Dockspotter at £180 , 000
Page 19
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by Colin Sowman • Large hauliers might be used to spending more than half a million pounds on vehicles and trailers. Tell them that the equipment will only be worked flat out for eight hours a week and they're likely to tell you that care in the community has gone too far! But that is just what is happening on berth 44 of Tilbury docks.
Swedish paper producer Transforest has bought three Sisu TR181 RO-RO terminal tractors coupled to Rolux R904 translifters at around ,E180,000 for each rig. They are used to unload cassettes loaded with paper rolls from three new purpose-designed RO-RO ferries.
The 4x4 Sisus are fitted with a console which rotates through 180° ensuring that the driver is always facing the direction of travel. Power is provided by a 241hp (180kW) Volvo Penta TID 730ME industrial engine which drives through a Clark 5451 torque converter. Clark also provided the 3200-Series rangechange transmission which has three high and three low ratios.
Both the front (steer-drive) and rear axles are manufactured by Sisu. Up front is a DEB hubreduction axle with five planet pinions and a static rating of 27 tonnes. The Sisu 13TH rear axle can handle 50 tonnes of static loading and uses four planet pinions for its hub reduction. The front axle ratio is 16.57:1 while the rear is 16.41:1 giving a small amount of transmission wind-up—in practice the vehicles never travel far enough in a straight line for this to be a problem. When the lowest gearbox ratio is selected the Sisus would theoretically pull 115 tonnes up a 20% (1in-5) gradient.
The fifth wheel uses a casting rated at 50 tonnes but is de-rated to 32 tonnes when engaging a 2in kingpin. On this operation the maximum loading will he 26 tonnes. A hydraulic lift gives the fifth wheel up to a metre of movement to raise the front end of the cassette. The cassettes are lifted and transported on eight. wheeled Rolux 1904 translifters.
All wheels are hydraulically steered and can be raised 550mm to lift the cassettes. When the combination is moving forward a wedge locating in the fifth wheel is used to activate the trailer steering. In reverse the driver can steer the translifter's wheels using a joystick. If full lock is selected on the joystick the translifter will move sideways while remaining parallel rather than turning in an arc.
Each translifter weighs 14 tonnes and can (wry a payload of 90 tonnes but they cannot travel far at speed as the solid tyres would overheat. Not surprisingly, the translifter's hydraulics are controlled and co-ordinated by computer. Once the translifter enters a cassette, proximity sensors signal the computer which automatically straightens the wheels.
The rolls of paper are loaded on cassettes which, from either end, look more like sledges with two runners and a "tunnel" down the middle. During the voyage 141 cassettes sit on two decks almost touching each other and without being lashed down.
When the time comes to move the 12.2m cassettes, the translifter is reversed through the "tunnel" of the sledge. Once fully engaged the far end of the translifter is raised using the hydraulics on each wheel. At the tractor end the fifth wheel is raised to lift the cassette clear of the deck.
The cassettes are so close together there is a danger of trapping someone.
To guard against this a TV camera is mounted in the far end of the translifter with a monitor in the cab. The camera is also used when manoeuvring into the tunnel or reversing with a high load.
To make the whole job easier and quicker, not only does the rotating driving console have full logic: if the driver wants to move the way he is looking he pushes the gearlever forward— if the seat is facing rearwards, reverse gear will be selected automatically. If the driver wants to turn right then the right hand indicator is activated. If the seat is reversed, the indicators will be switched automatically and so will the steering.
Left-hand-drive versions were chosen because the linkspan arrangement on the berth means the vehicles have to turn right on full lock. When they are doing so in reverse the driver is on the water side and can see the edge of the linkspan.
The payoff for this investment comes in three ways: • It now takes three people less than five hours to unload and load each vessel—using the previous system this took up to 24 hours using 11 people on each shift; • With fewer handlings of the actual paper rolls there is less damage and so less scrap; • The quicker turnround allows the vessels to make more sailings every week.
Transforest has three of these purpose-designed RO-RO ferries on 15-year charters. When you're paying thousands of pounds a day to charter each vessel, their utilisation is more important than that of the vehicles which load and unload them.