Ultimate Seven Product
Discussion
If you look here https://www.goodwood.com/grrc/columnists/mystery-m... you'll see that Graham MacDonald talks about an Ultimate Seven Product that their engineers are giddy about which Caterham are about to announce. Anyone know what it is?
Equus said:
The Reynolds butted tubing project has been in the public domain for some time though, so it would hardly be a new announcement?
At the NVN Symposium earlier this year, they were talking about it as a potential £1-£2K pricing option and envisaged about 20% customer uptake.
20% uptakes seems extremely optimistic - I thought the weight saving was only small (7kg?) and while weight saving is a GOOD THING I can't see many paying that much for such a modest saving. Sounds like carbon fibre nose and wings would be at least as cost effective. You could, of course, not paint the car and save yourself a similar amount of weight as well as over £1000.At the NVN Symposium earlier this year, they were talking about it as a potential £1-£2K pricing option and envisaged about 20% customer uptake.
Edited by Equus on Thursday 21st July 19:43
BigRabs said:
Do we think the new 310 is the "ultimate product"?
Nigel can you confirm?
If it is I'm a little disappointed to say the least. Lovely spot in the range and very desirable, but probably falls well short of what I'd call an 'ultimate seven product'.
Don't be silly! It's the LED headlights!Nigel can you confirm?
If it is I'm a little disappointed to say the least. Lovely spot in the range and very desirable, but probably falls well short of what I'd call an 'ultimate seven product'.
Seriously though I suspect it IS the ultimate product referred to, they are talking it up on their website as if it is something really special. If so its a bit OTT, but I suspect it is the sweet spot in the range.
glailey said:
Have to agree with BAC, Elemental, Zenos, Vuhl all (much smaller, less well established companies) producing ultra lightweight basic sportscars I'm disappointed that Caterham can't do something more radical. The 21 has (I fear) rather knocked the stuffing out of Caterham. I think that's a shame - it's not that the 21 was a bad car - simply that Caterham were unfortunate to come up against the Elise - which was a better one. There is a (new) Elise-sized hole in the market which, of course, Lotus are trying to fill - but someone else with ambition might. RegMolehusband said:
IMHO as a hill climber with a lot of Caterham experience, they shouldn't go any lighter. And that is because the car would become hopeless in the damp and wet as a result of the tyres being less squished into the road to help clear the water. Narrower tyres would offset this a little but then you're not maximising its capability in the dry.
I can't see that. If the tyres are comparably narrower grip wet and dry should remain the same so long as the sprung to unsprung weight ratio remains the same. However reducing weight is going to make setup more difficult because of the big percentage variation of driver passenger and fuel weight.
[quote=Equus
...and the whole point of developing an 'ultimate Seven product' would be to transcend the limitations of the current car, which would be quite easy to do... chassis stiffness:weight, suspension design, aerodynamics; all are pretty woeful by modern standards, if we're honest with ourselves.
[/quote]
But the CSR addressed stiffness and suspension design quite well, and made minor aero improvements but hasn't sold and showed no speed advantage.
Carbon fibre is the only way to make significant chassis weight savings but is too expensive.
Bike engines could save weight but have serious installation supply and cost issues.
And the aero 7? Stillborn? I still think aerodynamics are the answer but producing low drag without adding weight will be difficult.
...and the whole point of developing an 'ultimate Seven product' would be to transcend the limitations of the current car, which would be quite easy to do... chassis stiffness:weight, suspension design, aerodynamics; all are pretty woeful by modern standards, if we're honest with ourselves.
[/quote]
But the CSR addressed stiffness and suspension design quite well, and made minor aero improvements but hasn't sold and showed no speed advantage.
Carbon fibre is the only way to make significant chassis weight savings but is too expensive.
Bike engines could save weight but have serious installation supply and cost issues.
And the aero 7? Stillborn? I still think aerodynamics are the answer but producing low drag without adding weight will be difficult.
Equus said:
Yep, small (and light) is good, rather than throwing ever more power at it. Though I guess we have to be realistic and acknowledge that since the average male is no longer 5'8" and of slight build, there's a place for SV and CSR sized cars in the range.
