“Conventional inboard installations were beginning to seem like a dead-end – it simply was not possible to squeeze much more out of the technology,” notes Lennart Arvidsson, technical project leader for the IPS system. “Instead, we gave free rein to our creativity and utilized the unique know-how that exists within Volvo Penta regarding marine propulsion units and propeller technology for high-speed boats.”
Forward-facing propellers
The first visual impression of IPS can seem surprising – the propellers are mounted at the forward end of the propulsion unit, facing in the boat’s direction of travel, so that they pull rather than push like conventional propellers.
“Forward-facing propellers are in fact entirely logical; it’s just that no one has taken this approach before in our industry,” says Lennart Arvidsson. “Because the propellers are mounted at the forward end of the propulsion unit, they can function in undisturbed water and thus achieve maximum efficiency. The propeller backwash is absolutely parallel with the bottom of the boat, so that all the power developed drives the boat forward. Efficiency is further enhanced by the twin-prop technology with counter-rotating propellers, since rotation losses are canceled out.”
The same principle of pulling propellers is used for propeller-driven aircraft, which normally have propellers facing forward in the aircraft’s direction of travel.
In Volvo Penta’s IPS system, the propellers are made of a special nickel-aluminum-bronze alloy in nine different sizes, for boats with a maximum speed from 25 to 45 knots.
Electronic control
The IPS system is designed for twin installation. Each engine is connected to its own propulsion unit, which is steerable and functions like a rudder for the boat. Because the propulsion units turn, the entire propeller thrust is aimed in the desired direction, making maneuvering and driving highly efficient. There is a noticeable difference compared with a conventional installation with a fixed propeller and rudder.
“All boat owners want simple, safe and intuitive driving, and the best way to achieve this is through steerable propulsion units. But we did not stop at that. By controlling the steering electronically, we can improve both performance and operating safety,” explains Lennart Arvidsson.
The entire system – from steering wheel to propulsion units – is electronically controlled and integrated with Volvo Penta’s EVC electronic platform. Each propulsion unit is linked to a stearing gear powered by an electric motor. The system processes the driver’s steering-wheel movements and instantaneously converts them into steering movements of the propulsion units. It is a highly sophisticated system that takes into account how the water flows along the bottom of the boat at different speeds. The steering is progressive, making it easier to turn the wheel at low speeds.
“During development of the steering system, safety was a high priority, the primary consideration being that it should be possible to reach harbor safely under any circumstances. All functions are duplicated, and in the worst-case scenario it is possible to turn the propulsion units manually. We spent thousands of hours testing in every conceivable situation in an effort to provoke problems and thus assure ourselves that the safety functions are effective,” says Lennart Arvidsson.
Volvo Penta is launching an integrated autopilot in conjunction with IPS. The autopilot’s steering unit is coupled to the EVC system to become an integral part of the electronic control system. The driver controls the autopilot from whichever helm station is in use and can rapidly and easily switch it on or off.
Well-damped mounting
Each IPS unit is mounted in a hole integrated in the hull structure. Each propulsion unit is lifted into place from beneath the hull, together with two heavy-duty rubber rings for sealing and vibration damping. Finally, a clamping ring is mounted, completing the installation without the need for any hole-drilling or plastic-work.
The propulsion unit handles all the propulsion forces, and the vibrations that occur are effectively absorbed by the double rubber rings. The efficient damping of propeller-generated vibrations also means that the engine is not affected by propeller forces, which in turn enables the engine to be soft suspended so that engine vibration is effectively damped.
One lead through for everything
The propulsion unit also functions as exhaust pipe, noise damper and cooling-water intake, so that boatbuilders do not need to create any extra hull lead-throughs. This simplifies and speeds up installation and increases reliability. Combustion gases are expelled via the propulsion unit into the propeller backwash beneath the boat, reducing unpleasant combustion odors, fumes and noise on board.
“Reducing the need for maintenance was a key objective during the development work for IPS,” says Lennart Arvidsson. “The way combustion gases are handled is a good example of a low-maintenance solution.”
Engines with low emissions
The engines used in the IPS 400 and IPS 500 systems are in-line six-cylinder diesels with a cylinder volume of 5.5 liters and common-rail fuel injection. It is basically the same engine as the Volvo Penta D6, adapted to the requirements of the IPS system. Both of the IPS engines have turbochargers with aftercoolers, and the IPS 500 also has a mechanical compressor to generate maximum torque directly from low rpm. Exhaust emissions are extremely low and will meet the overall emission requirements planned to be introduced in the EU and the US in 2006-2007, as well as enhancing onboard comfort in combination with the IPS system’s efficient handling of combustion gases.
Robust design
IPS has excellent corrosion resistance. All components that come into contact with the water are made from either bronze or stainless steel, and the propellers consist of a special nickel-aluminum-bronze alloy. The propulsion unit itself, including bearings, couplings, etc., is extremely robustly dimensioned. Efficient seals give longer intervals between oil changes.
The engines are produced at Volvo Penta’s plant in Vara, western Sweden, and the propulsion units at the Volvo plant in Köping, central Sweden. A complete new production line has been built at the Köping plant, which also has advanced equipment for quality-testing and development. Each propulsion unit is tested exhaustively and test-run fully assembled. The key test data for each individual unit are stored so that they can be used when needed in the future.
Rigorous testing
The first boat incorporating the IPS prototype was launched in 1998. Since then, IPS units at various stages of development have undergone many thousands of hours of testing in Europe and the US, but principally at Volvo Penta’s own marine testing center at Krossholmen near Gothenburg.
“We have also been conducting rigorous field-testing in a 15-meter boat that is used in extremely severe conditions in northern Norway. The boat, equipped with twin IPS 500 propulsion units, has been operating continuously for more than a year without any major problems,” says Lennart Arvidsson.
Technical data
IPS 400 IPS 500
Crankshaft output: 310 hp/228 kW 370 hp/272 kW
Corresponds to
conventional inboard-
engine output of: approx. 400 hp approx. 500 hp
Cylinder volume: 5.5 l 5.5 l
Configuration: In-line six-cylinder marine diesel with common rail
Turbocharging: Turbo, intercooler Turbo, compressor intercooler
Gear ratio: 1.94:1 1.94:1
Voltage: 12 or 24 V 12 or 24 V
Emissions: Will meet future comprehensive emission regulations
to be introduced in EU and the US in 2006-2007.
Developed for: Twin installation in planing hulls with a maximum speed from 25 to 45 knots.
For further press material please go to http://www.volvopenta.com/ or visit our campaign site www.volvopenta.com/ips/gb
For further information, please contact Ann-Charlotte Emegård, AB Volvo Penta, phone:
+46 31 66 84 18, E-mail: ann-charlotte.emegard@volvo.com