Construct a car which is propelled solely by wind energy

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Discussion Overview

The discussion revolves around the construction of a car that is propelled solely by wind energy, specifically focusing on the challenge of driving directly into the wind. Participants explore various ideas and mechanisms that could achieve this goal, including windmills and sails.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests using a car-mounted windmill facing into the wind to drive the wheels through gears or chains.
  • Another participant expresses a desire for a more interesting solution to surprise their teacher.
  • A participant references a previous discussion on engineering forums, reiterating that sails are ineffective for driving directly into the wind and recommending a cup anemometer as a potential solution.
  • One participant proposes that a pair of sails might work by tacking in different directions, although they express uncertainty about its feasibility.
  • A participant explains that a tacking sailing craft requires a force vector from the sails to react against another force from the wheels, which is not possible when driving directly into the wind.
  • They also suggest the idea of using small wheeled vehicles to pull the main vehicle in a zig-zag pattern as a wind-powered equivalent of a horse-drawn wagon.
  • Another method proposed involves flying controllable kites from the vehicle to power the wheels, though this participant doubts its practicality compared to a windmill.
  • A vertical axis windmill is recommended as it could provide forward drive irrespective of wind direction, while a horizontal axis windmill would require complex machinery to orient it correctly.

Areas of Agreement / Disagreement

Participants generally agree that sails are not effective for driving directly into the wind, but there is disagreement on the potential effectiveness of using multiple sails. The discussion remains unresolved regarding the best approach to achieve propulsion solely from wind energy.

Contextual Notes

Participants express various assumptions about the mechanics of wind propulsion and the effectiveness of different designs, but these assumptions are not fully explored or validated within the discussion.

Jurij
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I must construct a car which is propelled solely by wind energy. The car should be able to drive straight into the wind.
Have you got any ideas?
 
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If you want to drive directly into the wind, rather than just tacking like a sailboat, a sail is no use to you.

What you need is a car-mounted windmill facing into the wind, and have the windmill drive the wheels through gears or chains or pulleys etc.
 
It's good idea but I want something more interesting. I want to surprise my teacher.
 
This thread came up recently in one of the engineering forums. As Ceptimus rightly points out, sails (as used on a yacht) are useless, and a windmill type configuration would be your best bet. Do some googling for a 'cup anemometer', that should be fruitful, and interesting enough for your teacher.
 
I'm not entirely convinced that sails won't work. Clearly, a single sail will not work but how about a pair of them? They could tack in different directions with the lateral components of lift being equal and opposite but with the forward components adding. I'm not convinced it will work either but I can't dismiss it out of hand.
 
A tacking sailing craft, whether it be a boat, sand yacht, or ice yacht has to react a force vector from the sails against one from the keel / wheels / skates to provide a component of force in the direction of travel.

If the direction of travel is directly into wind, this is not possible. The force vector from the sail can't act at better than right angles to the wind. And even if it could act at right angles (which requires an infinite lift/drag ratio) it still wouldn't create any forward component when combined with the reaction force from the wheels (which again can't act at better than right angles to the direction of travel, even given perfect frictionless wheels and zero energy loss grippy tyres).

For the same reason, you can't just use two or more sails reacting against each other. The sails each provide a sidways 'lift' component, and a backwards 'drag' component, and there is no way to combine these to end up with the required forward facing component.

I suppose you could have one or more tacking small wheeled vehicles pulling the main vehicle. This would be the wind powered equivalent of a horse drawn waggon, except that the horses would be running zig-zag. :smile:

Another method would be to fly controllable kites (two or more strings) from the vehicle, and use the varying line tension, and angles to power the wheels. This is really just the same as the windmill, except that you replace the windmill with kites. I don't think it would be anywhere near as practical as the windmill method.

I like the idea of a vertical axis windmill (like a cup anemometer, or a Savonious rotor). This would provide forward drive irrespective of wind direction - with a horizontal axis mill, it would be necessary to point the rotor into the direction of the local airflow, requiring complex machinery - the vertical axis method eliminates this, though at the cost of efficiency.
 
Last edited:
Ceptimus,

Aha! I hadn't thought it through all the way but that makes sense. Scratch that idea.

Thanks.
 

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