Six Link Watts-1 Suspension System

Carlos · Post 13 Apr 2007, 04:37

The double wishbone suspension system has been the standard of F1 design for over 50 years. This suspension system uses 6 links to defeat the problem of excessive camber change - possible application to Formula 1?

http://web.mit.edu/pccs/pub/2004/deo-automotive-1.pdf

DaveKillens · Post 14 Apr 2007, 01:46

Wow, I like it. As the article states, the disadvantages are increased parts and higher unsprung weight. But the advantages may outweigh the disadvantages.
I have to admit the math and method is over my head. I had to print the article and read it a few times to digest. But it's very interesting.

Carlos · Post 14 Apr 2007, 03:03

I have no math then I thought to look up "linkages" on Wikipedia which made things more understandable - I built models of popsicle sticks - I had been looking for a suspension system called the "X Link" a few days ago and came across this - I have never considered anything more complicated than 2 sections with a pivot point. The Watts1 is such an elegant solution to all the problems of suspension geometry. Perhaps our university students and engineers may take a look. I would not know how to even describe it - I wish I could do more than just post links

http://web.mit.edu/pccs/pub/2004/deo-automotive-1.pdf
http://en.wikipedia.org/wiki/Linkage_%28mechanical%29

Edit - This suspension system uses 6 bars, a conventional double wishbone suspension is a 4 bar system - Watts1 is a 6 bar system jointed in an articulating fashion to create a suspension system that does not suffer from camber, toe-in or caster problems - a front wheel can be manipulated to always be perfectly upright - thats the way I understand it - could someone with mechanical engineering experience and "computer display" skills than I take a look at this paper - when time allows - Thanks you.

MMUK · Post 14 Apr 2007, 04:08

Interesting stuff indeed, just wondering if it contradicts any FIA regulations...

ARTICLE 10: SUSPENSION AND STEERING SYSTEMS

10.2 Suspension geometry:

10.2.1 With the steering wheel fixed, the position of each wheel
centre and the orientation of its rotation axis must be completely and
uniquely defined by a function of its principally vertical suspension
travel, save only for the effects of reasonable compliance which does
not intentionally provide further degrees of freedom.

I'm not sure but the design may contradict with this article.

DaveKillens · Post 14 Apr 2007, 07:11

Wow, there's a rule open to interpretation. "defined by a function of its principally vertical suspension travel" Principally? hmm..
"reasonable compliance". Reasonable for who? If this sytem ever found it's way into F1 it would be up to the lawyers...

But I like the way different requirements are decoupled from each other. Eliminating tire scrub as a function of wheel travel. Same with bump steer and other properties. It sure could lead to making life easier for the tires.

Gmuze · Post 14 Apr 2007, 12:29

Carlos wrote:Edit - This suspension system uses 6 bars, a conventional double wishbone suspension is a 4 bar system - Watts1 is a 6 bar system jointed in an articulating fashion to create a suspension system that does not suffer from camber, toe-in or caster problems - a front wheel can be manipulated to always be perfectly upright - thats the way I understand it - could someone with mechanical engineering experience and "computer display" skills than I take a look at this paper - when time allows - Thanks you.

I haven't been able to read the article yet, because my adobe is not working as it should. But I do have some comment on what you said about the double wishbone suspension. Conventional double wishbone suspension uses 5 bars! You are forgetting the track and tie rod.

A wheel should only have 1 degree of freedom (DOF), that is rotation in the longitudinal direction. So you need 5 bars to restrict the other 5 DOF. I can imagine adding a sixth bar is used for proper guidence of the wheel, but as I said I have not read the article yet.

Ciro Pabón · Post 14 Apr 2007, 15:38

Gmuze wrote:... I haven't been able to read the article yet, because my adobe is not working as it should...

