The Voith-Schneider Propeller

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[mvsmith]

The posts indicate confusion about how the VSP works. Not only how it’s controlled, but how it pushes the ship.
The VSP is old, mature technology dating from 1928 when the first prototype was installed on the launch Torquero.

Although it pushes the ship in a manner similar to a Z-drive or azimuthing thruster, it does it in a very different way. Its operating principal is more like that of a helicopter than any other ship propulsion system.
A large, horizontal, rotating disc is set flush with the hull and turns at constant speed in a single direction.
A number of large blades—usually 5—hang vertically from the disk. The length of the blade is usually 65% of the blade circle diameter. For a size 36 VSP the blade circle (the orbit of the blades) has a diameter of 3.6 meters with a blade length of 2.3 m.
For shallow draft operation, smaller units can have blade lengths only 40% BSD.

The blades have a shape similar to an airfoil and produce thrust in a manner similar to the way a wing produces lift. As the blades orbit the disc, they rotate on their own axes so that they all produce thrust in the same direction relative to the ship centerline.

The angle of each blade is controlled by a very complicate linkage of arms and cranks. The far ends of all linkages are connected to a common bearing near the center of the blade disc. When that bearing is at center, no thrust is produced. As the bearing is moved farther from the center, more thrust is produced. The direction of thrust is determined by the azimuth of the bearing.

The bearing is moved by a vertical arm that has 3 ball joints, one at each end and one near the center. The middle ball is held in a fixed socket, the lower ball is held in the kinematics bearing, and the upper ball is moved by two hydraulic cylinders at right angles to each other.
“Kinematics” is used both to refer to the mechanical linkage assembly, and to refer to the mathematic equations governing the blade angle.

The hydraulic cylinders can be controlled in different ways, including by joysticks through a computer.
Control stands like the ones on Red Eagle usually do so by electric telemotors. On Red Eagle, the side wheels move the kinematics in a radial direction from center to control the amount of thrust. The top wheels move the kinematics in a circle around the blade disc center to control the direction of thrust.

The wheel inputs must be translated into the X/Y coordinates for the hydraulic cylinders. This is usually done in the valve assembly on top of the drive. That unit also constrains the motion of the kinematics to avoid extreme blade angles.

[mvsmith]

Here is a drawing of VSPs on a double-end ferry.
This happens to be the Red Falcon, built 1993 for the Southampton—Isle of Wight run.

[mvsmith]

As others have posted, there’s a very good animation on Voith’s site. I recommend downloading and studying it.
http://www.voithturbo.com/vt_en_pua_marine_ivsp-interactivevsp.htm (http://www.voithturbo.com/vt_en_pua_marine_ivsp-interactivevsp.htm)

Here are two diagrams looking down at the blades and a simplified representation of the Schubkurbelkinematik.
What? How would I know. Ask Botman.

Crank kinematics is the latest (as of 2000) refinement of the mechanism that varies the angle of each blade as it orbits the blade disc. Since 1927 there have been seven different kinematics developed, each one represents a refinement of the hydrodynamic theory, and a major engineering effort to design a mechanism to implement the mathematical pitch profile.
SKK was used on 1,921 propellers as of year 2000, about as many as all of the previous six kinematics totaled.

The top diagram shows the blades in the zero thrust position. Any thrust developed by a blade is balanced by thrust diametrically opposite. Note that the steering center—the center bearing in the kinematics—is directly over the center of the blade circle.

In the lower diagram, the steering center has moved away from the center of the blade circle, and thrust is developed toward the right.

[sniperonthehill]

So the red eagle 4 has these?

Cheers

[muns]

So the red eagle 4 has these?

Cheers

Yes, Red Eagle uses two VSPs.

[sniperonthehill]

Yes, Red Eagle uses two VSPs.

Vstep should put them on the model! added realism.

[mvsmith]

Vstep should put them on the model! added realism.

They are on the model.

[sniperonthehill]

They are on the model.

Not underneath! I flipped her over once and it was just a hull

[mvsmith]

You probably stare at Spambot’ shiny MaryJanes too.
Seriously, I meant that the propulsion and controls are emulated on the model, but I think you know that.
There’s a lively debate on the forum as to how realistic the controls are on the sim versus the real Red Eagle.
My position is that the control system that VSTEP chose is a reasonable one for a double-ender, and is easy to operate.
The VSP controls can be configured so that they behave in a way familiar to helmsmen accustomed to conventional screw and rudder ships, or they can be configured to fully take advantage of the VSP’s superior maneuverability. The latter requires the seamen to acquire new skills.
In any case, the Red Eagle in the sim is challenging, but fun to drive.

[mvsmith]

This diagram of a VSP shows the control rod [4], which is pivoted in the middle.
The top end is moved by hydraulic cylinders.
The bottom end moves the steering center—the center bearing of the kinematics.
After four centuries, we are back to steering with a Whipstaff.

[mvsmith]

This is R/V Knorr, operated by Woods Hole Oceanographic Institution on Cape Cod.
Like her sister R/V Melville (SIO), she was originally fitted with fore & aft VSPs.

She was Bob Ballard’s ship when he found Titanic, and she was my hotel during the Fisher-Spassky chess match in Reykjavik in 1972.
http://www.whoi.edu/page.do?pid=8496 (http://www.whoi.edu/page.do?pid=8496)

[mvsmith]

Views of a blade for a size 36 VSP, and of the stern of Helgoland (Hamburg-America Line, 1939).
Resort ships were an early adopter of VSPs because they could dock without the assistance of tugs.

