Gravity Racer Design - Aero & Other Bits...

[Paul]

I'd look at eco-marathon winners for inspiration, as those competitors chase similar goals. I'd pay most attention though to driver/rider safety and track choice.

[bill shoe]

Huge loophole...

Would this really work? You'd need to convert the kinetic energy of the falling weight into propulsion. I'm not sure if that's partially possible, or just not possible at all. Or if the lowering of the CG would make any difference.

OK, yes, it would need a mechanism such as a one-way chain drive between falling ballast and road wheel to convert potential to kinetic. But yes it would work and would be fully compliant with rule that says: "1. All gravity cars must be gravity powered only."

EDIT: Not so much. Theory is fine, but world record is approx 100 mph. At that speed, a 100 kg ballast falling 3 m only gives enough energy to boost speed a little more than 1 mph, and on practical level never mind.

[LVDH]

Not sure if more weight really helps, it also adds to rolling resistance and makes breaking more difficult. A larger brake will create more drag.
On the design on top I would remove the two rear wheels and only use one inside of the fairing.

[ChrisDanger]

Inboard brakes?

[jimcroisdale]

On the aero situation I basically have 2 options as I see it:

1) Smooth "tube" with plenty ground clearance

2) Flat, road hugging body with minimal ground clearance.

If the body is essentially flat to the road, what implications does the interaction with the road surface have? If there was a 5cm gap under the car, and a smooth undertray what would that do as regards additional drag/downforce? There are some very fast cars that use this design (Google "bodrodz"). Obviously, the lower centre of gravity would be advantageous, and any small amount of downforce could help stability, but not at the expense of drag. it would also make the car easier to design, as assuming a flat bottom makes half of the design decisions for me.

Thoughts?

Jim

[LVDH]

I think Option 2 sounds best. If you have two basic designs, that would reflect the size you are thinking about I could run them through CFD.