That remarkable reputation which is now universally accorded to Rover cars has been acquired by a considered policy of making changes in design only when very definite improvements have been carefully envolved and most thoroughly tested before going into production.
Such a policy operates slowly, and if current conditione have further delayed the arrival of a post war Rover new car, the ultimate result has been to give more latitude for the customary thoroughness of testing.
Now that the new P3 Rover has arrived, it makes a very considerable advance in automobile design. It is likely to arouse the enthusiasm of every connoisseur owner, fot it centainly runs like "pure silk", and has that rare and indefinable charm of behaviour which attained only by the best cars in the world.

Current Rovers are indisputably good cars, yet the new design secures not only a considerable improvement in performance but at the same time a reduction in fuel consumption, which is a remarkable double achievement in engineering, and is the result of an entirely new form of cylinder head and valve arrangement.

Before going into details, here is a brief outline of the Rover programme. In order to conform with the national economy endeavour, for 1948 there will be what is substantially only one model, the P3.
This car has an original type of chassis, provided with special form of independent front suspensions and is able to take either the new four cylinder "60"or the new six cylinder "75"engine.
On this chassis may be mounted a fourlight or a six light saloon body. So there will be a choice of four combinations.

The current 10 and 14 h.p. models disappear, and 12 and 16 h.p. models are superseded by the new 60 and 75. The transmission with the famous Rover controlled free wheel, is altered only in detail, the four wheel brakes are quite new, and automatic chassis lubrication has been superseded by the complete elimination of ponts which used to require regular attention to lubrication for such joints are now fitted with rubber bushes, or are permanently packed with lubricant and efficiently sealed.

Different hydraulic dampers for the suspension have been adopted. A special form of interior heating and ventilation has been stadardized. The coachwork is wider, the seats are more comfortable, and there are very many points of detail advance. In appearance the P3 does not differ greatly from the current models, except that the bonnet is slightly less long because the bodywork is mounted farther forward and the wheelbase is slightly shorter than on current 16 h.p. cars, changes brought about by improvement in weight distribution and conservation of weight.

The unusuel appearance about the new engine of the P3 Rove gives an indication of the mechanical advance of its design

The new engine is onbiously the first matter of interest. It could baldly be classified as one with overhead inlet valves and inclined side exhausts, but such a classification is quite inadequate to cover a step forwarrd which is duly patented. The truth is that the cylinder head, combustion chamber, piston crown, valve arrangement and plug position have been specifically designed and coordinated so as to secure a new advance in sheer efficiency of operation, especially on fuels of relatively low octane value, and also in essentially practical utility, meaning that the efficiency can be maintained without frequent recourse to adjustment or replacement. These points will be explained.

First let us refer to the cross section of the P3 engine on the right. It will be seen that the joint between the cylinder block and the cylinder head is inclined at an angle. In the cylinder head, at right angles to this joint, the inlet valve is set overhead, and to one side of the cylinder bore. The valve is a large one and has a relatively shallow lift. The exhaust valve is carried in the cylinder block and ennters the combustion chamber at a considerablly inclined angle. The the crown of the piston is carefully shaped so that the space between the closed inlet valve and the piston crown is at a minimum. The side of the piston crown adjacent to the exhaust is shaped so that the resulting combustion chamber is approximately the half of a sphere. The sparking plug is in the centre of the flat side of this hemishere.

Now to count up the engineering advantages which this very carefully developed arrangement should provide. It is, in fact, a development of automobile engine design which is more tan likely to prove superior on all counts to the long cherished ideal of a hemispherical combustion chamber with inclined overhead valves. First, on the physical side, the Rover P3 head places the sparking plug in the centre of the flat side of a hemisphere, so that the lenght of flame travel is equal in all directions, and at a minimum. This reduces combustion time, shortens the flame travel, and permits the use of an increasedexpansion ratio. Then the small volume left between the inlet valve and the piston crown ensures that the "end gas"- that is , the gas remote from the point of propagation of the flame, namely the sparking plug - presents a very small area, ans also is surrounded by relatively cool walls. That reduces the tendency to detonate.

Again, the shape of the head and piston crown causes a controlled turbulence of the charge under compression, giving an assured homogeneity to the charge. It also causes a scouring effect over the sparking plug. Finally, the combustion space can be easily machine to shape.

Because of these and other gains it becomes possible to use a high compression ratio with low octane fuels, and at the same time to burn satisfactorily under all conditions a weaker mixture; that is, a mixture with a higher ratio of air to gas. Moreover the operation is less than usually sensitive to ignition timing. The net result of all these points in plain language is that the new engine produces considerably more power for considerablly less fuel consumption, is able to deal with poor fuels as well as good ones, and is much less liable to pinking than ordinary engines. It also has a considerablely increased felxibility.