Even Kent engined Formula Ford cars are considerably more sophisticated than Caterhams, though - much better aero, stifffer chassis, more advanced suspension. A 1960's Formula Ford (which is where Caterham are still at in terms of chassis technology, and behind in terms of aero) wouldn't see which way a current car went.
Accepting what you say about driver size I think you may be missing my point re FF1600. Even Kent engined Formula Ford cars are considerably more sophisticated than Caterhams, though - much better aero, stifffer chassis, more advanced suspension. A 1960's Formula Ford (which is where Caterham are still at in terms of chassis technology, and behind in terms of aero) wouldn't see which way a current car went.
Tiff Needell showed his 1989 Ff1600 was quicker round Hethel than an elise cup. So by today's standards an ff1600 is a fast car despite a 108bhp engine, chassis design and suspension fundamentally no more sophisticated than a CSR (arguably less) but as you say vastly better aero.
So my point is there is scope for significant improvements without getting radical. Caterham (unlike many rivals) produce cars in large enough numbers for commercial issues such as long term supply of engines to be serious issues.
Equus said:
If they were really clever, then more advanced chassis technology needn't necessarily mean more difficult or less profitable.
Heavily triangulated spaceframes are actually very expensive things to manufacture, due to the amount of skilled manhours required. Ironically, the latest Caterham innovation - butted tubes - makes that situation worse, not better.
Gordon Murray's iStream process of a very simple, untriangulated spaceframe, panelised with composite sandwich panels, Zenos' hybrid aluminium backbone/composite platform, Ginetta's Niche Vehicle Composite Tub (using simple, shallow-draught composite panels to form a bonded structure) or even Lotus' bonded extruded aluminium structures show a variety of possible ways forward.
You make a valid point about the cost of spaceframes. It's not clear that aluminium alternatives are cheaper or lighter though. Heavily triangulated spaceframes are actually very expensive things to manufacture, due to the amount of skilled manhours required. Ironically, the latest Caterham innovation - butted tubes - makes that situation worse, not better.
Gordon Murray's iStream process of a very simple, untriangulated spaceframe, panelised with composite sandwich panels, Zenos' hybrid aluminium backbone/composite platform, Ginetta's Niche Vehicle Composite Tub (using simple, shallow-draught composite panels to form a bonded structure) or even Lotus' bonded extruded aluminium structures show a variety of possible ways forward.
More rigidity hasn't translated into lap times with the 7
The CSR is twice as stiff as the 7 of the same vintage and, while full cages add a lot of stiffness but not laptime gains.
Equus said:
The Elise chassis is pretty much identical in weight to the Caterham spaceframe (lighter by about 4kg, I think), and the retail price for a replacement chassis appears to be near-as-makes-no-difference the same (Elise chassis is a mere £75 cheaper, from a quick Google - still, £75 per car on 600 cars per year would pay someone's wages).
I accept that the designs are not directly comparable, of course, but that suggests you might be looking for about the same weight advantage as Caterham's butted tube chassis (for which they were suggesting a £1K-£2K premium on cost, don't forget), and about three times the stiffness, with no price premium. With a lighter car overall, like the Caterham, though, you might be able to reduce the size/thickness of the aluminium extrusions to gain a bigger weight advantage.
As an interesting comparison, Pilbeam had a carbon fibre direct replacement for the Elise chassis designed that saved approximately another 26kg (though they didn't declare the stiffness, so I don't know how much better it was in that respect, and doubtless the price was a bit scary as it was a conventional pre-preg tub). As I said, there are cheaper ways to do CF than a conventional pre-preg tub, though.
Where are you getting the stiffness figures from for the CSR, by the way (and what absolute figures do you have for the standard and CSR chassis)?
I'm working on circa. 2,500lb.ft/degree for the standard chassis, fully panelled but uncaged, but the best information I have is that the CSR whilst better, isn't anything like twice as stiff as the standard item.. the figures I've heard quoted by the company suggest 'only' a 25% improvement.
