The lower links on the LD setup are angled inboard (plan view) for a very specific reason, and it's not tire clearance. In doing so, they form a lateral resistance that in conjunction with the bellcrank position (which in this case defines the rear roll center height), defines the rear roll axis. Trust me, I know the guy who researched and designed this setup (he's kind of a difficult person to deal with). With the angle of the lowers in plan view, and more importantly the fact that there is only one upper link (relative to Terry Satchell's design illustrated), one additional constraint is needed to appropriately locate the rear laterally (Watts, in this example). Actually, even WITH the modest lower angle, the lowers would be sufficient enough to locate the rear laterally IN THE CASE of a Satchell. However, it would be very impractical in that the entire system would need to be made so strong as to eliminate any bending and flexing, or the system wouldn't work, which is why the typical angles on those types of setups approach or exceed 45 degrees (nature likes that number...).
The LD setup was designed to have a bit of liberty to adjust the rear roll center height to accomodate roll resistance and jacking force reduction, as a primary adjustment. One could also use the system to define the rear roll axis as a primary setup and let other parameters "float," but typically this is not the case. The entire adjustment envelope of that system is such that even at the extremes, nothing gets too far out as to create a diabolically handling car, at least at the rear.
Quote:
|
As I mentioned earlier, ideally we would like to keep the lower links as straight (to chassis centerline) and level to the ground as possible. The bigger the tires and engine (torque output), the more important this becomes, regardless of what we are doing with the upper links. The more the lower links are triangulated, the more the "push" from the rear tires/axle is going to try to move the housing around.
|
That is certainly one design approach, but there is more than one way to skin a really fast cat. The LD approach considered this, and designed differently for very sound engineering reasons. In terms of force application being an issue with angled lower links, again, if the structure, links, rear housing and all other mechanicals are sufficiently rigid, this is not an issue. Certainly within the traction potential of a 345 wide R Racing compound road race tire in this example, a "modest" contemporary "Pro Touring" inspired engine (750 HP?), and portly curb weight (3400-3600 lbs, more?), there is not an issue with this approach. Honest. And I'm not trying to get into a wee-wee contest at all, there was a LOT of thought put into that system and virtually no design element was done without regard for consequence. You need to pick your battles, as you can't have it all in one package.
Back to your regularly scheduled program.
Mark