On diesel consumption

THE MIDDLE of this month saw reports in the Press indicating that diesel sales in October fell by 8.2 per cent (retail) and by 9 per cent in direct bulk sales over the same month last year. This was accompanied by much hand wringing because diesel consumption, one of the supposed ``primary indicators of the health of the economy'', is showng a steady downward trend since early this year.

It is true that high speed diesel sales have fallen by between 2.8 and 8.4 per cent every month this fiscal year except in September when sales went up by 9.6 per cent. The September anomaly and the comparatively low fall in August (2.8 per cent), are obviously because of the hoarding that occurred before the long delayed, but widely publicised, price increase in October. By the same token, the steep (8.2 per cent) fall in October must have been accentuated by September's hoarding.

In contrast, diesel sales grew by 9 per cent during the first half of last year and by 3.7 per cent in the second half over the previous year. Commentators have dubbed the growth in 1999-2000 as ``healthy'' in contrast to the situation this year when significant quantities of diesel and furnace oil have had to be exported. While this might be true from the perspective of the likes of Reliance, which has put up the world's largest refinery in Gujarat, it is not true from the nation's.

In addition to a `secular' slowing of the economy since the mid 1990's, it has to be recognised, India imports about seventy per cent of its crude (with both the quantity and proportion rising from year to year) and with crude prices having more than tripled from the beginning of 1999, an intolerable burden is being placed on the nation's finances. At least from that perspective, the decrease in diesel consumption is desirable, especially as more than half the crude is converted into diesel. The latter is a peculiarly Indian phenomenon and places a high burden in terms of both choice of crude and its `economical' conversion.

Secondly, diesel consumption is not always one of the primary indicators of the health of an economy. As with the consumption of electricity, the opposite is often true and is an indicator of improving factor productivity. One has only to compare India to Japan in the Seventies and Eighties. The consumption of both in Japan fell in response to the massive oil price hikes of 1973 and 1979, while the gross national product grew rapidly.

India's oil consumption in the corresponding period, in contrast, showed a secular increase contributing not a little to rapid inflation and a severe balance of payments crisis. Indian industry is, at last, realising the importance of increasing energy efficiency. For example, no integrated cement plant is considered efficient today if it uses more than ninety units (kWh) of electricity per tonne of cement produced. Ten years ago there were many units that used more than 200 kWh per tonne!

Similarly, diesel consumption in agriculture is coming down because many tractors are now fitted with fuel efficient, direct injection diesel engines. All tractor manufacturers have followed the lead of Mahindra and Mahindra which got AVL (of Austria) to convert its nearly fifty year old International Harvester indirect engine to an efficient direct injection design.

Moving from indirect injection engines to direct injection typically reduces fuel consumption by 15 to 20 per cent. This has been followed more recently by Telco with the introduction of turbo-charged diesel engines right across its commercial vehicle range in collaboration with Cummins of the U.S.. These new Tata Cummins vehicles are not only more fuel efficient, they are also more powerful and emit fewer pollutants. In addition, these more powerful engines have facilitated the rapid introduction of multi-axled trucks which has further reduced fuel consumption per tonne of freight carried. Damage to road surfaces is also less with these vehicles.

All in all, let us rejoice that diesel consumption is coming down - the health of the economy and that of humans deserves nothing less.

Afterword

A careful reader of Motoring Matters has pointed out that the Morris Minor of the late 1940's was not the first volume production car to be `truly chassisless' - it was the Austin A30 from the early 1950's. Without getting into a discussion on what is `truly chassisless', it is worth exploring this subject in some detail from a historical perspective.

The integration of frame and body functions into an all-embracing shell is variously known as `integral', `unitary', `chassisless' or `monocoque' (from the original French) construction. The introduction of the `all steel' welded body is a concept that was developed in America by Budd Manufacturing Company for Dodge cars in the late 1920's. Although a separate chassis frame was still used, it no longer functioned as the only load carrying member.

Integral construction proper was introduced by Citroen in France during the mid-1930s and was also evolved in consultation with Budd Company. It was based on the principle of stressing the outer skin of the body shell to perform a load carrying function, which contributed to the strength and rigidity of the inner structural members, thereby eliminating the need for a separate chassis. This monocoque method of a more efficient structure was already well known to aircraft designers to whom increasing strength without weight was critical.

In modern practice, the principle of integral construction is modified in various ways, notably by combining it with separate `sub-frames' for mounting various parts of the vehicle. The aim is chiefly to suppress noise, vibration and harshness (NVH) from the body interior by the use of rubber (or hydraulic) isolators and also to simplify the assembly of the mechanical units to the body. Use of these subframes was widespread only for the engine, but is now spreading to the suspension as well. This particular form of `semi-integral' construction was pioneered by Mercedes- Benz in the early 1950's.

`Space Frame' construction is now coming in to vogue with the various parts of the body being bolted on to a rigid frame typically made of steel tubes. This type of construction is very strong and rigid and is particularly well suited to relatively small volume production. A prime modern example is the rather unusually shaped, but immensely practical Fiat Multiplia. The space frame is obviously very similar to the old chassis. Have we come full circle?

C. Manmohan Reddy

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