Save the PDF and use Sumatra to open it (a minimalistic, 1Mb, fast to open PDF reader). Download it here, for Windows:

Sumatra installer: http://fastdl.org/SumatraPDF-0.5-install.exe

Sumatra website: http://blog.kowalczyk.info/software/sumatrapdf/

You can associate pdf files with Sumatra using Windows Explorer's "Tools/Folder Options/File types" menu. Change the program you use to open PDF files. Voilá, no more Adobe problems.

On thread: the Koenigsegg CC8S uses Watt linkages for anti roll-bars at rear suspension. Upper A arm has a horizontal coil. The roll is limited by this Watts link mounted to the gearbox. You don't have to damp torque on a normal anti-roll set up. The I beam section on the Watts is out of phase by 90 degrees. The arms of the central member serve as leaf springs, otherwise the whole thing would lock up in roll.

The Honda Accord, Lincoln Continental and Alfa cars have lateral Watt's linkage. It's the same thing? Here is an Alfa:

Carlos · Post 14 Apr 2007, 16:20

Ciro - Yes - the pictures - I'm familiar with this device - a 3 piece linkage for lateral stability of the suspension systems we are familiar with - the classic Watts link used for the last 50 years - the Watt1 is a suspension system itself - something very different and new - innovative.

The Koenigsegg CC8S - hadn't seen that picture before - the upperwishbone and shock absorber location was something I first noticed on one of the evolutions of the Ferrari 312 F1 rear suspension. If memory serves.

Carlos · Post 16 Apr 2007, 20:04

Perhaps these diagrams will help add insight into the Watts1 suspension system - only one diagram applies - the text points out which:

http://www.mines.edu/fs_home/dgolson/WattOneB.html

This link for designing Watt1 linkage may be of interest to our mechanical engineers:

http://www.mines.edu/fs_home/dgolson/WattOneC.html

EDIT - This gives an idea of how to design a 4 bar linkage with CAD - maybe it may give some direction on how to design a 6 bar linkage. The article is "Finding The Missing Links."

http://www.machinedesign.com/ASP/viewSe ... te&catId=0

checkered · Post 16 Apr 2007, 20:55

There was also

this animation on the site ... http://www.mines.edu/fs_home/dgolson/Figure6a.html#1 ... it illustrates the limited degree of freedom of that one bar, creating its constantly parallel dynamic position. But tbh, I haven't yet invested much time in considering the pros and cons of this ... a quick overview of the documents revealed that body roll might pose new challenges. Are there schematic or interactive models of a whole vehicle's dynamics with Watts I suspension?

K-nowledge · Post 18 Apr 2007, 23:54

In response to the original question, is there any possible application to formula 1, I would have to say no. Suspension, as it is in F1, is not at all concerned with ride comfort or hardly any other parameter used in passenger vehicle design. In fact, suspension in F1 is hardly suspension at all. There is so little kinematic movement that geometry is compromised completely at the expense of aero.

I mean, if you look at an F1 car in a 3G corner, there is hardly any body roll. They run super high ride rates to compensate for highly variable aerodynamic down force and a very low ride height. Its all about platform control, and minimizing downforce changes due to pitch or roll. The tires are doing at least half of the "suspension" nowadays.

Carlos · Post 19 Apr 2007, 21:15

I agree completely with your points, K-nowledge, and have included them in my thinking - it could use the same "hard" dampening and rebound characteristics as current F1 suspension - and also supply a solution to camber change and other suspension geometry problems of double wishbones - but I am also fascinated with technological novelty, innovation and rebellion in general

K-nowledge · Post 20 Apr 2007, 07:01

Carlos,...when designed correctly, double wishbone does not need a solution to camber change. Dynamic camber change (from + to -) due to body roll is beneficial to overall cornering power, so the wishbone geometry is perfectly ideal. That being said, it doesnt really matter either way because so little suspension movement is being used during normal handling. Basically, the static camber of the tire almost never changes because of massive spring rates. That is why they run such damn high static camber,...3 or more degrees negative!