INDYCAR DW12
One option for addressing the weight distribution issue is to alter the wheelbase by sweeping the DW12’s rear A-arms back, placing more weight on the nose. However, this would entail major alterations to the bodywork and place undue stress on mechanical components at the rear, so is an unlikely solution
they’d open up negativity for a different reason and make the cars nervous through a too-short wheelbase, rather than gain the benefit of a half a per cent forward weight shift.’
TYRES AND PODS As with everything on a racecar, any change inevitably affects something else, and so as work continues towards fixing the DW12’s weight distribution, Firestone, IndyCar’s official tyre partner, is having to keep pace with changes of its own. As with any spec racing series, tyres are tailored to the specific needs of the chassis and Firestone’s 2011 IndyCar tyres were developed to match the IR07’s weight and its weight distribution. During testing of the DW12
that ran through mid-October, 2011-spec Firestones were used but, once engine manufacturers took over testing duties from mid-October through mid- December, the company began testing its 2012 tyres, in conjunction with the factory Chevrolet and Honda programmes. Further adding to the
problems are the bulbous, new-for-2012, rear wheel anti-interlocking devices, dubbed ‘rear wheel pods’ by Dallara, which weigh in at almost 15lb (7kg). The three-piece structures,
comprising a main beam, which mounts to the larger 2012 crash attenuator, and the pair of pods that affix to the ends of the beam, spreads more mass behind the car and outward past the rear wheels. However, for the purpose it serves – to prohibit cars taking flight by riding over the rear tyres – the extra weight and rear weight distribution bias it adds is a necessary performance penalty for everyone to carry.
DRAG REDUCTION If the well-documented problems and possible solutions to rectify the DW12’s weight / weight distribution issues weren’t enough to tackle, the anticipated massive reduction in aerodynamic drag is also in need of an immediate fix.
While the 41 / 49 per cent
weight distribution forced drivers to avoid the throttle in Indy’s corners, the car also experienced an unexpected excess of drag. The result was average lap speeds in the 208-216mph range, compared to Alex Tagliani’s 2011 Indy 500 pole average of 227.4mph, and alarm bells went off when the DW12-Honda driven by Franchitti and the DW12- Chevrolet driven by Kanaan were unable to get within 10mph of Tagliani’s speeds in the old (but trimmed out) Dallara IR07.
60
www.racecar-engineering.com • February 2012 With engine manufacturers
playing things somewhat conservatively during the early tests at Indy, having more power on tap would almost certainly bump speeds over the 220mph mark, and with the lighter rear components on the car, speeds would jump appreciably as the drivers would be able to carry some degree of throttle through the corners but, to get close to Tagliani’s pole speed, shedding drag is still a requirement.
testing and validation on the old IR07 chassis, Dallara was able to produce accurate and reliable aerodynamic figures that translated from a virtual environment to the racetrack, but it does not have that luxury with theDW12, so the programme has moved to Fontana, southern California. ‘Fontana [is] basically like a big open section wind tunnel,’ says Phillips. ‘We can do back-to-back changes there and learn what that correlation would
“even further down the
undesirable ‘too much downforce / not enough power’ path”
‘At the Speedway we aren’t
matching where we should be in their theoretical world, and that’s what they’re trying to work on right now,’ says Phillips, who wants to see qualifying speeds of 225mph and race speeds of 221mph. ‘So instead of being at 222mph, they’re running no quicker than 216. They run the car at 214, for example, do various changes and that next run correlates to what the change should be, but they’re still 5-6mph off where they think they should be.’ With almost a decade of
be for Indianapolis.’ With the first half of the 2012
chassis orders delivered on 15 December, Phillips confirmed that the initial fleet would be updated with the new lightweight items and drag-improving components after the cars have shipped, provided of course the parts perform as expected in testing.
DOWNFORCE AND GRIP Not much has been said about an excess of downforce at Indy, but on the road courses, where the estimated 700lb of additional downforce really
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