Alt-BEAM Archive
Message #07328
To: beam@sgiblab.sgi.com
From: JVernonM@aol.com
Date: Wed, 3 Nov 1999 08:38:35 +0100
Subject: Re: aquabot
> In a message dated 10/30/99 4:36:36 PM Eastern Daylight Time,
> gpowell@engr.uvic.ca writes:
>
> > What if I put distilled water in the graduated cylinder and a thin layer
of
> > oil on the top. Thus no bacteria and no evaporation or contamination,
yet
> > light still gets in.
> I haven't tried that. Let me know if it works.
>
> See ya,
> Jim
> http://www.geocities.com/SoHo/Exhibit/8281/beamart.html
7329 Wed, 03 Nov 1999 00:31:42 PST [alt-beam] Re: magnets beam@sgiblab.sgi.com "Timothy Flytcher" Wow Bob!
True perpetual motion!!! something that can induce energy and change on
something ells and still retain 100% of it energy!!! Were can I buy those!!!
> > >A magnet stuck to the front of your refrigerator does not loose any
> > >strenght
> > >in the process of sticking there, for months or years.
> >
> > Yes it dose... try running a guise meter over a refrigerator door after
>you
> > have removed them...
>
>This is getting off topic, but a magnet hanging on the refrigerator does
>not
>loose
>any energy at all. A magnet floating over a supercondutor also does not
>loose
>any energy while levitating.
>
>In fact, when a bit of metal is drawn to a magnet, say a paperclip being
>picked
>up off a desk, is not taking any energy from the magnet at all. Thats
>simply
>not
>how the physics of magnetic fields works. (in fact, the magnetized
>paperclip
>hanging from the magnet is in a lower energy state than when it was sitting
>on
>the desk!)
>
>All the energy the magnet appears to use in drawing up the paperclip is
>payed
>back, with interest, when you remove that paperclip. The same is true when
>you
>remove
>the magnet from the refridgerator.
>
>You can also make magnets (like the spot where your fridge magnet hung)
>without
>'taking' any energy or magnetism from the original magnet used to make the
>second magnet. So just because your fridge has a magnetic spot left behind
>does
>not mean that 'energy' was taken from the magnet, or that it 'used' any
>energy
>while it hung there.
>
>To do this, you simply place a bit of iron next to your magnet pole, and
>hammer
>on the iron bit. Viberation from the hammering will realign the magnetic
>moments
>in the iron, and they will move into alignment with the field of your
>magnet.
>In this case the energy used to magnetize the bit of iron came from the
>hammering, not from the magnet. Thermal viberations will also do this over
>time, depending on how long you let your fridge magnet hang, so will the
>motor
>viberations, etc.
>
> > >PM motors will loose efficiency if the armature becomes magnetized,
>which
> > >happens much quicker if the motor overheats, and then cools again (this
>is
> > >how
> > >many mangets are made in the first place).
> >
> > This is how a few magnets are made...very few! it is simply too
>expensive!
>
>Not according to many manufactuers. As most modern magnets are ceramic
>based rare earth magnets, they have to be formed above their curie points
>anyway.
>A huge zap from a capacitor is dumped into a copper sheet around the form
>as its
>quenched, and there you go...one supermagnet, ready to ship.
>
> > Only end product magnets are shipped magnetized...I once worked for EB
> > making guitar pickups. I can't remember the composition of the material
>but
> > its qurie point was 530' a little high for the card stock that we used
>to
> > mount the windings...And yes guitar pick-ups loose there strength with
>time
> > and use... some say they mellow... I can and have reproduced this upon
> > request... :)
>
>Maybe pickups do age, I have no idea, but the reason why they age may not
>be
>what you think it is. Bucking magnetic fields can also depoloarize
>magnetic
>materials, and other materials can easily become saturated (like Mu metal).
>
______________________________________________________
7330 Wed, 03 Nov 1999 10:24:19 +0100 [alt-beam] Re: directional antenna? beam@sgiblab.sgi.com Wouter Brok Hello Bram,
>An unidirectional antenna would be something like a wire straight up.
>Just think about a car antenna. That's a uni-directional antenna.
In this I totally disagree with you: a wire straight up is much more of an
omnidirectional antenna than a unidirectional one. In fact it broadcasts in
or receives from all direction except this ones in the line of the wire.
Thus there is some directionality, but this isn't usefull to determine the
direction out of which the signal is coming, unless you use the zero (that
is my name for the directions in which the wire is pointing): if you would
rotate the antenna so that it will more and more point to the source you
will detect a rather large signal-gradient, towards no signal. This in
itself could be usefull to determine direction, but it poses some problems
since you don't have a signal from your antenna when it points in the
proper direction.
The straight wire antenna is a so called dipole antenna, of which you can
find specifications in every single book on antennae I think. An antenne
with a better direction-sensitivity would be a quadrupole or octupole
antenna. These are rather hard to construct (at least for me).
I have been thinking about making a navigation system for my robots based
on 'directional antennae' and ideas like a cage of Faraday (this isn't the
proper term in English), but then open on one side, crossed my mind (this
is the shielding that has been mentioned in an email on this subject).
Measuring phasedifferences with different antennae could be possible
perhaps, but then you would need to have a carrier-frequency whith
wavelengths in the order of cm's, which means the frequency is quite high
(100 MHz-FM-radio signals have a wavelenght of approxiamately 1 meter I
beleive) and this gives a problems, since wavelengths in the order of a cm
are hindered by obstacles with dimensions more than a cm .... interesting
things could be done perhaps with the shadow Wilf was talking about. There
were some other practical problems I have not mentioned yet ... have to
think a bit for that, it's been a while since I have been busy with antennae.
Well, in all I abandoned the idea since I didn't have enough knowledge or
time to experiment (which are good substitutes for eachother in BEAM).
Maybe any of you guys will manage to make a nice system .... that would be
nice.
Regards,
Wouter Brok.
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