Late last year the snoop was musing about dragging his old seven out of the shed, straightening it out and getting it back on the track. Given the substantial rear end damage, that would open up an opportunity to rebuild the back with independent suspension. The factory itself did occasional conversions, and all went very well indeed. Here a story about them. The internet being a marvelous thing there are even some pretty pictures to go with it.
A Potted History of 7s.
The seven has a hallowed place in Lotus mythology. But the myth is not as rosy as it seems. A seamy financial thread runs through it. The series one cars of the late 50’s were race cars that could be used on the road. Many were. “A car that brought the fun back into motoring, and to hell with the discomfort”. But by 1960 Lotus were functionally broke. The all glass fibre Elite was a technical masterpiece but a commercial failure. Drastic moves were needed to balance the books. The series two seven was one of those moves. The original was reformed as a road car that could be used on the track. The series one cars had been expensive to make (Space frames are labor intensive beasties). So for the series two the frame was revised by “removing chassis members until the point of collapse was reached” and cladding the result with aluminium panels. The intent was that the paneling would take the loads that the removed chassis members used to absorb. Technical wise there are some very good reasons why this is not a good idea, but it certainly worked commercially. A series two seven with a bog standard 105E engine could be had in kit form for less than 500 quid. They sold like hot cakes, but they also broke on a regular basis. It is strange what commercial pressures will do to the work of a structural genius. The series 3 was a tidied up series two.
A few years on and Lotus were moving out of kit cars and into the role of a proper manufacturer. Market expectations had changed. The hairy chested seven had done its dash. It was by now a commercial oddity, and a comparatively expensive one as well. The series 4 was a little plusher, a little softer and a little cheaper. It had fibre glass body units on a revised frame. Neither fish nor foul, the purists shunned it and the mass market pretty much ignored it.
From a purist point of view that stance is well vindicated. The series 4 rear suspension is a nightmare that attempts to make a great big anti roll bar out of the rear axle. Things that shouldn’t break do.
The Independent Rear Suspension 7s.
All of the production sevens retained the live rear axle of the original, an arrangement already obsolete on a serious race car when the series one first hit the tracks in 1957. OK for those racing formulae where it was mandated fitment, but with handling limitations elsewhere. But people will play with cars and rules, and so the first independent seven was born.
The 7½ (or 7 – 20).
In 1962 a crashed series one was returned to the works for repair. It ended up in the care of Hugh Haskell, one of the design engineers for the FJ Lotus 22 and its sports car counterpart the 23. The crashed seven emerged as a quite different beast. A revised and stiffer chassis, the engine a bit further back in the frame, revised front suspension and the rear end of a Lotus 20 FJ car with the differential unit of a de dion Lotus 11. All bits apparently from the surplus parts bin at the factory. This was not an official factory project but it was done with factory knowledge and support. Colin Chapman drove it himself on occasion. It was presented and raced as the production car it had started out as, but which by now it certainly was not. It could be relied on for BTD or a class win whenever or wherever it raced, but eventually got tut-tutted out of production racing and pushed instead into formula libre. Haskell built or supervised a further 4 similar cars. The internet suggests that a few other people may have had a go as well.
The Three Seven.
In 1965 a new UK clubmans formula was introduced. This formula did not mandate a live rear axle. A prototype seven for it was built up on a series two frame, with the stiffening tubes put back in. Rear suspension was originally based the fixed length drive-shaft arrangement of the Lotus FJ 22/F3 31 (they are at heart the same car), but later notes indicate a top link and radius arm arrangement. It dominated clubmans racing for the next few years, but never was put into production.
The 37 was originally raced by a John Berry, a Lotus employee, but by 1969 it had found its way into the hands of Tim Goss, still fast enough to share the championship but by now showing its age. Goss commissioned an updated version. This was built as a test mule for the chassis ideas being planned for the upcoming series 4 seven. Its body profile looks more like a series 4 as well. It swept all before it. Firstly as a factory car, and later when in private use by Goss and others. The rear end this time was purloined from the contemporary Lotus 61 Formula Ford, with power feed from an Elan differential. Lotus Components almost put a de dion rear axle version into production. The rumors that the series 4 chassis was originally designed with a few more bracing tubes would probably relate to either or both of these prototype chassis.