Gravity Racer Suspension - Is 3 The Magic Number?

[AngusF1]

I don't, the air resistance is very important. The acceleration of a gravity racer is basically determined by its ratio of mass to air resistance. If you can keep the air resistance the same and increase the mass, the acceleration will increase.

At the limit case, where the mass is huge and the air resistance negligible, the racer will accelerate at 1G times the sine (I think?) of the slope angle, and increases in speed will not result in any significant reduction in the acceleration, because the ratio of the air resistance to the mass will be very small.

A practical example would be the difference between a leaf and a ball bearing.

[Tim.Wright]

It seems obvious to me that with a car weight limit of 100kg, the fatter the driver the better. The car with the fattest driver will accelerate much quicker, and the weight limit is high enough to allow tyres large enough to corner the fatter man nearly as quick as a lighter man. A large-boned individual with dense muscle would do the trick in terms of maximising weight for the smallest drag.

I wonder whether there is a limit on driver "clothing". One could carry ballast in the back pockets of one's trousers - "which was the style at the time"....

I wonder why you think a large stone will accelerate more quickly than a small stone, ignoring air resistance.

Because you can't neglect air resistence and mechanical drag.

Your motive acceleration is the equal to the gravitational force minus air-mech resistence all over mass. The larger the mass and the smaller the resistence, the faster your car will accelerate. Obviously, there is a theoretical maximum equal to 9.81 x Sine(HillInclinationAngle) when your air resistence is zero.

[Rodak]

Okay, fair enough, then why not just set a maximum all up weight? That would seem totally fair to me and everyone would be at that weight. When I was racing FF the minimum weight, in a reversal, was 1100 pounds; I had to add 50 pounds ballast but that seemed fair.

[AngusF1]

I'd be interested to see what the optimum weight actually is. It can't be infinite, because then the car wouldn't turn.

That said though, yes, I don't understand why they set a max car weight rather than total weight. It seems to incentivise heavy drivers, chugging 2L of water before the race, eating pies and sewing 20kg barbell plates to one's trousers.