The fuel tank, like the radiator mentioned in Motor Sport Feb. 1980, is a tiresome part of a racing car that does little to help performance or handling but is a necessity. Invariably designers drew their cars and put the fuel tank in as an after-thought, wherever there was available space for it. In the early days it took the form of a thing like an oil drum mounted across the rear of the car, when engines were at the front. Then it began to be an accepted part of the design and was mounted under the tail and later became part of the tail itself. As engines grew more thirsty and more fuel had to be carried an additional tank was squeezed in, some of these occupied part of the cockpit, others were formed into the scuttle in front of the driver. All the while designers were very conscious of the great mass of weight represented by 40 or 50 gallons of fuel, plus the fact that this mass of weight diminished as the fuel was used up. The 1938 Mercedes-Benz had a tank forming the tail and another in the form of a saddle over the driver’s legs, with large flexible pipes running through the cockpit, joining the two tanks together. In the fifties Maserati used a large tank on the back, which formed the tail, and a supplementary tank in the cockpit. In one Maserati racing/sports car, in which I rode as a passenger, we had a huge tank in the tail and a supplementary one holding 18 gallons in the cockpit, which formed an arm-rest alongside my seat!
One of the avenues of design that was followed by many designers was the low-polar-moment of inertia theme, in which the aim was to keep all the weight masses within the wheelbase, to give the car neutral handling and “dodgeability” and avoid the dumbell effect caused by weight masses beyond the wheelbase. The fuel tank for these designers was really troublesome, remembering always that we are talking of old racing cars with the engine at the front. Lancia had the fuel tanks on out-riggers between the wheels, to achieve their objective. Vanwall used big cockpit fuel tanks and kept the tail tank as small as possible.
Through all this there was one shining example of what to do with the fuel tank, and that was Auto Union, designed by Prof. Ferdinand Porsche, but he could only come up with the best answer by using a totally radical (for 1933) layout putting the engine at the back and the driver at the front, in complete contrast to the accepted pracuce. On the Auto Union the fuel tank was a single container mounted between the driver and the engine. This put the weight of fuel as close as possible to the centre of gravity of the car and as the fuel was used the weight distribution varied little. Nobody believed in Prof. Porsche’s layout, Mercedes-Benz, Alfa Romeo, Maserati, Bugatti, Delahaye and the rest stuck to the front engine layout with a big fuel tank in the tail. Delahaye began to see the light on their V12 “monoplace” and used side tanks, hung low alongside the cockpit. Elsewhere in this issue the Bi-Motore Alfa Romeo is described, and this carried its fuel in side-mounted pontoons, but only because the tail space was occupied by the second engine. The drawback to the Auto Union layout was that the driver sat very far forward and could not see or feel what the tail was doing on corners, which called for a special driving technique. When von Eberhorst took over Auto Union design in 1938 he endeavoured to move the driver further back and did this by moving the fuel tank and using pannier tanks on each side of the cockpit.
In present day design the advent of the monocoque chassis, made from sheet aluminium in the form of rectangular boxes, provided ideal stowage for fuel, and aircraft-type rubber bag fuel carriers were inserted into the walls of the monocoque. Aircraft development on fuel tanks has been passed on to motor racing and today fuel is carried in rubber bags filled with a special foam sponge-like substance that soaks up the fuel and prevents surge or a flood if a tank splits. These rubber bags are contained in aluminium or honey comb material boxes which are part of the chassis structure.
The next step forward was the advent of under-car air effects, or ground-effects. With this aerodynamic principle it was essential to have as much space as possible under the car, so instead of wide monocoques containing fuel bags on each side of the cockpit, the monocoque became very slim, the driver was moved forward and all the fuel was put into a simple container between the driver and the now universally rear-mounted engine. Apart from increasing the ground-effect by clearing the sides of the monocoque the handling and balance was greatly improved by concentrating the weight mass of 40 gallons of fuel on the centre-line of the car and close to the centre of gravity. It all suggests that Prof. Porsche was right in 1933. Improvements in suspension design have eliminated the disadvantages inherent in the Auto Union and today’s drivers sit well forward, even to having their feet ahead of the front wheels in some cases, such as Alfa Romeo.
Hand-in-hand with design changes have been rule changes on the construction of Formula One cars, and in some cases the rules have been made first, in others the design change came first. Today the Formula One constructors have quite a powerful effect on rule changes, especially if driver safety is under consideration. With the arrival of ground-effects the rules were changed to permit all the fuel to be carried in one tank. Previously the capacity of any one tank was limited, to minimise fire risk in the case of an accident, when tanks were carried pannier-wise. The single tank rule now allows the fuel to be carried in the safest possible place, in the centre of the car, protected from accident damage by the engine behind it, the cockpit monocoque in front of it and the side pods on each side of it. Fire risk is as minimal as it has ever been.
It is now universal to carry the fuel in a rubber bag container, foam filled, carried inside a rigid box which forms part of the chassis monocoque structure, and in the main bulkhead between engine and driving compartment. The only variation on this is the Ferrari, with its wide flat-12 cylinder engine, and this has two fuel containers, a large wide one low down and a smaller one above, both being in the now conventional space between engine and cockpit.
As everyone is using fuel injection the fuel systems are all very similar, and if you use a Cosworth V8 you receive detailed drawings from Cosworth Engineering on how to construct your tank and fuel system layout. If you deviate from these instructions you have to be very sure of yourself, for in effect you are suggesting that you know more about the Cosworth V8 and its requirements than Keith Duckworth. Tank capacity is left to the individual designer and they are all around the 40 gallons mark, some keeping their fingers crossed with 38 gallons, others playing safe with 42 gallons. In the bottom of the rubber bag container is an aluminium collector tank holding in some cases ½ gallon of petrol, in others 1 gallon. This collector tank is fed from the main container through one-way flap valves, for fore-and-aft movement of the fuel in the main bag, and for side-ways movement, so that whatever the car is doing, accelerating or braking, or cornering to left or right, the petrol is fed into the collector tank, which means that it is kept full. A delivery pipe rises vertically from this collector tank to the top of the bag and out through a union on the top of the monocoque. From here the pipework goes two ways, one through an electric high-pressure pump, and the other through a mechanically driven high-pressure pump. To start an injection engine the electric pump is switched on, which primes the injection system ready for starting. Once the engine is running and warm enough to run at high r.p.m. the mechanically driven pump takes over and the electric one can be switched off. This is why you will often see a driver being given a pit signal which reads PUMP OFF. Current from the battery is needed for the ignition system, so you do not want to waste electrical energy on a fuel pump that is not needed. The injection system will work quite satisfactorily with both electric and mechanical pumps working, but the mechanical pump driven from the engine is more than adequate on its own.
In the injection system, whether it be Lucas or Bosch, the metering unit takes just sufficient petrol for the engine’s needs and the surplus petrol is piped back into the fuel tank and directly down into the internal collector tank, thus making doubly sure that it is always receiving sufficient feed to keep it topped up.
Fuel tank design has gone something of a full circle, from the single large oil drum type of container, through multiple tanks, back to the single container. At one time three, four and even five small tanks were used and the pipe-work and switching gear was very complex. Another phase with multiple tanks was tarries of one-way valves to progressively use the fuel from front tanks first and rear tanks last or vice-versa, depending on the weight distribution and layout. Than we had switch gear to control right and left hand tanks, and a driver could play with this during a race to even the weight change on either side. All that is now finished, fuel tanks have returned to the simple single-container with very few complications, but more by accident than design. — D.S.J.