Re CSR stiffness, the claim is from Caterham themselves though I have seen no figures. I believe some of the improvement has been fed into later s3/5 chassis. I accept that the designs are not directly comparable, of course, but that suggests you might be looking for about the same weight advantage as Caterham's butted tube chassis (for which they were suggesting a £1K-£2K premium on cost, don't forget), and about three times the stiffness, with no price premium. With a lighter car overall, like the Caterham, though, you might be able to reduce the size/thickness of the aluminium extrusions to gain a bigger weight advantage.
As an interesting comparison, Pilbeam had a carbon fibre direct replacement for the Elise chassis designed that saved approximately another 26kg (though they didn't declare the stiffness, so I don't know how much better it was in that respect, and doubtless the price was a bit scary as it was a conventional pre-preg tub). As I said, there are cheaper ways to do CF than a conventional pre-preg tub, though.
Where are you getting the stiffness figures from for the CSR, by the way (and what absolute figures do you have for the standard and CSR chassis)?
I'm working on circa. 2,500lb.ft/degree for the standard chassis, fully panelled but uncaged, but the best information I have is that the CSR whilst better, isn't anything like twice as stiff as the standard item.. the figures I've heard quoted by the company suggest 'only' a 25% improvement.
The big problem (Re alternatives) is that aluminium body contributes significantly to chassis stiffness but adds relatively little weight. As the S4 and Westies show using fibreglass costs weight.
Here http://www.autocar.co.uk/car-review/caterham/seven... though that's not the only place I have seen it. What I read was that 25% was initially achieved, but the aim was to make the effect of a cage undetectable. And they ultimately made it 100% stiffer to achieve that.
coppice said:
I think we are missing the point; despite many attempts to diversify Caterham has signally failed to do so. Unless it can design , develop and build a product which is entirely novel in concept and execution it is swimming with the sharks who already compete in the extreme lightweight track/ sports car like Zenos, Ariel and Radical. I can't see it beating them in the same market.
I don't think Caterham are or should try compete head on with those cars. The 7 has just enough weather protection and luggage space to make a weekend away a practical proposition, they don't. The 7 is narrow, they aren't. Keep/enhance those advantages and there will continue to be a market. The next Elise could spoil the party but I doubt it will.
Equus said:
Since Caterham have built a business on parasitising Lotus' reputation, perhaps they might draw some inspiration from other Lotus sports racers and/or the early concepts work that Lotus did on the 'step-in car' that ultimately grew doors and became the Elise, and go mid-engined:
Lotus couldn't make such a minimalist mid-engined car work because they had to comply with full EU Type Approval, but Caterham only has IVA or LVTA to deal with, so they can do something more extreme.
I can't see mid-engined being either technically or commercially the route to go. Do that and you are competing with other similar cars. While a mid engine has advantages for a single seat race car - aero and traction in particular - on a road car it's far from clear. If you want balance and a car with adjustable, forgiving handling - and I've driven nothing better than a 7 in that regard, a mid FRONT engined car has advantages. It's much easier to make a front engined car narrow too. So I can see one of the USPs of the 7 is that it is front engined. Another is that it is (mostly) NA in an increasingly turbo world. That route is likely (legislation permitting) to yield a continuing niche market, which the (unrivalled) race series will continue to bolster. Certainly the long waiting lists (9 months?) don't suggest any falling of demand - more the reverse.Lotus couldn't make such a minimalist mid-engined car work because they had to comply with full EU Type Approval, but Caterham only has IVA or LVTA to deal with, so they can do something more extreme.
That's not to say the major aero advantages shouldn't be sought, or that Colin Chapman's mantra of "adding lightness" shouldn't still be fundamental to their DNA.
Yes but they are not produced in anything like the same numbers, and some are in a completely different price bracket. There have always been lots of players in the kit car field, but very few have ever produced cars in the hundreds as Caterham do. So they are not - in commercial terms - competitors to Caterham. Of course Ginetta or Westfield or one or two others could overtake Caterham - but there's been no real sign of that to date.
