Ship Simulator
English forum => Small talk => Topic started by: mvsmith on September 19, 2007, 17:55:48
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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.
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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.
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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.
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So the red eagle 4 has these? ???
Cheers
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So the red eagle 4 has these? ???
Cheers
Yes, Red Eagle uses two VSPs.
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Yes, Red Eagle uses two VSPs.
Vstep should put them on the model! added realism.
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Vstep should put them on the model! added realism.
They are on the model.
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They are on the model.
Not underneath! I flipped her over once and it was just a hull ;D
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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.
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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.
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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)
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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.
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Excellent topic, guys! ;D
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
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You probably stare at Spambot’ shiny MaryJanes too. :)
Do what? :-\
and is easy to operate.
The bloke is mad.. totally mad :o ;)
In any case, the Red Eagle in the sim is challenging, but fun to drive.
It is indeed fun! :D
Stu
[/quote]
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The bloke is mad.. totally mad :o ;)
Stu
That must mean I'm mad as well! ;D
I find Red Eagle incredibly easy to control. Need to spin her 360o? No sweat. Need to steer her into a harbour? Nae bother! 8)
I can't understand all this fuss about people unable to control her. ;)
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It does separate the men from the boys, Kev.
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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
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Or go directly to the link in my third post.
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Or go directly to the link in my third post.
Sorry didn't see that :( I will delete my post
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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
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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.
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That must mean I'm mad as well! ;D
I find Red Eagle incredibly easy to control. Need to spin her 360o? No sweat. Need to steer her into a harbour? Nae bother! 8)
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
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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.
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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
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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 itâ€.
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Hello mvsmith,
Thanks :) for the interesting infos!
While reading Voith Schneider Wiki pages, I found a pdf presentation of tugs and their operations http://www.comc.cc/pres/Allan%20Presentation.pdf
Being ??? unfamiliar with tugs and the tugging jargon (not ;) slang), I dont quite see the difference made between the popular à la Schottel propellers named (I think? Azimuth Stern Drive) AST and Z-drives. Also, to follow these texts is sometimes uneasy, concepts (or vocabular?) seemingly differing between Europe and US.
The best source I could find on it was http://www.solentwaters.co.uk/Site%20Map/
but :o couldnt find unambiguous vocabular about tugs/operations.
Do you have also some links or tips about tug operations?
Regards,
Luc
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Hello mvsmith,
Yeah, that's her! She was a smashing wee ferry when she came up in the Clyde as the Sound of Sanda. When she was offered for sale in 1988/89, a community group in the Lymington area wanted to purchase her with the plan of preserving her (because she was world's first ferry of her kind). Sadly the Hampshire Council didn't agree and decided not to award them any money, so the whole project collapsed.
Instead she was sold to a fish farming company who cut her upperworks right down to the car deck. She is now all but broken up, in bits, and lying on a beach at Loch Evite (near Oban) in Scotland.
A very sad ending for a pioneering ferry. :'(
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Luc, Thanks for the link.
Robert Allan is one of Canada’s leading Consulting Naval Architect firms, founded in 1930.
Three generations of Roberts have led the company.
The PDF of your link was an outline of a presentation to a conference in British Columbia.
You can see that there are many interesting developments in Tugboats, and the Pacific Northwest—B.C., Washington, and Oregon—is one of the centers of activity.
Developments are driven by a number of factors:
Ships are getting bigger, requiring not only more powerful ship-assist tugs, but greater maneuverability to berth those monsters.
The offshore oil industry requires tugs to tow the platforms, handle any ground tackle, and supply them. This has led to the development of Anchor Handling Tugs like the French Fairmount Sherpa and her sisters. These 200 tbp ships will soon be joined by a pair of 300 tbp AHTs ordered by Dreyfus. (tbp = Tons Bollard Pull)
Other big things such as oil refineries etc. are often fabricated in Asia and then towed half way around the world.
Another area that is serviced by Northwest firms is prevention and containment of oil sSpambot.
The link has some nice pictures and gives some comparison of the various approaches to tug design.
I’ll look for more details and links.
As for vocabulary and idioms, ask me about specific things and I’ll try to answer without using yet more confusing idioms.
If they are embarrassing questions, such as “What are Port & Starboardâ€, you can PM me. :)
Marty
Try these links:
http://www.smit.com/ (http://www.smit.com/) Nice screensaver & wallpaper
http://www.svitzer.com/Towage/Towage+Services/ (http://www.svitzer.com/Towage/Towage+Services/) Danish firm that bought Wijsmuller
http://agency.adsteam.com.au/about_adsteam_agency.asp (http://agency.adsteam.com.au/about_adsteam_agency.asp) Aussie, oowned by Svitzer
http://www.foss.com/ The home team
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Luc,
This is Nanuq—Polar Bear in the Inuit language. She is one of the most powerful Voith Water Tractors in the world at 10,192 horsepower and 210,000 pounds bollard pull at almost 16 knots.
