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FLEET
FEATURES
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 Main
Fleet
Features Voith Schneider Units |
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HOW VOITH SCHNEIDER UNITS WORK
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Text By Ships of CalMac & Voith Press
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Voith
Schneider® Propellers |
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Over 75 years ago a new propulsion system, then the only
one of its kind in the world was developed by Voith from an idea by the
Austrian engineer Ernst Schneider. It allows thrust of any magnitude to be
generated through 360º quickly, precisely and in a continuously variable
manner. It combines propulsion and steering in a single unit, with only the
propulsion blades protruding out beneath the vessel's hull.
This solution is relatively straightforward: on this revolutionary system, a rotor casing,
sitting in the ship's engine space, and which ends flush with the bottom of
the hull is fitted with a number of axially parallel blades and rotates about a
vertical axis. To generate thrust, each of the propeller blades performs an
oscillating motion about its own axis. This is superimposed on the uniform
rotary motion of the main casing. Blade excursion determines the amount of thrust, while the
phase angle of between 0° and 360° determines its direction. As a result,
the same amount of thrust can be generated in any direction, making a useful
variable-pitch propeller - especially for double-ended drive through ferries
like the Loch Class. Both variables - the magnitude and the
direction of thrust - are controlled by a mechanical kinematic transmission,
controlled by the ship's master. |
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Voith Schneider Propeller |
Sectional Drawing of Unit |
A CalMac
Loch Class Voith Unit |
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The ideal combination:
It is suggested that the quickest and safest ferry route is always the shortest. Increasing
safety, economy, profitability and environmental compatibility demands
call for vessels designed specifically for ferry traffic on their
particular route. Many of the shorter routes on the Calmac network
require a ferry that shuttles back and forth between the terminals -
essentially acting like so-called 'floating bridges'. The Loch Class
are a perfect example of this design, bringing with them
drive-through capability as well as being highly manoeuvrable.
The reliability of a bridge is determined by its pillars. in the same
respect it has been said that the
"pillars" of Calmac's Loch Class ferries, from Loch
Striven, the first of the original four 'Baby Lochs' to the
1991-built 'Super Lochs' Loch Fyne and Loch Dunvegan, are the Voith Schneider® Propellers:
the combined
propulsion and steering system adopted. They allow the vessels to
berth with speed and ease, unload and reload vehicles without having
to use mooring ropes to hold them in position and allow the ship to
sail in either direction without having to back away from the berth
and spin round. Tight locations are also not a problem - for example
a ship the size of Loch Fyne can turn easily in the narrow
confines of Lochaline, the Loch Buie can spin round in her
own length while at the same time avoiding the sandbanks in the
Sound of Iona, and the Loch Alainn can negotiate easily the
tight approach round the end of Largs pier to the designated
slipway.
In the Calmac fleet, it is not only the Loch Class ferries that use
this propulsion system. The Streakers also use this revolutionary
system to great effect. Not being of drive-through design, they have
to spin round to use their stern or side ramps. Thanks to the high
manoeuvrability allowed by the propulsion units down-below, tight
turns can be made on the approaches to Gourock, Wemyss Bay, Dunoon
and Rothesay - a factor that helps to keep the timetable on the
Cowal and Bute routes as accelerated as possible.
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Current Calmac vessels fitted with Voith-Schneider
Units: |
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Jupiter,
Juno, Saturn,
Loch
Striven, Loch
Linnhe, Loch
Riddon, Loch
Ranza, Loch
Dunvegan, Loch
Fyne, Loch
Buie, Loch
Tarbert, Loch Alainn,
Isle of Cumbrae,
Loch Shira |
Past Vessels fitted with the units:
Keppel,
Kyleakin,
Lochalsh |
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Left: Jupiter displaying her capability to
travel in any direction as she moves off Rothesay sideways using her Voith
Units. |
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Sequence Below: Loch Buie shows how easy it is to
'spin' on the spot as she rotates 180' at her Fionnphort berth. A full
video of this event can be seen on the SoC DVD available from the Site Shop. |
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Links: |
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Diagrams and Article Text From VOITH.
Additional text and photos by Ships of CalMac
For further information on the vessels that
use the Voith-Schneider units, see the individual pages of those mentioned
above of see the Fleet Feature giving details of the
Loch
Class |
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CalMac 2001 - 2008, unless otherwise stated.
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