From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Comparison of hollow steel blades against standard aluminium and a review of various variable pitch propeller designs.
| Identifier | ExFiles\Box 179\3\ img147 | |
| Date | 4th April 1932 | |
| -6- The blades are made from heat treated Chrome Vanadium steel S.A.E.6130. They are made in two halves but the weld is not along the edge of the blade. The weight of a 10 ft. diameter propeller is 32 lbs. 6 ozs. per blade, a 9 ft. diameter 28 lbs. 4 ozs. per blade. This saving in weight is increased when a variable pitch hub is utilised because the shank of the blade will take the screw threads etc, directly. Six of the hollow steel blades have been flying in a Sikorsky Amphibian for a year. During this time the plane did 450 hours flying time. These hollow steel blades show no sign of wear at all. The standard aluminium alloy blades under similar conditions have to be taken off for re-dressing of blade edges and surface every 10 or 20 hours of flight. At the present moment a squadron of seaplanes is being equipped with these blades. Variable Pitch Propellers. There are 4 variable pitch propellers that have been tested in the air. (1) Hamilton. This is a two position hub only, the take off pitch being obtained by oil pressure from the nose of the engine. It is very simple but needs a certain amount of design being done on the nose of the engine before it can be fitted, as oil pressure has to be carried to the hub. It is built with the standard Hamilton blades and is not particularly light as it is about 30% to 40% heavier than the standard propeller. (2) The Eclipse automatic variable pitch propeller. This propeller is manufactured by the Eclipse Aviation Co. and the pitch of the blades is varied by the thrust, working against helical springs. It is a fairly simple construction but again is heavy. (3) Curtiss variable propeller. Since we did not actually see this propeller being manufactured we have no first hand information about it but I understand that the pitch is variable by means of an electric motor driven through a very large reduction gear. | ||