hardingfv32 wrote:This design has a goal, unknown at this time to us, that required the use of a strut system inside the wheels. These struts could well be an engineering or materials problem that was never solved correctly. That does not negate the value of the underlying goal.
Underlying goal of a suspension... I separate into 3 items:
1. Control of lateral (or more properly yaw) dynamics
2. Body attitude control
3. Control of vertical dynamics
They're all intertwined but in my mind those are the general goals. These are unchanging, and chassis engineers merely have ideas for different approaches to meet those goals to an appropriate level for the given platform and end user / consumer.
The realist in me takes a look at this - a one-off F3 design from almost 20 years ago - and is pretty comfortable in writing it off as a failed approach and/or inappropriate goal spec (the relative importance of items 1, 2, and 3 to each other). We can stare at this thing all we want, but bear in mind there's nothing inherently there to say that any of this design process was a good idea. Don't get your hopes up too much. Also, to be fair, nothing inherently there to say it's junk other than the end result (which does speak strongly to me).
It seems what you are proposing is that we crawl into the mind of this chassis engineer and attempt to figure out what they were thinking when they came up with this design. I have a hard enough time understanding what's going on in my mind, much less someone else's. But doesn't mean we can't dive into it.
As far as the actual chassis is concerned, there's not much magic to Item 1 on a vehicle as linear as this. Quasi-steady state distribution of tire loads, inclination and steer angles is relatively straight forward to analyze within the constraints of a double a-arm suspension. Tires dominate this area more than anything anyway.
I'd go so far as to say that there isn't an awful lot of magic in the coupling of Item 1 and Item 2, particularly the geometric anti's with jacking coefficients. They are what they are, can achieve what you want by moving "roll centers," adjusting anti-dive rates, etc.
That leaves Item 3, which for me is harder to "eyeball" mostly in that I don't have much working experiencing. By changing the distribution of masses (sprung vs unsprung) as well as how the various force elements (corner springs, ride springs, dampers, bars, inerters if you have them) act you can change the dynamic response of the platform with regard to heave, pitch, and roll inputs. This is by far DaveW's realm more than it is mine.
Now that we know this though, if we circle back is this design really that unique in a fundamental sense? The pushrod ARB thing really fundamentally different than a conventional T-bar. Just acts directly rather than through a bell-crank. The only unique thing is what's going on with the chassis-side mounts of those pullrods and whether they are fixed or not. Hard to see. One would have to think so, though... to fix that wheel-side UCA point and let the shorty (shawty) coil spring become the main ride spring. I suppose that would give you the potential for some different kinematics, but the travel of that spring is so damn short it might not amount to anything. Hell maybe the whole thing just goes into coil bind at high speed, like landing on a bump-stop.
So what effect does fixing the wheel-side UCA point and putting the main ride spring within the wheel have? Who knows. With a given overall ride rate and sprung mass, I'd guess your primary ride frequency is no different. It's an easy damn thing to tune anyway. Some second order ride dynamics effect by moving weight to-and-from the body and wheel assembly? At the end of the day this --- really does boil down somewhat simply. Couple springs and couple masses at each corner, and some amount of direct linking between them (ARB).
Could very well be just an overly complicated approach to the problem, with too much time spent chasing something low on the "bang for your buck" list. In a series like F3, chasing second and third order things probably isn't the best use of resources.