Step 1: Tube to Keep Pack out of Spokes
A variety of different things can be used keep your pack out of the spokes. To test if it is going to work press it toward the wheel and see if it hits the tire easily. I have also used bamboo, however the bamboo eventually cracked and it was more work because I had to tie it together behind the tire adding more points to get loose.
Broken bike racks, rims and tent poles are all good materials to tie to your bike. Check your local metal salvage yard to see if what you need is there.