One has only to drive the car to appreciate that this is the truth. On 72 octane fuel there is no sign at all of pinking even ir one tries to produce it. And the engine has a response to the throttle pedal which is both powerful and elastic. In technical terms the particular development has been to raise the b.m.e.p., or brake mean effective pressure, to a figure of 126lb per sq in instead of the 104lb per sq in of earlier engines, and to maintain the high figure over a wider range of engine speed. Bearing in mind that this advance has been accomplished with 72 octane fuel, one cannot help wondering what the P3 engine could made to do with 85 octane fuel.

It may be recorded that the new Rover engine was nearing the production stage at the outbreak of the war. Since then te test record show that a total of test bed and road running equivalent to 600,000 engine miles has been built up.

Current Rover practice has been continued in the gear box, which provides four speeds with a particulary good sunchromesh mechanism on third and top. A neat short gear lever is brought well back close to the driver's left hand, and mounted on the chassis so that it is unaffected bu movement of the power unit on its rubber mounting. At the back of the gear box is an inbuilt controlled free wheel, which permits noiseless and easy gear changing without touching the clutch pedal, merely by releasing the throttle and moving the gear lever. Another excellent Rover feature is that the sliding telscopic joint for the propeller shaft is not exposed but is contained within a tail extension of the gear box, where it is automatically lubricated and protected from road grit. The tail of the gear box on the new car has been extended so as to allow a shorter open proppeller shaft to be used.

Next comes a very intersting departure from the orthodox, the new frame, which is designed to provide the utmost rigidity where it is wanted, and yet at the same time to conserve the weight of the car as a whole. This frame starts at the front end with a downwardly arched crossmember of large box section.
Running rearward from this there is on each side a box section side member which reaches a considerable depth at a point adjacent to the gear box position, and which then tapers again to its extremity. The frame ends are not at the extreme rear of the car, but reach only as far as the front ends or the half elliptic rear springs. The rear ends of the springs are anchored to a cross member in the tail of the steel coachwork, which is amply stron and rigid enough for the purpose.

This composite construction save weight, cuts out a redundant part of the orthodox frame, and permits greater strenth to be built into that most important part of a frame, the forward end. The side members are quite straight and flat in side view, but incline outwards toward the rear. They are very rigidly braced together by a box section cross member situated close to the back end of the gear box, and from the centre of this cross member channel section diagonal members run forward to meet the front cross member and the front ends of the side members. From the point where the main loads from the independent suspension occur, right back to the front ends of the rear springs, this frame is stiff in every direction, end to end, diagonally, and torsionally.

The Rover engineers have been somewhat slow to move over to independent front suspension for reasons which can be well appreciated. I.f.s. has been, and still is, by no means an easy nut to crack, for with the easier riding ans slow motion springing it is apt to introduce imperfect steering and a less certain stability.
Rover engineers of the well proven good features of current beam axle design when the did adopt i.f.s. That wish led to a very thorough study of all the problems involved and an equallly thorough examination of different designs, coupled with searching trials. As a result a form of i.f.s. was evolved which is not intrinsically novel, but which is most soundly designed.

Independent front suspension of the new Rovers

It reference be made to be illustration above it may be seen that the govering gactor in this suspension is the employment of radius arms, which have their rear ends anchored in brackets attached well back to the diagonals of the frame structure, at a point which by a steel stiffener to the box sections side members. Each radius arm terminates a large ball, which is contained in a spherical rubber bush carried within a box housing. To follow out the structure is will be easier to regard the suspension on one side. The front end of the radius arm is rigisly attached to the lower endof an approximately verical yoke forging, which has on its outer side the boss for the steering swivel pin carrying the stub axle, brake drum and front wheel. At the foor of the yoke and on its inner side is the housing for a rubber bush, and to each end of the pivot pin of this is attached the outer extremity of a channel section twin armed link, or wishbone.

At a short distance from the pivot pin these twin arms swell apart and are joined together by a circular pan which provides the lower abutment for the slow rate coil spring of the suspension. The wishbone continues inwards and forwards to a point close to the centre of the large box section front corss member of the frame, where there is a bracket containing a rubber bush and a pivot pin anchorage. Incidentally this bracket also provides a vertical bearing for the central arm of the steering connections. Going back to the yoke, it will be seen that at its head is a rubber bush bearing at the outer end of a link which is carried at its inner end by an Armstron twin piston hydraulic damper mounted on the top of the frame.

Ther is no direct metallic contact anywhere between the linkage and the fram, but always rubber bush insulation to damp out shock and road noise; and no lubrication is needed. The use of radius arms attached rigidly to the yoke ensures that rubber can be used without introducing too much flexibility into the steering. An extension of the bracket carrying the hydraulicdamper provides the upper abutment for the suspension coil spring, inside which are rubber snubbers. The ends of the spring rest on rubber pads, so there is not metallic contact at those points.

