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  • From: "WILLIAM JONES" <billj AT harborside.com>
  • To: <homestead AT lists.ibiblio.org>
  • Cc:
  • Subject: [Homestead] Heat Engine: Some Design Considerations
  • Date: Tue, 19 Jun 2012 15:11:37 GMT

OK, so why not use balloons as bladders?  It's because they require wasted
energy to blow them up.  We want bladders that inflate effortlessly.
Now how long should we make those lever arms that hold the floats?  That
turns out to be the biggest question of all.  Intuitively, the hotter the
weather, the deeper the floats can be.  We'll be using calculus to find the
optimal placement of the floats, which will really save time and effort by
trial-and-error.
Which float should we connect to a given bottle?  This is very important,
since it would be a disaster if a float inflates before it gets on the
correct side.  The floats would oppose each other.  Intuitively, the hotter
it is, the closer the angular displacement would be to 180 degrees, minus the
angle of elevation of the sun.  To see this, imagine instantaneous heating. 
You would want the float to be just past the six-o'clock position just as the
bottle is facing the sun, right?
Finally, like the toilet paper roll in the bathroom, it can run over-handed
or under-handed.  If the sun is straight overhead, as at the equator on the
equinox, then by symmetry it can't make any difference which we choose. 
Intuitively, if you think that cooling is easier than heating, as it is here
in Oregon, then we should place the floats so that the corresponding bottles
see the sun right after coming out of the water.  In really hot places, it's
probably better to do the opposite.


  • [Homestead] Heat Engine: Some Design Considerations, WILLIAM JONES, 06/19/2012

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