At 11:07 10/5/2000, HERMANN DE BOER wrote:
>I need to retrofit my ac-less 87 Westfalia with air. Preferrably  something
>that runs on 12V as well as 120V. Any recommendations??

The only thing you could get that would run on 12v (within reason and given
a Vanagon) would be a swamp cooler which cools by evaporating water into
the cabin air.  At least somewhat effective in dry climates.

In *theory* you could build an absorption cooler like the Dometic fridge
but much larger, but you'd have to build a serious bonfire to stoke
it.  That cycle is extremely inefficient; its *only* good point is that it
uses direct heat input.

A 7500 BTU/hr air conditioner that draws say ten amps at 110v won't run on
DC, but if it would it would need about 100 amps at 12 volts.  And that's
probably half the capacity of the stock Vanagon A/C.  The only practical
way to get that sort of power density in a vehicle is by burning fuel, I
think, which at the moment means a generator -- or setting up a small
engine to drive an A/C compressor directly or by hydraulics.  However, if
you're in a sunny place and have engineering capabilities available to you,
might look into a sun-seeking reflector dish driving a Stirling engine --
noon sun at the equator delivers something like 1200 watts per square
meter, so I would think that a three-meter (or maybe even two-meter) dish
would give you interesting amounts of power to work with.  With a one-meter
dish you could cook hot dogs <g>.  The sun-seeking part is (comparatively)
trivial, and you might find that stretching aluminized mylar film over the
back of a mesh-type satellite dish would give a good enough focus to be
useful -- you'd have to open out the mesh some, no doubt.  And I think
you'd need to mount the whole thing permanently on a trailer -- with an
electric fence around it to keep the kiddies from vaporizing curious hands.

david
ps -- Friday, you ask?  C'mon, it could be done!

David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"