[Kevinmcg_ships]

Excellent topic, guys! 

I love VSP vessels. They are always a marvel to watch. There is a Clyde ferry called Jupiter which was built in 1974 (and still going strong!) and is driven by VSP units. She and 2 other sister vessels are affectionally called 'Streakers' because of their ability to move away very rapidly.

There is an excellent book which covers the early years of Voith Schneider and is quite very detailed. It is called "Lymington - The Sound of Success" by Alan Brown (1988, published in English language) but has lots of diagrams and pictures of mostly British VSP ferries. It also covers the world's first VSP car ferry MV Lymington which was built in 1938 for the Lymington to Yarmouth route and also covers several more British VSP ferries built since. The River Clyde gets a mention because during the 1970's and 1980's a large number of VS ferries were built and introduced on various routes in the Clyde. The book is long since out of print, but occasionally you might find a copy on eBay or second hand book websites.

I would highly recommend this book for anyone who takes great interest in the early history of Voith Schneider, and how it managed to break into the British market, despite the difficilties faced by the VS company due to the outbreak of the Second World War.

Kev

[Stuart2007]

You probably stare at Spambot’ shiny MaryJanes too.

Do what? 

and is easy to operate.

The bloke is mad.. totally mad 

In any case, the Red Eagle in the sim is challenging, but fun to drive.

It is indeed fun!

Stu
[/quote]

[Kevinmcg_ships]

The bloke is mad.. totally mad 

Stu

That must mean I'm mad as well! 

I find Red Eagle incredibly easy to control. Need to spin her 360^o? No sweat. Need to steer her into a harbour? Nae bother!

I can't understand all this fuss about people unable to control her.   

[mvsmith]

It does separate the men from the boys, Kev.

[mvsmith]

Kevin, when I read posts by those who complain that they can’t get their heads around Red Eagle, I have to ask if there is any real ship handling involved in the way they use the other, more familiar, ships.
Marty

[mvsmith]

Or go directly to the link in my third post.

[Agent|Austin]

Or go directly to the link in my third post.

Sorry didn't see that I will delete my post

[LucAtC]

Hello mvsmith,
Perhaps could you add that the major advantage of VSPs vs other orientable propellers is the speed of the response to direction/ thrust changes?
Regards,
Luc

[mvsmith]

I think I mentioned it, perhaps in a Red Eagle thread, but it’s a point that certainly should be stressed.
Thanks Luc.
Not having to rotate a large mass to change thrust direction is a big advantage.
In fact, the change could be nearly instantaneous if it were not deliberately slowed by constriction in the hydraulics—to prevent the high stress that could put on the hull and the mechanism.
 

[Stuart2007]

That must mean I'm mad as well! 

I find Red Eagle incredibly easy to control. Need to spin her 360^o? No sweat. Need to steer her into a harbour? Nae bother!

I can't understand all this fuss about people unable to control her.   

I was just messing about! Whether R E beats the PoH in the list of favourites I'm not sure, but I do actually find it very easy to control once you get used to it having 2 powered units.

Stu

[mvsmith]

Kevin,
Here’s your Lymington. She was the world’s first double-end ferry with VSPs.
This—for the day—radical design was to solve the problem of the narrow, winding channel leaving Lymington, with its fog and side winds.
She was built by W. Denny Brothers Ltd. in Dumbarton for the Southern Railway. Her acceptance trials were in April 1938.
She was later renamed Sound of Sanda and served the Lymington – Isle of Wight route for forty years.

Voith’s penetration of the British market depended upon being blessed by Lloyd’s Register of Shipping. This finally happened after a lecture before the Society of Scottish Shipbuilders at the Kelvin Hall in Glasgow. The first order was for Lymington’s props.

[mvsmith]

Here is a post on how to drive Red Eagle from the stern controls, which I wrote for jeffmorris.
http://www.shipsim.com/ShipSimForum/index.php/topic,2439.msg25640.html#msg25640

[mvsmith]

Luc,
Other advantages of the VSP were discovered during the 30s and 40s:
The sea keeping ability was first demonstrated when Helgoland was drafted into seagoing service. The VSP was discovered to be less likely to break free in a swell. The propeller wash adhered to the stern and damped the pitching somewhat.

A 27m, 220 Hp, 200-passenger ship operated by Société des Auto-Bateaux de Nantes on the Loire, with many stops, was able to reduce the normal trip time from one hour 15 minutes to 45 minutes because off her superior docking ability. She was able to stop in her own length from 12.7 knots.
There were similar experiences on the Rhine, beginning in 1936.
The ferryboat Durme, on the River Schelde was the first Belgian ship to use the VSP. (1936)
Six new motorboats were fitted with VSPs for use on canals in Venice because the wash is upwards and does not extend low enough to undermine foundations.

After the war, the US Navy wanted to get an undamaged German minesweeper, and found the 20-knot R148 in IJmuiden. After an unsuccessful attempt to get a transport vessel, they decided to send her across the Atlantic under her own power with a German naval crew under Oberleutnant Richard.
Lieutenant M.J. Talbot and three GIs went along as guards. Don’t ask me what they expected to do in the middle of the ocean if the crew turned out to be sore losers.

After fitting out with 12 tons of fuel in barrels, she left Le Havre on October 17, 1945. Past the Azores, she ran into a hurricane with 7.6 meter waves. The bow rose 11 meters out of the water on the crest of a wave. She began to roll by as much as 47 degrees. In his log, the captain wrote: “A minesweeper with screws would not have survived this swell because waves 20 degrees on the port bow would have capsized it”.