The Rover Jet Cars

When the world seemed to be breathlessly waiting for a new motive power for cars...

by Julian Edgar

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The 1950s were a very different time to today. The Allies had won the war only a handful of years earlier; Germany and Japan were rebuilding after the destruction of the war - and were furthermore working under quite restrictive terms set by their conquerors.

Britain had optimism and confidence… mixed with trying to overcome the terrible financial, economic and social toll that had been extracted during the war years. The confidence was largely in technical matters: the inventers of radar and (so they considered) the gas turbine engine – not to mention, for those in the know, the electronic computer.

It was a time for innovation and development – so meet the gas turbine Rovers.

Already involved in developing the jet engine through their wartime work, it was shortly after the war ended that Maurice Wilks of Rover suggested to his brother Spencer that they should consider developing gas turbine cars. By the end of 1945, work had begun.

The first successful engine – the T5 – produced 100hp at 55,000 rpm compressor speed. It also weighed less than a then-standard Rover car engine. The more powerful T8 engine was tested in a boat and then installed in a modified P4 Cyclops 75 car, appropriately equipped with the (real!) number plates: Jet 1.

Jet 1

Jet 1 was the world’s first gas turbine powered car. Compared with a normal P4 75, the turbine car had its top removed and the bodywork smoothed – even to the extent that the rear doors were welded into place. Large air inlets were positioned on the flanks ahead of the rear wheels.

It first ran on March 4, 1950. In this initial form, Jet 1 was capable of 85 mph, had a 0 – 60 mph time of 14 seconds, and had a best fuel consumption of 6 mpg.

In 1952, Jet 1 was restyled slightly and was fitted with an uprated engine boasting 230hp. It then achieved a world record speed for gas turbine cars of 152.69 mph.

Jet 1 had a mid/rear mounted engine, was not fitted with a heat exchanger (to capture otherwise wasted heat) and used a twin-shaft design. The main engine section used a centrifugal compressor and an axial turbine. Power was taken from another turbine that drove the output shaft through helical reduction gears.

The compressor operated at up to 40,000 rpm (with light-up at 3,000 rpm) while the power take-off turbine had a maximum speed of 26,000 rpm. Again, best fuel consumption was 6 mpg. The fuel tank was located at the front of the car; behind the front air intake was an oil cooler, the same unit used on the Land-Rover. The exhaust outlet of the turbine was directed upwards through two grilles placed on the horizontal deck behind the seats.

Mounted in the centre of the woodgrain dash were no less than 12 gauges. These included a 140 mph speedo (presumable the needle was off the scale during the record run!), bearing temperature, oil inlet and outlet temperatures, compressor pressure (the gauge calibrated to 60 psi), oil and fuel levels, oil and fuel pressures, compressor rpm and turbine outlet temperature, and an ammeter.

T3

The T3 was the first Rover specifically designed around a gas turbine engine. In October 1956, Rover produced a brochure detailing the car. From the brochure:

Since experimental work on 'JET 1', the world's first gas turbine car, began in 1946 there has been intense activity at Solihull, headquarters of The Rover Company. In 1955 a second prototype was produced which had a rear mounted gas turbine in a normal saloon body. [This second turbine car was so ugly that photos of it were stamped ‘secret’ and it was never publically trumpeted.] But now comes 'T.3', Rover's first practical, specially designed gas turbine-powered motor car.

One of the most important results achieved during the years of research has been the development of a gas turbine engine, less than half the size of the original. Thus 'T.3' represents tremendous technical progress and puts Britain well ahead with its advanced specification. With its heat exchanger, fuel consumption approaches reasonable figures and further research in this direction is expected to result in considerable improvement.

This model is in no way a final design, representing only another stage in Rover Gas Turbine development. There are still several problems to be solved, both in respect of body style and engine arrangement, before a truly operational car can be produced.

The chief advantages of a turbine-engined car include lightness of the unit relative to the power it will develop and the absence of radiator or other cooling equipment, clutch and multi-speed gearbox. The Rover 'T.3,' although only a preliminary design, makes full use of these advantages and is a roomy two-seater saloon of small overall dimensions and light weight.

