Posted 28 January 2009 - 21:22
Apologies for intruding, but I feel the need to respond to some comments about what I advocate & I do to some vehicles.
I won't comment on Ben's introductory quote, but his statement that Dave Williams is an advocate of linear damping is not exactly true, although I do believe that linear damping can yield optimal and consistent mechanical control.
Dampers are multi-functional. They play a large part in handling both road and driver inputs and determine how CPL varies whilst this is happening. They also influence transient lateral balance & affect steering time constant and driver "feel". The relative importance of these functions depends upon the driver, the vehicle and what it is required to do. So, for example a good damping "style" for Silverstone is unlikely to be optimal at Sebring, and "oval" damping styles would certainly not be appreciated in a WRC vehicle. Damping style is also affected by damper architecture. Greg Locock clearly favours a rebound-biased style, and this is probably a good strategy for, say, a Penske or a TT44. It is also a good strategy to counter a minimum static ride height rule. However, a compression-biased damping style demonstrably has the better contract patch load control (but worse ride) &, I suppose, most race vehicles I see now use this style of damping.
Fat Boy was a little unkind about the Multimatic DP vehicle. After all, it did win the first Rolex race. However, it was 100 kg overweight at the time, and an exercise to put that right sadly removed more than the weight. I would like to know which "lower formula car" we "put into left field", however. We see around 100 race vehicles a year on the two Multimatic rigs. Most teams return, suggesting that we add value some of the time, anyway.
On to the subject of rig testing. It is true that we will use swept sine heave inputs during a rig test more than anything else, but not exclusively. However, the objective is not to simulate track inputs (murpia), it is to understand the dynamic response of the vehicle. In fact, developing a working understanding of suspension setting limits and the effect of suspension changes is as good a reason as any for rig testing. The fact that we can often improve track performance directly is secondary. Why? Extracting performance from a race vehicle depends upon many parameters, only some of which are controllable (or even visible) during a rig test. If the mechanical set-up is a long way from optimal it is likely that other parameters have been compromised in order to compensate, in which case they will have to be unravelled before the vehicle is likely to deliver its potential performance.
It is certainly true that we tend to optimize damper set-up around team spring selections, as a first (low risk) step, anyway. The reason is that springs affect, and have to work with, vehicle properties in ways that are not obvious during a rig test. However, we do have a views about springs, and we often nudge teams in a direction that will improve mechanical set-up. As Ben suggested, slightly more speculative changes often include tyre stiffness (pressures).
And then there are drivers.... I sometimes think that most drivers would gladly throw away the suspension if the result could be made to work. I recall a (now) well-known driver stating, in his F3000 days, that a particular team's car was "sh*t, but puts you on pole". Says it all, really. More seriously, taking account of driver preferences (usually observable from a start set-up), is a) possible & b) advisable when optimizing the mechanical set-up of a race vehicle.
Enough of the epistle. I hope some of it is of interest - and I would appreciate an answer from Fat Boy...
