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Sporting Cars on Road & Track: No. 1, The Three
Litre Bentley
By "Open Throttle"
Published in "Motor Sport", July 1924
The sporting car, as a class, has characteristically
more distinction than that possessed by touring types.
Being essentially out of the ordinary, and representing
the result of concentration upon a design intended to
emphasise particular motoring qualities, the sporting
car usually has quite an individuality of its own. Some
sporting cars, of course, are much more conventional
than others ; whilst there are those which seem to stand
quite apart from orthodox standards.
In the latter category one may place the three-litre
Speed Model Bentley. This car embodies all the qualities
which one has come to consider essential in a sporting
car. In addition, it has features and characteristics
quite its own.
A brief review of the chassis reveals at once how interesting
a proposition the Speed Model Bentley is, and this opinion
is vastly enhanced when one takes the car for a trial
on the road.
The engine is a four-cylinder monobloc of 2,996 c.c.
capacity and 15.9 h.p. on the R.A.C. rating. Its design
has much originality, which has been well justified
by the results obtained. There are two inlet and two
exhaust valves in each cylinder, arranged in the head
and operated by a totally enclosed overhead camshaft
and rockers, running in oil.
Both crankshaft and camshaft are carried in five bearings.
The pistons are of aluminium, designed for high compression
service. Cooling is by pump circulation controlled by
an automatic thermostat. Ignition on a sporting car
is, of course, a factor demanding the most careful attention.
One usually has to "drive on the spark" more
than is requisite on a touring car, and if one desires
to obtain really the best running from the Speed Model
Bentley one makes no exception to this rule with it.
On this car one finds two M.L. high-tension magnetos,
having a synchronised firing point control. This system
of dual controlled magnetos enables one to obtain particularly
effective ignition. Lubrication is by pressure to the
main bearings and big ends, and by splash to the pistons
and gudgeon pins. There is a pressure lead from the
main oil supply to the hollow crankshaft, through which
the camshaft bearings, cams and valve rockers are lubricated.
Carburation is by a five-jet water-jacketed Smith-Bentley
carburetter. A notable point is that a petrol consumption
of 25 m.p.g. at 30 m.p.h. is guaranteed. The speed model
Bentley, considering its wide capabilities, is not under
any condition excessive in fuel consumption. The clutch
is of the inverted cone type, lined with Ferodo. It
has compensated withdrawal mechanism automatically lubricated,
and there is a special automatic lubricator for the
clutch spigot. The four-speed gear-box gives ratios
in the forward speeds of 9.35 to 1, 5.78 to 1, 4.72
to 1, and 3.53 to 1.
It is operated by a simile right-hand gate change carried
on an extension of the box. The frame of the chassis
is of particularly strong construction, and does not
rely on the engine or gearbox for part of its bracing.
Double Hartford shock absorbers are fitted to the back
axle and single to the front. There are oil lubricated
Wefco gaiters on all springs. Steering is by worm and
wheel.
In a car of such advanced design as the Bentley, one
naturally expects to find front wheel brakes, and the
system of fully compensated internal expanding brakes
operating on all four wheels and controlled by pedal
is very effective. The hand brake operates direct on
the rear wheels. Wear on the four wheel brakes can be
taken up by a single adjustment.
The tank holds eleven gallons of petrol, and a two-way
tap near the filling cap gives access to a reserve supply
of two gallons. The cardan shaft is hollow and is loaded
with oil through a plug, this reservoir providing an
oil supply for the back universal joint. Chassis lubrication
is by oil, supplied from an oil-gun through screwed
oil plugs. The only grease cup on the chassis is situated
on the water pump. After the chassis has been lubricated
it can be run for three months of normal mileage without
further lubrication, apart, of course, from the engine's
requirements.
The wheelbase of the sporting Bentley is 9 ft. 91 ins.,
and the wheel track 4 ft. 8 ins. The weight of the chassis
is 19 cwts., and it runs on 820 X 120 m.m. tyres. The
annual tax is £16. From the foregoing it will
be appreciated that the Speed Model Bentley is a particularly
interesting car. Our road experiences with this model,
although not at the moment as extensive as we should
like, have convinced us that this car must possess a
fascination for every sporting motorist.
