FIG. 29. A simple method of forming a propeller from sheet metal.
The simplest method of making a small metal propeller is to cut a piece of sheet aluminum into the shape shown by A in Fig. 29. Fold along the dotted lines so that the result is like B in the same illustration. The shaft may be a small piece of piano wire passed through the hole in the centre and bent around as shown.
FIG. 30. A built-up metal propeller made of aluminum.
Another method of making a metal propeller which is more suitable for large machines than that just described is illustrated in Fig. 30. The blades are cut out of sheet aluminum to the shape shown and set in the slots in the end of a small aluminum tube. They are held in position with aluminum solder. Ordinary solder will not accomplish the work and cannot be used. The shaft is soldered into a hole in the tube halfway between the two blades.
FIG. 31. Metal Propeller.
The propeller shown in Fig. 31 is extensively used by manufacturers of model aeroplanes because of its simplicity and strength. The propeller is cut out of sheet aluminum and then bent and folded. The shaft is held in place by a brass eyelet riveted firmly over on both sides.
FIG. 32. Method of carving a propeller of the truly helical type.