#31
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That's the formula for spoke length, where d = radius of rim (ERD/2), r1 = flange radius, r2 = flange offset, a = spoke angle (= 720 degrees x number of crosses / number of spokes), and r3 = radius of the flange spoke hole.
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#32
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I thought spoke length came from the magical all-knowing website calculator.
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#33
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#34
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https://leonard.io/edd/ https://www.wheelpro.co.uk/spokecalc/ https://bikeschool.com/index.php/res...oke-calculator Who remembers the ''good' old days' with Sutherlands 5th edition?? Chapter 11..kinda like celestial navigation..but harder..
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Chisholm's Custom Wheels Qui Si Parla Campagnolo |
#35
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I put together a post about spoke length calculations on my blog. Take a look at this.
Calculate bicycle spoke lengths the old way
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Dale, NL4T |
#36
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Chisholm's Custom Wheels Qui Si Parla Campagnolo |
#37
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I get it - I was mainly curious about how the lengths were calculated. With a minor in mathematics, seemed reasonable. it's nice sanity check for the online calculators.
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Dale, NL4T |
#38
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Below is a link to paper by Henri Gavin of Duke University, who studied stress/strain in bicycle spokes to see how lacing pattern (number of crossings) influenced spoke fatigue. In this paper, Gavin compared mathematical models of spoke loads to direct measurements on wheels (tires installed) with the spokes instrumented with strain gauges. He measured the strains in the instrumented wheels both statically and dynamically (actually riding the wheels on the road). He found that the tire did act to spread the load over a short span of rim, and the peak spoke strains on the real wheel were a bit smaller than in the models that used a point load; but just like the numerical analyses predicted, the vertical load was distributed only among a small number of spokes at the bottom of the wheel, and was especially concentrated on the bottom most spoke. http://people.duke.edu/~hpgavin/pape...heel-Paper.pdf |
#39
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Using on-line pre-programmed spoke length calculators is fine when using standard components and lacing patterns, with equally spaced spoke holes on hubs and rims. But some wheels use non-standard patterns or non-standard spoke spacing. In these cases, you have to go back to the fundamental formulas and make the necessary adjustments for the non-standard geometries. This may be case even when starting with 'standard' components, such as making a 24 spoke triplet laced wheel with a standard 32 hole hub and 24 hole rim.
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#40
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But as an aside..one thing that is really vexing these days is the YUGE variableness of spoke holes in the hubs..I try to 'predict' those which has a big effect on spoke length(for this guy who is picky about 1mm differences) but, altho not really 'bitten' yet, I have built 2 shimano rear hubs and found the spoke holes bigger than previous iterations(SLX and XT)..Why I tend to 'round down' with shimano, Bitex, Dynamo type hubs(Dynamo cuz the holes are counter sunk..)...
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Chisholm's Custom Wheels Qui Si Parla Campagnolo |
#41
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...for everything else, there is Mastercam...
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#42
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Chisholm's Custom Wheels Qui Si Parla Campagnolo |
#43
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For some combinations, especially when reusing proprietary straightpull hubs, i like to do a simple centerline 3D Drawing using Mastercam to check spoke length calculations.
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