The list: Torsional Rigidity

[K-A]

There is a difference between Torsional rigidity and Compressive strength(which some members confused for Torsional rigidity) so I don't think we ought to place too much emphasis on it alone.
I think it will be more prudent to look at the system(shell in this case) from the perspective of the 3-principal stresses: Torsional, Axial(Compression/Tension) and Bending.

The number that I quoted for the Cruze (17.66 KNm/degree of deflection), is that the same as 17,660 nm/deg? Or are those two numbers using different metrics? I noticed that the former uses a "." in place of a "," and obviously is a 4 digit number, with a "KNm" as opposed to an "Nm".

 

[Monster]

The number that I quoted for the Cruze (17.66 KNm/degree of deflection), is that the same as 17,660 nm/deg? Or are those two numbers using different metrics? I noticed that the former uses a "." in place of a "," and obviously is a 4 digit number, with a "KNm" as opposed to an "Nm".

The K in front means Kilo which equals to 1000. So 17.66 KNm is the same as 17 660 nm

 

[Sunny]

lol, looks like someone skipped elementary school.

 

[Monster]

lol, looks like someone skipped elementary school.

Ops, forgotten about not quoting, my apology.

 

[K-A]

Does anyone know what a 996 Carrera (Hard Top only)'s rigidity is?

 

[Mr. Mercedes]

Do we know how stiff the new S-class is?

 

[Wolfgang]

^ Looks like 40,500 Nm/degree?

Body: maximum stability and high-quality lightweight design

A high level of crash safety, outstanding rigidity for excellent handling with extremely low levels of noise and vibration. These were the aims when developing the third-generation aluminium hybrid bodyshell for the new S-Class. The lightweight index – the torsional rigidity in relation to weight and vehicle size – has been improved by 50 percent compared to the preceding model.

Since the 220 model series was developed in the 1990s, with an optimally coordinated materials mix, the hybrid lightweight construction has been further developed into an aluminium hybrid bodyshell. During this period the share of aluminium has increased to more than 50 percent. It has therefore been possible to maintain practically the same body weight for 20 years and even slightly reduce it, despite far more stringent comfort and safety requirements and additional functions. In addition to this, structural foams are used at specific points in nodal areas in the new model series. The entire outer skin of the S-Class, including the roof and the front section of the body, consists of aluminium. The high percentage of aluminium is possible thanks to the use of a complete range of semi-finished products (casting, extrusion, sheet metal). The safety passenger cell is made using an extremely high percentage of high-strength steel.

This lightweight design by material and geometrical optimisation coupled with highly complex joining technology allows the new S-Class to further raise the bar in the demanding luxury saloon segment – without adding weight. With a torsional stiffness of 40.5 kNm/degree (predecessor: 27.5 kNm/degree), the S‑Class achieves a new record in its segment.

http://media.daimler.com/dcmedia/0-921-1549267-1-1608034-1-0-0-0-0-0-11702-0-0-1-0-0-0-0-0.html

 

[martinbo]

New S-Klasse - unimpeachably superior. 40,500 Nm/degree? For a luxo-limo? WTH?!? How did they achieve that?

 

[EnI]

New S-Klasse - unimpeachably superior. 40,500 Nm/degree? For a luxo-limo? WTH?!? How did they achieve that?

RR Phantom (2003) also has a torsional stiffness ratio of 40.5k Nm/degree.
And even the LWB version was somehow able to retain the same ratio despite longer wheelbase!!!!

So, it's obviously possible to achieve such stiffness ratio in even in a (ultralong) luxo-limo. and it was obviously possible to achieve that even 10 years ago.

So, getting the same result 10 years later in a much shorter car & lower car doesn't sound groundbreaking at all. Although the result is rather impressive nevertheless. Thumbs up for MB engineers. Still the best result in the segment (eg. 7-series F01s ratio is 37.5k Nm/degree) though.

 

[martinbo]

Great. Now, how much does a Roller cost vs. an S-Class and how much additional torsional rigidity can be had from an extra 500 kg?

 

[Sunny]

(eg. 7-series F01s ratio is 37.5k Nm/degree) though.

Eni, you have a source for that? I read somewhere the figure for E65 was 35000Nm/deg and according to this article F01 is 20% better, which would put it at 42000 Nm/deg.

