Now I know that we've previously discussed the Walker/DAX Camber Compensation and Anti-Roll (CC&AR) suspension (
http://walker-partnership.com/cc&ar_text.htm) a few times before. And while I also know that it's not perfect (namely 1 wheel bump camber like a live axle [very minor IMHO], complexity and component count [minor IMHO], and packaging [that can be improved IMHO]), it does offer numerous very interesting attributes as well. Something I decided to explore further.
For those that don't know, it's a mechanical linkage that connects the upper left control arm to a rocker that the upper right control arm is mounted to, and vice versa. In doing so, it pushes the UCA mounts outward in pure bump (preventing unwanted negative camber gain), pulls the UCA mounts inward in pure droop (preventing unwanted positive camber gain), adds extra negative camber gain to the outside tire and extra positive camber gain to the inside tire in roll, and has an anti-roll (and anti-jacking) component when lateral loads are applied to the tires.
Even though I had already spent considerable time figuring out a conventional suspension geometry for the rear that I was pretty happy with, and was getting close on the front, I still wanted to better understand this. Also, I felt that they were missing something in their application of this concept. They built a car that has a compliant ride but corners extremely flat and with no real camber loss/gain to speak of as a result of it. This may be great for very wide and low profile tires. But since most tires actually develop the max cornering grip at a non-zero camber angle, this seemed to actually be undermining the full potential of the design. I mean, what's the point of camber compensation in roll if you don't have (allow) any roll in the first place? So I used the magic of Excel to create (multiple iterations of) a CC&AR calculator that I could manipulate.
The first thing I did was move the cross link from being between both UCA's, to having it be actuated by the LCA to vary the opposite UCA position. Admittedly, part of this was to get around the patent, which specifically stated cross linking the uppers. However, I just recently found that Walker did not continue paying to maintain the patent on the CC&AR system, so it has since expired anyways. During this more recent research, I also found an RC car manufacturer (Serpent) that has created a system linked essentially in the manner I'm talking about (upper to opposite lower) for their DLS (Direct Link System).
First of all though, for what I was trying to achieve, the suspension had to be allowed to roll. This meant lowering the roll center, which Walker/DAX claim is simply at the intersection of the two LCA lines of action. Even if I'm not sure I buy that, I'm confident min will be at least a few inches lower. Would it be enough lower to allow the movement I'd like to see? I'm not totally sure, but I think it should certainly do more so than the Walker/DAX layout. It also helped with the packaging considerably, even if not the complexity or parts count. Might even be adaptable to a production car chassis some day. There is also the anti-roll and anti-jacking component, but as far as I can tell that actually should not be overly strong in preventing roll, but will still hopefully be enough to (at least mostly) balance out the suspension with minimal (or 'no') need for sway bars. Of course this is all very much hypothetical still and based on very rough math at this point, but if you couldn't tell by now, I'm strongly considering putting this hypothesis to the test on my build... Whenever I get manage to get going on it again.
And here's the big explanation of why: The typical 'independent' suspension has somewhere in the ballpark of 1.0 degree of camber gain per inch in bump, and 0.5 degree of camber recovery per degree of roll. So lets put that into roughly approximated numbers aimed at maximizing cornering grip, while keeping streetable suspension rates. If the car corners at 2 degrees of body roll, that means the suspension needs to have -3 degrees of static negative camber to get -2 degrees of dynamic negative camber on the loaded wheel. Unfortunately, as the unloaded tire (that wants positive camber) tries to assist, it has -4 degrees negative camber. As the suspension is loaded (the more important end) in a straight line, it also gains another degree of negative camber. So this too is -4 degress, which is certainly not optimal for acceleration/braking either. It does help the unloaded end, but sill leaving it at -2 degrees.
Meanwhile, I have found a rear geometry for the Thunderbird spindles, that I believe will allow for a very street friendly -0.5 degree static negative camber. In doing so, it will achieve the same -2 degrees dynamic negative camber in roll on the loaded wheel, but also +1 degree dynamic positive camber on the unloaded wheel. In both bump (loaded) and droop (unloaded) scenarios for straight line performance, it very closely maintains the -0.5 degrees dynamic negative camber, actually moving closer to 0 at the limits of acceleration/deceleration based suspension movement. At more extreme suspension movements due to flying through the air and then slamming back into the ground, the suspension does wander a little further, but no more than 1.5 degrees at absolute maximum two wheeled bump travel. So at the same loaded cornering wheel angle, it is vastly improved on the unloaded cornering wheel angle, substantially improved wheel angle in two-wheel bump, and even noticeably improved wheel angle in two-wheel droop. This should increase total grip in all steady state maneuvers, as well as improve tire wear patterns across a wide variety of driving. Additionally, it actually compresses the suspension slightly in roll (anti-jacking) that would hunker the car down that much more while the majority of anti-roll rate is also fully damped.
Just thought I'd share some of what I've found as I've played with this over the last year, and open it up for public consumption/discussion.
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