Article: UltraChassis Implementation (Chassis Flex Model)

6. Chassis Flex, and Design Freedom
Yup, the biggest one, and quite significant in the case of the BT44B Brabham. I think it's no secret that, as a generality, older cars were not as stiff as their modern counterparts. The BT44 is no exception, as we'll see later on.
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I'm sure Michael is well aware of this but the above might give a misleading impression to some about older cars. The effect of chassis stiffness depends on suspension stiffness. Older cars were not as stiff as their modern counterparts BUT their suspension wasn't as stiff either. A modern F1 car has suspension 10 times stiffer than say a 60s F1 car, so needs to have a chassis stiffness 10 times stiffer too - just to keep the effect of the chassis stiffness the same.
 
Hi David, you're right I could have phrased that a little better. A couple things, obviously I would have to agree that with stiffer suspension you would generally want a stiffer chassis. Also cornering G's have strong influence. It's really the roll stiffness discrepancy between front and rear that has an impact here. If the car had an equivalent roll stiffness front and rear, on a flat road, in steady state cornering, you would essentially have 'no flex' (with our current system). Yet going beyond the way flex is simulated in rF2, that flex can influence the geometry which is more sophisticated than the system we have. Although we could theoretically do it with UltraChassis, it's still a bit expensive on current hardware to make run in real-time. When I made that statement, I was also thinking on broader terms. While this covers the Brabham in depth, I try to think of this in general modding terms. If you look at road cars of the 70's, they often had abysmal chassis rigidity, in the region of 2500-8000 Nm/°. Modern cars are generally stiffer, but not hugely so, and you'll find that most current cars have something in the region of 15,000-42,000 Nm/°, and they're certainly not 5x more stiffly sprung. The Brabham has front wheel rates around 40kN/m, the FISI 2012 has 144kN/m (default setups). A modern F1 cars' stiffness is close to 30,000Nm/° compared to ~6,000Nm/° of the 70's Brabham. The cars do both weigh in around 650kg (or close enough). So the springs are 3.6x stiffer and the chassis about 5.0x stiffer. Therefore, the overall effect on vehicle dynamics is probably still slightly higher in the Brabham. Thank you very much for your input.
 
85 degrees of freedom with a typical vehicle setup in rF2 !!!

Congratulation. ISI You Win.

My friend have project DIY Motion sim. If he know these 85 DOF.
He will be have big problem :)


When I'm student and have examination about 6 DOF calculate by manual. Make me headache a lot.
This is 85 DOF. How do yo do that?

Thank you for sharing hard work behind the scene.
 
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