She and her sister Tan’erliq (Black Bear) were designed by Crowley Marine Services under contract with Alyeska Pipeline Service Company for tanker escort operations in Valdez Harbor and Prince William Sound, Alaska.
Nanuq is powered by two Caterpillar 3612 engines driving twin Voith Schneider Propellers.
She is fitted for tanker escort services, ship handling, firefighting, and emergency and spill response in Alaskan waters. Design features include a hydrofoil-shaped skeg, welded steel construction, transverse framing, wing tanks, and ice belting.
Nanuq was constructed at Dakota Creek Shipyard in Anacortes, Washington.
Two smaller VWTs for similar service, Abeille 31 and Abeille 32 are in service on the northern coast of France.
The VWTs Tystie and Duster do escort duty at the Sullom Voe terminal in the Shetlands.
This follows the Amoco Cadiz disaster off the Brittany coast in 1978, and the Aegean Sea at La Coruna, and the Braer in the bay of Quendale in the Shetlands.
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Thanks, very interesting indeed, I also read the discussion how the escorting was modified to optimize the service, with the probable drift of tankers without escort.
http://www.seas.gwu.edu/~dorpjr/Publications/JournalPapers/TSMSIMerrick2002.pdf
I suppose Voith Water Tractor because of the main towing line being to the front instead being to the rear? Other tractor tugs being commonly Z-drive, or AST?
I couldnt find Abeille 31 and 32 position in France...
About RPA12 (not quite a tug), I dislike the fixed position because looking straight ahead, you have a wide spacer between 'windows', so that you cannot see where you are going.
Regards,
Luc
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Luc,
Here are two links that may be of interest. The first is to Fairmount Marine. You can find information on Sherpa and the rest of the fleet.
http://www.fairmount.nl/page.php?idObject=369 (http://www.fairmount.nl/page.php?idObject=369)
This link is to Louis Dreyfus Armateurs, the French owners of Fairmount Marine.
http://www.lda.fr/ (http://www.lda.fr/)
The Voith Water Tractor was named that by analogy to farm tractors, which are mostly stern drive, :) except for big articulated four-wheel drives. It does not mean tractor in the bow drive sense.
In fact the builder of a VSP can put the drives at either end or in the middle.
ASD means Azimuthing Stern Drive, a designation used by the Dutch builder Damen. Tugs of that type use something like a z-drive or azipod, usually 2, on the stern.
Damen’s site is www.damen.nl/ (http://www.damen.nl/)
Those two bees might not still be in service; I'l try to track them down.
Abeille 31 has been renamed Baobab. I haven’t located her, but there is a Baobab Marine Terminal, a Floating Production and Storage Offtake (FPSO) vessel moored 18 miles off the Ivory Coast, just west of Abidjan, West Africa. Perhaps she is working there.
Abeille 32 was renamed Flamboyant. I have no idea where she is.
Both bees are 4800 Hp; built in 1981.
Regards,
Marty
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Luc,
Here is a link to an extract of a paper on how Pilots should work with ASD tugs: http://www.pilotmag.co.uk/articles/article.aspx?id=152 (http://www.pilotmag.co.uk/articles/article.aspx?id=152)
ASD tugs have some type of thrusters that can rotate 360 degrees mounted at the stern.
Azimuthing thrusters are of two basic types: Z-drive and AZIPOD.
Z-drives are mechanical drives where an inboard engine drives the propeller through a vertical shaft and two right-angle couplings—usually bevel gears. The propeller can be turned to face in any direction.
They were first developed Hollming in Finland in the 1960s.
AZIPODs are electric drives with the motor in a pod behind the screw. The whole pod is rotated through 360 degrees. The electric motor is usually driven by variable frequency AC through slip rings.
AZIPOD is a brand name of ABB (Asea Brown Boveri, the merger of the Swedish and Swiss firms) (ABBA is the North American subsidiary of ABB—not to be confused with Agnetha, Björn, Benny, and Anna-Frid …but I digress.) :)
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Hello Marty,
A very good magazine, surely.
I knew reasonably well how Z-drives are functioning, for I knew the Schottel firm from 1969 on until 1986, having followed the developments of Rudder-Propeller and Pump-Jets, and visited Spay am Rhein some times.
Also of a US Z-drive with a MTBF of 68 hours, that Schottel intended to replace on board of MOFABs in the seventies (1978, I think).
