04
Dec
10

All linky, no thinky: (second) special edition on suspension geekery

(Previously.)

I’ll say this up front: if you’re not a motorsports nerd, you almost certainly won’t care about this post.  If you come here for the rants, Ken at PopeHat, skippystalin at Postcards of the Hanging, and Tyler Cowen at Marginal Revolution have some good stuff you’re sure to enjoy.  Have fun, and check back soon!

…okay, let’s get our vehicle-dynamics on.  First, Mike Kojima over at MotoIQ has an article on camber adjustment:

A lot of it is pretty basic stuff if you’re the sort of person who’s likely to keep Race Car Vehicle Dynamics within easy reach of the keyboard, but the virtue of this article is that it combines a fair bit of data, from tire properties to suspension compliance, into a single cohesive whole.  It also gets into some of the issues involved in making your car’s Macpherson-strut front suspension not suck, which more and more seems to me to be a matter of just not letting the damn thing move.

Next we up the ante with this Craig Scarborough post on heave-and-roll rear suspensions in Formula One:

“Spring-less” is a bit of a misnomer: turns out that some F1 teams are running their rear suspensions without corner springs, but of course the heave spring and antiroll bar are still there.  It’s much like a monoshock (which I’ve usually seen on the front of a single-seater), but with two dampers that activate in roll as well as pitch.  Notably, not having to package a pair of rather long torsion springs somewhere on the gearbox makes the car designer’s life much easier; this explains (in hindsight) how Red Bull were able to run such a small damn rear end on the RB5 and RB6.  I wonder whether the same thing could be applied to the front to enable an extreme vee-section?  Granted that there are limits to what one can do with the nose, as it needs to pass a pretty strict impact test, but still….

Finally, Jersey Tom blows my mind with a bit of extra suspension-kinematic complexity:

Briefly:

Tire rate also can change with camber – significantly. Typically it goes down the more you lean a tire. This in itself isn’t anything earth shattering.

…well, not if you’re a proper automotive engineer, but I’m just a glib dilettante and this is the first I’ve heard about it.  Probably glossed right over that part of Paul Haney’s book.

So, more camber gain in bump gives you more camber thrust from the outside wheel in roll (which is good) and a lower tire rate (and thus lower overall wheel rate) — which probably gives you better compliance, which is also good… but camber gain now affects your dynamic cross-weight in the same sort of way as the roll couple.  As far as I can tell, in a reasonable car that rolls more at the rear than at the front this just does more of what you’d expect in terms of wedge, provided that front and rear camber changes are about the same and everything’s linear and a bunch of other assumptions that don’t hold in the real world.  Well, no-one said it would be easy….

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