Cyclorotor

A cyclorotor, cycloidal rotor, cycloidal propeller or cyclogiro, is a fluid propulsion device that converts shaft power into the acceleration of a fluid using a rotating axis perpendicular to the direction of fluid motion. It uses several blades with a spanwise axis parallel to the axis of rotation and perpendicular to the direction of fluid motion. These blades are cyclically pitched twice per revolution to produce force (thrust or lift) in any direction normal to the axis of rotation. Cyclorotors are used for propulsion, lift, and control on air and water vehicles. An aircraft using cyclorotors as the primary source of lift, propulsion, and control is known as a cyclogyro. The patented application, used on the ships with particular actuation mechanisms both mechanics or hydraulics is named from the name of the German company that produces them: Voith–Schneider cycloidal propellers.

Cyclorotors produce thrust by combined action of a rotation of a fixed point of the blades around a centre and the oscillation of the blades that changes over time their angle-of-attack. The joint action of the advancement produced by the orbital motion and pitch angle variation generates a higher thrust even at low speed with respect of any other propeller. In hover, the blades are actuated to a positive pitch (outward from the center of the rotor) on the upper half of their revolution and a negative pitch (inward towards the axis of rotation) over the lower half inducing a net upward aerodynamic force and opposite fluid downwash. By varying the phase of this pitch motion the force can be shifted sidewise or downward. Before blade stall, increasing the amplitude of the pitching kinematics will magnify thrust.

The origin of the rotocycloid propeller are Russian and relates to aeronautic domain. Sverchkov's Samoljot, St-Peterburg, 1909, or "wheel orthopter" has been the first vehicle expressly thought for using this propulsion. Its scheme came near to cyclogiro, but it's difficult to classify it precisely. It had three flat surfaces and a rudder; rear edge of one of surfaces could be bent, replacing the action of an elevator. Lift and thrust had to be created by paddle wheels consisting of 12 blades, established in pairs under a 120° angle. The blades of a concave shape were changing an angle of incidence by the means of eccentrics and springs. In a bottom of the craft 10 hp engine was arranged. Transmission was ensured by a belt. Empty weight was about 200 kg. "Samoljot" was constructed by the military engineer E.P.Sverchkov with the grants of the Main Engineering Agency in St.Petersburg in 1909, was demonstrated at the Newest Inventions Exhibition and won a medal. Otherwise, it could not pass the preliminary tests without flying. In 1914, Russian inventor and scientist A.N. Lodygin has addressed to Russian government with the project of the cyclogiro-like aircraft, which scheme wabs similar to Sverchkov's "Samoljot". The project was not carried out. In 1933, experiments in Germany by Adolf Rohrbach resulted in a paddle-wheel wing arrangement. Oscillating winglets went from positive to negative angles of attack during each revolution to create lift, and their eccentric mounting would, in theory, produce nearly any combination of horizontal and vertical forces. The DVL evaluated Rohrbach’s design, but the foreign aviation journals of the time cast doubt on the soundness of the design which meant that funding for the project could not be raised, even with a latter proposal as a Luftwaffe transport aircraft. There appears to be no evidence that this design was ever built, let alone flown. Based on Rohrbach’s paddle-wheel research, however, Platt in the US designed by 1933 his own independent Cyclogyro. His paddle-wheel wing arrangement was awarded a US patent (which was only one of many similar patents on file), and underwent extensive wind-tunnel testing at MIT in 1927. Despite this, there is no evidence Platt’s aircraft was ever built. The first operative cycloid propulsion has been developed at Voight. Its origins date to the decision of the Voith company to focus on the business of transmission gear assemblies for turbines. The famous Voight propeller has, based on its fluid-dynamics know-how gained from previous turbine projects. It was invented by Ernst Schneider, and enhanced by Voith. It was launched with name of Voith-Schneider Propeller (VSP) for commercial vessels. This new marine drive could significantly improve the manoeuvrability of a ship as demonstrated in the successful sea trials on the test boat Torqueo, in 1937. The first Voith Schneider Propellers were put into operation in the narrow canals of Venice, Italy. During the 1937 World Fair in Paris, Voith was awarded the grand prize – three times – for its exhibition of Voith Schneider Propellers and Voith turbo-transmissions. A year later, two of Paris' fire-fighting boats started operating with the new VSP system.

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