DELTA WING
confirming the accuracy of the firm’s initial projections. To use the narrow Michelins,
BBS produced bespoke three-lug front wheels, again to Bowlby’s specification. ‘The front wheel and tyre weigh 8.4kg (18.5lb),’ he confirmed. ‘The wheels are unique for the DeltaWing. We designed them hand in hand with Roman Miller and BBS. He loved the project and did this special design. They’re sort of maxed- out FEA specials at the lightest possible weight. The Michelin tyre is 6kg (13.2lb)…’ Bowlby also explained the
Rear suspension is a combination of conventional pull and pushrod suspension thinking, with the dampers overdriven in roll but not in heave as the roll damping of the whole car is achieved solely at the rear
and other functions normally expected from a cornering system. ‘Other than positioning of the roll sensor, there is no camber gain or anything like that to speak of,’ Bowlby confirmed. ‘It’s not designed that way. Basically, you run zero camber on the front suspension when there are steering angles applied.’ With such a compact front suspension, and the rear suspension responsible for most of the DeltaWing’s handling performance, the design team continues to keep things as simple as possible. ‘The front tyres, which are
only four inches wide, have one millimeter toe out on each front wheel. Other than that, there’s not much set up at the front. It was beautifully sort of juggled with by John Ward. And I think it’s an extremely elegant layout. So far we haven’t bolted an anti-roll bar in as the drivers tell us the car is so solid in the front and rear that it doesn’t need any more support. The simulations tell us the car will be slightly better with a bit more anti-roll stiffness, but there still might be a penalty on things like that. I think we will just have to see what the tyres and the car needs.’ Contained within the front suspension module is a minute, non-traditional steering rack, which required the last-minute help of one of Bowlby’s trusted friends to produce: ‘The steering rack is a DeltaWing design. It’s
Zack Eakin and Simon Marshall’s work,’ he said. ‘It’s a very elegant bevelled gear, so we’ve got a pinion drive that’s a bit like a Go Kart, where you end up having a pinion arm – for lack of a better word – assembly that allows the steering to activate.’
BESPOKE TYRES Finding the right tyre supplier to build the radical fronts and the more conventional rears came in a partnership between
from the fact that the vehicle comes from an area beyond our experience base. Part of any feasibility study is an assessment of the resources required and whether we have the capacity to properly support a programme. Fortunately, we have been able to accommodate the DeltaWing development,’ he said. Anticipating the DeltaWing’s
performance through simulations of its own and striving to hit the target needed for the car in its
“They’re sort of maxed-out FEA specials at the lightest possible weight”
DeltaWing and Michelin, with Bowlby providing the renowned manufacturer his dimensional requirements. Silvia Mammone, Michelin global project leader for the DeltaWing, and Michelin technical liaison, Karl Koenigstein, used that data to produce the narrow front tyres at the same time as the company was manufacturing wide fronts for the likes of Audi and Peugeot. Designing and manufacturing
bespoke tyres for a car that did not exist and which had no real-life data to draw upon was daunting, at best, says Koenigstein: ‘This was one of the concerns, not only from the standpoint of accuracy of the underlying assumptions, but also from the incertitude coming
12
www.racecar-engineering.com • May 2012
virtual form was a crucial element of Michelin’s pre-planning. With the time and resources alone that would be required to generate the 4.0/24.5 R15 fronts, Koenigstein and the rest of the team had a very small and precise window to hit. ‘Producing the narrow
fronts required not only a dedicated mould, but also some modifications to the tyre building machines,’ he explained. ‘We tried to minimise the risks by conducting some sensitivity studies to see what happened if our simulations were not completely accurate.’ Based on wear rates during
initial track testing, it’s believed Michelin’s front tyres would go as long at 8-10 stints at Le Mans,
unexpected choice of wheel studs and lug nuts for the front of the car: ‘The reason we’ve gone for three lugs is for about as many reasons as you could possibly imagine,’ he said. ‘First of all, in our analysis it was slightly lighter. In the front of the car it was particularly important to have light weight. Secondly, if you have multiple wheel lugs, you don’t need a locking system. That’s really important because it’s weight saving. If you had a central locking system the whole wheel has to be so offset it’s hanging out in the air stream and it’s not really essential from a practical racing standpoint.’ At the back, the DeltaWing uses a more traditional single-lug design to carry the 9kg (19.8lb) 12.5/24.5 R15 Michelin tyre and 5kg (11lb) BBS wheel.
AERO EXERCISE
With the DeltaWing being a largely aerodynamic exercise, Bowlby went into detail on the various traits and philosophies that went into the car. ‘We’ve said all along that the DeltaWing is meant to be half of most values found in an LMP1 car. It’s half the weight, has half the power and, in this instance, half the downforce and less than half the drag. The drag is, roughly, 550lb at 90m/sec at 201.34mph, with 2700lb of downforce.’ Like most of the car’s dynamic
performance capabilities, the majority of the aero balance is shifted rearwards. ‘We’re running around 25 per
cent on the front,’ said Bowlby. ‘And we have an aero mass characteristic where, in fact, the balance stays remarkably consistent. The car makes much
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100