Frame Question

[dbfenton]

Frame Question

What model year & S/N did Caterham start building the upgraded / stiffer / stronger frame? Where can I find some history on this upgrade?

Don

[xflow7]

There have been several updates to the chassis over time as the cockpit was lengthened, the De Dion made available, the front suspension reworked, and more recently with the change to Metric chassis, etc.

 

However, I think the primary stiffening was done when the so-called "Long Cockpit" was introduced which - according to Jeremy Coulter's "The Lotus and Caterham Sevens" - was with chassis number LCS/4140/MKRM. Not sure of the year, but I think it was early '80's.

 

Edited to add additional info from another section in the book:

 

1974: Initial chassis as S3 with added triangulation in engine bay and cockpit sides

1981: Long cockpit introduced

1985: De Dion introduced, tubes added along transmission tunnel

1986: Symmetrical chassis introduced, front mounted radiator.

 

The book was published in '86 so doesn't list anything after that time.

 

Dave

Edited April 1, 2012 by xflow7

[dbfenton]

xflow7,

 

Thanks, this is just what I was looking for. As I'm shopping for a Caterham, I'm thinking I want a S3-haven't decided which drive train but it will be for street / touring use only so 135-175 HP should suffice.

 

Don

[11Budlite]

Don,

 

To add to Dave's info, here's a link to Lotus and Caterham chassis numbers: http://7faq.com/owbase/ow.asp?ChassisNumbers

[bball7754]

Don - A good source for unofficial info is Blatchat. This post has some info on some of the changes during the '90's.

 

http://www.blatchat.com/t.asp?id=85042

 

From the post:

 

"The main changes to the De Dion chassis happened mid.1996 ( 96.5 type chassis ). The revisions were quite extensive:

 

* De Dion 96.5 chassis had a fully triangulated space frame structure in the tunnel which increased torsional stiffness by 30%.

* New dashboard instruments with ' Caterham ' branding.

* Standard roll-over bar 40mm taller and sloping forwards.

* FRONT and REAR suspension geometry revisions. At the front, repositioning the wishbone pick-up points reducing roll-on camber change and track width variation.

 

* As Alex and Angus say, a degree of anti-dive was incorporated, instead of the pro-dive traditionally used.

 

* Progressive rate springs introduced on the rear.

* Bilstein damper revisions.

* Smaller front anti-roll bar. * Rear anti-roll bar not fitted as standard but provision to fit if required.

* Steering rack development. "

 

And there are other features that have changed over time. My '98 does not have tabs behind the seats to mount crotch straps - there are only attachment points for the lap and shoulder straps. They went away for awhile, then came back. And my rear ARB mounts over the differential, while they now mount beneath.

 

And then there was the change to the "metric" chassis around 2006. Previous chassis were imperial measurement and hand built by Arch. The metric chassis is built by a company called Caged (although that may have changed) by robots.

 

Steve

[Alaskossie]

Caterham brought the metric (automated, jig-welded) chassis in metric dimensions on line for the Seven S3 in rhd around 2006

 

However, Arch Motors was still making the lhd S3 (brazed, Imperial-measurement) chassis when I bought mine in 2007. i believe the metric chassis for the S3 in lhd came in late 2007, or 2008. I believe Arch was making the chassis for the CRS. lhd or rhd, until fairly recently.

 

i understood that Caterham gave Arch a chance to acquire the necessary jig-welding equipment to make the metric chassis, but Arch decided the outlay would be too expemnsive, so Caterham turned to Caged.

 

The Caged Company was originally the maker of the metric chassis; the company was bought by Caterham later, and I believe it is now a division of Caterham.

 

One objective of the metric chassis was to have as few differences between lhd and rhd chassis as possible. the metric chassis has the same rod-actuated clutch and brake master cylinders as the CSR, with the cylinders located below the level of the scuttle. I don't know if this might pose problems with some engine installations or intake/exhaust layouts, on lhd cars.

[Klasik-69]

How much difference is there between an imperial chassis and a metric chassis ? My R300 was built in 2004 and I assume to be an imperial chassis. Fasteners are US/imperial threads. Maybe there is no difference in the chassis, maybe only the dimension references changed from inch to mm..............don't really know.

[danilo]

IMO Caterham Constantly dicked with the chassis specs.

Likely in some addled attempt in keeping it 'current' and in the news, a genuinely profitable business clearly , perennially, eluded them.

Results of this constant putzing about are glaring/obvious in their parts listings.. One needs a bloody program to figure out the myriad (mostly inconsequential) 'improvements' made every year or 2.

Frankly IMO the older the better; Fewer dicky improvements :-)

[Alaskossie]

Klasik-69,

 

If your chassis is a 2004, it is an imperial chassis built by Arch Motors, the original Seven chassis builder. The change to the metric chassis occurred sometime in 2006-07 as to rhd S3 cars, and a bit later for lhd S3, I believe.

 

There are detail differences between the late imperial and the metric chassis, such as to mounts for the master cylinders, engine-bay bracing, and other details I'm not familiar with.

 

One objective was to have as few differences as possible between lhd and rhd chassis. The structural difference is that the metric chassis is jig-welded by automated welders, not hand-brazed by human beings as the Arch chassis is (was).

 

I believe Arch still makes replacement chassis and chassis parts for pre-metric cars.

 

Danilo,

 

I think Caterham's chassis changes were a gradual evolution in thinking about chassis design and also availability for a wider, taller variety of drivers. It was not some mis-guided attempt to "stay in the news;" I've seen no evidence of that.

 

After all, this was originally a 1957 design -- name one other 1957-origin car design that has gradually evolved to still be one of the quickest cars on the road today. That is the genius of Lotus and Caterham, under C. Chapman and G. Nearn.

 

Further, Caterham is just a slightly grown-up British "cottage industry," with all the advantages and disadvantages that the term implies. It is not GM (thank God for that!).

[ayseven]

Yes, but it is nice to see companies actually making money, allowing for further development, etc. I haven't been able to figure out if anybody makes money on kit cars, or glorified kit cars, in C'ham's case. I own a decent business, and can add. On the other hand, I have a theory that many British companies are now owned by other companies, based in other countries, merely to avoid paying tax. No names here of course... there are bound to be a few lawyers around.

[Guest Terry]

xflow7,

 

Thanks, this is just what I was looking for. As I'm shopping for a Caterham, I'm thinking I want a S3-haven't decided which drive train but it will be for street / touring use only so 135-175 HP should suffice.

 

Don

 

Hi Don

 

My advice would be buy a De Dion car and think about the motor secondly. The ride quality of the DD cars is far Superior. You wont regret it.