Anyway the impressive figure for it's time is Phaeton with it's 37000 NM/deg.

 

[EnI]

Great. Now, how much does a Roller cost vs. an S-Class and how much additional torsional rigidity can be had from an extra 500 kg?

Sure Phantom costs more than S-class & it has all-alu body frame, but I'm not sure it cost that much more due to so much R&D money invested in body frame & chassis etc. I have no info as of yet how much Phantom & S-class R&D & body production costs are. But don't be fooled by the MSRP. Since it does not reflect the costs. Mind those are cars with extremely high profit margin per car!!!

Regarding additional weight: I doubt it comes from body frame since it is all-alu and it weights 550kg (body frame only; SWB version). So, I guess Phantom's gross weigh has no affect on body rigidity per se. It's more about body frame architecture strength (and materials used) than the pure weight. Also mind the Phantom is MUCH longer, especially in LWB version which also has 40.5k Nm/degree ratio.

Eg. A8 & XJ also have ASF - how rigid they are? I guess a lot, since ASF architecture leads to great body rigidity. I wonder how rigid the CFRP body frames are compared to all body frames.

Eni, you have a source for that? I read somewhere the figure for E65 was 35000Nm/deg and according to this article F01 is 20% better, which would put it at 42000 Nm/deg.

Nope, the E65's ratio was ~31,200 Nm/degree, while F01's is indeed 20% better: ~37,500 Nm/degree.

http://www.londonroadgarage.com/images/F01 Workbook - Module 1.pdf (Page #10)

 

[Smithee]

Eni, you have a source for that? I read somewhere the figure for E65 was 35000Nm/deg and according to this article F01 is 20% better, which would put it at 42000 Nm/deg.

Anyway the impressive figure for it's time is Phaeton with it's 37000 NM/deg.

I remember reading about this about 2 years ago, anyway here is the link

BMW 7 Series Live Webcast

Is the new 7 Series structurally stiffer than the previous generation?
Through the intelligent mix of structural materials and the use of high-strength steels, the torsional rigidity of the new 7 Series has been improved to 37,500 Nm per degree (vs. 31,200 Nm per degree for the previous generation).

BTW Audi A8 D4 is stiffer than the W222 S Class and the F01.

1. Audi A8 D4 45,000 nm
2. Mercedes-S Class W222 40,500 nm
3. BMW 7 series F01 37,500 nm

For the w222 see the post by Wolfgang above.

For the A8 D4 here are the links;

Audi Reveals New Long Version Of Its Revolutionary A8

2011 Audi A8 (D4) NWB Quick Reference Guide - USA - AudiWorld

The first link tells you the D3 was 36,000 nm, the second link tells you the D4 increased by 25% making it 45,000 nm.

 

[Mr. Mercedes]

Hmmm. @Smithee, the MB press release states that they achieved a new class benchmark with the S-class. And I tend to believe MB's press realeses over the others when it comes to the S-class. I'm a bit skeptical of the A8 measuring 45,000 based on the methodolgy above. It would be nice to see it reported in real terms and not as a % increase.

Eni why would the Phantom have a superior rigidity to the F01? Do they not share the same platform? I think Martin has a point, that 500kg extra has certainly gone somewhere.

 

[EnI]

BTW Audi A8 D4 is stiffer than the W222 S Class and the F01.

1. Audi A8 D4 45,000 nm
2. Mercedes-S Class W222 40,500 nm
3. BMW 7 series F01 37,500 nm

The first link tells you the D3 was 36,000 nm, the second link tells you the D4 increased by 25% making it 45,000 nm.

Indeed. The official figure for D3 is 36k Nm/degree. And Audi press release stated the D4 rigidity was 25% better than the one of D3. Which indeed is 45k Nm/degree. Although Audi haven't stated any absolute figure at all. I wonder why, since 45k Nm/degree is an astounding ratio - something everybody would brag about. Just like they did years before with D3's 36k Nm/degree figure.

As said: ASF frames are (despite being lighter) extremely rigid compared to steel or steel-alu body frames

Eni why would the Phantom have a superior rigidity to the F01? Do they not share the same platform? I think Martin has a point, that 500kg extra has certainly gone somewhere.

No, RR Ghost shares the architecture with F01 7er, not the Phantom!

