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-   Solstice and other Automotive Related News (http://www.solsticeforum.com/forum/f13/)
-   -   New Lambo "roadster" (coupe w/targa top) (http://www.solsticeforum.com/forum/f13/new-lambo-roadster-coupe-w-targa-top-74277/)

Shadofax 02-05-2013 08:25 PM

New Lambo "roadster" (coupe w/targa top)
 
Very nice, very expensive, nice article:

Lamborghini Aventador Roadster, ready for takeoff: Motoramic Drives | Motoramic - Yahoo! Autos

but getting down to the removable top, this was interesting:

"And when it came to the carbon fiber convertible roof, Lamborghini freely admits sacrificing some ease-of-use for beauty: “We told the designer, you can do whatever you want – it just has to look the best,” says Stephan Winkelmann, Automobili Lamborghini’s elegant chief executive.

The result? No bulky folding hardtop or shapeless cloth pup tent to break up those suggestive body lines. Instead, two glossy, ridge-backed panels of carbon fiber, weighing just 13.2 pounds each, pop into the roof -- and take up nearly the entire under-hood cargo space when not in use. Storing or fitting the roof takes some practice and steady hands. Owners will want to keep a sharp eye out for sudden thundershowers."

:lol:

Well....at least we didn't spend $450k+ AND be fighting with a removable targa.

What could have been......I think Pontiac would have redesigned the targa top into 2 pieces that would have fit in the trunk after a year or two more coupe production.

wspohn 02-06-2013 07:17 AM

I've wondered why GM didn't opt for T tops for the coupe because I would think they could have been designed to be stacked in the back of the car when removed.

Anyone know if the addition of a permanent member between rear and front window areas would have constituted an officially different body model and required complete recertification and crash testing? That's one reason I thought might have prevented what would otherwise seem a preferable course to the rather odd set up we ended up with a top that you can take off with nowhere to put it.

Of course I would also have liked a roof that increased torsional stiffness the way the Aventadors apparently does! I was never sure that was even posible with a removable panel until I saw that article. Too bad GM missed a bet.

Shadofax 02-06-2013 07:25 AM

Well, Hopefully the thought of Ttops would have never entered their minds....I just can't get past that being a 70'/80's thing. A targa that comes off in half would be the preference. And that increased safety and stiffness cost the car in weight to the tune of 110 pounds. Seeing as we don't have a top speed of more than 200mph I would have hoped that the top redesign really would come with little or any added weight.

wspohn 02-06-2013 07:41 AM

Know what you mean about T tops, I just regret the missed opportunity to up to double the stiffness of the chassis for no significant cost by making it a real coupe!

OSUCherokee 02-06-2013 11:24 AM

New Lambo "roadster" (coupe w/targa top)
 
Quote:

Originally Posted by wspohn (Post 1110603)
Know what you mean about T tops, I just regret the missed opportunity to up to double the stiffness of the chassis for no significant cost by making it a real coupe!

I think double is a bit over-estimating.


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wspohn 02-06-2013 11:40 AM

Quote:

Originally Posted by OSUCherokee (Post 1110612)
I think double is a bit over-estimating.


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I could understand how you might think that, but see this on the BMW Z4 sports car:

Quote:

Scoring 14,500Nm/degree in BMW’s torsional stiffness test, the M Roadster is pretty stiff for an open car, and despite its wide 225/45 and 255/40 rubber on 8.0J and 9.0J x 18-inch alloys rubber, scuttle shake on poor roads in minimal. Even so, it does not come close to the Coupé’s impressive 32,000 Nm/degree, which is more than double the Roadster’s rigidity.

(BMW Z4 M Coupé - PistonHeads)

Anyone have a torsional stiffness figure for our favourite 'flexible flyers'?
Ah, wait, I found an old thread on this http://www.solsticeforum.com/forum/f...roll-ect-5388/

The Solstice is apparently 8,000 Nm/degree or half as stiff as the convertible BMW. No wonder the factory found out they needed special kits to keep the rear suspension under control when they went racing! Mind you that thread quotes lower figures for the BMW than the pistonheads article did too.

DDM may have something to add although I seem to recall asking Dave if they had actual torsion measurements regarding their Backbone and I think they just had some measure of droop indicating effect, but not a conventional value in Nm/deg. of twist.

LiquidPT 02-06-2013 11:56 AM

Quote:

Originally Posted by wspohn (Post 1110614)
DDM may have something to add although I seem to recall asking Dave if they had actual torsion measurements regarding their Backbone and I think they just had some measure of droop indicating effect, but not a conventional value in Nm/deg. of twist.

I believe you're right...

OSUCherokee 02-06-2013 02:47 PM

New Lambo "roadster" (coupe w/targa top)
 
Quote:

Originally Posted by wspohn (Post 1110614)
I could understand how you might think that, but see this on the BMW Z4 sports car:



(BMW Z4 M Coupé - PistonHeads)

Anyone have a torsional stiffness figure for our favourite 'flexible flyers'?
Ah, wait, I found an old thread on this http://www.solsticeforum.com/forum/f...roll-ect-5388/

The Solstice is apparently 8,000 Nm/degree or half as stiff as the convertible BMW. No wonder the factory found out they needed special kits to keep the rear suspension under control when they went racing! Mind you that thread quotes lower figures for the BMW than the pistonheads article did too.

