Ron,
  Winding a coil using a lathe (or any other means of spinning the coil
form) is easier if you put the spool of wire on the floor.  Stand the
spool on end so that the wire comes off the end.  This means that the
spool does not need to turn, i.e., no tension is placed on the wire by
accelerating the spool.
Bob


"Westfall, Ron" wrote:
> 
> Travis
> 
> I believe I have heard other people on the list say they were using coils
> from speakers.
> 
> For my coils, I used #34 magnet wire (real thin copper wire with a
> transparent plastic coating, looks orange-reddish due to the copper) to wind
> my coils.  I got a bunch of it from an electronic parts, ham radio supply
> store.
> 
> I used a wooden dowel, kitchen countertop laminate from the hardware store,
> and brass bolts (non-magnetic) to create a coil form.
> 
> The size of my coils was limited by the horseshoe magnet I was using.  The
> coil width had to be less than the width of the magnet gap.  The depth was
> practically limited by the possible motion through the gap towards the
> bottom of the U of the magnet.
> 
> I was using a metal lathe for another project and one night I set it up to
> turn at a slow rate (I eventually sped it up to about 100 RPM).  I mounted
> the coil form on a wood dowel in the lathe chuck.  I put the spool of wire
> on a piece of pipe so it would turn freely.  I put on some gloves to protect
> my fingers.  As the lathe turned, I fed the fine wire through the gloves to
> keep enough tension for efficient wrapping and to direct where it was laid
> down.  With my other hand I turned the reel of copper wire so that at no
> time was the full force placed on the wire.  This approach worked pretty
> good.  It required a couple of hours to wrap a coil, so over the course of a
> couple of nights I wrapped 2 or 3 of them.
> 
> Even with so crude a wrapping mechanism, I found that moving the coil
> through the gap of the horseshoe magnet by hand generated as much as 1 volt
> on the output of the coil.  This produces good results on the seismograph.
> 
> If you are using a horseshoe magnet, part of the solution is to get a magnet
> with a gap large enough for a reasonable size coil.
> 
> If this was any use to you, and you want more details (e.g. part details,
> supply sources), let me know.
> 
> Ron Westfall
> 
> -----Original Message-----
> From: Travis Farmer [mailto:travis5765@.............
> Sent: Thursday, May 03, 2001 2:18 PM
> To: Psn-L
> Subject: Interesting sensor pickup.
> 
> On my Lehman sensor I have been using a homemade coil that provided moderate
> output. I seem to have stumbled across something that works even better.
> >From an old (dead) hard drive,  I pulled the head positioning component and
> gave it a try. I drew up a (bad) picture of the piece I am talking about. It
> can be viewed at http://home.midmaine.com/~cgf/graphics/hd_sensor.jpg .
> I rigged up a linkage to the seismo and gave it a slow 1"/sec swing. I got
> an output of 0.026 V. the coil has a DC resistance of 18.1 Ohms.
> 
> Anybody else tried a setup like this?
> 
> -Travis
> 
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