With the engine mounted at the rear it has been possible to design a body having a low bonnet line which, together with a deep wrap-round windscreen and large rear window, gives exceptionally safe visibility. Bodywork is of glass-reinforced plastic, while four-wheel drive and a De-Dion rear axle are included in the technical specification. Four-wheel drive is considered a desirable safety factor on a car that has such a high torque to weight ratio.

The engine is a development of the well-known 1Sj60 industrial gas turbine, and consists of a single stage centrifugal compressor with a maximum speed of 52,000 r.p.m. driven by a single stage axial turbine re-designed so that it takes only sufficient power from the gas stream to drive the compressor and fuel and oil pumps. A second single stage power turbine has been added which takes the remaining power from the gas stream and drives the front and rear differential units. This reduction gear also incorporates a reverse gear which can be selected by a central control lever.

A plate-type secondary surface contra flow heat exchanger is mounted on top of the engine and takes heat from the exhaust gases to heat the compressed air before it enters the combustion chamber. The exhaust is ducted at about 200°C. to a square opening in the top of the boot lid, which also incorporates an ejector orifice to ventilate the engine compartment. At 52,000 Compressor r.p.m. the engine develops 110 B.H.P. with a pressure ratio of 3.85/1, a maximum temperature of 830°C. and an air mass flow of 2 lb/sec. The self-sustaining speed of the engine is 15,000 r.p.m.

As with all turbo cars, the only pedal in addition to the accelerator is the brake, which together with the handbrake and the reverse gear constitute the total controls. The four instruments under the eye of the driver are for jet pipe temperature, compressor r.p.m., speedometer and combined oil pressure, fuel level and ammeter.

Fuel consumption figures were quoted as being:

Steady 40 mph

13.8 mpg

Steady 60 mph

14.3 mpg

Steady 80 mph

12.8 mpg

The standing start 0- 60 mph time was 10.5 seconds and the 0 – 80 mph time was 17.7 seconds – both very rapid in 1956.

Unlike Jet 1, in the T3 the engine was mounted over and behind the rear wheels, rather than ahead of them. Reduction gearing from the power turbine to the wheels took place in three stages: two helical gear sets and then the final drive that comprised a crown-wheel and bevel. The four-wheel drive system used a freewheel between the front and rear differentials.

Many ideas from the T3 turbine car were integrated into the production P6 model of 1963. These included the De Dion rear suspension, four wheel disc brakes, and all-coil suspension. In fact, the production P6 had an odd front suspension designed to allow room for a bulky gas turbine to be fitted to it. However, neither the turbine nor the all-wheel drive were ever seen in the production car.

T4

The T4 was as close to a road-going turbine car as Rover produced. Based on the P6 2000 model (still two years away from release) but equipped with a different nose, the 2S/140 engine located at the front drove the front wheels.

Oddly, rear suspension went from the T3 (and production P6) De Dion rear end to independent swing arms, although still with coil springs.

At the time of release, Rover claimed that the T4 could be produced in three years – if the market was ready to accept it at a price of £3,000 – £4,000. (At the time, the most expensive production Rover cost only £1,948.)

However, it is suggested that even Rover realised by this time that the writing was on the wall for turbine-powered cars.

Author Graham Robson got to drive the T4:

Starting drill is simple but drawn out - turning the key actuates the special Lucas starter motor which winds away for several seconds. A faint, distant whine rises in pitch and intensity before light-up occurs and the engine settles down to 'idle' at 35,000rpm. This is enough to cause the car to creep along the road if the brakes are not applied, as there is about 4bhp residual at idle.

To get moving engage forward gear and depress 'loud pedal' - after a jet lag of about 3 seconds, the engine speed rises rapidly to 50,000rpm and the car whooshes off up the road leaving engine noise behind (although this is quite acceptable to passers-by). 60 mph is reached in 8 secs (a la 3500S) with very civilized handling.

Rover-BRM

The last of Rover’s experimental gas turbine cars was the Rover-BRM racecar. A widened BRM Grand Prix chassis was used as the basis of the car, and the 150hp engine was a development of that used in the T4. Drive from the rear-mounted engine was to the rear wheels through a gearbox that gave both forward and reverse (however, reverse gear was fitted only because race regs required it - it wasn’t to be actually used). Fuelled with kerosene (the other Rover gas turbine cars could run on a variety of fuels, including kero and petrol), the car used a 48 gallon tank.

