Increased RWD 3link design freedom
Increased RWD 3link design freedom
(OP)
Commonly, a 3link is considered to have 2 symmetrically positioned links, in plan view, with a third more centrally located link. Page 40 of my site provides a spreadsheet which allows much more design flexibility. (The site is essentially devoted to the presentation of foundational suspension material for the young people engaged in dragracing, but I believe Page 40 might be of interest to other automotive engineers.)
The user can pick any 3 points along the axle for the link rear pivots. Of course, there must be sufficient point spread in the Z and Y directions. Among other parameters, he inputs the distance forward to the instant center and the desired percent antisquat. He is free to use different link lengths for the 3 links. The spreadsheet output provides the 3 link angles for the desired percent antisquat AND which provides complete cancellation of the driveshaft torque effect.
http://www.racetec.cc/shope
The user can pick any 3 points along the axle for the link rear pivots. Of course, there must be sufficient point spread in the Z and Y directions. Among other parameters, he inputs the distance forward to the instant center and the desired percent antisquat. He is free to use different link lengths for the 3 links. The spreadsheet output provides the 3 link angles for the desired percent antisquat AND which provides complete cancellation of the driveshaft torque effect.
http://www.racetec.cc/shope





RE: Increased RWD 3link design freedom
Goran
RE: Increased RWD 3link design freedom
With a properly configured 3link, the car can have equal rear tire loading at the beginning of the run and maintain that equal rear tire loading throughout the run.
http://www.racetec.cc/shope
RE: Increased RWD 3link design freedom
A 4 link that has not parallel bars, or worse, a very short Ic, this will lock up the motion of roll, which will not happen with a 3 link. However, a drag racing car with 4 link is equipped with a fairly stiff swaybar to prevent from roll, (but soft vertical suspension to use the "rise" to plant the tires). Most of the time you are using non-parallel 4 link, so there's really not much roll present if any, which leads me to believe that there is no advantage with a 3 link, since we do not want sideway motions.
Just a thought from me.
Goran
RE: Increased RWD 3link design freedom
http://www.racetec.cc/shope
RE: Increased RWD 3link design freedom
But for a street car that sees the dragstrip now and then the 3 link would be very good. In fact many roadracing cars that have liveaxle will benefit from a 3 link.
Goran
RE: Increased RWD 3link design freedom
(Dragracers commonly keep the lower link of a 4link nearly horizontal and make adjustments only with the upper link. This keeps the instant center relatively close to the rear axle or "short." But, the same antisquat changes can be made with adjustment of both links while keeping the instant center further forward or "long.")
http://www.racetec.cc/shope
RE: Increased RWD 3link design freedom
Then I wonder if not the attachment points of the chassis will be of less quality places, at certain anti-dive%, with parallel rods?
I can, for comparison, refer to both the Corvette and Viper that have both anti-dive and antisquat, and none of the cars have parallell A-arm attachments and fairly short Ic, around 1500mm. Any thoughts?
Goran
RE: Increased RWD 3link design freedom
I do not, however, cover matters of structural integrity relating to suspension attachment points.
http://www.racetec.cc/shope
RE: Increased RWD 3link design freedom
I have built some 4 Link for pure drag racing cars, and do not see that it is so easy to build very different from the normal. BUT, it is easy to be blind to, so therefore I am always looking for inputs.
Goran
RE: Increased RWD 3link design freedom
Sadly I work on IRS at the moment, that takes all the fun out of it.
Cheers
Greg Locock
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