I just did an axel replacement for the 1"OD tube for the smaller wheels. Original wall thickness was 1/4", and I found it at ...

http://www.metalsdepot.com/products/alum2.phtml?page=rndtube&LimAcc=%20&aident=

I tried using the 1/8" wall pipe, but it wasn't heavy enough for it. I got an 8' section for about 60 bucks with shipping. UPS maxies out at 10' for shipping. If I had ordered a 12 foot section it would have been about $170.00

Rich