The car was entered in the 1963 Le Mans 24 hour race, where it would have finished eighth, had it been a formal entry within the existing classes.

In 1964 it was fitted with a new body and the engine was modified to incorporate a heat exchanger that used ceramic discs made by Corning Glass Works of the US. However, the car did not compete in that year’s race because of a lack of test time and the car sustaining damage in transit.

In 1965 it ran in Le Mans as an official entry, with Graham Hill and Jackie Stewart driving. In this race, it achieved 10th place, averaging 98.8 mph (159 km/h).

In 1966, the motoring media scored a road(!) test of the 1965 Le Mans car.

The first two things everybody wants to know about a turbine car are whether it uses a lot of fuel and whether there's a big acceleration lag. The car we tested had the latest Owens Corning rotating ceramic heat exchangers, which had made an enormous difference in thermal efficiency. If you drove it fast the consumption (of kerosene) was not excessive relative to the performance. When idling, or at lower speeds, fuel consumption was poor, but of course this car wasn't designed for that kind of use.

We found that the acceleration lag was very pronounced. It is essential to anticipate by at least two seconds the need for full power; this leads directly to the one great, modification necessary in driving techniques - the left foot must be used for braking, the right for acceleration and the two must be played against each other simultaneously.

For some reason we expected a complicated starting routine. In fact, it is simpler than a conventional car; you switch on the ignition and push a spring-loaded starter button - no need to hold it down because it has an automatically engaged circuit to keep the electric motor engaged. By 20,000 rpm the engine is just about self-sustaining; the starter cuts out at 30,000 (a green warning light goes out) and the engine accelerates to the impressive idling speed of 35,000 rpm. All this takes rather a long time of course -some 12-15 sec - but on the other hand, you can then drive it flat out because there is no such thing as warming-up.

When you bang your foot down on the accelerator, the tachometer of the compressor turbine accelerates at an increasingly rapid rate until it reaches its governed maximum of 65,000 rpm. As it approaches this speed, the acceleration becomes impressive - until it does so it tends to be leisurely, so the performance available depends strongly on successful anticipation.

Starting from rest you simply hold full throttle until the compressor turbine revs reach 65,000 and then release the brakes. Under these conditions the engine develops its maximum torque but with a Le Mans final drive ratio and no lower gears, there is no question of wheelspin; it will, in fact, re-start slowly on a l-in-4 gradient but not on a l-in-3. So from a standstill to 50 mph takes 9 sec, about the same as an MGB or a Porsche SC.

But at this stage it is just reaching the conditions for which it was designed and the next 50 mph up to 100 mph comes up in only 16.4 seconds.

On a banked circuit we timed a speed of 127 mph and this represented a very unfavorable condition since the car had to be held hard down on the banking. From our experience with other cars we estimate that this corresponds to a maximum speed in the region of 140 mph. During our short possession it was not possible to check this, but at Le Mans the car was officially timed at 141-142 mph on the Mulsanne straight. Since that time it has acquired a slightly more efficient heat exchanger which has reduced its output by a few bhp.

The engine is always perfectly smooth although far from quiet. The whole feel and sound of the unit and the way its revs rise to a constant value during hard acceleration is exactly like that of a jet aircraft taxiing on the ground.

With the latest rotating ceramic heat exchangers, which are fitted to this engine, we found that fuel consumption at high speeds is very moderate; for example, it does 17.5 mpg at 100 mph and there are very few sports cars indeed which will equal this figure. In the region of 40-50 mph it returns figures about 25 mpg and by far the best results are obtained by dropping below this speed as little as possible.

Over nearly 700 miles running we averaged about 11.8 mpg. The worst average was 9.9 mpg on the performance testing day when there was much standing around, and the best figure of 14.1 mpg resulted from a fast 120 mile run on quiet minor roads.

All the main Rover gas turbine cars are on display in UK museums – the T3, T4 and Le Mans cars at the Heritage Motor Centre, Gaydon; and Jet 1 at the Science Museum, London.

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