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Date:	Sat, 6 Oct 2012 19:59:24 -0400
Message-ID:	<CALSZ9go3Du=s-V18RSrVG3Y6fAHjKmYvyoZ=ZAAqaDpkejvu=g@mail.gmail.com>
Subject:	[geda-user] Magnetic Bike Theory Question
From:	Rob Butts <r DOT butts2 AT gmail DOT com>
To:	geda-user AT delorie DOT com
Reply-To:	geda-user AT delorie DOT com

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 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?

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Content-Transfer-Encoding: quoted-printable

<font size=3D"3" face=3D"Times New Roman">

</font><div style=3D"margin:0in 0in 0pt" class=3D"MsoNormal"><span style=3D=
"font-size:12pt"><font face=3D"Times New Roman">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&quot; in diameter. On one =
end
of the roller shaft there as an aluminum disk about 4.5 inches in diameter =
x
1/8&quot; thick. On either side of the aluminum disk are disks the same siz=
e
holding six what appear to be 3/4&quot; diameter x 1/8&quot; 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&#39;t eclipse at al=
l and
the magnetic field across the center disk is negligible.</font></span></div=
><div style=3D"margin:0in 0in 0pt" class=3D"MsoNormal"><span style=3D"font-=
size:12pt"><font face=3D"Times New Roman"></font></span>=A0</div><font size=
=3D"3" face=3D"Times New Roman">

</font><div style=3D"margin:0in 0in 0pt" class=3D"MsoNormal"><span style=3D=
"font-size:12pt"><font face=3D"Times New Roman">It works for the bike train=
er
but not so much for the arm bike. I am using a 5.75&quot; diameter aluminum
center disk x 1/8&quot; thick. The magnets are ceramic 1&quot; diameter x
3/8&quot; thick with no telling the strength since I got a bunch on ebay (y=
es,
don&#39;t stop reading if you&#39;re this far ~ cheap) and I&#39;d say mayb=
e 2 or 4 lbs
holding force. Since, I have found and ordered 1&quot; diameter x 1/8&quot;
thick neocadmeum N52 magnets with holding force of 22 lbs. The gaps between=
 the
disks are al the same.</font></span></div><div style=3D"margin:0in 0in 0pt"=
 class=3D"MsoNormal"><span style=3D"font-size:12pt"><font face=3D"Times New=
 Roman"></font></span>=A0</div><font size=3D"3" face=3D"Times New Roman">

</font><p style=3D"margin:0in 0in 0pt" class=3D"MsoNormal"><span style=3D"f=
ont-size:12pt"><font face=3D"Times New Roman">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&quot; 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?</font></span></p><font size=
=3D"3" face=3D"Times New Roman">

</font><div style=3D"margin:0in 0in 0pt" class=3D"MsoNormal"><span style=3D=
"font-size:12pt"><font face=3D"Times New Roman"></font></span>=A0</div><div=
 style=3D"margin:0in 0in 0pt" class=3D"MsoNormal"><span style=3D"font-size:=
12pt"><font face=3D"Times New Roman">Does anyone have any
suggestions?</font></span></div><font size=3D"3" face=3D"Times New Roman">

</font><p style=3D"margin:0in 0in 0pt" class=3D"MsoNormal"><font face=3D"Ti=
mes New Roman">=A0</font></p><font size=3D"3" face=3D"Times New Roman">

</font>

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