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    I need help locating a post

    Someone posted a scan from a magazine within the last week or so(I think) that showed the torsional stiffness values for a number of cars. I only glanced at the post and I don't even remember now which cars were listed.

    I have been looking for this post for several hours and can't seem to find it. I have obviously been working hard, but not smart.

    Can anyone help me locate this post or direct me to where I might find this information? Or, more specifically, the torsional stiffness(the actual number) for the Carrera GT, GT2, GT3 and Cayman S.

    Thank you in advance.

    Greg A

    Re: I need help locating a post

    teflon,

    Any success?

    Re: I need help locating a post

    Maverick,

    Sorry, I missed your post until now. Thank you for your interest.

    Unfortunately, no. Maybe I've gone crazy and imagined the post's existence.

    Greg A

    Re: I need help locating a post

    Quote:
    teflon said:
    Maybe I've gone crazy and imagined the post's existence.




    I know I'm crazy so here are approximate numbers I was able to find from Google and the Rennteam search feature:

    Static Torsional Rigidity:

    Cayenne -- 36,900 Nm/degree
    Source:
    www21.porscheengineering.com/pdf/1-2003_PE-Magazine_e.pdf

    996 GT3 Mk II -- 25% more than 996 C4 narrow-body
    The steel foundation for the bodyshell of the 911 GT3 comes as before from the 911 Carrera 4. To match the enhanced performance of this new sports car, the bodyshell has been further reinforced at all essential points, thus offering an even higher standard of passive safety and enabling the new 911 GT3 to pass all the requisite crash tests with flying colours. At the same time these reinforcements serve to increase static torsional stability by no less than 25 per cent, providing ideal conditions for stable roadholding and exact suspension control.
    Source: http://www.rennteam.com/showflat.php?Cat...h=true#Post8096

    CGT -- 26,000
    Source:
    http://www.pistonheads.com/roadtests/doc.asp?c=105&i=8496

    Cayman S -- 31,500
    911 Coupe (997) -- 31,500
    ...approximately 31,500 Newton metres per degree is almost the same as on the 911 Coupé, meaning that it would take the maximum torque of approximately 92 Cayman S engines to bend the body of the car by just 1*. This extremely high level of stiffness has direct repercussions on the precision of the chassis and suspension. With even severe bumps on the road having only a minor effect on the geometry of the body structure, the geometry of the chassis and suspension remains almost unchanged even when the going gets tough, the Cayman S driving like on those proverbial rails.
    Source: http://www.schwab-kolb.com/porsche/en/porpr121.htm

    Another old thread mentions additional interesting numbers:
    http://www.rennteam.com/showflat.php?Cat...=11&fpart=1

    996 C2 -- 16,500
    Source:
    http://www.pistonheads.com/gassing/topic.asp?f=70&t=94016

    Now for some faulty calculations:

    If the 996 GT3 Mk II is approximately 25% stiffer than the normal 996 C2/C4 narrow-body (16,500), and if we assume that the GT2 is 25% stiffer than the 996 TT (a whopping 27,000 which does not make sense), the 996 GT2 may possibly have a torsional rigidity of 33750 which is more than the 996 GT3's estimated 20,625 but still less than the Cayenne.

    Re: I need help locating a post

    Quote:
    teflon said:
    Someone posted a scan from a magazine within the last week or so(I think) that showed the torsional stiffness values for a number of cars. I only glanced at the post and I don't even remember now which cars were listed.

    I have been looking for this post for several hours and can't seem to find it. I have obviously been working hard, but not smart.

    Can anyone help me locate this post or direct me to where I might find this information? Or, more specifically, the torsional stiffness(the actual number) for the Carrera GT, GT2, GT3 and Cayman S.

    Thank you in advance.

    Greg A




    Maybe this one?

    http://www.rennteam.com/showflat.php?Cat...true#Post106673

    Re: I need help locating a post

    Brilliant post MAVERICK, very interesting.

    Michael

    Re: I need help locating a post

    Quote:
    Michael Russell said:
    Brilliant post MAVERICK, very interesting.




    You are generous with your praise, Michael. Thank you.

    Re: I need help locating a post

    i don't really undersand how the Cayenne can have a better torsional rigidity than a piece of carbon fiber like the cgt....that sounds odd. Maybe the cgt is too wide or too long.

    Re: I need help locating a post

    Quote:
    Lazy Cat said:
    i don't really undersand how the Cayenne can have a better torsional rigidity than a piece of carbon fiber like the cgt....that sounds odd. Maybe the cgt is too wide or too long.



    One reason of many is the Cayenne has an integrated roof.

    According to a Porsche project leader, a convertible loses approx. 70% of its torsional rigidity.
    Source: http://telegraph.co.uk/motoring/main.jhtml?xml=/motoring/2005/04/30/mfpors30.xml

    If the CGT only lost a conservative 50% of its rigidity by being a roadster, then it might have had a minimum of approx. 39,000 Nm/degree static torsional stiffness as a coupe.

    Re: I need help locating a post

    Quote:
    MAVERICK said:
    Now for some faulty calculations:

    If the 996 GT3 Mk II is approximately 25% stiffer than the normal 996 C2/C4 narrow-body (16,500), and if we assume that the GT2 is 25% stiffer than the 996 TT (a whopping 27,000 which does not make sense), the 996 GT2 may possibly have a torsional rigidity of 33750 which is more than the 996 GT3's estimated 20,625 but still less than the Cayenne.



    Hi Mav,

    Just to throw a wrench into the works, I asked Roland Kussmaul what the resonant frequency of the CGT chassis was when I met him at the Porsche "booth" at the 2003 Geneva auto show. He said he didn't know, but he recalled that the CGT was greatly stiffer than the 996 GT2 chassis.

    Re: I need help locating a post

    I haven't been on the forum for a few days and it was nice to log on and see that some people had finally responded.

    Thank you all very much for the info!


    RC, that wasn't the thread I wanted, but thank you for trying.

    Maverick,

    The numbers I found while searching were a little different. I do not know, but I think the value for the CGT is not correct. I could not find it listed anywhere in any of the official Porsche material I have.

    Thank you all for your help though! I really appreciate it.

    Greg A

    Re: I need help locating a post

    Quote:
    W8MM said:
    Hi Mav,

    Just to throw a wrench into the works, I asked Roland Kussmaul what the resonant frequency...



    Hi Dubya,

    Thanks for the tool . Do you know if there is a conversion factor between torsional resonant frequency (Hz) and static torsional stiffness (Nm/degree)?

    teflon,

    You are welcome.

    Re: I need help locating a post

    Quote:
    MAVERICK said:
    Do you know if there is a conversion factor between torsional resonant frequency (Hz) and static torsional stiffness (Nm/degree)?




    No, I don't.

    It's surely more complicated than a simple conversion factor. There are a number of possible resonant modes: beaming, torsional, etc. The resonant frequency would be a result of mass as well as stiffness, so I don't think it can be a 1:1 relationship.

     
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