DDM may have something to add although I seem to recall asking Dave if they had actual torsion measurements regarding their Backbone and I think they just had some measure of droop indicating effect, but not a conventional value in Nm/deg. of twist.

It would appear from Solsticeman's post that its almost impossible to accurately compare car "stiffness" from one car to another given all the variables.

I'm not arguing that a coupe wouldn't be stiffer. I'm just saying I doubt it would double the perceived stiffness of the car.

I do also believe that Dave found the weak link in the car with the tunnel brace. GM was on course to make those updates to the car to stiffen it up. The pro beam is a perfect example. They just ran out of time. :(


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wspohn 02-06-2013 02:56 PM

Quote:

Originally Posted by OSUCherokee (Post 1110635)
I'm not arguing that a coupe wouldn't be stiffer. I'm just saying I doubt it would double the perceived stiffness of the car.

Not sure I follow.

The BMW convert was already stiffer than the Solstice and converting it to a proper coupe more than doubled the stiffness. Why wouldn't doing the same thing to the Solstice result in at least that much improvement?

And not sure what you mean by 'perceived' stiffness. We are talking about measured numbers, not seat of the pants impressions.

The figures in my quotation were from BMW and presumably can be regarded as gospel; I'm not sure where the poster in that thread I dredged up got his figures.

TomatoSoup 02-06-2013 04:13 PM

Quote:

Originally Posted by wspohn (Post 1110636)
The BMW convert was already stiffer than the Solstice and converting it to a proper coupe more than doubled the stiffness. Why wouldn't doing the same thing to the Solstice result in at least that much improvement?

And not sure what you mean by 'perceived' stiffness. We are talking about measured numbers, not seat of the pants impressions.

The figures in my quotation were from BMW and presumably can be regarded as gospel; I'm not sure where the poster in that thread I dredged up got his figures.

If you read that post more carefully, I think you'll see those figures were JUST examples for comparison. NOT actual figures for those cars. So the BMW may - or may not - be stiffer than the Sol.

wspohn 02-06-2013 04:21 PM

Quote:

Originally Posted by TomatoSoup (Post 1110639)
If you read that post more carefully, I think you'll see those figures were JUST examples for comparison. NOT actual figures for those cars. So the BMW may - or may not - be stiffer than the Sol.

You are right. I don't think there is much doubt that the Solstice will be less stiff than the BMW though - that car is better than most.

I wonder if we have any factory guys that have actual figures - I searched and couldn't find any.

TomatoSoup 02-07-2013 07:27 AM

No, I couldn't find figures either. I did find this though with a list of cars (not ours) and thought it interesting... http://www.germancarforum.com/commun...igidity.12334/

Especially these bizarre juxtapositions near the bottom: :lol:

Land rover Freelander 2 - 28,000 Nm/degree
Lamborghini Countach 2,600 Nm/deg

wspohn 02-07-2013 07:49 AM

Interesting.

I get into arguments with guys that race old MGs. My MGA has a very sturdy frame, further reinforced by a careful roll bar installation and is a pretty stiff platform. The MGB guys have a unibody made up of welded together stampings which gives you a decently stiff chassis that can quickly deteriorate when the rocker panels rot and people bodge them and don't repair properly, resulting in extreme cases where you can't open both doors at once and expect to be able to close them again.

The MGB owners somehow manage to ignore the second part, about how bad it can get with any rust and assume they all have pristine mint cars that are as stiff as when they left the factory.

I guess we don't need to worry about rust as much on the Solstice, but I have a vision of some junior engineer analyzing the torsional stiffness of the original design, putting his stamp on it as being 'good enough' and then having to eat his words when the factory first sponsored solo competition and found out that his calculations had been garbage and the chassis flexed far to much for a competition setting.

They probably made him design the rear suspension kit (elaborate and expensive) to fix that and probably sent him off to shred the original figures on the stock chassis, never to be released to the public.

IIRC the Miata is also bad in this respect - at least the first guys fitting Ford V8s to them found that they twisted all over the place.

Shadofax 02-07-2013 08:07 AM

Quote:

Originally Posted by wspohn (Post 1110640)
You are right. I don't think there is much doubt that the Solstice will be less stiff than the BMW though - that car is better than most.

I wonder if we have any factory guys that have actual figures - I searched and couldn't find any.

The Sol has done well on road coarses at sanctioned events. If you want that there are cages out there for it. Our car seems to handle pretty darn well having the backbone, probeam and LV brace installed. I want the car to stay light.

Just line that BMW up for me on a nice straight 1/4 mile......

wspohn 02-07-2013 08:23 AM

Quote:

Originally Posted by Shadofax (Post 1110677)
Just line that BMW up for me on a nice straight 1/4 mile......

I'll save you the humiliation -

Solstice GXP 1/4 mile around high 13s
Z4M 1/4 = 13.2 or so.

I don' really care that much about 1/4 mile times anyway, I am much more interested in how the cars handle on a winding road.


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