Voith Schneider Propeller
Vertical axis cycloidal propulsion: blade kinematics, four to six blade units and the eight blade eVSP, and the Voith Water Tractor.
The Voith Schneider Propeller is a vertical axis cyclorotor. A rotating casing carries blades set perpendicular to the disc, and an internal gear varies each blade’s angle of attack in phase with rotation, so the unit produces thrust of any magnitude and in any direction without a rudder and without the unit itself being rotated. Invention is credited to Ernst Schneider, with production from 1926.
Conventional units carry four, five or six blades; the electric eVSP is an eight blade design. Voith states more than 800 Voith Water Tractors in service in more than 120 harbours. In tug service a VSP tractor produces 12.5 to 14 tonnes-force of bollard pull per 1,000 kW of installed power, below a ducted azimuth stern drive tug at 15 to 17, and buys instead an immediate and continuously variable thrust vector.
The full article will cover blade kinematics and the eccentricity control, the thrust envelope, the aft skeg on a water tractor, maintenance and the hull opening it requires, and the comparison against steerable ducted thrusters for harbour and escort work.