Jerry Everard, Canberra, Australia
Leonardo da Vinci's helicopter is reputedly based on a child's toy popular for about 100 years before Leonardo drew his design for a full-sized one. While there are no surviving images of the toy, I have attempted to make a plausible recreation based on toys known to have been around in Leonardo's day. The key to this toy is the spinning mechanism based on string-pull spinning tops.
To make the toy you will need the following:
Drill a centre hole in each of the plates to make a tight fit on the dowel. Cut the following shapes from the base of the two plates. The shaded areas are waste.
Lay the larger piece on the smaller one so that the two straight edges line up. Tape them together top and bottom so they can be gently pulled into a spiral shape. If the plates show a tendency to tear, add a small piece of tape top and bottom at the ends of the centre round cuts.
Using the hole saw cut out a disc of wood from the length of pine. The hole should fit the dowel with a tight push fit.
Trim the pine off square and then make two cuts in the end and chisel out the centre, leaving 'U'-shaped cut-out. This will be the launcher.
Holding the drill vertically, carefully drill a 6.5mm hole through both the fingers of the U so that the dowel will fit loosely and spin freely.
Now fit the dowel through the holes and mark on the dowel the halfway point between the two fingers of the U and drill a 2mm hole in the dowel at that point.
With the dowel sitting upright in the launcher on a firm surface slide the wooden disc onto the dowel and slide it down until it rests on the upper finger of the launcher.
Then carefully fit the lower rotor plate onto the dowel, but before pushing on the top rotor plate, gently separate the two into a spiral and insert the rubber or plastic tubing to act as a spacer to maintain the spiral shape. Now gently press the top rotor onto the dowel and push this assembly until it is about halfway down the dowel.
Now cut a length of string about 500mm long and tie a loop in one end. Carefully thread the other end through the small hole in the dowel between the fingers of the launcher and rotate the rotor backwards to wind up the string.
Finally, hold the launcher firmly in one hand, grasp the loop of the string and pull firmly and rapidly to make the rotor spin, and with luck, as the string pulls free the helicopter should rise clear of the launcher and make a short flight. While it does not fly vigorously, this design does demonstrate a capacity to generate sufficient lift to fly clear of the launcher.