Another Unidentified Cobra

[shep]

Just for the record, I have several photos of me in the Orange Cobra when I was racing in AMOC Intermarque in the '90s, with the inside front showing an inch of daylight. That was before anyone started mucking about with chassis stiffness. Also I believe I have seen a photo of Bill Bridges' Hairy Canary (one of THE most original Cobras to be found) lifting a front wheel last year at the revival with Ludovic Lindsay at the helm. It was also of interest that our Orange Cobra would trade places with John Pogson in his competition Ferrari F40, which was an out and out racing car. We indeed had a finely honed banana!

[rstainer]

I'm with Trevor on this one. The Friedman/Christy definitive pictorial history, Carroll Shelby's Racing Cobra, has over fifty photos of race Cobras cornering at the limit: not one is three-wheeling.
   
   The MSA's historic racing definition (earlier in this string) includes "....prevent modifications of performance and behaviour which could arise through the application of modern technology." I simply do not see how a car that three wheels now but didn't in period does not have modified behaviour; further, I can see no reason to modify the Cobra's behaviour other than to achieve performance gain.
   
   What, therefore, is historic racing, if it isn't racing cars as they were? It would be interesting to see a succinct practical definition that its proponents could put, via the MSA, to the FIA.

[Cobra Ned]

I must disagree with the prior note regarding the originality of the Hairy Canary, which was used as an example of an original Cobra that could corner on three wheels. Following its restoration here in the US back in the early 90's, I talked at length with the shop that did the work, and they noted substantial effort had gone into stiffening the chassis at that time. This supports Robin's assertions that the cars simply did not evidence the ability to lift an inside front wheel as originally built.

[shep]

I bow to superior knowledge, but also suggest that fresh 2014 Dunlop Ls and Ms have much more grip than tyres in period. That could change the suspension dynamic. Hell I'm sure I have a photo of me in my Ace Bristol on Dunlop L 250x15s with the inside front barely kissing the track, and I guarantee there is absolutely no chassis or body stiffening on my car. Bishop cam steering and 150 bhp is all you need! I'll see if I can post a photo, if that is allowed in the Cobra section.

[SB7019]

Andy.
   I have plenty of photos that attest to you ability to lift a wheel in an Ace - though had always put it down to your penchant for pleasing the crowds!

[SJ351]

I think Robin is right. Historic racing has moved from enthusiasts racing old cars to a sort of WW11 re enactment scenario  in many ways, with professional drivers mixing it with the amateurs in the top series.
   
   When you see a (admittedly very well driven) Cobra beating GT40's at the LeMans Classic you realise just how far these technically advanced cars have become ie little to do with how they raced in period and would be slaughtered if they were. The spectacle is the greater for it though.
   
   It is possible to build a very stiff chassis that looks original but in fact has stronger, thicker main tubes and gusseting inside. Metallurgy has moved on. Once the end is capped off, no one will know.
   
   On the question of three wheeling, the Hairy Canary was three wheeling on every lap of the Godwood RAC TT, lifting the inner wheel a good 9"" off the ground at Lavant. Many things could be responsible here. Whilst the car is certainly original in terms of the continuous history argument, it has had a good deal of surgery and this is no secret in AC circles. I saw some pictures of it a couple of years ago in the AC Heritage archive that show the 'before'.
   
   However, Andy is right that fresh sticky modern rubber compounds and a certain driving style  could produce the desired effect. Also, if you have ever played around with a race car it is surprising the difference that ride heights and spring rates can make, as well as the updated modern dampers that are available with custom valving. The latter can really stiffen a car up. These days there is a lot more understanding of chassis dynamics by professionally prepared Cobra teams than there generally was in the '60's. this knowledge is translating into quicker lap times than in period, although the 'cheat' cars are also benefiting from a little bit more than this.

[rstainer]

"...fresh 2014 Dunlop Ls and Ms have much more grip than tyres in period....that could change the suspension dynamic."
   
   I can't find any evidence to support this suggestion. Dunlop's aim, agreed with the FIA, is to produce a tyre with a performance as close as possible to period tyres. As far as I can see Dunlop's 204 compound does just that.
   
   I cannot find a single modern image of a Cobra made by AC in period running on Dunlop Ms or Ls and three-wheeling that has a correct period chassis and three-point forward-braced roll bar.
   
   All Ned and I can do is examine the available evidence that points to only one conclusion: leaf-spring Cobras did not have the ability to lift an inside front wheel as originally built. Putting it the other way round, if a Cobra is three-wheeling, it is not built to period specification (including Homologation #115 specified modifications); it has performance and/or behaviour modifications through the application of modern technology.
   
   RS

[3.5 Pints at the Bar]

"...it has performance and/or behaviour modifications through the application of modern technology."
   
   It doesn't automatically follow that modern technology is involved. Understanding of the old technology becomes gradually wider spread over the years, too.
   
   Regarding 3 wheeling, as I explained earlier, simple mathematics shows that chassis stiffness is a very small factor. An infinite increase in stiffness will only increase wheel lifting by a minute amount. I've measured twist on my 2 Litre using the car's static weight to twist on 3 wheels, and this produces 0.1 inch deflection at the wheel. Most car chassis from the 1930s onwards can be made to 3 wheel if you provide a big difference in front and rear roll stiffnesses.
   
   The pertinent question is "why would you want a big difference in front/rear roll stiffness?" It's probably pointless on a beam-axled car. It makes sense on a Lotus Cortina because the front roll-centre is lower than the rear one. On an AC Cobra, it may be a question of sharp handling, balance, etc. Maybe also as a knock-on effect of other mods (old or new tech)?

[rstainer]

Ian,
   
   With respect, this is not the point. The MSA's historic motorsport definition is very clear: "Competitions under a set of rules that preserve the specification of their period and prevent modifications of performance and behaviour......."
   
   Three wheeling, no matter how achieved, is a modification in behaviour. There only two ways it could be shown not to be a modification in behaviour:

By providing evidence that Cobras three-wheeled in period, and demonstrating that Friedman/Christy's 50+ race Cobras cornering at the limit photos don't show the full story

By providing evidence that today's drivers can get their cars to dance in ways that yesterday's (Bondurant, Sears, Gardner, Miles etc) couldn't.

   To repeat, I simply do not see how a car that three wheels now but didn't in period does not have modified behaviour; further, I can see no reason to modify the Cobra's behaviour other than to achieve performance gain.
   
   What, therefore, is historic racing, if it isn't racing cars as they were? Perhaps the three-wheelers (Ian, Andy + any others) could come up with a succinct practical definition that would put this more recent behaviour into the 'historic' category.
   
   RS

[3.5 Pints at the Bar]

I was simply addressing a technical issue raised by others in this thread, and not the overall topic.