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TransDev Hopes Venice will REAP
the Benefits of Hybrid Power

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of the printing and typesetting industry.

With 550 water taxis and buses serving its tourist industry of 32 million visitors a year, plus 1000’s of powered private boats, Venice suffers from alarming levels of air, noise pollution, and vibration. Dorset based power transmission specialist TransDev have become a key engineering partner and sponsor of a green hybrid power project that hopes to transform marine transportation.

REAPsystems Hybrid Power

REAPsystems based in Hampshire are creating a clean drop-in hybrid diesel electric engine that can be installed by any boat builder and fitted into all existing boats, starting with a Venice water taxi to demonstrate the technology.

This hybrid system uses the latest diesel engine technology paired with a high-power, compact and efficient electric motor & inverter, as well as a modern lithium-ion battery and advanced system control unit. The electric engine utilises a high performance CONTI® SYNCHROCHAIN CARBON timing belt and specially manufactured pulleys from TransDev to drive the propeller. A Hybrid System Control Unit (HSCU) is connected to the clutch. The clutch is engaged when diesel operation is needed and disengaged when electric motor is needed.

Apart from the environmental benefits REAPsystems estimate an average fuel saving of at least 50%, if compared with current diesel engine boats. The short-term aim is to develop a hybrid electric taxi-boat prototype that will be demonstrated and endurance tested in Venice next year, then to influence the new regulation on vehicle emissions to be imposed by the Venetian local authority. Longer term the aim is for adoption in Venice with a roll-out to other applications to follow.

Marine Hybrid Electric Engine

The hybrid system comprises two systems in one. Hence, the operator will benefit from high reliability and a peace of mind backup/redundancy. In the city, the engine can be ‘clutched out’ to allow pure electric drive. Here, at low speed and where it matters most, users will benefit from all the advantages of the electric motor: no noise, no pollution, no vibrations and no fuel consumption. During fast transits of the diesel engine, the electric motor may also assist in order to reduce exhaust emissions. During medium to high speed, such as when transiting the lagoon, the diesel engine automatically and smoothly takes and works as a generator, recharging the batteries and pushing the engine into a more efficient engine loading.

Creating a Compact Drive

As a drop-in and compact solution the hybrid electric drive-train can be installed into all existing diesel boats by any boat builder, either as a replacement or as an add-on to an existing diesel engine. There is virtually no compromise on passenger or cargo carrying capabilities.

The hybrid module design for the hybrid diesel-electric engine is very compact, light in weight, powerful and flexible. This enables it to suit a range of different engines, configurations and types of propulsion system. The hybrid module can work with the stern drive, gearbox and shaft configuration.


When it came to the drive belt and pulley solution REAPsystems turned to TransDev and ContiTech. The high tear resistance and high dynamic load carrying capacity of the CONTI® SYNCHROCHAIN CARBON’s high performance belt allows for synchronous drives even where boat engine compartment space is at a premium.

A saving of up to 80% on overall belt width can be achieved, based on conventional timing belts when transmitting the same power requirement. This saving establishes ideal conditions for the design of economically compact, lightweight drives, such as the one in the REAPsystem hybrid engine.

Power and Performance

This high-performance CONTI® SYNCHROCHAIN CARBON timing belt, with its CTD profile, also makes extreme applications such as the hybrid engine possible. The newly developed CTD-profile (Conti Torque Drive) features an arch-shaped pulley-entry geometry, on the one hand, and a higher tooth, on the other, providing harmonic tooth meshing and therefore ultra-smooth running. At the same time, it provides excellent protection against belt slip at high torque. CONTI SYNCHROCHAIN® CARBON’s design and materials ensures the hybrid engine pulleys deliver reliable power transmission for high torques and high dynamic stressing plus longitudinally stable operation.

Low and High Speed

The electric motor is very responsive; it can operate down to zero rpm and change smoothly from forward to reverse rotation. This gives the driver impressive manoeuvrability and more controlled and safe operation in the confined spaces of Venetian canals – all without gear changes.

CONTI® SYNCHROCHAIN CARBON timing belts were designed for applications with extremely high acceleration forces as well as for the reliable transmission of high torque at low speeds. It is also well suited to transmission of lots of power involving a high dynamic load at belt speeds of up to 40 m/s.

To deal with the impact loads occurring in the case of abrupt boat acceleration and deceleration, the belt employs a polyurethane compound which absorbs even maximum surges and guarantees maintenance-free functioning in continuous service.

A Tough Environment
The engine compartment of any

boat is a challenge for belts and pulleys to operate in when you have the combination of cold, heat, oils, diesel, salt water and general contaminants. Venice is a salt water lagoon whilst the city canals can suffer from a wide range of man-made pollutants, both domestic and industrial.

The CONTI® SYNCHROCHAIN CARBON belt , consisting of polyurethane teeth and backing, carbon cord tension members and specially treated polyamide fabric, is highly resistant to oils, grease, fuel, UV and ozone, tropicalized and resistant to temperatures from -40 to +80 degrees centigrade.

REAP Hybrid Boat Trials

Boat trials were conducted in the Solent.

Bringing Peace to the Canals

Boats are an essential part of the private and commercial lives of many Venetians, but the sound of buzzing, growling, or throbbing engines often fills the air. Venice needs quiet, low vibration at low speed inside the canals of the city. CONTI® SYNCHROCHAIN CARBON’s arch-shaped pulley-entry geometry, on the one hand, and the higher tooth, on the other, provide harmonic tooth meshing and therefore ultra-smooth running.

TransDev manufactured matching SYNCHROCHAIN pulleys for the hybrid drive from unalloyed medium carbon steel with through holes and flanges. The optimized sectional match between timing belt and pulley and a belt construction with a multiply treated polyamide fabric, plus a dramatic reduction in the required timing belt width that using CONTI® SYNCHROCHAIN CARBON high performance timing belts afford, all make for considerably less noise, even at high belt speeds.

The Need for Reliability

One of the reasons for the slow uptake of clean hybrid technologies in the marine market is the high reliance on the reliability of the engine. A standard 9 metre water taxi typically has a long, hard 20 hour day.

The CONTI® SYNCHROCHAIN CARBON belt is essentially maintenance-free. The precise tooth match between belt and drive pulley ensures a high degree of synchronicity and reliably prevents belt ratcheting. The belt construction and the materials used help ensure a constant belt tension. No lubricating or re-tightening is required. The stretch of the high-tensile carbon tension member is also 50% lower compared with aramid cord. This stiffness results in initial tension losses dropping almost to zero over the lifetime of the belt, representing a further enhancement in drive efficiency. Overall service live is increased by up to 100% compared to belts using aramid cord which also helps reduce overall system costs.

With REAPsystem’s solution the diesel engine only runs when high output is required. This is what they are actually designed for. No need for long, inefficient and damaging idle operation. In short, it will run less and better, increasing engine life, reducing emissions and minimising maintenance.

Next Steps

ContiTech and TransDev have continued to work closely with REAPsystems, performing on-site checks of the electric motor belt tension and alignment. They remain fully committed to the success of such an important project. Trials of the boat are expected to continue through the winter with a Venice debut due soon.

Next Steps

ContiTech and TransDev have continued to work closely with REAPsystems, performing on-site checks of the electric motor belt tension and alignment. They remain fully committed to the success of such an important project. Trials of the boat are expected to continue through the winter with a Venice debut due soon.

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