As far as I know, the Z-drive SRP was invented in 1950 by Schottel and was installed on motorboats from then on.
Since then, thanks to all these drives, harbor tugs have taken new dimensions, gigantic thrust as well as new concepts for braking or steering while escorting.
I tried to simulate escorting, but my tugging skills are limited, the more one has to jump from tug to ship. It is nevertheless very pleasant.
Thank you, very informative sites indeed, my knowledge of tug operations is improving!
Regards,
Luc
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We learn something new every day... :)
I wonder why they don't use these vsp and other such things on large ferries? I presume that to make them work on such a large ship they would need each blade thingy to be too long for shallow water?
Stu
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Indeed, a ferry like PoR would then undergo a major surge in redundancy of the propellers, with 10 VSPs installed.
Also, a gigantic improvement of gasoil consumption, thanks to the speed limited to some 15knots.
No longer endangering HM frigates thanks to dynamic positioning and no need of tugs, at the relatively small cost of the relative increase of complexity vs CPP/rudders. The manoeuvrability would be fantastic!
Of course, the 10 VSPs would need to be protected by grounding plates, with the benefit of an ability to moor in drying harbors. Moreover, the ferry could be a welcome attraction for the harbor, some kind of a monument to which Voith workers will be paying tribute.
As a secondary benefit, it could serve to control rolling of the ship.
But I couldnt find the unit price ? Would it be a problem?
Regards,
Luc
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Did you know there is a model version of Voith Schneider? (OMG!)
I once went to a model train exhibition that sometimes have model boats on display. I came across one half-completed model kit of Caledonian MacBrayne's MV Jupiter, a ferry which is driven by Voith Schneider units. He had drawn up an A4 showing his progress and that he was ordering miniature VSPs (he needs 2) for his model ferry. The exhibition is every November so I'm hoping go go there again next month and see if the model ferry has been completed.
Also I came across a website for a German model shop and they're selling a model kit of a VSP tug PARAT:
http://shop.graupner.de/webuerp/servlet/AI?ARTN=2095&language=en
There are a couple of nice pics, especially the underneath shots of the VSP's fitted to the model tug.
I would love to get my hands on this but unfortunately my model making skills is only restricted to building Airfix, Tamiya, Thumpeter kits!
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Stu,
Here’s a Kort nozzle on a Thrustmaster Z-drive, for the Peruvian tug Cabo Blanco in Callao.
Built for Agencia Maritima Cosmos, she has a pair of Cummins KTA-50-M2 main engines—each delivering 1600 bhp @ 1800 rpm.
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Hello Marty,
Just seeing the important debate about the VS tug's I would like to make my comments too.
The VS Tugs are well designed to operate at the vessel's Stern (Sccort as previous mentioned by you) The only problem found with the VS Tugs are the draft limitation due to the location of it propulsion units (Under the Hull) those units are protected by a hydrofoil under under the blades wich are designed to stabelize the tug and protect the blades in case of grounding.
Here in Brazil i had participated on the sea test of the MORPHEUS and MORAS The newest VS Tugs that we have here also the Harbour and Towning test was really nice, during the bollard pull test of the MORAS the Capt had agrounded the tug was the test was taken into the port of Itajai (South of Brasil) this port is located into the Itajai River within 200m width.
The test was stoped and the Tug was pulled back to the yard after landing and several exames and survey no damages was found to the grounding plates and or propulsion units and its blades.
these 2 tugs are 80tons bollard pull and goes closer to 14Knots. I will send you some pictures soon
About the robert allan project the SMIT TAK has just bought the REBRAS and ordered the 18 builds of the ASD's 8x80tons bollard pull and 10x50tons bollard pull
But on my opnion the must maneuvarable tug still the ROTOR TUG's wich can assit the vessel's during scort and even on the FWD for berthing and umberthing. I think do you know those tugs better than me. But I gonna meet then now in 2008 in Rotterdam during my pilotage course.
Here in Brazil we frequently working with ASD's tugs as these type does not suffer many restriction due to her draft. Is commom for us here to work with ASD's at the ship's stern and Double screw at the FWD for berthing and umberthing maneuverings.
Cheers
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Hello Marty,
Here in Brazil i had participated on the sea test of the MORPHEUS and MORAS The newest VS Tugs that we have here
Tavares,
Thanks for adding information to this topic.
DJM will be pleased to hear that a tug has been named for him! :)
Best regards
Marty
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Haha, yes. DJM wil be pleased! :D
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ROFL you guys :D
I'd like to make a skin for my own P6 to be honest......DJMegaCop on the side of it :P ;D
Regards.
DJM.