current F1 front suspension
current F1 front suspension
(OP)
newbie here,
current F1 front suspension layout would seem to indicate the front roll centre at perhaps ground level or lower. Is this the case, and if so would this not aggravate the "jacking effect". Have been out of the design loop for a long time am I missing something or is there a heavy "aero" package influence here that I am unaware of, any comments would be greatly appreciated from what appears to be very well informed panel.
with thanks.
current F1 front suspension layout would seem to indicate the front roll centre at perhaps ground level or lower. Is this the case, and if so would this not aggravate the "jacking effect". Have been out of the design loop for a long time am I missing something or is there a heavy "aero" package influence here that I am unaware of, any comments would be greatly appreciated from what appears to be very well informed panel.
with thanks.





RE: current F1 front suspension
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: current F1 front suspension
On F1 cars, the upper and lower A-arms are pretty much horizontal at normal ride height. There's no jacking effect at all in that situation. The instant center is at infinity. Whatever slight jacking effect might be present, will be overwhelmed by the extremely high spring rates that don't let the suspension move.
RE: current F1 front suspension
again with thanks golfpin
RE: current F1 front suspension
The kinematics of double wishbones haven't changed.
I would say that geometric RCH gets less emphasis than it used to, force based RCH is easier to work with.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: current F1 front suspension
thanks again for your replies. Greg could you elaborate on "force based RCH" please.
Would I be completely wrong in assuming that the position of some of the inboard points on current cars is dictated to more more from a packaging point, and perhaps getting the drivers feet and pedal assemblies into those "drop snoot" front ends, I have not been near an F1 for so long that trying to guage dimensions from pics. and tv is for me, impossible, hope this not to far out of the tech question frame.
with thanks,
Denzil Schultz RSA
RE: current F1 front suspension
that is it is the height of the pivot of the equivalent beam axle with a single pivot on the centre line. In other other words it talks about weight transfer due to lateral forces at the contact patch.
Yes the inboard end locations are driven by packaging which is largely driven by aero.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: current F1 front suspension
HAD AN ALL TO BRIEF A CHAT WITH MIKE PILBEAM A FEW MONTHS AGO, HE WAS OUR HERE IN RSA WITH ONE OF THE LMP CARS I TRIED TO GET TO GRIPS WITH THE DYNAMICS OF THE "HEAVE ANTI-HEAVE" LAYOUT ON THE CAR BUT THE TRACK NOISE AND MY FAILING HEARING DID NOT GO FAR TO CLARIFYING HOW IT WORKED! NOT EVEN A PHOTO!!TRUTH BE KNOWN COULD NOT GET CLOSE ENOUGH TO THE LAYOUT[BAD EYESIGHT]
APPRECIATE YOUR PATIENCE ,
UNTIL THE NEXT TIME
PS COULD I TROUBLE YOU FOR CLARITY ON FORMULA FBRCH=D etc I STILL US A SLIDE RULE SO AM A LITTLE LOST WITH MODERN DAY COMPUTER TYPE NOMENCLATURE
RE: current F1 front suspension
RE: current F1 front suspension
Jeff
RE: current F1 front suspension
THANKS FOR THE INFO I WILL NOW GO AND SIT IN THE CORNER AND WEEP AT MY STUPIDITY, BUT IN DEFENSE I DO NOT HAVE ANY CLEAR PICS OF F1 FRONT SUSPENSION SO I MADE AN ASSUMPTION, THAT HAS BROUGHT OUT A WONDERFUL BUNCH OF GUYS THAT ARE PREPARED TO SHARE THOUGHTS AND INFO, THANK YOU TO ALL.
GOLFPIN
RE: current F1 front suspension
don't worry, no need to go sit in the corner and wheep. Your observations were more than valid and I am amazed on some of the comments I have seen here by people that actually have never seen an F1 car, let stand alone have designed one. No offence but an F1 car has got literally nothing to do with a road car. The simplest example of that is putting more front weight on the car if the car is understeering too much because the low mass causes not enough heat in the tire causing understeer. Try explaining that to a road car tire .....
Then, no designer of an Formula 1 car would be out of his mind to design an F1 car with a roll center that high as indicated in the youtube video. The jacking forces would multiply the vertical load by the friction coefficient of roughly 1,6 causing a horrible understeering and lifting car whilst cornering. Imagine a std road car with a CoG of approximately 550 mm with a roll center height of 100mm that "gets multiplied in its effect" by 1.6 (=160mm). That would be like going back to the dark ages of the worst handling cars of all times.... and now think of the same thing on a car with a CoG of 250 mmm ..... bloody hilarious ain't it ?