Phantom features a dedicated all-alu ASF body architecture (just like eg A8, Xj etc or Z8 etc). The SWB Phantom's body frame only weights 550kg (the figure was included in the official Phantom's press releases), while the total weight of the car is (by DIN = without driver & luggage) is 2,550kg. So additional two tonnes are coming from elsewhere, not from the body - mind body rigidity depends only on body architecture & materials, not the weight. Therefore all-alu body frames are lighter & at the same time more rigid than body frames made of steel. And all-CFRP body frames are even lighter & even more rigid.

 

[Smithee]

Hmmm. @Smithee, the MB press release states that they achieved a new class benchmark with the S-class. And I tend to believe MB's press realeses over the others when it comes to the S-class. I'm a bit skeptical of the A8 measuring 45,000 based on the methodolgy above. It would be nice to see it reported in real terms and not as a % increase.

Eni why would the Phantom have a superior rigidity to the F01? Do they not share the same platform? I think Martin has a point, that 500kg extra has certainly gone somewhere.

The 25% increase in torsional stiffness came from Audi of America. As ENI said above ASF frames are extremely rigid compared to steel or steel-alu body frames.

BTW the previous generation Porsche Cayenne was 36,900nm, here is the link - www.porscheengineering.com/.../Porsche-Download.pdf?..

I remember reading the new Cayenne is 15% stiffer making it around 42,500 nm. (sorry cannot find the link)

 

[Wolfgang]

Here's the Audi USA press release when the A8 won the Euro Car Body Award 2010!

The stiffness/weight ratio increased 20%, but the weight decreased about 30 kg. Thus we have:

D4 stiffness = D3 stiffness times 1.2 times 231 kg divided by 261 kg. If this data and calculation are correct (Please check ) this results in an excellent 38,200 Nm/degree torsional stiffness?

This luxury-class model manufactured in Neckarsulm dazzles thanks in large part to its stiffness/weight ratio: the relationship between torsional rigidity and the body’s weight. At a weight of just 231 kilograms (509.27 lbs), the aluminum body is about 40 percent lighter than a comparable version made of steel. In addition, it weighs nearly 30 kilograms (66.14 lbs) less than its predecessor; at the same time, its stiffness/weight ratio has increased by 20 percent.

 

[Wolfgang]

More body tec info might become available soon.

22-24 October 2013 Bad Nauheim, Germany

English/German simultaneous translation
EuroCarBody 2013
15th Global Car Body Benchmarking Conference
Car body presentations

Car body announcement of the EuroCarBody 2013


Alfa Romeo 4C
BMW i3
Ford Transit Custom
Honda Fit
Infiniti Q50
Lamborghini Aventador
Lexus IS
Mercedes-Benz S-Class
Opel Cascada
Range Rover Sport
Renault Captur

Car body presentations / EuroCarBody 2013 / Review - Automotive Circle

 

[Smithee]

Here's the Audi USA press release when the A8 won the Euro Car Body Award 2010!

The stiffness/weight ratio increased 20%, but the weight decreased about 30 kg. Thus we have:

D4 stiffness = D3 stiffness times 1.2 times 231 kg divided by 261 kg. If this data and calculation are correct (Please check ) this results in an excellent 38,200 Nm/degree torsional stiffness?

This luxury-class model manufactured in Neckarsulm dazzles thanks in large part to its stiffness/weight ratio: the relationship between torsional rigidity and the body’s weight. At a weight of just 231 kilograms (509.27 lbs), the aluminum body is about 40 percent lighter than a comparable version made of steel. In addition, it weighs nearly 30 kilograms (66.14 lbs) less than its predecessor; at the same time, its stiffness/weight ratio has increased by 20 percent.

http://audiusanews.com/newsrelease....easer=audi-a8-wins-euro-car-body-award&mid=19

Thanks Wolf, great work as always. If your calculation above is correct then the S Class indeed is the segment leader with 40,000 nm.

BTW do you know if the W222 is based on the new MRA architecture or is it a modified W221 platform?

I have read in some places that the new C Class W205 will be the first car based on the new MRA.

 

[Wolfgang]

Hard to say, as it appears to be a gradual transition lasting from 2006 to about 2016 and also includes the new modules.

Mercedes-Benz distils platform strategy