whburling, two reasons to go with a standard wheelchair quick-release system. One, they work. The axle is hardly going to spin, It is a cantilever with half the weight of the user plus chair sitting 3" beyond the end of the sleeve. (If it does spin, those "bearings" are in desperate need of service or replacing.) Second, with a standard QR wheel, your friend can go to any pharmacy and get a replacement. (He may have to send a clueless friend since once one of his wheels dies, he is going nowhere.)
Ben