Alt-BEAM Archive
Message #07760
To: beam@sgiblab.sgi.com
From: Bruce Robinson Bruce_Robinson@bc.sympatico.ca
Date: Tue, 16 Nov 1999 12:44:56 -0800
Subject: [alt-beam] Re: BEAM Prism ??
Dan Larson wrote:
>
> ... the angle between the sun and the
> wall spot would not remain constant.
> The sun moves but the wall doesn't, so
> I will have to have a mirror, also
> rotating, to reflect the beam exiting
> the prism toward a constant spot on
> the wall angle of the prism to track
> the sun. Might be tricky, geometry-wise
> that is....
This comment and the ensuing discussion stirred up some faint memories
from a couple of decades ago. I managed to dig out a pencil sketch that
was buried in my files.
The beginning: an article in The Mother Earth News (a magazine) showed
how a large solar collector could be made to track the sun with no
external power source. Two large copper tubes, painted black and filled
with freon (!!) were mounted on the solar collecter, one on either side.
Each one was connected to an air cylinder adapted from a screen door
closer. When the sun struck one of the tubes from the side, it would
increase the pressure of the freon, causing the cylinder to tilt the
collector toward the sun. The pressure would equalize when the panel was
pointed directly at the sun. This arrangement is the mechanical
equivalent of a light-seeking head mechanism. The Soler Power Smart Head
is a perfect equivalent.
Problem 1: Up here above the 49th parallel, it was desirable to adjust
the tilt of the solar collector as well. Solution: mount the complete
rotating collector in a frame, and use a second freon-powered system to
tilt the frame. Equivalent to a Solar PSH with a horizontal axis (and
well balanced).
Problem 2: In the midst of the forest I live in, the only suitable place
to erect a solar collector was 40 metres North of my house. This meant
having to pipe the hot water from the collector a long way through
insulated pipes. Solution: mount the solar collector on the North side
of my house, and place a tilting/rotating mirror on the north edge of
the clearing. Mirror to be made from a sheet of stiffened plywood
covered with tin-plate.
Problem 3: The tilt/rotate mechanisms would point the mirror directly at
the sun. Solution: mount the mechanisms separate from the mirror, and
use a 2:1 reduction unit to drive the mirror. This would cause the
mirror to point exactly half-way between the moving sun and the fixed
solar collector. I planned to use a simple chain drive to do this.
This is exactly analogous to your problem. Use two Solar PSH units to
rotate and tilt your mirror, using 2:1 reduction between the heads and
the mirror (mirror turns 1 degree for every 2 degrees of PSH movement).
Mechanically a bit of a challenge, but with all the work being done on
the Solar PSH, electronically it would be pretty straightforward. The
time of year doesn't matter. The time of day doesn't matter. The
mechanism will track the sun whenever it is shining.
I never built the solar mirror. I gave copies of my sketches to a
colleague who produced some nice engineering drawings -- and then left
town in a hurry (that's another story). Shortly afterwards, freon turned
out to be a bad guy, and the whole idea became impractical. It would be
most interesting to see it on a small scale.
My pencil sketch is pretty crude, but it might be scanable. If anyone is
interested in pursuing this, e-mail me off the list & I will attempt to
get a copy of the sketch to you.
Regards,
Bruce
7761 Tue, 16 Nov 1999 13:02:57 -0800 [alt-beam] Re: If you can't come to the museum, a virtual version of themuseum will beam@sgiblab.sgi.com Bruce Robinson "John A. deVries II" wrote:
>
> I don't know how many of you will be
> able to visit the Los Alamos National
> Laboratory between here and Jan. 31, 2000
> to see the excellent exhibit of Mark
> Tilden's robots. For those of you who
> can't, I am attempting to bring some of
> the experience of the exhibits to you
> via the Heretics site:
Many, many thanks, Zoz. I know there are a great many of us who won't
have an opportunity to be there in person -- this is great!
Bruce
7762 Tue, 16 Nov 1999 13:03:27 -0800 [alt-beam] Re: Cholroplast thingy "'beam@sgiblab.sgi.com'" Wilf Rigter Finally tried it with green LEDs for photosensors and ... no go: the =
leds
just don't have the photovoltaic oompf! I'l try PDs next.
Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493=20
fax: (604)590-3411
> -----Original Message-----
> From: Wilf Rigter [SMTP:Wilf.Rigter@powertech.bc.ca]
> Sent: Tuesday, November 16, 1999 9:46 AM
> To: 'beam@sgiblab.sgi.com'
> Subject: RE: Cholroplast thingy
>=20
> This may work but it is untested. The PD or green LEDs act as =
photovoltaic
> generators and steer the 100K resistor current to the MPSA12 with =
the
> lower
> light level. Try adding a little positive feedback by crosscoupling =
the
> collectors to the opposite bases.
>=20
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> tel: (604)590-7493=20
> fax: (604)590-3411
>=20
> <>=20
> > -----Original Message-----
> > From: Richard Caudle [SMTP:richard@cqc.com]
> > Sent: Saturday, November 13, 1999 10:15 AM
> > To: BEAM
> > Subject: Cholroplast thingy
> >=20
> > _____ =20
> >=20
> > =A0
> > Good day, BEAM cats!
> > =A0
> > I'm building some Christmas presents and I've hit a bit of a =
snag.=A0
> > Attached is the hookup of the thing that I'm working on at the =
moment,
> but
> > both motors won't run.=A0 All that runs is one of them.=A0 If I =
unplug the
> > running one, the non-running one runs.=A0 The motors that I'm using =
are
> from
> > CDROM drives.=A0 I think they are the ones that eject the CD.=A0 =
Any
> > suggestions?
> > =A0
> > Richard Caudle
> > www.geocities.com/frankendaddy =
<http://www.geocities.com/frankendaddy>
> > Home ICQ - Frankendaddy
> > =A0
> > Guardians of the sacred words: Nee, Ptang, and =
NeeWhon!=A0=A0=A0=A0=A0=A0=A0=A0 <<
> File:
> > chloroplast2k.bmp >> << File: photochlor.gif >>=20
7763 Tue, 16 Nov 1999 17:12:27 -0400 [alt-beam] Re: BEAM Prism ?? alt-beam@egroups.com michael.hirtle@ns.sympatico.ca (Michael Hirtle) Sorry to tell u but to sun doesn't move, it's the earth :-)
Timothy Flytcher wrote:
> Idea... the sun moves in an arc... so that it moves up and down as well as
> side to side...
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