Rover P6

In the 1950s, Rover had a reputation for providing solid, reliable, if conservative, cars for the upper-middle-classes. Not without reason was the P4 (released in 1949), nicknamed Auntie: it was sturdy, dependable, well-built and comfortable – and just the sort of car Auntie would buy.

The P5 was an altogether larger, more luxurious and conventionally designed car, powered by a 3lt six-cylinder engine and was the choice of the successful company executive.

But there was another side to Rover that was at the forefront of automotive design.

The Land Rover was released in 1948 and virtually created the civilian 4WD market. The Range Rover was a later development from Land Rover that effectively invented the up-market recreation vehicle.

During the Second World War the Rover company was involved in making Meteor engines for the Cromwell tank and, most importantly, the development of Frank Whittle’s jet engine.

After the war, Rover engineers were certain that gas-turbine (jet) engines could be used to power motorcars and set about creating a number of prototypes. This was to become an important aspect in the development of the P6.

Rover was led at the time by the brothers Spencer (General Manager) and Maurice (Chairman) Wilks. The team working on the Turbine and P6 projects was led by Maurice’s son Peter, under Chief Engineer Robert Boyle, with Peter’s cousin Charles Spencer “Spen” King, Gordon Bashford and stylist David Bache.

The first gas-turbine prototype, TX1, but better known by its registration JET1, appeared in 1950 and by 1956 the T3 prototype, with a steel baseframe with fibreglass outer panels, was almost production ready.

In 1961 the design had been refined on the T4, which embodied most of the ideas that would eventually end up in the P6.

In terms of styling, the body of the T4 appeared much as the P6 would, with the main difference being it had a sharply sloping front with headlights that sat proud, much like the Bugeye Austin-Healey Sprite.

Thankfully, this design was neatened up considerably by effectively cutting the front of the body off square and installing dual headlights in the slightly recessed grille.

But four main problems with the jet engine were proving difficult to overcome. These were significant lag in throttle response, high exhaust temperatures, the cost of production and, probably most importantly, fuel consumption: reportedly as high as 10mpg.

Rover hadn’t given up on the idea of a turbine car and development of the P6, which was destined to replace the P4, continued along the lines of this power source hopefully being used in the future.

The engine bay of the P6 was therefore designed to be large enough to take the turbine engine, as well as a conventional petrol engine.

It was also important that the front suspension had to be compact enough that it didn’t intrude into the engine bay. The result became known as the “bell crank” or “round the corner” system, whereby the top control arm acted through a linkage onto coil springs, which were horizontally-mounted directly on the scuttle, the strongest part of the structure. The long-travel suspension provided excellent road-holding but with a supple ride.

This was helped by the independent rear trailing arm suspension which incorporated a sliding-tube De Dion rear axle (an improvement on the regular De Dion axle) that was stabilised with a Panhard Rod, while the differential casing was mounted directly to the body on rubber bushes.

Added to this were four-wheel disc brakes, with the rear discs mounted inboard, acting directly on the drive shafts, thus reducing the unsprung weight.

The basic body structure was to be a monocoque baseframe: being a “base unit” that formed a “safety cage” onto which all the outer panels were bolted, including the roof.

Meanwhile, development continued on an all-new petrol engine for the car, in 2lt (1978cc) overhead camshaft form.

This incorporated an aluminium Heron head, which was distinguished by having the combustion chambers in the tops of the pistons, rather than in the head itself.

Examples of other engines that have used Heron heads include the Ford Kent crossflow, Jaguar V12 and Volkswagen Wasserboxer (water-cooled boxer).

With a single HS6 (1¾”) SU carb, Rover’s engine gave a maximum torque of 112 ft lb at 2,700rpm and power of 99bhp (74kW) at 4,700rpm – which was always considered a little under-powered for the car.

The gearbox was also a new design and incorporated synchromesh on all four forward gears, which was another rarity of the time.

Part of the plan involved building an all-new factory to handle the production of the car, but in this there was a snag.

At the time, expansion of the British motor industry was controlled by the UK government’s ruinous decentralizing policy of only granting permission for new factories to be built in “development” areas – that is, of high unemployment – rather than being close to where the main factories already existed. Rover reached a compromise and was permitted to expand its factory at Solihull to assemble the P6, but had to build a new factory at Cardiff, Wales (about 120 miles, or 195km, away), to produce the gearboxes and rear axles.

Delays caused while the Cardiff factory was built actually worked to Rover’s favour in one respect. It gave them the time to thoroughly test the fifteen prototype cars, which covered a combined distance of over 445,000 miles (about 720,000km).

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The BMC Experience Issue 8. Jan-Mar 2014 Magazine

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