And as you did correctly see parallel links do more or less always result in a roll center height of 0mm. Considering this and the fact that F1 cars have always suffered from low speed understeer (and lately of extended tire wear) no designer with some sense of physics would go for a front high rollcenter. In fact it has been for more than a decade around -20/-40mm, at least kinematically. Due to camber compliance this value will inevitably go above 0mm (ALWAYS) but many teams have put a lot of effort into reducing camber compliance in order to keep it as low as possible (as they should since the laws of physics are valid for everyone - eliminating the part of load transfer due to RCH will produce higher lateral-g). During almost a decade in F1 and other racing series I have learned to put the appropriate attention to details. In F1 the old saying "aero, engine, tires" remains more than valid nowadays but that does NOT mean that the basic principles of good engineering are not valid. In fact the front rollcenters are positioned as low as possible and will be positioned as low as possible, independent of any aero constraints, so your observations were very correct Golfpin.
RE: current F1 front suspension
RE: current F1 front suspension
RE: current F1 front suspension
Regards, Ian
RE: current F1 front suspension
RE: current F1 front suspension
I still maintain that these vehicles have extremely high spring and antiroll rates (by road car standards). You can make any suspension geometry work, if you don't let it move. Camber in the wrong direction? Doesn't matter, the suspension barely moves. Jacking effect? Doesn't matter, the high spring rates won't let it have any effect.
If this geometry works out better for aerodynamics and vehicle structure then the F1 engineers will find a way to make it work.
You do not want to design a road car with spring rates that normal people will tolerate with geometry like that.
RE: current F1 front suspension
RE: current F1 front suspension
OK Paul, what is your estimate of the GRC of that suspension?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: current F1 front suspension
My estimate RCH would be as I said before around 0 mm.
As indicated in the picture I attached in a previous writing I think that the links in the front are NOT parallel but inclined "wrongly" in such a way that the instantaneous center of rotation is "outside"of the wheel . This in combination with a possibly longer upper-link than lower-link provides "in theory" sufficient room to create a geometry with 0mm or negative roll center height (I used always a "spacing difference" of 5mm - meaning the links are not parallel in front view but inclined "wrongly" to get a negative roll center height of -20mm to -40mm - and I presume that looking at the front view inclination of those two links the difference here must be around 15mm to get the roll center to the value that I am thinking where it is) The picture of the Ferrari is unfortunately not a design drawing so there will remain plenty of room for discussion.
In case none of the above would have been implemented by Ferrari and the links would all be "classically" arranged as was assumed in the video I would expect a RCH of around 70mm. But that again would not be so good.
Cheers,
Paul
RE: current F1 front suspension
Sorry if I'm sticking my nose where it may be lopped off, but I have a question. If aero downforce is as dramatic as I am hearing, seeing the car at rest doesn't tell the whole story, as it would with, say, a Rolls Canardly. I suspect that the dynamic system, the car progressing around a circuit, loaded with driver and aero effect, would be a better starting point for discussion. "Static, in a Formula One car, then, might be taken as meaning at a given (average) velocity.
Once in motion, the reaction point would move further away from the CL of the car, and also up, slightly, correct? Therefore, the the roll center would move down. So, my question is: Why is "static" even considered in the same way for a production sedan as it is for a high downforce racing car? Wouldn't it make more sense to look at the vehicle at some steady state that is more representational of its "norm?" Maybe that normative value is the average velocity around a track, and has to be different from one track to the next?
Thanks in advance,to anyone willing to edify,
Bernard.
RE: current F1 front suspension
RE: current F1 front suspension
Norm
RE: current F1 front suspension
Best,
B.
RE: current F1 front suspension
Given that the FVICs lie outboard of their respective wheels, are you suggesting that the FVICs and the GRC would both move upward with downward chassis travel?
Norm
RE: current F1 front suspension
RE: current F1 front suspension
There is also a Side View IC (associated with pitch rather than roll), so using "IC" by itself isn't a sufficiently descriptive term (unless you're talking to most drag racers, who don't much care about suspension behavior in front view).
