Question about Rear Formula 1 Suspension ! help !

[firasf1dream]

hello guys,
i would like please your help
i need to know something about Formula 1 rear suspension, does the same design rules for the front suspension like Kingpin Angle, scrub radius, Caster angle, Camber angle goes for the rear ? and should the rear have the same angles default configuration as the front ?

here are pictures of my front suspension design :

Instant Center http://i96.photobucket.com/albums/l196/ ... klbelg.jpg

Suspension arms geometry http://i96.photobucket.com/albums/l196/ ... ft5dyj.jpg

Camber Angle http://i96.photobucket.com/albums/l196/ ... eo8wbq.jpg

Kingpin Angle and Scrub Radius http://i96.photobucket.com/albums/l196/ ... vd1out.jpg

Thanks everyone in advance

[Shooty81]

Depends on your steering angle in the rear

No really as first step it is not wrong to have a similar geometry as in the front.

You don't need to care about the steering-specific items as caster and scrub radius.

[firasf1dream]

Depends on your steering angle in the rear

No really as first step it is not wrong to have a similar geometry as in the front.

You don't need to care about the steering-specific items as caster and scrub radius.

hahahahahahahaha ! right ! i don't know how i missed that ! yes that is right the caster and scrub are for steering stability and feedback for the driver !
So about the rear there will be no caster or scrub but there will be + camber and Kingpin angle ?

[Greg Locock]

KPI doesn't matter much for a rear suspension, neither does scrub radius. I'm tempted to say the same for castor.

All these things will affect how the suspension reacts to forces at the contact patch, but that's just a design issue.

I would be a little careful with castor gain in particular, as that directly affects your mechanical trail, which will change the balance of the car.

[bill shoe]

I would be a little careful with castor gain in particular, as that directly affects your mechanical trail, which will change the balance of the car.

Greg, I understand how castor gain changes mechanical trail, but how does a change in mechanical trail change handling balance?

[Greg Locock]

As your mech trail changes in length it varies the torque created on the suspension as a result of lateral force , so it'll steer the wheel directly on the arm/bush/body compliance. (I previously posted a longer version that was wrong)

The counterargument is that the effect due to castor gain on the inside wheel is the opposite on the outside wheel, so as an axle effect the two will more or less cancel.

However the effect of compliance steer is additive, that is, if the inside wheel toes in due to lateral force, the outer wheel will toe out at the same time. Keeping your signs straight is trickier than the maths!

[bill shoe]

OK so it's a function of the inevitable suspension compliance, whether or not the suspension is desired to have compliance around the castor axis. Thanks.

[firasf1dream]

hello Greg Locock,
thank you for your reply,
so i understand that on the rear upright we must give a slightly opposite castor to the front suspension ?
about KPI and scrub, i can give 0 angle from the normal axis ?

[Greg Locock]

You can do any of those things, and I don't think they are necessarily a terrible place to start, but as someone once said, if you design a suspension using rules of thumb, you get a thumb, not a suspension.

[firasf1dream]

You can do any of those things, and I don't think they are necessarily a terrible place to start, but as someone once said, if you design a suspension using rules of thumb, you get a thumb, not a suspension.

yes but i need to know what should be done to design good rear suspension ?

[Smokes]

get hold of Race car vechicle dynamic by miliken and create a bicycle model in excel spread sheet also look at concepts like this

http://www.rc10talk.com/viewtopic.php?f=35&t=38327

regards

[firasf1dream]

get hold of Race car vechicle dynamic by miliken and create a bicycle model in excel spread sheet also look at concepts like this

http://www.rc10talk.com/viewtopic.php?f=35&t=38327

regards

yes i have it but these days the F1 is different, through my design process i made research after i read the vehicle dynamics theories about front suspension and i found out that most of these theories still applies for front except for the anti-dive ! which in most f1 cars they make both suspensions near the 100% parallel in side view, near not 100 because of aerodynamics reasons to guide the air flow to the sidepods (i might be right with this conclusion and i might be wrong if so correct me please ), and they use some other antis on the tips of the wishbones near the upright, and of course the flexibility of the arms is studied to the max (which i can't do much in my capabilities), still in my design as you can see in the pictures i decided to use the book's laws and applied an anti dive in the positioning of the arms connection point on the chassis, about the rear i see more difference