The Voith Schneider propeller, also known as a cycloidal drive is a
specialized marine propulsion system. It is highly maneuverable, being able to
change the direction of its thrust almost instantaneously. It is widely
used on tugs and ferries. Operation
From a circular plate, rotating around a vertical axis, a circular array of
vertical blades protrude out of the bottom of the ship. Each blade can
rotate itself around a vertical axis. The internal gear changes the angle of
attack of the blades in sync with the rotation of the plate, so that each
blade can provide thrust in any direction, very similar to the
collective and cyclic of helicopter flight controls.
Unlike the azimuth thruster, the Voith-Schneider drive merely requires
changing the pattern of orientation of the vertical blades. In a marine
situation, this provides for a drive which can be directed in any direction
and thus does away with the need for a rudder. It is highly efficient and
provides for an almost instantaneous change of direction. These drives are
becoming increasingly common in work boats such as fireboats and tugboats
where extreme manoeuvrability is needed. Azimuth thrusters have both advantages
and disadvantages when compared to cycloidal drives. The azimuth thruster
is less efficient and slower to manoeuvre, but is likely to be cheaper
in the short term. Life cycle costs favour the Voith solution, something
reflected in the residual value of a Voith water tractor. A choice is made on
the basis of perceived performance requirements. Instead of a Kort nozzle,
VSPs are often fitted with a "thrust plate" or "propeller guard" which acts
as a nozzle at low speed, protects the VSP against grounding and provides
another blocking location during drydocking.
A low acoustic signature favours the device's use in minesweepers by
minimising cavitation as the rotor does not need to rotate as fast for a given
thrust. The underwater sound signature of the MV North Sea Giant dynamic
positioning vessel was measured by the International Centre for Island
technology whilst installing a foundation monopile for the Voith tidal
energy device in the Falls of Warness, Orkney.
VSPs are offered with an input power range of 160 kW to 3900 kW
History The Voith Schneider propeller was
originally a design for a hydro-electric turbine. Its Austrian inventor, Ernst
Schneider, had a chance meeting on a train with an employee of Voith's
subsidiary St. Pölten works; this led to the turbine being investigated by
Voith's engineers, who discovered that although it was no more efficient than
other water turbines, Schneider's design worked well as a pump by reversing the
flow through the device. By changing the orientation of the vertical blades, it
could be made to function as a combined propeller and rudder.
In 1928 a prototype was installed in a 60-hp motor launch named Torqueo and
trials were carried out on Lake Constance. A number of German
minesweepers were fitted with VSPs; the first of these was the R8, built in 1929
by Lürssen. By 1931 VSPs were being fitted in new vessels on Lake Constance
run by the German State Railways. The first such ship to use the Voith
Schneider propeller was the excursion boat Kempten. Two German 1935-type M
class minesweepers M1 and M2 were fitted with VSPs.
The first British ship to use Voith Schneider propellers was the
double-ended Isle of Wight ferry MV Lymington, launched in 1938. Some 80
ships had been installed with VSPs by the end of the 1930s, including the
uncompleted 1938 German aircraft carrier Graf Zeppelin, and the Japanese
submarine cable laying ship Toyo-maru. The three vessels currently used by the
Woolwich Ferry feature Voith-Schneider propulsion systems. They were built in
1963 by the Caledon Shipbuilding & Engineering Company of Dundee and
feature one VSP in the bow and a second in the stern for remarkable
maneuverability. The US Navy built twelve VSP-equipped
Osprey class coastal minehunters in the 1990s. These vessels have been
decommissioned and are being sold to foreign navies. The French Navy operates
sixteen tugboats of the RPC12 type, that can provide a 12-tonne bollard pull
thanks to two Voith Schneider Propellers.
The same device, mounted on a horizontal rather than a vertical axis, has been
used to provide lift and propulsion on a few experimental aeroplanes, known as
"cyclogyros". None of them were very successful.
See also Azipod
Azimuth thruster Dynamic positioning
Cycloid HMS Challenger
References Brown, R. Allen; Lymington: The Sound of
Success, Allan T Condie Publications. ISBN 978-0-907742-62-3
External links Voith Turbo marine website
"Sea Going Eggbeaters" Popular Mechanics, March 1950, pp. 102 - 103.
"Download of PC application iVSP"