Norm
RE: current F1 front suspension
"Simplicity is the ultimate sophistication." L. da Vinci
- Gian
RE: current F1 front suspension
Just let go of all links and so on, just concentrate on the knuckle/upright. The "vertical" movement of the knuckle/upright can be seen as a rotation around an axis. This axis may be nearby or far away. This axis is called the Instantaneous Axis of Rotation of the suspension and where this axis "hits" the axle center line it is called the Instantaneous Front View Center and where the axis hits the Track Width Plane it is called the Instantaneous Side View Center. From the movement of the Wheel Center and The Contact Patch all suspension characteristics can be derived via vector algebra (the actual position of the links is completely irrelevant).
Now this "Instantaneous Axis of Rotation" has some very particular characteristics that allow a fundamental approach to define Suspension Types:
1) If the axis of rotation is more or less stable in space the suspension is called a "Plane Suspension" Plane revers to the fact that the suspension can be "easily" drawn "in plane" on a 2D drawing book. Typically SLA suspensions and McPherson Struts are "Plane" Suspensions and do not have many interactions between parameters. This means that their instantaneous FV & SV centers are quite well "tunable" and over wheel travel remains pretty much constant
2) If the axis of rotation moves BUT always goes through one specific point the suspension is called "Spherical Suspension" due to the fact that one point of the actual suspension is always acting as a spherical center for the instant axis of rotation (the axis "cones" around that joint). These type of suspensions are not so easily to be drawn on a 2D piece of paper and need the help of some 2,5D tricks in order to design them (on paper). Most famous representative of this type of Suspension is the BMW E36 (M3) or Toyota RAV4 where the "Spherical Joint" the trailing arm to Chassis Joint is On these suspensions you will always find a strong interaction between Toe, Camber and Roll Center Height. Due to the interaction of Toe Camber and Roll Center the FV instantaneous center can only be "tuned" marginally whereas the SV IC is almost always "fixed" next to the trailing arm. A computer program helps here a lot.
3) If the axis of rotation moves in space and is also characterized by a "thread movement" fore/aft along the axis the axis will be called "Momentary Screw Axis" and the suspension becomes a true fully 3 dimension multilink suspension. These suspensions cannot be calculated on a piece of paper and are characterized by a very significant interaction off all Parameters. Changing one point will change almost all characteristics. This means that the movement of FV IC and SV IC can be a lot and most of all change a lot over wheel travel. Without a computer and vector algebra one is completely lost.
I hope this helps understanding the FV & SV IC, I have btw started a new thread about my new suspension design tool. If you like have a look at it !
Cheers,
dynatune, www.dynatune-xl.com
RE: current F1 front suspension
(.general.roll_center.y}]VSUSP.COM)
[url=http://vsusp.com/?tool=2d#0.7%26project_name%3AVSU...]VSUSP.COM[/url]
RE: current F1 front suspension
YOURS IN ENGINEERING,
GOLFPIN
RE: current F1 front suspension
"Simplicity is the ultimate sophistication." L. da Vinci
- Gian
RE: current F1 front suspension
have just reread your last posting and wanted to thank you for a great effort. It helps enormously for people like myself who think they know a bit about suspension geometry to be updated so to speak, am out of the design loop by quite a few years but appreciate and enjoy the effort that people such as yourself, and many others, who give of their time to explain.
Thanks again and all the best for the coming new year.
Golfpin RSA
RE: current F1 front suspension
Thank you for the kind words. As a "teacher" it does make a lot more fun to have "students" that are willing to learn
I have lived and breathed suspensions (and cars) now for more than 25 years and I had the fabulous opportunity when I was a starting engineer that I came to work for an "old" experienced engineer. Although the guy was close to retirement he was driven by passion for his job, he told me all his achievements and his biggest errors. I was amazed, like a baby in a candy shop. He was one of those people that wanted to share without "protecting" his position (not that anyone could be a danger) and I understood there that a pupil will always honor a good teacher and by now, I now that the greatest satisfaction for a good teacher is to see his pupil proceed into unknown territory. So this guy did for instance have a "library" of every article published on suspensions starting somewhere in the 50s of the last century and I was allowed to copy them all and read read read. What a time. He challenged me, making bets that for any question I could not answer I had to pay him a beer, for any question he could not answer I was offered a crate of beer .....needless to say that I did never win. From there on I did have the fortune to work on almost everything that had wheels on it, from a 40t 18 wheeler truck to an F1 car. So this little story is basically the main reason why you find sometimes replies here and why I did bother to write the dynatune software.
Cheers and a happy 2014 to all of you !!
Paul