13 gauge spokes

Here is a photo of DT alpine III spokes they are 13 gauge at the elbow 15 gauge at the shaft and 14 gauge at the threads. The shaft on these spokes are 1mm longer than their 14 gauge spokes this make them a poor fit for the hub shown. The 2.3mm elbow fit in every hub I had on hand and in fact they fit  loose.  Wheelsmith tested 76 spokes to failure and HP Gavin http://www.duke.edu/~hpgavin/papers/HPGavin-Wheel-Paper.pdf came up with a formula to predict the life of a spoke when the gauge is changed.  It is Log S = -.3 Log N + 4.12 where S is the stress and N is the number of cycles.  Going from a 14 gauge spoke to a 13 gauge spoke will increase the life of the spoke by a factor of 2.5.  Since spokes usually break at the elbow The DT alpine III spokes or the wheelsmith or Phil Wood 13/14 gauge spokes are an improvement. The threads of good spokes are rolled instead of cut this makes the outside diameter of the threads of a 2mm spoke 2.2mm. The spoke holes in the flange will need to be 2.2mm or larger for the spoke to fit. In fact they are generally 2.5mm this is poor engineering practice. Studies on rivets and bolts have shown that the tighter the fit the better will be the life of the bolt or rivet as well as the material the bolt or rivet goes through. Here is a photo of the wheel after I was hit by a truck in pahrump nevada This dishless wheel stayed true enough that it didn’t rub against the chainstay this let me bring the bike to a safe stop. There was no noticeable deformation of the spokes or the flanges. I put on a new rim and am still riding it after 2 years or about 8000 miles.

reducing dish

One way to reduce dish is to move the cogs closer to the spokes the photo shows one way this method moves the cog one cog thickness closer to the spokes about 1.78mm. And here is a photo of the cog notice the largest has the splines filed deeper.

broken axles

Threaded axles always break on the inside of the cone on the heaviest loaded side. Cassette hubs tried to solve this problem by moving the cone 20mm. A freewheel hub has a distance of about 40mm from the dropout to the inside of the cone cassette hubs have a distance of about 20mm from the dropout to the inside of the cone. This makes the side opposite the cassette under more stress since the distance from the dropout to the inside of the cone is about 30mm this reduces the stress on the axle to 20/30 or about two thirds. So far so good however  a zero dish wheel removes this advantage. One partial solution is to use a solid axle these are about 30 percent stronger. Another partial solution is to use a hub with a brake boss. In shimano hubs the spline brake hubs move the cone out 5mm the six bolt hubs and the threaded tandem hubs move the cone out 10mm. The best solution is to get rid of the axle threads. Threads create what engineers call a stress raiser. This information was hard to find because engineering handbooks assume you are not stupid enough to load a bolt on the threads however threads increase the stress by a factor of 3.3.  Hi E bullseye and Phil Wood got rid of the axle threads. They also used larger diameter axles this makes them much less likely to break.

Hello world!

after many miles of faithfull service this wheel was put out to pasture

This blog is about good design the wheel shown is a dishless wheel that I built and put 20000 on. The wheel was loaded with about 160 pounds it uses an alivio hub DT 14 gauge spokes and an araya VP 20 rim. The cassette was sanded down to 29mm this allowed 8 cogs with 9 cog spacing and a 135mm rear spacing. There were no broken spokes nor any rim cracks throughout the life of this wheel.  There were however 3 bent solid axles more about how to solve this problem later. I built a new wheel with DT alpine III spokes a deore spline brake hub and a weinmann 519 rim and am testing it now.