I am happy to say that I have a wealth of ignorance about the soapbox derby, but I believe that it is a challenge to produce the fastest car powered solely by gravity, running down an incline.
So.
How about having quite large (but light) wheels, with toothed (I may mean splined) axles. The vehicle body has, on its undernetherparts, four vertically mounted racks (as in rack-and-pinion) which engage with the toothed axles.
At the beginning of the race, the body (and driver) are raised to the maximum height permitted by the racks. Upon being released, the weight of the body and passenger drive the racks downward, thereby turning the wheels.
The device is still gravity powered, but the weight of the driver falls through a greater distance, thereby giving additional power.-- MaxwellBuchanan, Jan 18 2013 Red Bull Soapbox Races https://en.wikipedi...d_Bull_Soapbox_RaceDownhill all the way. [8th of 7, May 01 2018] Also I think you'd want to go through a whatsis [edit: Brachistochrone] curve with the body while the wheels went with the course.-- FlyingToaster, Jan 18 2013 Like all brilliant innovations in racing, it's totally against the rules. Soapbox cars are not allowed to incorporate any form of propulsion device.
It's still a cool idea. [+]-- Alterother, Jan 18 2013 //Soapbox cars are not allowed to incorporate any form of propulsion device.// Well, that's another world record placed on the high shelf.-- MaxwellBuchanan, Jan 18 2013 I imagine there is a height restriction otherwise one hundred foot high contraptions would abound... eh not a bad idea as it turns out. Un croissant au naturelle.-- xenzag, Jan 18 2013 Perhaps a version of a soapbox racer where the driver is flung horizontally into the car at a very high rate of speed just as the starting gun goes off.-- AusCan531, Jan 19 2013 I went and looked up the rules.
There is very little discretion in the construction. You have to use certain specific mechanical parts and no others.-- Kansan101, Jan 19 2013 Ironically, not with soap boxes?-- Ling, Jan 19 2013 What we need, clearly, is a HalfBakery soapbox derby. A standard course would be provided. Rules:
(1) The clock starts with the driver standing on the ground beside their vehicle, and stops when they cross the finish line.
(2) The vehicle may not contain any stored energy in the form of previously tensioned springs; batteries; fuels; compressed gas reservoirs; charged capacitors; antimatter etc.
I think two rules is probably as many as are needed here. Thus, a rack-and-pinion drive would be acceptable, as long as the driver's time taken to climb up into the cab is included (as it would be). Equally, the driver is welcome to pedal or row the vehicle; or to perform rapid autoliposuction and thereby fuel a diesel engine.-- MaxwellBuchanan, Jan 19 2013 Human muscle power is a form of stored energy. For that matter, so is human fat.-- Alterother, Jan 19 2013 And so is gravitational potential energy by virtue of the gradient.-- MaxwellBuchanan, Jan 19 2013 Listen pal, don't get all sciency with me. Hare-brained clockwork mechanisms are one thing, but if you add muscle power it's just a funny-looking pedalcar race.-- Alterother, Jan 19 2013 I think you'll find it's "sciencey"...-- MaxwellBuchanan, Jan 19 2013 Are you challenging a very-nearly-professional writer to a quasi-spelling match?-- Alterother, Jan 19 2013 Why 'quasi-' ?-- MaxwellBuchanan, Jan 19 2013 If it had an engine, and an extra bulge to accommodate it, would it be a quasi-motor?-- xenzag, Jan 19 2013 Because, by dint of it not being found in the OED, 'sciency' (alt. sp. 'sciencey') is a quasi-word.-- Alterother, Jan 19 2013 You could potentially fuel an engine by burning your own wooden chassis.-- mitxela, Jan 19 2013 You could, but I think in that case the wooden chassis would constitute "fuel". You'd also have to include steaming up time.-- MaxwellBuchanan, Jan 19 2013 And the only way to have anything left in which to cross the finish line would be to build the chassis with more wood than necessary, which would make the racer heavier, requiring a larger motor to propel it, which would require a greater volume of wood for fuel, which would make the racer heavier...-- Alterother, Jan 19 2013 I see swing-steer propulsion hasn't been ruled out, yet (the kids toys that you steer left and right hard, and it makes them go along).-- Ling, Jan 20 2013 May the driver contain or invoke any stored energy besides that which is biologically occuring?-- RayfordSteele, Jan 22 2013 I actually built a Soap Box Derby car once. The axles and wheels are provided, and thus are standard for all entrants. There is no way to do anything like what is suggested in the main text here, or what [Ling] mentioned in an anno.-- Vernon, May 01 2018 The Red Bull soapbox races <link> leave the details of the vehicle almost entirely to the discretion of the builders. Three and four wheel designs are permitted. The main criterion seems to be that the axles are unpowered.
However, additional propulsion by the "Fred Flintstone running feet" method has been observed on more than one occasion.-- 8th of 7, May 01 2018 // The main criterion seems to be that the axles are unpowered.// So, basically similar to an Airbus A380? Or, indeed, the Valiant tank?-- MaxwellBuchanan, May 01 2018 The axles are unpowered, but may I place a large magnet at the end? Or a fan at the beginning? Or on the vehicle?-- Voice, May 01 2018 You'll have to ask the organizers.
// So, basically similar to an Airbus A380? //
No. Soapbox racers are generally constructed in sheds by complete amateurs with only the vaguest ideas of mechanical engineering, often valuing appearance above functionality.
They travel relatively slowly, and rarely leave the ground for more than a few seconds, usually unintentionally. Many crash or disintegrate before reaching the finish line.
However, since they are almost entirely devoid of carbon fibre, die-by-wire avionics, badly tested software, flammable liquid fuels, and lithium-ion batteries, as a form of transport they are completely superior to the A380 - or any other current commercial aircraft - in every meaningful respect.
// Or, indeed, the Valiant tank? //
Good-ish idea at the time, but doomed to failure.-- 8th of 7, May 01 2018 random, halfbakery