Series One of unknown competitive history, had a tube break on the driver's side of the rear of the transmission tunnel about where the lateral axle support connects to the chassis. I believe the break to be due to rusting and/or abuse of some incident or accident (Perhaps the rear wheel was clobbered).

The front end structure appears to be of the original S2 design except for the addition of two straps running back from the steering rack towers to the lower cross tube. The car competed in 21 events from 1993 to 1997 before a major chassis failure occurred. The failure consisted of a fracture in the rear lower cross tube between the two straps. This caused the front suspension to vibrate significantly under braking and in going over bumps. Examination of front structure after the failure revealed an additional two cracks forming at the lower corners of the front lower cross tube. The fix consisted of adding the bracing specified in the SCCA Production Cars Specs for all Lotus 7s as well as box gussets at the junction of the rear lower cross tube and the longitudinal rail.

An early race car, when it was decided to restore it completely... upon drilling out all the rivets in the body work, the frame fell into three pieces. One crack across the cowl and cracks on both sides where the tubes join where your elbow would rest as it were.

1964 Cosworth 1500 developed a crack in the vertical tube where the bolt for the rear of the wishbone passes through it.

Chassis both rear horizontal link mounts. Cracks where steering rack mounts are welded to frame. Various cracks where tube carrying front rear wishbone mount joins to rest of the frame at the bottom. Mainly on LHS (when sitting in the drivers seat). Also crack at very front of frame between vertical and bottom horizontal member.

I assembled a new/old kit in 1978 that was a 1340 series 2, the front A arm attachment stud broke off after about 40 miles of hard driving.

Series 1 failures include the diagonal attachment at the seat back bottom -- solution was to box the attachment point. Old repairs to the front of the engine bay had to be replaced and cracked top link mounting.

Intersection point of the top side tube of the cockpit where it joins the arched tube forming the wheel arch at the seat back. My car/chassis only has about 2,500 miles on it the aluminum skin is showing signs of fatigue fracture due to chassis flexing at this point. I am not certain if the weld in the chassis members themselves have deteriorated or the general flexibility at this point has resulted in the skin fractures.

Weld fatigue is the cause of most failures but very few people understand it. If you understand simple structural facts of life, then you can see why some people will have trouble in their car while others don't. You can also see why some models are trouble free and others break for no apparent reason. [Following is] a separate bit explaining how we did the design on the early Lotuses. Only Colin, Frank Costin and I were involved so as the other two are dead I am the only person who can do it. You will see that we used strict aircraft practice and were able to produce very light but very strong cars right up to the Mk II and the first Elite, but then I 'Committed Matrimony', Hazel's term, and the calcs were not done but the same sizes were used and not surprisingly failures were common. Graham Hill and Dave Kelsey persuaded Colin that a fabricated frame to carry the kink loads in the top chassis member on the first single seater was not necessary and tubes would do. Graham always 'knew' very positively and Dave thought welders knew everything about welds but they were wrong and Graham had to finish a race watching the chassis opening and closing by his elbow - served him right! I suspect the same on the top tube of the 7, by your elbow. On the 11 it was a 3/4" x 20swg up to the rear frame and the load was quite high on bumps but it never broke. The curved tube may be 1" x 18swg but it will be subject to a lot of bending because of the offset and you don't need much bending to whack up the stress. Add that to a tricky match up where the three tubes meet and weld fatigue is not a surprise. That tube should be straight and the bodywork should be made to do the tricky bit.   (click image to enlarge) Where there are two load paths, the steel tubes and the aluminum skin, load will travel down the stiffer path until it breaks. Aluminum has an E value of 10x10 to the 6th lb/inch squared against steel's 30x10 to the 6th so it is inherently one third the stiffness even if it is rigidly attached, which it isn't. Wrapping over with the odd pop rivet is not a very good structural job. One of the emails said something about leaving off the bottom skin. That would be a very bad move as the chassis relied on the bottom skin to carry the shear loads due to differential thrust from the brakes or the back axle. These loads may be higher on later cars with sticky tires but it's the bump loads that do the damage.

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