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This is interesting. Anyone know anyone with a chassis in Sweden? He should be very wellcome to visit me for a torque test.
In my site
http://hem.passagen.se/hemipanter/
uder "Chassis and components" I have a few words about twisting chassies, together with som Tq numbers for different cars.
Goran Malmberg
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Goran, your web site contains much useful information. I like your car, too! I looked up your chassis stiffness information, and I'll quote it here:
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As for references. Lamborghini Countach 1900 fp/degree. Ferrari 360 spider 6250 fp/degree. Viper gts has a "tube space frame" and 9000 fp/degree. Viper gts-R (Le Mans 24 hr) is reinforced to 13600 fp/degree. Lamborghini Murcielago also uses a high strength tube frame supported with honeycomb carbon fibre to 15000 fp/degree. It clearly shows that the Ferrari has no roof. Here we have cars with cromolly tube frames, carbon fibre, etc. Exotic material, loudly advertised as great stuff that makes those sport scars outstanding. Let me mention that the new SAAB 9-3 Sport Sedan, steel monocoque has a torsional stability of 16000 fp/degree. Showing that good engineering is more important than the use of fancy materials. Embarrassing for the SUPER cars? The Panoz racing car tub carbonfibre monocoque has a stiffness of 45000 fp /degree, but due to the front motor installation the axle to axle ratio is 30000 fp/d, at a weight of 110 pound. A street car that uses a tub monocoque is Koenigsegg . Also made of carbon fibre. This tub is said to have strength of 20500 fp/degree. As this, like the Panoz, is a tub number, the axle to axle ratio should be less. With the same reduction as the Panoz, we should land at 13600 fp/degree. This show that a monocoque is the way to go, even if made in sheet metal. The reason for using steel tube frames is the ease of production in a small numbers. A steel monocoque takes a tremendous investment in tools and engineering.
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Could you explain the axle-to-axle ratio? My understanding is that chassis stiffness should be measured by securing the chassis at the rear suspension mounting points and one of the front suspension mounting points while putting a load on a moment arm outboard of the other front suspension mounting point and measuring the applied torque (moment length x mass) and the resulting deflection. I imagine if you measure from points in front of the front suspension or in back of the rear suspension then the torsional ridgidity value will be less, but in my opinion the only thing that matters is the chassis stiffness between the suspension pickup points (at least for a mid-engine car).