The sporting Bentley is naturally a fast car. But that
is by no means the sum total of its outstanding attraction.
Very few sporting cars are really docile in control,
many are not at all comfortable to ride in. The Speed
Model Bentley is a happy exception to this too prevalent
rule. We drove the Bentley quite comfortably on top
gear at an exceptionally low speed, and found it very
docile in traffic and those places wherein ' sporting"
characteristics are not over appreciated. Owing to its
high gear range one must, of course, remember that the
four speeds are there to be used.
Gear changing is so easy a matter, however, that one
finds not the smallest objection to always starting
on first and to a fairly frequent use of the lower ratios
in traffic. On each gear the car is instantly responsive,
its life and acceleration under all conditions being
admirable.
There is one feature of the Bentley that may be described
as unique, and to this we would give due prominence,
How many Sporting cars, or cars of any sort, will do
seventy miles an hour on second gear ? Their number
must be very few indeed. The Bentley, however, makes
light of this. One can speed up in the ordinary way
on the successive gears until one is going along smoothly
and comfortably at, say, forty-five miles an hour on
top gear. One then changes down direct to second gear,
missing third — and things begin to happen!
With a slight pressure on the accelerator one can then
speed up the Bentley in a few yards to fifty, fifty-five,
sixty, sixty-five, and seventy quite easily—all
on second. The leap forward when the increase of engine
revolutions Is permitted by the sudden change from top
to second speed, is a thing to be experienced to be
appreciated. The acceleration is quite remarkable, as
remarkable as the fact of changing down at forty-five
miles an hour itself. The Bentley will hang on to round
about the seventy mark on second gear indefinitely,
and the change down at speed with a quick double-clutch
is not unduly difficult.
One can change into top at practically any speed, slow
as well as fast, and the Bentley will attain the neighbourhood
of the eighty mark without much forcing.
Steering on the Bentley is delightfully easy, comparable
in its comfort to that experienced on a high quality
light car. The four-wheel brakes, operated by pedal,
are remarkably powerful, and very easy and smooth in
operation. Although there is not an over abundance of
seating room the Speed Model Bentley is quite comfortable
to ride in.
The electrical and other equipment is very complete,
and the general lay-out of the car very pleasing to
those who desire a high quality sporting vehicle which
is quite practicable for ordinary touring and exceptionally
attractive amongst sporting designs for town and general
use.
The price of the Speed Model Bentley with fourseater
body is £1,125 and with two-seater body £1,100,
purchasers being afforded the option of choosing the
colour of body and upholstery. The manufacturers are
Messrs. Bentley Motors, Ltd., 3, Hanover Court, Hanover
Street, London, W.1. The extensive Bentley factories
are at Cricklewood, London, N.W. 2.
Interest in the Bentley is naturally enhanced by this
car's splendid victory in the French Grand Prix D'Endurance
last month. The Bentley was the only British car amongst
some forty competitors, and its outstanding performance
throughout the race provides a notable tribute to British
engineering in general, and to Bentley design and workmanship
in particular.
Magnificently driven by Duff and Clement, the Bentley
maintained a thrilling struggle with some of the best
representatives of French automobile science throughout
the twenty-four hours that the race occupied. This event
is indeed appropriately named, a trial of endurance,
for it is difficult to imagine a more exacting test
under road conditions than this gruelling struggle of
speed throughout a day and a night.
The Bentley had no mechanical trouble, and at the end
of the race was in good condition and still lapping
consistently. The distance covered by the Bentley in
twenty-four hours with Duff and Clement alternately
at the wheel, was exactly 2,188 kilometres, or 128 laps
of the course. Second place was taken by the Lorraine-Dietrich,
driven alternately by Stoffel and Brisson, with 2,061
kilometres to its credit.
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