continued from above
The 2nd trunk we acquired for the ESP spoiler was re-used and can now be quickly switched from spoiler to wing and back. An outside designer who is an aero specialist that has worked on professional road race teams as well as Bonneville record holding cars, helped us with the wing placement and upright design. After making wooden uprights to test the design and verify fore-aft placement (Tuesday), we took the 3D designs and turned them into engineering drawings (Wednesday), then had water jet cut parts made (by Thursday). Our fab team tweaked and welded up the bases and uprights, then shortened some adjustable rod end struts for the wing adjustment, and fitted the wing to the car Thursday afternoon and Friday morning. We trimmed the wing at the lowest angle of attack, loaded it into the trailer for TWS, and we were on the road by 4:45 pm - this made for a hectic few days of drafting and fabrication work in the shop.
We kind of neglected one variable (what's under the base, in the trunk structure?) and so we had to move the mounting bases rearward about 4" from where we had first laid them out. The back of the wing now sits behind the car by more than the amount allowed in AI - but it's still TTS legal. We're even street testing the wing this week - just to see how well the mounting base and uprights hold up to regular use (not that anyone would be crazy enough to drive on the street with something like this). Once we get our hands on another straight style wing (not "3D"), we will modify the mounting uprights for proper height, improve the adjustment range, and tweak the rearward placement of the wing to stay within AI rules. No, this car is never going to AI, but we want the wing to be AI legal as well.
Other Wing Examples
Some people wondered why we simply bolted our wing mount uprights onto the trunk lid, so I shot several examples of other wing mounts at the same NASA TWS event. Many uprights passed through trunks and bolted to frame rails, others bolted to trunks directly, but had supports underneath to the trunk. Like our car, others simply sat right on the trunk lid structure only. This is how we had to do it to
not modify the trunk or to add structure underneath it so we can avoid running afoul of ESP rules even with the wing removed. We did see some flex in the rubber bumpers that locate the rear of the trunk (height) at the back, which we will replace with custom Nylon bushings before the next event where we use the wing.
Here's a Corvette with the wing uprights bolted right to the trunk panel, braced underneath. Above right is a G-Stream wing on a factory Boss 302S Mustang race car - also bolts to the trunk.
Above we have a Fulcrum Wing on Mike P's 4th gen F-Body American Iron car, which won both AI races Saturday - handily. It bolts to the frame and passes through the trunk lid. Another wing is shown on a multiple time NASA ST2 winner's SN95 Mustang - this one with a wicker bill/Gurney flap, bolting right to the trunk.
Rear Diff Rebuild
During and after the ProSolo event (and looking back, at some previous events as well), I noted considerable problems with the OEM Limited Slip Differential - the Ford TractionLok, clutch-style diff. After the 30+ runs at the ProSolo with 315mm wide R compounds, it was finally toast. We had a handful of days to get a functional diff in the car before NASA at TWS, so instead of gambling on getting a WaveTrac or Torsen T2R in time, we went with a known fix and ordered the Ford Racing "Carbon Clutch" rebuild kit -
M-4700-C. This is one of two kits that FRPP still offers for the 8.8" TractionLok and the "C" version comes with upgraded carbon fricton material and different steel plates for
a whopping $108. The non-carbon kit (
M-4700-B) retails for for $70 and even comes with the friction modifier, but the Carbon kit is the one to use for best performance. It's even SCCA F-Stock legal, thanks to a TSB from Ford - we installed one of these in a 2007 Mustang Shelby for FStock class autocrossing a month ago.
As soon as they pulled the old diff apart, it was obvious that the clutches were done since the friction material was coming apart. The new discs were soaked in the fluid, then the discs and steel plates went in and the rear end was topped off with fresh 75W140 gear oil and friction modifier. OMFG that stuff stinks something fierce! The shop reeked of gear oil smell for 2 days.
We didn't have time to do much testing on the rebuilt diff, other than a few laps around the parking lot. "Feels good!" I said and onto the trailer it went.
Please check back tomorrow below for Part 2, where I talk about how all of this worked at the TWS Time Trial event...
Thanks,