I've only gotten this far, but it's a start.
Then I discovered an article written by John Allen on how to build a luggage cart, and I decided to modify his design a little and try my hand at it.
Here's his design.
Here's my progress so far on a card model version. I've added an extra rack to the back, per some prototypes, along with lettering on the side. Allen's wheels were acetate with the spokes drawn on; I decided to cut the spokes out, add rims and wrap a paper band around the outside.
