Interesting axle data
I have been building dishless axles since 1995. Since then I have averaged 12 miles a day with 170 pounds on the rear wheel. This design places less stress on the spokes and rims but more stress on the axle. Solid axles on the rear last about one year or 4000 miles though you can double that by reversing the axle at regular intervals. In 2006 I built a wheel using a Shimano spline brake hub. http://share.ovi.com/media/currentre...resident.10069 This hub moves the cone 5mm and places less stress on the axle. I have just disassembled this wheel and the axle is slightly bent after 16000 miles. http://share.ovi.com/media/currentre...resident.10062 so it looks like changing the moment arm from 38mm to 33mm will double the life of the axle. The axle also has crushed threads enough that I had to force the cone off and broken threads that I have never seen before. Notice being hit by a truck did not bend the axle. The axle also was not bent by a misaligned frame like bicycling magazine claims. I have now built a new wheel using a Shimano 6 bolt brake hub that moves the cone an additional 5mm. If you are using the Shimano tandem hub you can expect that axle to eventually break it will not bend and give you warning. My conclusion is 170 pounds is the limit for threaded axles if you want to carry more weight get a hub without threads.
Not relevant for us.
Over 230,000 miles on tandem bicycles. Have NEVER bent an axle.