Here's a few pictures of the start of my trolley build. Trolley will be appox 10" wide by 24" long (height to be determined). The motor, sprocket and chain are from a scooter. Used 3x4", 1x2" box steel and some flat stock. Wheels are from a rollerskate, guide wheels are from casters. Motor will run at 5vdc - although this is yet to be determined. Will use pick-ups for power.