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    The Quest for Perfect Weight Distribution.....

    ~From "EVO" Magazine

    "Front mid-engined: Is this the future?"

    "The arrival of the Ferrari 612 Scaglietti reveals the depth of radical thinking going on at Ferrari-Maserati. Like the new Maserati Quattroporte, the 612 S has an unusual mechanical layout. The engine is set right back in the chassis behind the front axle line, while the gearbox is mounted onto the back axle. The result is a weight distribution of 46/54 per cent front/rear - remarkable for a front-engined car, particularly for a genuine four-seater.

    Ferrari has staked its future on this unconventional approach - one which will be extended to Alfa Romeo's flagship (see page 14). Intriguingly, Maserati's technical director, Roberto Corradi, told evo that he regards the ideal weight distribution to be 42/58 front/rear. 'This is the value we are trying to achieve when we build a rear-mid engined car.' The front-mid-engined Quattroporte and 612 S aim to get as close to this as possible.

    'The layout guarantees similar performance to a rear mid-engine car,' said Corradi. 'Tests with the Quattroporte have shown that its maximum performance on high-speed bends is very close to what can be achieved with a good front-engined, rear-drive coupe. The BMW solution of 50/50 distribution is the best without a transaxle and we think it gives good performance when, say, a bend is a constant diameter and speed is constant. But in real life you rarely see this ideal scenario. Our transaxle system is complex and expensive, but a valid solution once it is developed.'

    Audi is known to be interested in the system. Its cars currently suffer from a layout which (A3 aside) has the engine ahead of the front wheels. Having so much weight so far up front is undesirable in a performance car.
    However, engineers within other companies are surprised that Ferrari-Maserati is aiming for such a rear-biased balance. 'Surely the Quattroporte will become very tail-heavy carrying four people and a bootful of luggage,' said one engineer.

    Aston Martin has adopted a front-mid-engine/transaxle layout but a senior engineering source said 50/50 was best: '45/55 or worse is a bad idea. What I really want to achieve is to get the car's yaw axis [that's the vertical axis about which the car rotates] as close to the driver's stomach as possible.'

    If the axis is too far in front of the driver, for example, the car would feel slow to turn into a corner. Such sensations dictate whether a car feels responsive to the driver's inputs. 'Too much weight at the back and you start to get the pendulum effect' our source claimed.

    Senior Lotus sources told evo that they also regard 50/50 as the optimum distribution. 'Ideally, we'd want 50/50 with low yaw inertia [the amount of effort needed to get the car to turn from straight ahead] and the same size tyres front and rear. If a car's responses are too fast, the driver can't cope. If the initial turn-in is too quick, it's not a secure feeling. You need to feel a build-up of lateral force as you turn.'

    Interestingly, the Lotus experts also said that rear-wheel steering - expected to appear on future Maseratis and the new Alfa - has huge potential for both safety and driving pleasure when combined with rear-drive and active suspension. Siting the engine behind the front wheels will also help with upcoming pedestrian impact regulations which demand plenty of crush space between the bonnet and the engine.

    Only when we get behind the wheel will we know whether Ferrari-Maserati's radical approach is the right one."



    I thought it was a pretty interesting article. Does anyone have any thoughts on the idea of a perfect weight distribution?


    Re: The Quest for Perfect Weight Distribution.....

    Quote:
    What I really want to achieve is to get the car's yaw axis [that's the vertical axis about which the car rotates] as close to the driver's stomach as possible.'

    If the axis is too far in front of the driver, for example, the car would feel slow to turn into a corner. Such sensations dictate whether a car feels responsive to the driver's inputs. 'Too much weight at the back and you start to get the pendulum effect' our source claimed.

    ... snip ...

    I thought it was a pretty interesting article. Does anyone have any thoughts on the idea of a perfect weight distribution?



    This source seems pretty smart to me.

    His statement means the optimum weight distribution can be somewhat different, depending on where the designer puts the driver's seat. In the case of a front-mid-engined layout, the driver's seat is well back in the car. To put the yaw axis (plan view center-of-mass) through the back part of the car would ordinarily mean a rearward weight bias. This rearward bias also helps acceleration out of a corner in a rear-drive car.

    It's a very interesting question with many aspects to consider.

    Here's a great book to stimulate more discussion.

    Re: The Quest for Perfect Weight Distribution.....

    I just secured 360lbs (164kg) of sandbags to the tailgate of a borrowed 95 Toyota pick-up (that I use in the snow), so now I'll have the same weight distribution as my other two cars (73 Carrrera 2.7 replica and 96 993 C2)

    Re: The Quest for Perfect Weight Distribution.....

    Mike,

    I have been thinking about picking that book up for a while, but never have. The only testimonials I've heard are from people who have heard it was good by reputation. Perhaps I should stop thinking about it.

    Re: The Quest for Perfect Weight Distribution.....

    Justin,

    I own the book and it is quite comprehensive. It's a text book, and not exactly light reading, but it is very informative. It would help one to have spent time in engineering school, or to have taken some college level math and physics, to get the absolute most out of it. Having said that, it is also good for skimming to get the basic ideas. It's quite comprehensive.

    The senior author, Bill Milliken (while working for Calspan), was instrumental in the original "friction circle" g-g diagram research made famous by Mark Donohue and Roger Penske.

    I am quite familiar with the book. The Millikens (father, Bill, and son, Doug) were very helpful during the initial development of the g.Analyst (17 years ago). In return for their help, some g.Analyst instructional materials were released for use in their classroom workbook that accompanies the text book.

     
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