Simon was a commission piece. He is made entirely from found or donated nuts, bolts, screws, washers, spark plugs, lug nuts, nails and many other bits and pieces of metal. All of the welds are done on the inside so it presents a "pure" aesthetic. There is quite a bit of extra design when you build inside-out.
His head and neck are counter-balanced, so they can swing from front to back. He is perfectly balanced in order to obtain the maximum swing time.