Jersey Tom wrote:But correlation does not = causation. There's a reason why ONLY one manufacturer uses a pull rod setup. It's not like it's a new invention or anything... and all the teams know how critical aero is.
... & they might just be aware of the importance of c.g. height, which is why everybody copied them this year ...
Apologies, JT. I jest.. Not now, though:
Jersey Tom wrote:With regard to pullrods being compliant... not sure if I believe that. Sure, you don't have to worry about buckling... but even a 0.500" OD x 0.035" wall x 24" long steel tube pullrod has a springrate of 64,000 pounds per inch if I did my quick dirty math right.
That's about as small a pullrod I can imagine... and that's not exactly what I'd call compliant given that it's well over an order of magnitude higher than the wheel rate.
I imagine your calcs are sound, but you haven't extracted your loads from the pull rods, yet.
The lowest front installation stiffness I have seen for an open wheeled carbon chassis vehicle was the Arrows A21 at < 1 KN/mm. The pull rod Dallara IRL is not much of an improvement (certainly not an order of magnitude greater than its "wheel rates"), & is a factor of 2 (roughly) down on its push rod predecessor.
p.s. If there is one thing you can be sure of, it is that every team on the grid did a detailed cost/benefit analysis of a rear pull rod layout when designing this year's cars. They clearly missed something, probably the freedom it offered to implement another performance enhancement.