It is cool to see one in motion. The bar going up to the seat is like a spring follower so that the wheel stays on the ground for turning, when you lean over it is compressed for a left turn and extends for a right turn. They are a beautiful thing to behold, but the last one I saw was expensive, I think 3,000. Have fun Dave
PS: There was a cart made with a Maytag Washing Machine motor, it also fetches a pretty penny. Google (Maytag racer) at auction one sold for 13,000, it was a 1936 model. You could make a replica and use one of the Happy time motors.