Although this is for my G-gauge equipment, the general idea would work for folks running O-gauge outside.
I wanted to have a way to store my trains inside, but easily take them all outside for running. This cart features the equivalent of 80 feet of track storage in a rack that only takes up 2' x 4' of floor space in the house.
The shelves and sides are plywood with 1/8" Masonite strips to act as track to keep the items aligned. The two main wheels are Harbor Freight $5 wheel for hand carts and the swiveling caster was $1 at a flea market. The shelves are attached to the side panels with 1" x 1" extruded aluminum angle. I added small wooden strips across the end and some removable vertical 1/8" rods to keep cars from rolling off the end, but I am still working on a more positive system.
I had to build a ramp to get the cart smoothly downhill 3" from the den to the patio surface.
My entire collection of G-gauge engines and rolling stock will fit on the cart. I may add one more layer on top for buildings and other accessories that I don't want to leave out in the weather.
I tried to keep costs to a minimum. Originally, I envisioned a steel frame with plywood shelves as inserts. I wound up with a 4' x 8' sheet of plywood (cut down to 2' x 4' shelves by the Home Depot guy), a 2' x 4' piece of plywood I split lengthwise down the middle for the sides, $10 for the pneumatic tires/wheels with ball bearings, $1 for the caster, and the aluminum extrusion, bolts, nuts and washers.
