[Motor Sport Photograph. THE 25 H.P. ROLLS-ROYCE
THE TRAITS OF THE LARGER CHASSIS, ACKNOWLEDGED TO BE THE BEST IN THE WORLD, EMBODIED IN A DIGNIFIED, YET BRISK MOTOR-CAR
LONG acknowledged supreme in the realm of large motor cars, Messrs. Rolls-Royce in 1922 recognised the demand that existed for a smaller and less costly vehicle particularly suited to the owner driver, and the 20 h.p. made its debut. The engine size was increased in 1930, and by this alteration and other slight modifications the performance of the smaller car, the 20-25 as it is officially termed, has been made little inferior to its larger brother, though of course the maximum speed is not so great. We were privileged to try one of these delightful cars after its return from a six months’ strenuous tour of the Continent. The successful test was ample proof of the stamina which is allied to the more equally important Rolls-Royce qualities of silence and good performance.
The six-cylinder engine is mounted in unit with the four-speed gear-box, and the unit is suspended from four points. Two arms, one from each side of the front end of the crankcase, join in front of the engine and rest on a pivot on a cross member. Two more arms at the rear end of the engine take the weight of this part and a fourth support on the gear-box complete the suspension. Special dampers on either side of the engine limit the movement, and all these precautions make the power unit as smooth at high speed as at low. A monobloc casting is used for the cylinders, and the detachable head carries push-rod operated overhead valves. Two , valves per cylinder are used, and a single
-. sparking plug is placed on the off side. Coil
ignition manufactured by Rolls-Royce Ltd. is used for normal running, but in the unlikely event of its failure a Watford magneto can be brought into operation by moving a hand-adjusted coupling into engagement with a dog on the end of the dynamo. The lead from coil to distributor is detached and replaced by one from the magneto, and the car is ready to proceed. A large Autovac tank on the dash supplies fuel to the Rolls-Royce car
Engine: 6-cylinder 3f in. and 4 in. bore and stroke (81.6 mm.. and 114.3 mm.). Capacity 3,699 c.c. R.A.C. Rating 25.3 h.p. O.H.V.
push rods. Single Rolls-Royce carburettor. Coil ignition with emergency magneto.
Gearbox , 4 speeds and reverse : Silent third. Easy change mechanism for third and top gears. Ratios 4.55, 6.25, 9.41, and 15.04 to 1.
Rear Axle : Spiral bevel. Full floating.
Suspension : Half elliptic, with hydraulic shock absorbers.
Dinumsions : Wheel base lift. Track 4.11. Sin.
Price : Chassis ;C1,050. Hooper Sports Saloon as tested :C1,625. burettor, a precision instrument which can be dismantled practically without the
use of tools. It is fitted with an economy control operated by a lever on the steering column, and an auxiliary starting carburettor supplies a rich mixture which ensures an instant start even after the car has been idle for several weeks.
The carburettor is mounted on the offside of the block and the mixture is warmed by its passage to the induction pipe on the near side. A centrally disposed exhaust pipe keeps heat and fumes well away from the driving compartment.
Alloy pistons which are as silent when the engine is cold as when it has warmed up, and a seven-bearing crank-shaft, complete the specification of the magnificent power-unit. The detail work, such as the lay-out of the control rods and the Large number of securing bolts or studs used for securing any parts which are subject to strain help to maintain the Rolls-Royce reputation for longevity and freedom from trouble.
The single-plate clutch is of normal design, and behind it is the four-speed gear-box. An easy-change mechanism is fitted to third and top gears, which are true silent ratios.
On the near side of the gear-box is mounted the mechanical servo-braking system. A cross-shaft driven by worm gears carries a disc ; when the foot-brake is depressed, a clutch is forced into contact with the revolving disc, and the ensuing pull is used to apply the front and rear brakes. In addition, the brake pedal has a direct connection to the rear brake operating shaft, so that the pair on the rear wheels receive twice as much pressure as those on the front. With this arrangement, should the servo-mechanism fail, the pedal is still coupled directly to the rear brakes. A swinging lever balances the pull transmitted to the front and rear sets, and special compensators, which embody a bevel and pinion mechanism similar to that of a differential, equalise the effort between the individual brakes, The hand-brake operates separate shoes in the rear brake drums. An open propellor shaft with two special metal universal joints drives the back axle, through spiral bevel gears. The backaxle is of the fully-floating type in which the weight of the car is carried by the
casing, and the closely spaced bolts round the bevel casing ensure long life and a freedom from oil leakage.
The chassis is of orthodox type, dropped in the centre to lower the centre of gravity, and extremely rigid. The road-springs are of exceptional length and pass underneath the axles. Hydraulic shock-absorbers are fitted. The brake drums are of large size, and the brakes are cable operated.
We took over the” 25 “in a fairly busy part of London, and from the moment we occupied the driving seat we were impressed with the car’s smoothness and ease of handling. Second gear is used for for starting, and the clutch is finger light and absolutely smooth. The brakes were powerful and came on steadily with increasing pressure of the pedal. Third and top gears, the ones generally used, were inaudible, and changing was rendered quite fool-proof by the synchro-mesh mechanism. The change to second gear, which ran with a well-bred and faint hum, was as easy as could be contrived with sliding pinions.
