a few [?] years ago, i toyed with the idea of using a rack with a straight axle. as has been stated, you must use some kind of "slide" coupling with a rack attached to the axle because as the axle moves over bumps, the column attaching rod must move[shorten/lengthen] or parts will bind/break. "posies" built a rod using such a setup, but i have looked for such a sliding joint and the ones i have seen didn't appear to be strong enough for the intended task. as for the rack attachment to the axle, i could do a much better [stronger and better looking] mount than just welding a flat plate to the axle.