> > Hello, > > pardon my ignorance here, perhaps some one could shine some light on = this > situation for me. > > Today I purchased a cycle computer for my 28" uni. > > I have 2 problems. > > (1) What is the wheel circumference on a 28" wheel with a standard road = tyre > fitted?
When I installed my cycling computer on my 28" uni the instructions had me
measure my own wheel circumference. Start with the valve stem at the bottom,
mark the spot on the floor, and roll one revolution and make another mark.
Measure the distance in between. Lean on the seat some while you do this to
get the effects of weight. They also suggest making several readings and
taking the average.
> > (2) Where on the spoke am I meant to fit the magnet. Is it to sit at = near > the hub, near the rim, or somewhere in-between. If it is mounted in = the > wrong place then won’t the readings be incorrect?
Somewhere in between. You want it so that the sensor can get close to the
detector on the fork.
Beirne
> > Thanks in advance for any help that I will get. > > Wayne > > ----------------------------------- > > ------=_NextPart_000_0006_01BEF714.B8A23F80 Content-Type: text/html; > charset=“iso-8859-1” Content-Transfer-Encoding: quoted-printable > > <!DOCTYPE HTML PUBLIC “-//W3C//DTD W3 HTML//EN”> <HTML> <HEAD> > > <META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type> > <META content=3D’“MSHTML 4.72.3110.7”’ name=3DGENERATOR> </HEAD> <BODY > bgColor=3D#ffffff> > <DIV><FONT color=3D#000000 size=3D2>Hello,</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000 size=3D2>pardon my ignorance here, perhaps = some > one could=20 shine some light on this situation for me.</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000 size=3D2>Today I purchased a cycle computer = for > my=20 28" uni.</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000 size=3D2>I have 2 problems.</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000 size=3D2>(1) What is the wheel circumference = on > a=20 28" wheel with a standard road tyre fitted?</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000 size=3D2>(2) Where on the spoke am I meant to = fit > the=20 magnet. Is it to sit at near the hub, near the rim, or somewhere = > in-between. If=20 it is mounted in the wrong place then won’t the > readings be=20 incorrect?</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000 size=3D2>Thanks in advance for any help that = I > will=20 get.</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000 size=3D2>Wayne</FONT></DIV> > <DIV><FONT color=3D#000000 size=3D2></FONT> </DIV> > <DIV><FONT color=3D#000000=20 > size=3D2>-----------------------------------</FONT></DIV></BODY></HTML> > > ------=_NextPart_000_0006_01BEF714.B8A23F80– >
pardon my ignorance here, perhaps some one could shine some light on = this
situation for me.
Today I purchased a cycle computer for my 28" uni.
I have 2 problems.
(1) What is the wheel circumference on a 28" wheel with a standard road =
tyre fitted?
(2) Where on the spoke am I meant to fit the magnet. Is it to sit at = near the
hub, near the rim, or somewhere in-between. If it is mounted in = the wrong
place then won’t the readings be incorrect?
<!DOCTYPE HTML PUBLIC “-//W3C//DTD W3 HTML//EN”> <HTML> <HEAD>
<META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type>
<META content=3D’“MSHTML 4.72.3110.7”’ name=3DGENERATOR> </HEAD> <BODY
bgColor=3D#ffffff>
<DIV><FONT color=3D#000000 size=3D2>Hello,</FONT></DIV>
<DV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DVI><FONT color=3D#000000 size=3D2>pardon my ignorance here, perhaps = some
one could=20 shine some light on this situation for me.</FONT></DIV>
<DVII><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DVIII><FONT color=3D#000000 size=3D2>Today I purchased a cycle computer = for
my=20 28" uni.</FONT></DIV>
<DIX><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DX><FONT color=3D#000000 size=3D2>I have 2 problems.</FONT></DIV>
<DXI><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DXII><FONT color=3D#000000 size=3D2>(1) What is the wheel circumference = on
a=20 28" wheel with a standard road tyre fitted?</FONT></DIV>
<DXIII><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DXIV><FONT color=3D#000000 size=3D2>(2) Where on the spoke am I meant to =
fit the=20 magnet. Is it to sit at near the hub, near the rim, or
somewhere = in-between. If=20 it is mounted in the wrong place then
won’t the readings be=20 incorrect?</FONT></DIV>
<DXV><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DXVI><FONT color=3D#000000 size=3D2>Thanks in advance for any help that = I
will=20 get.</FONT></DIV>
<DXVII><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DXVIII><FONT color=3D#000000 size=3D2>Wayne</FONT></DIV>
<DXIX><FONT color=3D#000000 size=3D2></FONT> </DIV>
<DXX><FONT color=3D#000000=20
size=3D2>-----------------------------------</FONT></DIV></BODY></HTML>
(1) Measure the diameter and multiply by pi (=~3.142). You’ll get something like
88", depending on the tyre.