The steering wheel came right into the lap, and a correct driving position was easily found with the readily adjustable front seats. The hand-brake and gear levers were within comfortable reach, and the fact that the near side wing is clearly seen is a great help in traffic. By the time Brooklands was reached the control of the car had become instinctive. There the usual timed tests were carried out, and showed that the performance of the Rolls was definitely up to sports car standards, but in this case accomplished in almost complete silence. A figure which gives a true indication of the car’s potentialities was that of 10-60 m.p.h. in top gear, which, as will be seen, was only 2 seconds more than the figure achieved by using the gears. Interpreting these figures aright we find that the designers of the RollsRoyce car have produced a car that will
put up a fine performance without constant gear-changing, this operation being therefore only required—unless the driver enjoys playing tunes with the gear-boxwhere gradients or traffic bring the engine speed down to the neighbourhood of 500 r.p.m.
Experience on the open road confirmed this idea. On an undulating main road the car would maintain a speed of over 70 m.p.h. indefinitely, and slopes of 1 in 15 or so did not seem to slow the car at all. This untiring travel on top gear was
equally noticeable at a slower gait, the high torque at low engine speeds making it unnecessary to rush hills in order toavoid changing. The maximum speed on the level was found to be 76 m.p.h., while on favourable gradients 80 was attainable without fuss. On winding side-roads the gears were used to some extent, 45 and. 55 being reached comfortably in second and third.
These figures, satisfactory as they are for a touring chassis carrying a luxurious. saloon body, only express a small part of the charm of the 25 Rolls-Royce. An equally important feature of the car is. the way in which it responds to the controls and the untiring way in which its. passengers are conveyed on their journey.
Take, for instance, the steering. Light enough to be handled effortlessly by the so-called weaker sex, it yet combines the high gearing and self-centring action which one expects on the race-bred sports. car. An upright driving position with excellent visibility help to make prolonged driving effortless, and the controls cometo hand with the minimum of movement. The lightness and delicacy of action of the clutch and brakes have already been. remarked on. From 40 m.p.h. the brakesbrought the car to rest in 58 feet, in spiteof the locking of one of the back wheels. This trouble was probably due to oil in one of the drums, which would normally have been attended to when the car camein for overhaul after its Continental trip. With his left foot the driver can reach the one-shot lubrication pedal, which iscarried to all but four chassis points, none of which requires frequent attention. Closer are the starter pedal and the dipping switch for the headlights. This latter arrangement is very convenient, the only
disadvantage being that one is liable to depress the starter switch when wishing to dip the lights. On the latest cars the starter is controlled from the dash. The suspension is such that throughout the speed range the passengers are tm
conscious of the nature of the road surface. This suppleness is achieved without a trace of the objectionable rolling which is often the companion of flexible springing, and the car can be taken round fast bends in the most satisfying way. The comfort of the back seats was as great as that of the front ones, as they are well within the wheel-base, and we were able to make quite legible notes as the car was running at 60 m.p.h. along a road of inferior surface. The car which we tested was fitted with a handsome sports saloon body by Hooper, painted cream, luxuriously upholstered in olive green furniture hide. This particular leather has the advantage of being quite as comfortable as fabric, and is easily cleaned. The coachwork maintained the high standard of silence one expects on Rolls-Royce cars. The back seat is wide enough for three people, and by tilting forward the squab one gains access to a spacious luggage container. The ” 25″ lends itself particularly well to the fitting of the sports saloon type of bodywork, and a number of well known coachbuilders list them. From the front the plated shutters on the deep radiator give the car a dignified appearance, while the
11 foot chassis allows smart yet roomy bodies to be fitted inside the wheelbase.
Turning from the body to the accessories, one of the most important items are the lamps. Part of our joureny was accomplished in darkness, and the Lucas Biflex type fitted proved adequate for fast touring speeds. The dipping reflectors, operated by the foot switch already mentioned, enabled a fair speed to be maintained even when meeting oncoming traffic. Lucas P 80 or P 100 lamps are fitted as alternatives, and for really fast driving on the Continent their more powerful light would be agreeable. The windscreen wiper was a new pattern Lucas, in which the motor is carried at the near side of the screen, well above the line of vision of the passenger, and drives two large blades by means of a neatly enclosed shaft. In this road-test we have considered the 25 Rolls-Royce simply from the point of view of a sports car, an attitude amply justified by its acceleration, and all-out speed coupled with its road-holding qualities and the liveliness of its response to the steering and controls. In actual fact these sporting qualities are present not as an end in themselves, but as a result of the essential soundness of the car as a
whole. It is built simply as a refined vehicle of the utmost smoothnessand. flexibility, and it is equally happy at high speeds and when moving at a walking pace on top gear. All its work is performed with uncanny silence and absence of effort, qualities which make it the ideal town car. Such smoothness, allied to the magnificent workmanship which has always been the keynote of Rolls-Royce construction, must have a great bearing on the length of life enjoyed by the products of the Derby works.
Fortunate, then, is the owner of a 25 h.p. Rolls-Royce, for he has at his behest two or three cars in one. Crawling slowly through London traffic to Lord’s or Roehampton, cruising at 40 m.p.h. through the pleasant countryside of England, or all out along N 7 en route for Juan or Cannes, the occupants enjoy the same silent travel. The handsome radiator, modernised in line but still symbolic of the aims which lie behind the initials ” R.R,” and the dignified and graceful coachwork which of late years our English builders have learnt to produce, together combine to form the Best Car in the World.
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