Bob,
Yes, I did notice that! :)
(Other Teams might take GFR's Michigan-2015 results as reasonable evidence that while DASDs might not, in themselves, make the car much faster, they certainly DO NOT SLOW YOU DOWN!)
BUT (!!!) ... I am not sure I even want to contemplate this ..... but ... was it the DASDs that cost you 45 points in Design Event??? :(
~~~o0o~~~
Ritwik,
DASD Spring-Rate and Damper-Rate calcs are done the same way as with Rocker-Activated-SDs. But you must take account of the MR correctly. Which means MR must be used "right-way-up" (which depends on how you define it), and it is squared.
Some rough rules to get you in the right ballpark...
1. A DASD acting "vertically" above the wheelprint has MR = 1.
So SR and DR calcs can be done without consideration of MR. Call these the default, or "Wheel-", Spring-Rate and Damper-Rate.
2. A DASD acting at ~45 degrees to a ~horizontal Control-Arm (eg. wishbone) has MR = ~0.7, and MR-squared = ~0.5.
So in this case you use a SR and DR that is TWICE the default Wheel-Rates. Given that in your earlier post (calc'd with MR = 1) you had selected damper-valving between the softest and second-softest available DRs, means that in this MR = ~0.7 case you ONLY have to go up to about the middle-stiffness valving, from that graph. Also, buying a Spring-Damper with stroke of only ~40 mm is enough to give the mandated 51+ mm suspension travel, so a potentially lighter damper can be used.
3. A DASD acting at ~30 degrees to a ~horizontal CA has MR = ~0.5, and MR-squared = ~0.25.
So in this case you use SR and DR that is ~4 x the default Wheel-Rates. From your earlier post's graph, you would need the stiffest, or second-stiffest, damper valving. But this suspension would then also be good for ~130 mm (5"+) of suspension travel, so good enough for Baja+! Countless real cars over the years, both production and racing, have had MR = ~0.5. So NOTHING UNUSUAL here.
4. The car company best known for the most comfortable ride, and excellent grip on rough roads, and hence "really good suspension", is Citroen (with the DS and 2CV being the standouts). On these cars the typical MR = ~0.3, or less. Draw your own conclusions.
5. Worst case, on smooth-track racing such as FS/FSAE, "...any suspension will work, if you don't let it...".
So, worst case, stiffen your DASDs up as much as you want, and still OK. But I strongly recommend keeping the "main" SRs and DRs at the softer end of the range, and then make good use of your BUMP RUBBERS for the worst cases! These are squishy-rubber- (or better, foamy-polyurethane-) doughnuts-around-damper-rod. The dampers should bottom-out on these at least once per lap, at the worst road-bump, car-wobble, whatever.
6. The big decision here is really a structural one, related to the overall car/frame design. Pick a chassis mounting point for the top of the DASD that best suits the overall frame design, NOT because of some obscure "spring/damper equations". Roughly speaking, the DASD should have its lower-end pointing at the wheelprint, and its upper-end mounted at an already strong frame-node, and pointing roughly towards the car's CG. This way the DASD takes a large part of the worst-case wheel forces, making life a little easier for the other control-arms.
7. Finally, KEEP IT SIMPLE (but well executed)!!!
Z
(PS. Ritwik, Bob said that "...multiple shock pickups ... could be coupled with exchangeable [rod] extensions...". My guess is that GFR didn't think this extra complication was necessary to win AutoX and Enduro. It wasn't...)
