Leitner-Watts All-Metal Propeller
IT is stated that all but one of the problems of the metal pro peller have been solved in this device, and that one is weight. In their present form these propellers are very much heavier than corresponding wooden screws. The blades are each made up in the form of a shell of sheet steel and the necessary taper in thickness is obtained by using laminated construction, there being three laminations -one at the top, the second about half way between the tip and the buss, and the third at the root.
... third at the root. The laminations are-at present riveted together but later on it is intended to employ electric spot welding. The two halves of each blade are attached to one another at the edges only by welding, but in order to stiffen the shell thus formed small struts are placed between the two faces at intervals. The method of inserting these struts is shown in Fig. 4 . The struts are shouldered at both ends and the hole in one face of the blade is made just the right size to take the thin portion of the strut. In the other face of the blade is cut a hole large enough to accommodate the thick portion of the strut. From this hole runs a slot of a width corresponding to the shouldering portion of the strut. To place in position, the strut is inserted in the large hole, its other end being pushed into the small hole on the opposite face and the shoulder por tion is slid into the slot. The strut is then screwed in position by soldering washers over the two strut ends. The root of the blade is constructed in a rather substantial manner. Balance of the blades is secured by using small bal ance weights carried on short length of tube secured to the FIG. 4. METHOD OF INSERTING SMALL STRUTS BETWEEN FRONT AND REAR FACES OF THE LEITNER-WATTS ALL-METAL PROPE' LLER inner end of the central plug in the blade root. These pro pellers have an adjustable but not a variable pitch, which means that the pitch angle of the blades can be altered over a wide range (10 deg. each way) thus making the propeller suitable for a number of different conditions by setting the pitch according to requirements.