Top Spin

Black Hole said:
Hmm. Concept: wind turbine, forward facing, geared to screw propeller. Can the wind blowing directly onto the bows drive the ship directly into the wind?

The external force acting on the boat is backwards. Does the physics allow for the boat to move in the opposite direction to the applied force? I can probably work it out, but for the moment I am confused.
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I have a feeling you are approaching a perpetual motion machine :whistling:
 
EEPhil said:
Now if we had lots of solar farms reflecting heat and light, that might screw up the climate.
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Indeed. And similarly if we had lots of people using ground heat exchange systems to heat their homes then there may be an affect on the ecosystem and agriculture.
 
This movement directly against the wind possibility has been nagging at me.
I now wonder how tacking works - as a sometime sailor well used to the practice I know it works,
but I've no idea why this should be possible, while the direct forward, against the wind wouldn't be.

As to the original topic, The Mathematical Gazette had several articles on the subject of how spin can work - at least one of these was by my father, and the analysis went over my head at the time I read it (back in the sixties)
 
Every time I see the title of this thread I think of one of my favourite rides ...
Knotts_037.jpg
 
On the motion into the wind ... I would think that a wind turbine could produce power to drive a water propellor and move itself into the wind, but the 'gearing' would probably have to be quite low so the rate of progress would be a fraction of the wind speed.

With sails a fast boat tacking close to the wind can actually travel faster than the wind speed, but at an angle to the wind direction. It's all about vectors.
 
MikeSh said:
On the motion into the wind ... I would think that a wind turbine could produce power to drive a water propellor and move itself into the wind, but the 'gearing' would probably have to be quite low so the rate of progress would be a fraction of the wind speed.
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I would like to see some maths to prove that. The simplest case might be pulling on a thread wrapped around a bobbin with spool an rim dimensions such that the the bobbin rolls in the opposite direction to the pull (clearly impossible).

The wind turbine idea (whether driving a screw or some wheels) isn't as clear cut. The force of the wind is redirected into rotary motion in the perpendicular plane, which is then redirected to the opposite vector, so maybe it can work. Should be easy enough to build a wheeled model...
 
Black Hole said:
I would like to see some maths to prove that. The simplest case might be pulling on a thread wrapped around a bobbin with spool an rim dimensions such that the the bobbin rolls in the opposite direction to the pull (clearly impossible).
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If the bobbin is mounted a la monorail with the thread wrapped around a larger diameter than the part it travels on I'd think it would work. That is why I said the gearing would be low - in this case you'd be pulling thread off the spool faster than the motion.

Black Hole said:
The wind turbine idea (whether driving a screw or some wheels) isn't as clear cut. The force of the wind is redirected into rotary motion in the perpendicular plane, which is then redirected to the opposite vector, so maybe it can work. Should be easy enough to build a wheeled model...
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I was visualising a wind turbine mounted on a large wheeled/tracked platform. The power generated must be able to power the platform - it's just a case of how fast it could move.
 
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