The Lotus 78 was a Formula One racing car used in the 1977 and 1978 seasons, designed by Peter Wright, Colin Chapman, Martin Ogilvie and Tony Rudd. It was the first ground-effect car in Formula One and the class of the field in its debut season, winning five races.
Lotus 78 at a glance
| Seasons | 1977–1978 |
|---|---|
| Designers | Peter Wright, Colin Chapman, Martin Ogilvie, Tony Rudd |
| First race | 1977, first round |
| Key idea | ground effect from inverted aerofoil underbodies |
| Seals | brushes, then plastic, finally sliding rubber skirts |
| Engine | Ford Cosworth DFV |
| Chassis | aluminium and honeycomb monocoque |
| Fuel | three cells, two in the sidepods |
| 1977 wins | five |
| Built | five cars |
Based on one source (English Wikipedia).
History of the Lotus 78
Early in 1976, disappointed by the ageing Lotus 72 and the indifferent Lotus 77, Chapman wrote a 27-page document on low-drag air penetration. Having studied the de Havilland Mosquito’s wing-mounted radiators and the hot-air outlets designed to induce lift, he realised that an inverted version of the system could give significant downforce, and handed the document to his head of engineering, Tony Rudd.
Rudd appointed chief designer Ralph Bellamy, vehicle engineer Martin Ogilvie and aerodynamicist Peter Wright. Rudd and Wright had worked at BRM on an inverted wing profile before joining Lotus in 1970, but the project there had never got beyond experiments. Wright experimented with body shapes in a wind tunnel with a rolling road and found that as the road speed rose the shaped underbody was drawn closer to the surface; pieces of cardboard on the model’s sides showed a phenomenal level of downforce. Chapman gave the team free rein.
The underside of the sidepods was shaped as inverted aerofoils: air passing between the car and the ground was accelerated, lowering the pressure beneath the car and pushing the tyres harder onto the track. Copying the Mosquito, the radiators were placed so that their hot air passed over the upper bodywork, adding downforce. Because ground effect is a low-drag solution, cornering improved without a loss of straight-line speed. Brushes were first fitted to the base of the sidepods to keep the low-pressure area in place; plastic skirts wore out quickly, and movable rubber skirts finally sealed the gap to the ground. Andretti said driving the 78 was like the car was “painted to the road”.
The 78 was loosely based on the Lotus 72, sharing its wedge shape, but had a slimmer monocoque of aluminium sheet and honeycomb developed from the 77, a longer wheelbase, fibreglass body panels and fuel in three cells, two of them in the sidepods and controllable from the cockpit. The suspension came from the 77, stiffened to keep the aerodynamics working. Five cars were built, codenamed John Player Special Mk. III, and first appeared in July 1976; Andretti wanted to race the car that year but Chapman refused, not wanting rivals to see what Lotus had achieved. In 1977 it won five races and set the pattern for the ground-effect era that followed with the Lotus 79.
Design and features
- Ground effect: inverted aerofoil underbodies that sucked the car onto the road.
- Sliding skirts: rubber seals that kept the low-pressure area under the car.
- Radiator placement: hot air routed over the bodywork for extra downforce.
- Low drag: cornering grip without the drag penalty of large wings.
- Adjustable fuel: sidepod tanks controlled from the cockpit to trim weight distribution.
Lotus 78 versions
- Lotus 78 (1977–1978): five cars built, with evolving skirt and suspension details.
The 78 followed the disappointing Lotus 77 and was developed into the Lotus 79, which took ground effect further. More racing cars are in the Lotus collection.
Sources
- Lotus 78, English Wikipedia: ground-effect development, design, 1977 season
