Cars - Lotus Seven

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	Cars - Lotus Seven

The Lotus Seven is a small, simple, lightweight two-seater open-top sports car from Lotus, which has been called "a motorcycle on four wheels". It is the most successful inexpensive exotic sports car. It is characterised by extremely high acceleration (0–60 mph in 3.1 seconds) and a mid-range top speed (up to 155 mph, depending on engine). The drag coefficient is around 0.7, mostly because of the flat windscreen and the wheel arches.

The original Lotus Seven was launched in 1957, powered by a 40 bhp Ford Sidevalve 1172cc engine. The Lotus Seven Series 2 (S2) followed in 1960, and the Series 3 (S3) in 1968. In 1970, Lotus radically changed the shape of the car to create the Series 4 (S4), which was not widely accepted. The Series 1 was mainly intended for club racing, but the Series 2 and subsequent models were production cars intended for public roads.

An S2 Lotus 7 driven by star Patrick McGoohan was featured in the opening credits of the 1967–1968 television series The Prisoner.

In 1973, Lotus decided to shed fully its British tax system-inspired partial kit car image and concentrate on its more up-market models. As part of this plan, it sold the rights to the Seven to Caterham Cars. Caterham had been a Seven dealer since the very early days, and at this time they were the sole suppliers. After a brief period producing the Series 4, including assembly of the last "kits" supplied by Lotus, they introduced their version of the Series 3 car, and have been making, and refining, this car ever since as the Caterham Super Seven.

Replicas

Since the design of the Lotus Seven is so simple, over 90 companies have offered replicas or Seven-type cars over the years such as:

Locost
by Ron Champion
Stalker V6 Clubman
by Brunton Automotive
Several models by Westfield Sportscars Ltd
Raptor by Tornado Sports Cars
Several models from Robin Hood Engineering Ltd
Donkervoort
from Netherlands with Audi-Turbo-Engines
HKT from Germany also with Audi-Turbo-Engines
Hauser from Switzerland with BMW engines
Tiger Z100 from Z Cars Ltd
MK Indy
from MK Engineering (using Ford Sierra
parts)
ESTfield
from RaceTech (using Lada parts)
Esther
Dala7
(a taller and wider design using Volvo parts)
Rotus, built in Florida with Japanese components
Gregory
Fraser Clubman from Fraser Cars Ltd
Vindicator Sprint and the four seat Vindicator Family by Vindicator Cars

Analysis of the Seven's performance

Top speed

A Seven's top speed greatly depends upon the body configuration, engine power and gearing. In practice it is unlikely that even the most powerful current Seven's would exceed 150 mph easily, while more typical top speeds are in the range of 110–135 mph. The original models with open fendered non-envelope body layout, upright windscreen and bug headlights had difficulty exceeding 90 mph. In addition, the original (clam shell) style front fenders tend to lift the front end at higher speeds, increasing instability and resistance. Later cycle guards help alleviate this tendency, and recent low height wind deflectors that replace the windscreen improve top end speed.

Low speed acceleration

Nearly all Sevens, due to their extremely light weight (around 500 kg) have excellent acceleration, especially up to 70 mph, depending on power. For their time, the original late 1950s Sevens could beat most contemporary saloon cars—and by the early 1960s, with improved Ford-Cosworth engines could take on most high performance sports cars with 0–60 mph time in the low 7 seconds. More recent acceleration times (for top level models) are world beating for production cars with 0–60 mph below 3.5 seconds. The high power-to-weight ratio is excellent with almost any engine.

Braking

The choice of brakes vary considerably between models and over the evolution of the car. The less powerful early models had drum brakes all round, while more powerful and later models had drums at the rear only (especially on Live-Axel cars from the early 1960s) or disc all round. With the popularity of Semi-independent (DeDion) or Fully Independent Rear suspension most manufacturers have opted for discs all round, as is current common practice in the automotive industry.

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