The A7 Car
The following is
an extract from the 1928 “Modem Motor Car &
Commercial
Vehicles” - found for us by Hugh Girvan
SOME TYPICAL BRITISH MOTOR CARS
THE AUSTIN-SEVEN CAR
The
Austin-Seven car is, perhaps, the most widely used of any car in its class;
moreover, it has followed its original design very closely all the way through.
This
little car has a wheel base and track of 6 feet 3 inches and 3 feet 4 inches
respectively; the road clearance is 8 3/4 inches and the turning circle 33
feet.
The
engine fitted is a high-efficiency four-cylinder water-cooled one of 56 mm.
bore and 76 mm. stroke, giving a cylinder capacity of 745 c.c.
This
is shown in Plate III, Vol. I.
The
engine is rated at 78 h.p., but it generates 10.5 h.p. at 2,400 r.p.m., and
correspondingly higher horse-powers at higher speeds. Racing models of these
engines have attained
speeds
of 6,000 to 7,000 r.p.m.
The
engine has side-by-side valves, aluminium pistons of the three-ring type (the
lower being a scraper ring), a two-bearing crankshaft carried on roller
bearings and detachable cylinder head.
Fig.
42.—The Austin-Seven Chassis in Side View.
Lubrication
of the engine is by a submerged gear-driven oil pump which forces oil to the
crankshaft bearings; other parts receive their oil supply from the oily mist
created in the crankcase.
rig. 43.—Tbe
Austin-Seven Chassis in Plan View.
The
power is transmitted from the engine through a single-plate clutch to a
three-speed gear box, giving the following road ratios: first speed 16 to 1;
second speed 9 to 1; third (top) speed 49 to 1; reverse is 21 to 1.
The
gear lever is mounted centrally in a position convenient to the driver.
From
the gear box the drive is through a short intermediate propeller shaft having a
bearing fixed to the frame cross member at its rear end, thence the drive is
through a second shaft to the helical bevel final drive.
The
rear axle is of the three-quarter floating type with differential and torque
tube.
Four-wheel
brakes are fitted, the brakes being applied to all four wheels either by foot
or by the hand brake lever. The adjustments for the brakes are placed in
accessible positions.
The coil ignition arrangement and generator
of the Austin Seven
Ignition is by Lucas battery and coil, the
distributor unit being driven through the dynamo
Steering
is by worm and worm wheel, there being provision for taking up the wear. Over
the steering wheel are the gas and ignition control levers, and horn switch.
The
springing system consists of a transverse or semi-elliptic cross spring at the
front, with a forked radius rod to locate the front axle; at the rear
quarter-elliptics are fitted. Shock absorbers are fitted both fore and aft.
The
chassis frame, as we have previously mentioned, is of the simplest design
ending at the anchorings of the rear springs.
Three-stud
attachment wheels are fitted, the tyres being 26 x 3.50 inches, This car has a maximum speed of
about 50 m.p.h., with a cruising speed of
35/40 m.p.h. On good dry roads the
petrol consumption is about 40/50 m.p.g.