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Re: carbon fibre driveshafts

must be one of those wound-up shafts...........
-----Original Message-----
From: David Eaton <david.eaton@computerland.co.nz>
To: 'quattro@coimbra.ans.net' <quattro@coimbra.ans.net>
Date: Tuesday, January 27, 1998 5:02 PM
Subject: re: carbon fibre driveshafts

>thank you bob; phil, i stand corrected.  thinking of formula 1
>suspension components, clearly there is *no* flex in these applications,
>but you have explained it very well bob, thanks.
>so audi make c/f driveshafts with a deliberate degree of flex...
>actually thinking about it, maybe this helps to explain their habit of
>making amazing starts in the races...
>'95 rs2
>'90 ur-q
>>Date: Tue, 27 Jan 1998 14:57:17 -0500
>>From: "Robert K. Davis" <bob@btv.ibm.com>
>>Subject: RE: carbon fibre driveshafts 
>>Actually, I was a little hasty in my assumption that the carbon fiber
>driveshaft would fail with 10 degrees of twist.  The driveshaft I used
>in the example had 3.2mm wall thickness, 102mm I.D. by 3050mm long. For
>a 102mm I.D. by 3050mm long shaft of the same material with 0.2mm wall
>thickness, the  critical buckling torque is about 30,000 Nm.  Now, the
>critical buckling torque is dependent on the wall thickness raised to
>the 2.25 power.  So, for a 3.2mm wall thickness, the critical buckling
>torque would be on the order of 15,000,000Nm.  Given that the torsional
>stiffness is 45,000Nm/rad, this relates to 341rad, which does seem
>excessive.  If the claim is 2*pi rad of windup, then the critical
>buckling torque need only be 283,000Nm.  Clearly it seems that such a
>driveshaft is within the realm of possibility.