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Bravo73
12th Jun 2008, 22:55
Great launch vid for a new concept from BMW:

http://www.bmw-web.tv/en/channel/new


I don't know how knife proof it is though... :uhoh:

ShyTorque
12th Jun 2008, 23:09
Velorex did that 50 years ago!

Whirlygig
12th Jun 2008, 23:13
Doesn't that just go to show how old-fashioned BMWs are??? :}

Cheers

Whirls

jb2_86_uk
12th Jun 2008, 23:14
very cool!

love those rear light clusters.

Not only knife-proof issues though bravo, what about stone-chips and the like? :suspect:

Its no wonder no new cars have style these days. All the designers are busy getting high and designing cars like that!

JB

G-CPTN
12th Jun 2008, 23:42
Er . . .
The skin of a 'conventional' car body is also the structural strength that supports the mechanical components, so by abandoning this requires additional material to be used in order to restore 'rigidity'.
Anyone who drives an open-top version of a saloon car might be familiar with 'scuttle-shake' (though some manufacturers add bracing to counter this):- http://driving.timesonline.co.uk/tol/life_and_style/driving/features/article731967.ece

Another 'effect' would be the distortion of the flexible skin as the airflow altered as the vehicle speed increased (again, owners of (simple) soft-top cars will be familiar with the way the top 'balloons' at high speed (expensive models probably have double-skinned tops to counter this, but older cars such as Austin Healey Sprites had single-skin tops).
Even rigid-skinned vehicles can need bracing to counter 'oil-canning' of large panels due to air pressure.

Stone-chips shouldn't be a problem, especially if the 'skin' is an elastic membrane, in fact that would be an advantage.

Overdrive
13th Jun 2008, 01:03
It has great potential, now that the materials and engineering is available to possibly make it feasible as a product. If the extra structural weight in lieu meant a saving of only a third of the replaced panel weight, that would be something.

Agree about the panel distortion G-CPTN. Your 80 grand new Beemer can now look like an old 'plane when moving!

G-CPTN
13th Jun 2008, 01:35
If the extra structural weight in lieu meant a saving of only a third of the replaced panel weight, that would be something.If only it were to be that beneficial.
Decades ago, cars were built on a 'chassis' (a sort of ladder-frame) that acted as a structure to support the engine, gearbox and rear axle. Onto this was built a body, comprising a seating compartment with doors and outer panels (usually) bolted on. In some cases the bodywork was skinned with fabric or even leather.
In a move to save weight the 'unitary construction' method was introduced whereby a stressed 'tin box' had the original mechanical components fastened to this. Continued development of this technique has allowed greater rigidity to be achieved for less material content (ie less weight).
Of course there are still models (and manufacturers) that are less efficient designwise (often intentionally) and produce heavier structures (which usually have better rigidity and better NVH - noise, vibration and harshness - resiliance) ie luxury cars tend to be quieter and more refined but heavier, but, by comparison to vehicles retaining a separate chassis-frame (some SUVs) unitary construction vehicles are lighter.
Some vehicles (certain sportscars) are built using a spaceframe with either glassfibre or some moulded material that is non-stressed used as cladding. Some have stressed panels stretched and rivetted or welded to provide structural strength. It's a question of compromise of weight versus torsional rigidity to provide adequate 'refinement'.
I'm confident that a vehicle with a non-stressed (flexible) skin would need to be heavier than a stressed-skin structure for the same degree of rigidity. In other words you would need to add more weight or have an inferior structure. Saving any of the panel weight is not, in my opinion, feasible if you wanted similar 'quality' of ride and handling (and refinement). The extra weight needed would increase fuel consumption.

The body shell broke new ground for the company. As a unitary construction, it had a stiffer base, while being lighter than the traditional separate chassis and body build.

Monocoque, meaning 'single shell' in French, is a construction technique that utilises the external skin to support some or most of the load.

This is as opposed to using an internal frame or chassis that is then covered with cosmetic body panels.

Overdrive
13th Jun 2008, 02:18
I understand what you're saying there G-CPTN, and am aware of the science behind NVH, re. comfort, harmonics, torsion, etc. Modern suspension systems though can provide much better results in this area with lighter gross vehicle weights as well as heavier (though much of it is in a fight with 40 and lower series tyres!).

My point is that all else being equal, if the weight saving is available, which I think might be with a modern space frame design, then that's a good thing, particularly since the gains of the '80s in weight reduction have been reversed so much recently. Some of even the small modern cars even are heavy... with so much kit in them now.

For sports vehicles, as that prototype is, the needs are different (accepting the scuttle shake issue). I guess we'll see!

ShyTorque
13th Jun 2008, 09:33
Doesn't that just go to show how old-fashioned BMWs are???

I think it goes to show that most "new" things in engineering have already been tried before.

For example, courtesy lights that don't drop out when you slam the door were invented decades ago but some manufacturers apparently still fit the other type. :p

My open topped car weighs just 460 kgs, including its separate chassis. The scuttle doesn't shake. It stays still and the rest of the car shakes around it... :}

BarbiesBoyfriend
13th Jun 2008, 10:13
The GINA looks great.

Methinks it's typical 'graphic designer' arty-farty pishy design which looks 'out there' but in reality is a non-starter outside of it's creators overactive imagination.

What about security for starters? A stanley knife would gain access to any of it. There are certainly folk who'd have fun vandelising it in similar fashion.

What about the behaviour of the surface skin at high speed? Looks good when parked but it's be kind a rippley at 100mph.

In engineering you get nothing for nothing. As G-CPTN said every unit of stiffness or strength thats missing due lack of metal on the outside MUST be replaced with subsurface structure which will most certainly weigh even more than the relatively light metal monocoque.

It's innovative thinking but it's all been done before.

My own car has an aluminium monocoque (it's an Audi A8) which really IS the way fwd. Saving weight on a car is something thats always worth doing.

You get a benefit every time you accelerate it, brake it or corner it.

Best tho to let someone else suffer the depreciation tho.:ok:

Aaaaaaaaaaaaaaaargh!
13th Jun 2008, 14:40
I'm confident that a vehicle with a non-stressed (flexible) skin would need to be heavier than a stressed-skin structure for the same degree of rigidity.What about a horse? A horse is fairly flexible and we used them for hundreds of years.




A horse probably has better off road capability AND better gas mileage too.

Ozzy
13th Jun 2008, 16:08
It's missing the "VA":E:E

Ozzy

Capt.KAOS
13th Jun 2008, 17:28
Another fugly Bangle-car...:hmm:

ShyTorque
13th Jun 2008, 19:16
Ozzy, I thought that too. I would hope if they ever produce a V4 version they don't put the badge on the boot lid....

V4 Gina. You know what's likely to be inside... :oh:

Horses? The emissions are terrible. Rather than a catalytic converter you need a bucket and a shovel.