Equus said:
Point of order, but the De Dion was hardly a Caterham innovation: there had been examples of Lotus-built Sevens (and even Six's) with de Dions, going back almost to prehistory - they just never productionised it as an option because of cost.
And the de Dion is actually a heavily compromised design, with current levels of tyre grip, hence the need to cobble-on additional Watts linkages to brace it (a bodge that must have Chapman spinning in his grave, considering the amount of fuss he made over a single extra link being added to the Esprit's suspension!). Westfield showed them the way, with a proper IRS, but God knows it took them long enough to follow, with the CSR.
I'd disagree about de Dion. While IRS has advantages in unsprung weight and ultimate lateral grip - a De Dion gives better traction and, because there is no camber change, is more predictable. I think you miss the point about Watts linkages - they are put in to prevent the bump steer inherent in a Panhard rod (laterally) and trailing arms (longitudinally) - nothing to do with rigidity. Actually the ones used instead of trailing arms are not perfect - the rear arm is shorter than the front so it isn't geometrically pure. And the de Dion is actually a heavily compromised design, with current levels of tyre grip, hence the need to cobble-on additional Watts linkages to brace it (a bodge that must have Chapman spinning in his grave, considering the amount of fuss he made over a single extra link being added to the Esprit's suspension!). Westfield showed them the way, with a proper IRS, but God knows it took them long enough to follow, with the CSR.
Equus said:
bcr5784 said:
I'd disagree about de Dion. While IRS has advantages in unsprung weight and ultimate lateral grip - a De Dion gives better traction and, because there is no camber change, is more predictable.
DeDion gives better traction on perfectly smooth surfaces. In reality, the higher unsprung weight and the fact that a bump at one wheel is partially transmitted to the other more than negates any benefit.If you don't agree with this, then ask yourself why no modern race car (or proper, high performance road car, for that matter) uses a deDion.
Even Caterham themselves acknowledged at the time they introduced it that proper IRS would have been better, but said that they felt that (at the time) they didn't have the resources to design a proper IRS system. Obviously, they've now remedied that with the CSR.
bcr5784 said:
I think you miss the point about Watts linkages - they are put in to prevent the bump steer inherent in a Panhard rod (laterally) and trailing arms (longitudinally) - nothing to do with rigidity. Actually the ones used instead of trailing arms are not perfect - the rear arm is shorter than the front so it isn't geometrically pure.
Not true. They are put in to prevent deflection tramp of the deDion tube, caused by it having the lower a-frame pickup in the centre and the upper trailing arm outboard. Difficult to describe on here, without sketches, but basically flex in the deDion tube (and its bushes) can allow the hub to swing forwards and backwards to some degree with this arrangement, since it is only restrained at the top.
The upper trailing arm (which is retained, of course) still describes an arc which causes bump steer. I've not actually checked the geometry and measurements, but common sense suggests that the asymmetry in the Watts link is deliberate, to match this and so avoid binding.
Re De Dion you are simply wrong wrt bump steer. With a full set of Watts linkages on a de Dion tube the wheels move (practically speaking) vertically up and down on bump (that is the reason for having them) and when the axle squats or lifts under acceleration or braking again the wheels move vertically without lateral movement. See https://en.wikipedia.org/wiki/Watt%27s_linkage. Remember too that with IRS upward movement of one wheel produces lateral movement and hence a modicum of bump steer.
The reason the rear link is shorter than the front is simply that the rear link is attached to the rear of the chassis and you would have to make the car longer if the link was as long as it should otherwise be.
Why aren't they more commonly used? On mid engined race or road cars you generally cannot accommodate them because the gearbox gets in the way, and as I say ultimate lateral grip is (or can be) better with IRS. On road cars - de Dions take a lot of space if you have a decent amount of suspension travel (Remember the Rover 2000 - boot space was so compromised that the spare wheel was often mounted on the boot lid) . If you want forgiving predictable handling (the 7s forte?) De dions have a lot to recommend them.
That's not to say I'm anti IRS - just that I'm not convinced it would necessarily produce a better road car.
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