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# Vehicle Foot Propulsion

An extensible foot replaces the wheel for propulsion
 (+1, -2) [vote for, against]

Added to the already existing wheels (but can be driven from a different source of power) a foot contacts the road, and once firmly set, pushes energy from the motor in a more effective way than the wheels, staying in contact for a large distance and holding better control with less energy consumption. In case of failure the foot contracts and the wheels take on their former role.

This is only for propulsion (thinking "back wheel drive"), while steering and breaking would be left until the next generation of cars, where the wheel will finally be thrown away as an idea of the past (and be tought in the e- highschools for kids at age 4 - just before they are mature enough to go out into the real world).

 — pashute, Jan 12 2011

Baked? http://boingboing.n...heel-consistin.html
[pocmloc, Jan 12 2011]

Rrrun http://www.mthoma.com/rrrun.html
by Marta Thoma [pocmloc, Jan 13 2011]

I hope it clarifies the idea [pashute, Jan 16 2011]

 A foot will be less effecient than the wheels. The foot will have to be mounted to the vehicle, supporting a substantial proportion of the vehicles mass. This mass will need to be carried through a sliding bearing arrangement. Power will need to be converted from rotary to linear motion. There will need to be a mechanism to lift the foot and move it forward between steps.

 Each of these factors is inherently less effecient than wheels. The vehicle would also have to carry all the extra mass of the mechanisms.

I'd give it a bun if the car was shaped like a chicken, with the head of William Shakespeare, and hopped along the road on one big foot.
 — Twizz, Jan 12 2011

 There's a reason a bicycle is faster than running - the wheel is a more efficient method to support and propel a mass than an articulated limb and pad.

It is possible to generate more grip with a foot than with a wheel, as the contact area can be larger, but the mechanics of moving the vehicle with it are far more complex and inefficient.
 — Skrewloose, Jan 12 2011

 Should we then not use much bigger wheels or perhaps rather a lot of small ones?

I prefer harpooning the truck in front and saving fuel that way. Wow do trucks go some interesting places!
 — saedi, Jan 12 2011

 More contact area does not necessarily give more grip.

 Bigger wheels require more energy to turn, they're heavier and take up more space within the vehicle. It's also more difficult to steer, as wide tyres scrub. Wide tyres are also more prone to aquaplaning and losing traction on loose surfaces.

More wheels = more bearings, more brakes, more driveshafts etc.
 — Twizz, Jan 13 2011

Does this then lead to very few small wheels covered with superglue?
 — saedi, Jan 13 2011

 There is always an optimum tyre size for a given vehicle. It is a compromise between various aspects of performance, including acceleration and braking, cornering, fuel effeciency, cost, noise, etc.

 Wider tyres will give better dry braking and acceleration (up to the point at which the weight of the wheels & tyres becomes excessive)

 Narrow, high pressure tyres will give better fuel effeciency and less noise.

 Larger diameter tyres will roll more smoothly and require less rotational velocity of the drivetrain bearings.

Soft compound tyres also require more energy to keep rolling.
 — Twizz, Jan 14 2011

 Tyre? I thought that was a city in Lebanon since ancient times.

 Thanks [pocm], But the ideas are different. This is one single mechanical "leg" (nothing like a shoe) and of course without being any larger than the car itself. So the second image is a "grotesque" one of this idea... I'll try a quick drawing.

Efficiency mechanisms and weight - since its Extra to the wheels, it definitely will add weight, but since it is more precise and gives better power for longer periods of traction, I would suppose it would very possibly be MUCH MORE efficient than the wheel (only in the propulsion, remember the wheel is still there at the first stage of this revolution).
 — pashute, Jan 16 2011

 Tyre - as spelt by John Dunlop, the inventor of the pneumatic tyre to which we refer.

 Foot propulsion will absolutely be MUCH LESS effecient than wheel propulsion.

 Wheels seldom lose effeciency due to limits of traction and there is no reason to suppose that a foot would give any more 'precision' (presumably directional stability).

 The wheel moves continuously about a single axis and can be driven directly by the rotary motion of the motor.

The foot needs a linear bearing of some description of a series of semi-rotating elements to achieve linear motion. There is also the requirement for rotary a complex transmission. Everything about foot propulsion is MUCH LESS effecient than wheel propulsion.
 — Twizz, Jan 17 2011

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