This same illustration of the front suspension also shows the layout of the steering linkage, which employs a trak rod divided in the middle and coupled to a central arm. From this arm a drag link runs to the steering gear box. All the joints in the steering are either self sealed with lubricant or are rubber bushed. It mau be noticed that this sketch, and the large drawing of the complete car, show left hand steering. Cars for the home market will, of course, have the customary right hand steering.

Stability for cornering fast is enhanced by an anti-roll torsion bar which is mounted on the frame which has its ends coupled to the steering swivel yoke pieces.

To drive a P3 is to note in the first few miles how excellent is the steering in every possible respect; light, direct, and with no over steer. One notices also how directionally stable the car unqueationably is. It is quite an outstanding piece really effective design. Incidentally the geometry of the suspension removes any tendency for the front of the car to dip when the brakes are applied hard, and that in itself provides a pleasant sense of driver mastery. The half ellliptic underslung rear springs are now carried on rubber bushes, and the blades are lubricant packed and enclosed in sealing gaiters.

Not the least interesting feature is the arrangement of the brake system. Independent front suspension renders mechanical brakes ont he front wheels very awkward to embody; hence the general swing over the hydraulic operation of front brakes. The law, on the other hand, says that there must be a mechnically operated brake on the rear wheels. So the hydro-mechnical brake becomes the obvious solution, and that is what is used on the new Rover. But matters are carries a step further. The trailing shoe has been made into a hydrostatic type; that is to say, the shoe lining is always in light contact with the drum, and is self adjusting. Only the leading shoe needs periodic adjustment. Moreover the trailing shoe has no servo action, and hence can be hydrstatic without introducing any tendency towards overheating and grabbing. The next result is to obtain good brakes, light to operate and not sensitive to condition of linings.

To turn now to the new coachwork. Beyond the window arrangement, the difference between the four light and six light saloons is not great, except that the four light is a little lower in the roof. These bodies are about 2½ inches wider than previous models, and are mounted about 5 inches farther forward on the chassis. This brings the rear seat farther withing the wheelbase and gives an improved weights distribution for riding comfort and for slow rate suspension. The seats are a new design especially aimes at giving practical support to the back, as well as comfort.

On each side of the rear seat there is a softly padded elbow rest, and in the centre is a folding arm rest. These rests slope a trifle down as they run forward, which look unusual, but which proves to support the arms in a natural plane. There are also soft elbow rests on the forward doors. One excellent point about the front seats, which are adjustable for leg reach, is that the driving seat is also adjustable for height by means of an easily operated handle. There are pockets in all four doors, and draught preventing glass louvres over the drop windows. On eacht side there is a scuttle ventilator. A sliding roof is provided, and the window on the driver's side has a quick lift lever. Control of ventilation is therefore well planned.

But this is by no means the total, for the car has a standard equipement an inbuilt heater and air conditioning plant. On the front face of the dashboard bulkhead are mounted an eletrically driven fan and a small radiator unit. A large duct runs forward from the fan to an air intake concealed in the radiator shell and just above the header tank, so that the fan draws clean fresh air from the very front of the car, the radiator of the unit is fed with hot water from the front of the engine, and the supply is controlled by a cut off cock. Warm or cold air can be circulated as desired. The main outlet into the body is beneath the centre of the scuttle, but ducts are also provided which play a thin stream of hot air through a narrow slot running the whole length of the base of the windscreen, so preventing misting or icing.

The dash rail and facia board are nicely finished in walnut, and the instrument panel iis of the familiar Rover style, with dials grouped in the centre. Below this panel has been added another, which provides for the mounting of an H.M.V. radio set as an extra. The speaker is mounted in the peak of the roof.

There are some further goos practical driving points to mention. Now that control over ventilation and warmth has been established, together with demisting of the windscreen, there is no longer any need to make the screen open. It can be fixed, and so be better sealed, besides adding something to the rigidity of the front of the body. Also the new type of screenwipers can be adopted, in which the twin blades are set in motion or arrested by pressing a single switch. Another point is that ths main lighting switch is mounted very neatly on a bracket on the steering column, below the wheel, where it is convenient to reach. The dipt switch is at the centre of the wheel.

Perfection in refinement of running i not obtained on any good car without a great deal of unseen work being put into the matter. By looking at a Rover one would never guess that every single steel pressing or unit of the interior instruction that might be conceivably drum from small vibration, or transmit noise, is well coated with anti drumming compound. This is one of the reasons for the very quiet running on the road.

This very fine new British model is a great credit to its makers, and is likely still further to add to their specialist's reputation.