Tests and Reports

On August 10, 1949, an article about the ROVER project "M1" appeared in "The Motor" under the title Beyond the Back-room Door - two years after its discontinuation. As far as we know, this is the only article that dealt intensively with the "M1". And the article is based on an interview with Maurice Wilks, the ROVER chief engineer. That's why we don't want to keep it from you.

Beyond the Back-room Door
The Hitherto Unpublished Story of a Rover Economy Project Which Illustrates Both the Extensive Nature of the Experimental Work Which Goes on Behind the Scenes at Solihull and the incidence of Changing Economic Conditions on Current Manufacturing Policy
By Harold Hastings

„There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.“ - Shakespeare

From time to time members of “The Motor“ staff find themselves in the privileged position of driving cars which, officially, do not exist. For obvious reasons, a policy of silence is generally imposed where these experimental and prototype models are concerned, but this reticence is not without its unfortunate aspects. Were the public more fully aware of the vast amount and scope of the experimental work which goes on behind the scenes, there would be a greater appreciation of the enterprise which has gone into making Britain the largest exporter of cars in the world, and politicians would, perhaps, be less liable to put forward ill-considered suggestions for reorganizing an industry about which many of them have very little real knowledge.

lt is for this reason that l am particularly grateful to the Rover Co. Ltd., for permission to write about a prototype - which I was recently allowed to try - of a model which, for various reasons which will be dealt with later, may never be produced by its originators. The fact that this car happens to be a Rover I regard as singularly appropriate as illustrating the diversity of experimental work carried on in a factory which (apart from its work on gas turbines - which is another story entirely) is normally regarded as pursuing a consistent policy of development along well-defined lines.

Mr. Maurice Wilks, the Rover chief engineer, gave me the background of the M1, as the model is known in the works.
"As you know," he said, "we were engaged on the development and manufacure of Meteor jet engines during the war, and it was not until V.E. Day was in sight that we were able to consider the sort of motorcars we should make when peace came along.
“Obviously, we should have to restart production with a range of models closely corresponding to our pre-war types. At the same time, it appeared to us that there would be a big demand for economy. lt seemed plain that petrol would remain short for some years and that this would automatically create a large market for small-engined cars with low fuel consumption.

“As you know, this demand for minimum fuel consumption did not materialize and people still do not seem to be as interested in petrol economy as one would expect, if it involves the slightest sacrifice in passenger accommodation.
“To return to the M l, our idea was that there would also be scope for a really small quality car which would appeal to people who had run more-expensive types in the past and wished to retain the same standards, even if economy of running forced them to use much smaller vehicles.
"That was the origin of the Ml. The first idea was an open car. l think I can show you a small-scale model. Yes, here it is. Later, we decided that closed coachwork would be required, and we added a saloon top."

Mr. Wilks produced the two attractive streamlined models shown in one of the accompanying illustrations (Please the the 'Technology' page for illustrations - Webmaster).
"That was the original outline," he went on. “As you will see, the frontal appearance is entirely in keeping with what are now current ideas in styling. At the time, however, we felt that the public was not yet ready for such modern frontal treatment, and we later adopted the compromise between the old style and the new, which you have seen in the prototype car.
“Having developed the Ml to this stage, various things happened. First, we found that we could not get adequate supplies of steel for the planned production of the existing range, let alone for an additional model.
"Then there came the Government call for rationalization - you know, the 'one-maker-one-model' cry - coupled with an official emphasis on medium-sized cars in the belief that such models represented post-war requirements in the export field.

These political influences, backed by the changes in the taxation scale which took place, all tended to reduce the emphasis on the really small car.
“ln the face of so many external influences, we reluctantly decided that the place which we had foreseen for the Ml in the post-war market would not materialize."

Accordingly, development of the Ml was abandoned at the early prototype stage and the model illustrated on these pages must, therefore, be regarded as a basic conception rather than a finished product. Many notable features, however, emerge from an examination of the design, which was evolved with the primary objects of saving space and weight - both of paramount importance if adequate passenger accommodation and roadworthy performance are to be obtained with a small and economical engine. Perhaps the most interesting feature of the whole design is a breakaway from both the conventional chassis frame and from the popular alternative of a combined pressed-steel body~cum-chassis construction.
The basis of the Ml is a platform-like structure fabricated from light-alloy pressings. As will be seen from one of the drawings, main longitudinal stiffening is provided by a central backbone which encloses the propeller shaft, whilst additional longitudinal and transverse stiffening is obtained by flanged sides and channel-section ribs spot-welded to the platform to form box-section bracing. At the front of the platform, a further fabricated construction provides a boxed double dash, which serves both to give rigidity to the body and also to provide a mounting for the cantilever structure which carries the engine. At the rear, the platform is extended upwards and well braced by means of triangulated pressings to act as a support for the body and an abutment for the rear coil springs.

