I thought it would be cool to make a functional arrow board:
I mocked up the electronics first as I wasn't sure i could figure it out. Things went pretty well and I had a working proto in a few hours using an Arduino Uno. I doubt I coded it in the most efficient manner, but it works. There are three light configurations: Left progressive arrows, alternating diamonds and right progressive arrows which are selected by turning a potentiometer. The youtube video shows the function:
http://www.youtube.com/watch?v=1qfbTDtA0w4
I moved on to the structure via CAD. Frame will be 3/16" brass tube silver soldered together. Plastic parts (board, fenders, electrical enclosure) will be 3D printed to save me some effort. Tires will be Garden Trucking's smallest Wedico trailer tires (50mm OD). I need to rework the box to include power switch and potentiometer mounting. Battery will be 6V Nimh or 2S Lipo.
Soda can for scale. 6.85" wide, 9.38" tall, 8.45" long including tongue.