Lotus Seven

The Lotus Seven is a small, simple, lightweight two-seater open-top sports car, which has been called 'a motorcycle on four wheels'. It is characterised by extremely high acceleration (0 - 60 mph in 3.1 seconds) and a mid-range top speed (155 Mph), handling also is breathtaking and the ride is 'uncompromising'. The drag coefficient is around 0.7, mostly because of the flat windscreen and the wheel arches.

Mechanical details

Engines

After the English Ford flathead (L head or side valve) a BMC series A was used, then push rod overhead valve Fords of 1340 and 1500 cc with the intake and exhaust on the same side of the head. These were often Cosworth modified, making these cars Lotus Ford Cosworths, like the racing cars. The Cosworth 1,340 "Super Seven" had 85 hp. and the 1,500 "Super Seven 1500" had 105 hp. These were replaced by the cross flow, when it came out. The acceleration finally caught up to the handling when the Cosworth/Ford twin cam 1,600, as in the Lotus Élan, was used.

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There was also a model, sold in the US with a Coventry Climax engine and independent rear suspension.

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The fan was optional.

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Frame and body

It was front engine, rear drive like most cars of its time. It had a tubular steel frame with stressed skin aluminum bodywork. The body panels were flat to avoid the expense of more elaborate aluminum bodywork. The Nose and fenders were thin colored fiberglass. Often either the body nor the fenders were painted.

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It was a bit over three feet hight with the top up. The track was relatively wide. The ground clearance was 5 inches to the main frame tubes, but components extended at least half an inch lower. Because the upper frame tubes were high for rigidity, there were no doors, but only removable hinged side curtains. Bumpers were not standard, as they would have degraded the very low angular inertia (polar moment) as well as the total weight. A heater could be installed.

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Weight

Early Lotus Sevens weighed around 1100 lb (500 kg). Although the weight crept upward as production progressed, it remained remarkably low for a production car of over a litre displacement. Superlight production models weigh well under this and the latest high performance model reports a stunning, world class power / weight ratio in the region of 600 hp (447 kW) per metric ton or 3.7 lb per hp.

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Suspension

The front was by "A" arms and coil springs with an anti-roll bar serving as the front half of the top A arm. The rear had trailing arms, a triangular center locating member and solid rear axle.

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The geometry and high (relative to total) unsprung weight gave it some bump steer, which owners sometimes treated by moving the supports forward and lengthening the trailing arms.

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