(2) I don’t know this, but I expect the device works by counting revolutions,
in which case the position is irrelevant. It would multiply revolutions
by circumference to get distance, and divide distance by time to get
average speed.
> (2) Where on the spoke am I meant to fit the magnet. Is it to sit at near the > hub, near the rim, or somewhere in-between. If it is mounted in the wrong > place then won’t the readings be incorrect?
It doesn’t really matter, but closer to the hub is better. It’ll give the magnet
more time to trigger a reading for the computer since it’s going by it slower.
More important is where you put the magnet in relation to where your pedals are.
You want to place it where it won’t get a reading when you idle, or when you’re
stillstanding holding on to something. The best place is 1/8 a revolution from
the pedal that is down when you idle and
1/8 a revolution from the bottom of the wheel when you stillstand.
___________ =========================================== ___ /_/ / / / /
Kevin Gilbertson - <a href="mailto:mail@gilby.com">mailto:mail@gilby.com</a> / _ '/ / / _'\_ / Unicycling
T-shirts at <a href="http://www.gilby.com/">http://www.gilby.com/</a> \_ /_/_/,___/ / ICQ: 12611076 AIM/AOL:
IamGilby /\/ /__________/ Unicycled Across Minnesota to help others!
\__/ ================================================
You need to measure the distance with the tire at the inflation you usually use
and with you on board. I recommend having a friend help and going about 5-6
revolutions and measuring the distance in mm. Do this about 5 times, throw out
the high and the low and average the rest of the measurements. It may take a
couple of practice runs to get the hang of riding straight and getting the
measurement exact. I really recommend getting it right though - on a bike ride
last weekend, my wife noticed that the 5 riders had cyclometer readings varying
from under 70 to over 90 miles for the 75 mile ride.
Great idea from Gilby about magnet position to avoid triggering while idling!
I’m moving mine now!
pardon my ignorance here, perhaps some one could shine some light on this
situation for me.
Today I purchased a cycle computer for my 28" uni.
I have 2 problems.
(1) What is the wheel circumference on a 28" wheel with a standard road
tyre fitted?
(2) Where on the spoke am I meant to fit the magnet. Is it to sit at near the
hub, near the rim, or somewhere in-between. If it is mounted in the wrong
place then won’t the readings be incorrect?
> (2) I don’t know this, but I expect the device works by counting revolutions, > in which case the position is irrelevant. It would multiply revolutions by > circumference to get distance, and divide distance by time to get average > speed. >
Correct, The computer knows that the distance traveled everytime the magnet
passes the sensor is that number you have programmed.
Probably the most accurate way to measure the circumferance of the wheel is to
make a chalk mark on the bottom of the tire, line it up on top of a similar mark
on the ground, then wheel the tire forward a complete revolution. Mark the
finishing point, then measure–usually in millimeters–and plug that number into
your computer calibration.
> > (2) Where on the spoke am I meant to fit the magnet. Is > it to sit at > > near the hub, near the rim, or somewhere in-between. If > it is mounted > > in the wrong place then won’t the readings be incorrect? > > It doesn’t really matter, but closer to the hub is better. It’ll give the > magnet more time to trigger a reading for the computer since it’s going by > it slower. > > More important is where you put the magnet in relation to where your pedals > are. You want to place it where it won’t get a reading when you idle, or when > you’re stillstanding holding on to something. The best place is 1/8 a > revolution from the pedal that is down when you idle and > 1/8 a revolution from the bottom of the wheel when you stillstand.
Good advice from Gilby. Also important is the distance between the magnet
and the sensor. Usually these have to be really close together, which may
dictate where on the wheel the magnet is placed. Get them about 1mm apart
for good readings.
> (1) Measure the diameter and multiply by pi (=~3.142). You’ll get something > like 88", depending on the tyre. > > (2) I don’t know this, but I expect the device works by counting revolutions, > in which case the position is irrelevant. It would multiply revolutions by > circumference to get distance, and divide distance by time to get average > speed.
It is very important to measure the wheel while you are riding the uni as the
compression on the tyre reduces the diameter quite a bit.
> Probably the most accurate way to measure the circumferance of the wheel is to > make a chalk mark on the bottom of the tire, line it up on top of a similar > mark on the ground, then wheel the tire forward a complete revolution. Mark > the finishing point, then measure–usually in millimeters–and plug that > number into your computer calibration.
This is the method I use, except I am on the uni and the tire is pumped up as it
would usually be. This should give the most accurate measure possible, though it
might be a good idea to do it several times to make sure your mark is
consistent.