X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=l+E4+vg/MaiIURFeyEeZlfGEDE6KjYBZKlJ54R/FaUE=; b=I/bNCtUpnAfB2TuET2GXsF5V7t4Bjq4MZBkR/FVNwBTEjtDd4FL4sLoP3eIy0hPlJA kXxqSbxCzSCRESxQCLR7LU1DdndN5lNEugaWOKDSWzhHd+rmH4mvz9Hdc0+Qwi3TqO/r neSc2R79mfjf982mLI0Aebr3S3yKtHxhMYo28KflbaRUFOF7gRr2nT/bSJ167Ze+VP18 abgOZ1IUSUPLYUg8OM5dylz3mEgh1lZHD7ol8vJHOaK5bOlu1XiY3HvzcodRJ1ZBuLm/ g59p+EC0qloiRyK3qWJisSRtS9o+Ildz/GVjVIOHPZa6kukeNmzHHdDkKwjtx+LJF8DW Ee0w== MIME-Version: 1.0 Date: Sat, 6 Oct 2012 19:59:24 -0400 Message-ID: Subject: [geda-user] Magnetic Bike Theory Question From: Rob Butts To: geda-user AT delorie DOT com Content-Type: multipart/alternative; boundary=047d7b6788241e6e1904cb6cc725 Reply-To: geda-user AT delorie DOT com --047d7b6788241e6e1904cb6cc725 Content-Type: text/plain; charset=ISO-8859-1 I am trying to design a magnetically resisted arm bike. I have a magnetic resisted bike trainer that you take the front wheel off a road bike and lock the forks into brackets while the back wheel rests on a small roller about 1.5" in diameter. On one end of the roller shaft there as an aluminum disk about 4.5 inches in diameter x 1/8" thick. On either side of the aluminum disk are disks the same size holding six what appear to be 3/4" diameter x 1/8" thick ceramic magnets of unknown strength evenly spaced as if every 10 minutes around a clock and alternating poles facing out. One disk containing the magnets is fixed to the frame and unable to move. The opposing disk is allowed to rotate so that if in max resistance position the magnets mirror each other perfectly as if in a full eclipse and since they are opposite poles facing each other creating the maximum magnetic field across the spinning aluminum disk. As the resistance adjusting lever is moved toward easier the disk containing the magnets allowed to rotate moves so that each magnet on its face becomes more out of phase with the opposing disk containing the magnets until they don't eclipse at all and the magnetic field across the center disk is negligible. It works for the bike trainer but not so much for the arm bike. I am using a 5.75" diameter aluminum center disk x 1/8" thick. The magnets are ceramic 1" diameter x 3/8" thick with no telling the strength since I got a bunch on ebay (yes, don't stop reading if you're this far ~ cheap) and I'd say maybe 2 or 4 lbs holding force. Since, I have found and ordered 1" diameter x 1/8" thick neocadmeum N52 magnets with holding force of 22 lbs. The gaps between the disks are al the same. My bike spins freely in the easiest position and just enough harder that you knot that it is working and the resistance is slightly higher. I suspect it is not only the strength of magnets that makes the difference but also the speed at which the center disk is spinning. With the bike wheel rolling on the 1.5" roller the center disk of the trainer is spinning significantly faster than my armergometer. Do people agree with the theory that a slower spinning center aluminum disk is why we are seeing such a difference in resistance? Does anyone have any suggestions? --047d7b6788241e6e1904cb6cc725 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
I am trying to design a magnetically resisted arm bike. I have a magnetic resisted bike trainer tha= t you take the front wheel off a road bike and lock the forks into brackets w= hile the back wheel rests on a small roller about 1.5" in diameter. On one = end of the roller shaft there as an aluminum disk about 4.5 inches in diameter = x 1/8" thick. On either side of the aluminum disk are disks the same siz= e holding six what appear to be 3/4" diameter x 1/8" thick ceramic magnets of unknown strength evenly spaced as if every 10 minutes around a c= lock and alternating poles facing out. One disk containing the magnets is fixed = to the frame and unable to move. The opposing disk is allowed to rotate so tha= t if in max resistance position the magnets mirror each other perfectly as if in= a full eclipse and since they are opposite poles facing each other creating t= he maximum magnetic field across the spinning aluminum disk. As the resistance adjusting lever is moved toward easier the disk containing the magnets allo= wed to rotate moves so that each magnet on its face becomes more out of phase w= ith the opposing disk containing the magnets until they don't eclipse at al= l and the magnetic field across the center disk is negligible.
=A0
It works for the bike train= er but not so much for the arm bike. I am using a 5.75" diameter aluminum center disk x 1/8" thick. The magnets are ceramic 1" diameter x 3/8" thick with no telling the strength since I got a bunch on ebay (y= es, don't stop reading if you're this far ~ cheap) and I'd say mayb= e 2 or 4 lbs holding force. Since, I have found and ordered 1" diameter x 1/8" thick neocadmeum N52 magnets with holding force of 22 lbs. The gaps between= the disks are al the same.
=A0

My bike spins freely in the easiest position and just enough harder that you knot that it is working an= d the resistance is slightly higher. I suspect it is not only the strength of magnets that makes the difference but also the speed at which the center di= sk is spinning. With the bike wheel rolling on the 1.5" roller the center disk of the trainer is spinning significantly faster than my armergometer. = Do people agree with the theory that a slower spinning center aluminum disk is= why we are seeing such a difference in resistance?

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Does anyone have any suggestions?

=A0

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