weight claims

[Christopher smith]

I noticed that a new Caterham model is claiming the lightest production 7 ever. Not 100% sure but I see data that indicates my series 1 Lotus )1959 #475) was probably down closer to 725 lb back then. It has certainly gained some weight since new but is still pretty light.

[JohnCh]

Word choice is important in marketing.  They state it's "our lightest production seven of all time."  i.e. it's Caterham's lightest seven, not the lightest seven made by Lotus.  Although Caterham bought the design rights from Lotus, they have no claims on the sevens produced by that company.  

 

-John

[Christopher smith]

John-Thanks for catching that. It would be interesting to know in the evolution of Lotus , then Caterham just what changes were made and the effect on weight (other than engine/gearbox of course with some big weight differences). The series 1 had aluminium floor pan all the way back with a big round cut out under the center diff area. I presume that was to facilitate oil change. And they did not have the suspension attachment point under the center of the rear. If my various reading sources are correct, the  changes post series 1 were not so much Chapman directed as he apparently put his attention toward making the race cars faster (as in the 18, 19, 23 etc.) and then keeping the company alive. i certainly admire the newest 7s layouts

[JohnCh]

Some of this may be identified in the various books available on the model, but no idea which one(s) is best from this perspective.  Others may know.  BTW If you haven't seen it, @Croc posted a reading list article that is a great reference of published materials: 

 

-John

 

[SENC]

Lotus Seven Register - Home Page (lotus7register.co.uk) - a series of articles on the history under Lotus, by John Watson.

[SENC]

... and from the lotus7register site:

 

S1

WEIGHTS:
Pre-October 1959: Original 100E Ford model without spare wheel - 725lbs and Export 100E Ford model with spare wheel - 822lbs. October 1959: Ford 100E model - 918lbs and BMC "A" Series model - 896lbs.

 

S2

WEIGHTS:
Weight given in Owner's Manual 924lbs. However road test reports give: "A" Series car 960lbs. - 105E car 957lbs. - 109E car from 952/1015lbs. - 116E car from 1008/1064lbs.

 

S3

WEIGHTS:
None given in Owner's Manual. However road tests give the following:-
Autosport 1969 - Lotus Seven "S" - 1204lbs.
Autocar 29/1/70 - Lotus 7 Twin-Cam SS - 1254lbs.
Road & Track Oct 1970 - Lotus 7 Twin-Cam SS - 1210lbs

 

S4

WEIGHT:
Laden 1310lbs. (Twin-Cam Version).

[Christopher smith]

Thanks

 I had viewed that info a few times and it is indeed very good. I guess what I was curious about was the the differences in space frame and suspension designs. I have looked at some images to try to see the differences. Caterhams are quite different. I guess they noted some of the defects that came out on hard use and designed "fixes". SCCA had circulated quite some time ago their "allowed" modifications to the 7 frame with 3/4 inch round diagonal tubes up in the area of the radiator. I installed those as I did not want the frame to crack near the front suspension attachment points. adds weight but seems like a good idea to stiffen up that area given the dramatic differences in tyre traction since the skinny 15 inchers were in the original design.