This particular type of ball roller has always appealed to me.
The instructions for building it were found in Constructor Quarterly, june 2002, article by Alan Partridge.
The balls enter a loading chute and are fed, one at a time, into the passing cup by a four-bladed spinner. They then proceed upwards, from cup to cup, until they are tipped out at the top into a return chute, where they rattle their way down to the start.
the balls like to escape. Please retrieve them and pop them into the top of the return chute.