The result is a very light but strong structure, which not only serves the normal purposes of a chassis frame, but also provides additional stiffening for the light-alloy body, which fits round it like a shell and can thus be of lighter than normal construction without sacrifice of rigidity. A kerb weight of 13½ cwt shows how successful these measures proved.
A feature of the independent front-suspension system - which is by coil springs and swinging links - is that the upper member on each side serves only to hold the wheel in a vertical plane, brake thrust and torque reaction being taken by a forged arm which swings about a pivot point below the gearbox at its inner end and carries the king-pin boss at its outer extremity; the lower assembly is completed by a further link, which connects the outer extremity of the forged arm to a pivot point beneath the engine and thus gives lateral location, this link also incorporating the movable abutment of the coil spring. Thus, the lower assembly forms a triangle with an unusually wide base, and careful attention to geometry has made possible the use of rubber bushes throughout with a consequent elimination of lubricating points.
At the rear, coil springs are again employed and a conventional axle is used in conjunction with radius arms and a Panhard rod. As at the front, rubber bushes reduce maintenance to a minimum.

High-octane Design
As will be seen from the drawing, body space has been gained by mounting the engine unusually far forward, the rear of the cylinder block actually being almost level with the front hubs. ln general layout, the power unit may be regarded as a 700 c.c. edition of the design which has now become familiar in current Rover models, with the split between the cylinder block and head inclined at an angle to permit the use of a part-sphcrical combustion space, the overhead inlet valves being arranged at 22 degrees to the vertical and the side exhaust valves inclined at 55 degrees. As a result, extremely good breathing and turbulence are obtained, together with pronounced anti-knock properties. In the latter respect, it is interesting to note that a compression ratio of 9 to 1 figures on the prototype, this ratio being adopted in the expectation that pre-war fuels with an octane rating in the neighbourhood of 80 would have again become obtainable by the time the car went into production. This high ratio, in conjunction with the use of 80-octane fuel for the bench tests, in fact, accounts in part for the exceptionally high output of 28 b.h.p. at 5.000 r.p.m. and illustrates how designers are handicapped by present low-grade fuels.

Another notable point about the engine is the relatively square stroke/bore ratio, with its pronounced advantages in keeping piston speeds low. Thus, at the peak engine speed of 5,000 r.p.m. the piston speed is only 2.250 ft. per min., whilst with the high axle ratio employed a piston speed of 2,500 ft. per min. corresponds to a top-gear road speed (81 m.p.h.) well in excess of the normal maximum, In other words, this Rover Ml is one of those cars which can be driven indefinitely at its maximum speed in top gear without any qualms regarding overrevving.
This propensity for effortless cruising on the road was notably in evidence when I took the car for a short run. Naturally, the high axle ratio made the gear lover somewhat in demand when brisk acceleration was required, and third gear was also called for on main-road hills of the order of l in 20 if cruising speed were to be maintained. On the other hand, 50 m.p.h. proved to be a relatively effortless pace on the quiet third ratio, and it was quite obvious that very creditable averages could be put up by a driver who did not mind using the gearbox.
I was not able to test the actual top-gear maximum accurately, but it appeared to be in the region of 58-60 m.p.h. In a vehicle of this type an easy gear change is more than normally important, and the Rover showed up particularly well in this respect. Owing to the forward placing of the engine-gearbox unit, the designers were faced with the provision of some form of remote control and the type finally adopted incorporates a “walking- stick" type of lever protruding through the facia board, somewhat after the style found on certain cars with front-wheel drive, where a similar problem exists. This arrangement I found particularly satisfactory, with positive engagement and comparatively small lever movement.

Suspension and Steering Features
The suspension system provided a very comfortable ride of the moderately firm order with very little roll or pitching, the only obvious fault being a pronounced over-steer tendency, which became marked above certain cornering speeds. This, incidentally, is a characteristic of which the manufacturers are fully aware and one which would certainly have received attention had development continued, one possible solution contemplated being the use of an anti-roll bar at the front to increase weight transference on the front wheels during cornering and thereby alter the drift relationship between the front and rear tyres. The steering itself was notably light and although, at first, the l5-in. steering wheel seemed rather small, one soon became used to it and, in fact, to appreciate its advantages in a small car, where the steering effort required is slight in any case. A turning circle of only 28 ft. 6 ins. was also much appreciated.

Of the body itself, I do not propose to say very much since here, again, considerable modifications would probably have taken place had the car reached the production stage. Notable points were, however, the excellent elbow room at the front, brought about partly by the full-width body and partly by the use of sliding windows which permit fully recessed doors, which, in the case of the Ml, have made possible an internal width at elbow level of no less than 52½ ins. in a car with an overall width of only 56 ins. Good headroom (34½ ins. from seat to roof) was also notable.
On the prototype, the rear seats were of the occasional folding type intended for two children or one adult, but here, again, modifications were under consideration by which normal rear seating would have been adopted. These, and various other development plans, were under consideration at the time it was decided not to proceed with the project. Even so, the prototype as it stands represents a most interesting answer to the problems of providing a really economical small car of a type which would appeal to a large number of buyers, both in this country and abroad. Had economic conditions not prevented its further development, there is no doubt that the Rover Ml would have proved a most popular addition to the range of British cars, and one which, moreover, would have greatly enhanced Rovers popularity in a new sphere. It seems, in fact, most unfortunate that economic conditions should result in such a promising design being set aside.

Note:
The illustrations enclosed with the original article can be found under ⇒ ‘M1’ Technology