S
Snoopy
Guest
Or perhaps it's just me?
Whatever, I've been seeing what spoke lengths this calculator (Spocalc.xls) gives me for a wheel I
had built some time ago and it seems that it is giving me the 'wrong' answers (spokes it recommends
are too short, by a couple of mm). I am using DT swaged spokes so went the DT website and tried the
spoke calculator they had there. I got the same result (within measurement error), so I think the
problem is not in the 'spocalc' algorithm, but more in the values I am entering in and/or taking
out of it?
There are a couple of possibilites I have identified.
1/ Have I been measuring spoke length incorrectly?:
According to 'The Bicycle Wheel' by Jobst Brandt, the length of a spoke is measured from the inside
of the elbow to the tip of the threaded end. Exactly what does this mean? According to this website:
http://www.stormpages.com/spokeanwheel/
The spoke length is measured from the edge of the bend closest to the threaded end of the spoke to
the end of the threaded tip. So do I measure to where the bend starts curving, or do I measure to
the apex of the bend? Both I think can be classified as 'the inside of the elbow'. If I measure
right to the apex (which is what I had been doing) a given spoke appears longer by about 2mm.
2/ No allowance is made for the distortion of a spoke when it is mounted with a large anchor angle
and multi weaved into position:
In my case I have a 24 spoke wheel that is 2 crossed and has a 60 degree spoke anchor angle. I have
a wide diameter flange (63mm) linking to a 27" rim. This means that each spoke is in contact with
the hub for about 8mm of its length (near the elbow), and furthermore each spoke is laced under
another spoke before it gets to the rim. Thus the 2X sixty degree spoke is far from straight as
assumed in the Brandt book (Edition 3, Part 3 page 127 'SPOKE LENGTH'- I understand the equations
presented in this book are the basis for 'spocalc').
That distortion may not sound a lot, but I think this lacing arrangement has reduced the effective
length of the spoke by at least 1mm, possibly 2mm.
So could either 1/ or 2/ be the reasons I am having problems matching the results from 'spocalc'
with the spokes actually used in the wheel? Is there something else I have overlooked? TIA
SNOOPY
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Whatever, I've been seeing what spoke lengths this calculator (Spocalc.xls) gives me for a wheel I
had built some time ago and it seems that it is giving me the 'wrong' answers (spokes it recommends
are too short, by a couple of mm). I am using DT swaged spokes so went the DT website and tried the
spoke calculator they had there. I got the same result (within measurement error), so I think the
problem is not in the 'spocalc' algorithm, but more in the values I am entering in and/or taking
out of it?
There are a couple of possibilites I have identified.
1/ Have I been measuring spoke length incorrectly?:
According to 'The Bicycle Wheel' by Jobst Brandt, the length of a spoke is measured from the inside
of the elbow to the tip of the threaded end. Exactly what does this mean? According to this website:
http://www.stormpages.com/spokeanwheel/
The spoke length is measured from the edge of the bend closest to the threaded end of the spoke to
the end of the threaded tip. So do I measure to where the bend starts curving, or do I measure to
the apex of the bend? Both I think can be classified as 'the inside of the elbow'. If I measure
right to the apex (which is what I had been doing) a given spoke appears longer by about 2mm.
2/ No allowance is made for the distortion of a spoke when it is mounted with a large anchor angle
and multi weaved into position:
In my case I have a 24 spoke wheel that is 2 crossed and has a 60 degree spoke anchor angle. I have
a wide diameter flange (63mm) linking to a 27" rim. This means that each spoke is in contact with
the hub for about 8mm of its length (near the elbow), and furthermore each spoke is laced under
another spoke before it gets to the rim. Thus the 2X sixty degree spoke is far from straight as
assumed in the Brandt book (Edition 3, Part 3 page 127 'SPOKE LENGTH'- I understand the equations
presented in this book are the basis for 'spocalc').
That distortion may not sound a lot, but I think this lacing arrangement has reduced the effective
length of the spoke by at least 1mm, possibly 2mm.
So could either 1/ or 2/ be the reasons I am having problems matching the results from 'spocalc'
with the spokes actually used in the wheel? Is there something else I have overlooked? TIA
SNOOPY
--
Join the fight against aggressive, unrepentant spammers 'china-netcom'. E-mail me for more details
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