth. The main bearing lay-out is unusual, rollers being used in front, then two plain bearings, and at the rear
end two ball races. Between these last is a piston which meshes with the camshaft drive above and the oil-pump drive below. The oil passes through a pressure filter before going to the bearings. The ” Powerplus ” blower is mounted between the front dumb-irons, and being concealed by a fairing, is an exceedingly neat fitting, and the induction pipe embodies a hot-spot heated by exhaust gas led through
ducts between the connecting rods. An electric:7pump supplies petrol from a tank at the rear of the chassis, while ignition is by coil, a spare coil being also fitted. The dash is of rigid cast aluminium, and the tools are carried in a box on top of it.
Engine and gearbox are made in unit construction, with three point suspension. The front of the engine is supported by a silentbloc bush on the front crossmember. A stout tube at the back of the engine is supported on the chassis by similar bushes. A four-speed gearbox with silent third is fitted, a short lever mounted on an extension bringing the knob conveniently within reach. An interesting detail is the graphite-impregnated clutch thrust-race, which never requires attention.
An open propellor shaft is fitted, with a metal universal joint at each end, and a steady bearing and another universal in the middle. The back axle is of the semifloating type, the final drive being by spiral bevel.
The chassis frame is of sturdy construction, 6-in. deep in the middle, upswept in the front, and passing under the back axle in the rear, as in the 41-1itre model. Semi-elliptic springs are used ; those in front have a bronze trunnion bearing at their forward end and a silentbloc-mounted eye at the back, while the reverse arrangement is used for the back springs. Manes steering is used, and controls are grouped at the top of the steering wheel.
The brake drums are 14-in, in diameter, and the four brakes are operated simultaneously by pedal or hand lever. Two links connect the brake pedal shaft with the brake cross-shaft, thus avoiding operating shaft whip with consequent uneven application. The brake rods are all straight and run outside the chassis, so that they are easily got at and leave the back of the chassis free to allow the fitting of a well for the rear passengers’ feet.
The gear ratios are 6, 8.15, 12, and 22.9 to one, and seem low until one realises that the engine is designed to run up to 5000 r.p.m.
This new Invicta model should prove a popular one, for the car is extraordinarily large and roomy for such a small engine capacity. In fact the chassis is virtually that of the 44 litre model. The maximum speed of the car will be in the neighbourhood of 80 m.p.h., while the acceleration will be of the definitely sporting type.
With a tax of only £12, this new Invicta should have a wide appeal, combining as it does all the advantages of a roomy touring car with the high performance of an ultra sports model.
The price of the open 4-seater sports will be E465, and the manufacturers are : Invicta Cars, Ltd., The Fairmile, Cobham, Surrey.