German engineers in 1934 completed a unique feat of engineering when the Niederfinow Barge Lift, on the Hohenzollern Canal, raised for the first time barges weighing 1,000 tons a vertical distance of 116 feet
THE IMMENSE TROUGH in which barges are raised from one level of the Hohenzollern Canal to another. The trough is 278 feet long and 40 feet wide. It has a depth of 8 ft. 6 in. of water, and is able to accommodate one barge of 1,000 tons or four ordinary barges.
THE Germans have always held high reputations as builders of canals and as waterway engineers, but a few years ago they exceeded all their previous feats with the opening of the Niederfinow Barge Lift. For many years the conventional lock, slow-moving and cumbrous, has been the accepted device for passing floating traffic up “sloping” waterways, but at long last the German engineers have broken away from tradition and substituted a giant “lift” which bodily raises and lowers ships and barges up to 1,000 tons in weight through a vertical distance of 116 feet. By an ingenious planning of counterweights they have contrived to perform this feat without an undue expenditure of energy, so that transport is not hindered by prohibitive tolls.
The barge lift is situated in the important canal system which permits inland navigation between Berlin and Stettin, connected with the Baltic Sea. For many years this system has been one of Germany’s most important trade arteries, though, because of natural geographical obstacles, a slow and crowded one. As long ago as 1746 the Finow Canal, which linked Berlin with the Baltic, was opened by Frederick the Great and was capable of accommodating barges up to 250 tons in weight.
Many years later, in 1914, the system was enlarged with the building of the Hohenzollern Canal, which could take ships of 600 tons, but travel was still slow.
Barges travelling the length of the canal had to be raised or lowered a total of 116 feet, which represented the difference in level between the two ends of the waterway. For a long time this was accomplished by four large high-lift locks. These were built in groups of two, with a wide level stretch between in which barges could pass one another. Convoy working was thus possible but, even so, it took more than two hours for a barge to attain her new level. It was not until the growth of water transport some years after the war of 1914-18, however, that drastic reconstruction became of vital importance. Changing conditions made larger barges necessary and the increased traffic demanded greater speed than the conventional lock could possibly yield. So a dramatic step was decided on. It was proposed that locks should give way to a giant “lift” - by far the greatest and most powerful in the world - to raise heavily laden barges through the whole distance in minutes where the locks took hours.
The principle was fairly simple. The lift cage had to consist of a great water tank, as large as a big swimming pool, with heavy steel gates. The barge would enter this in a few minutes, just as she previously entered a lock. The gates would then be closed and the whole structure - cage, water and barge - would be lifted bodily up a shaft 116 feet high until it reached the level of the higher waterway. The gates would then be opened and the barge would continue on her way.
THE NIEDERFINOW BARGE LIFT, on the Hohenzollern Canal, Germany, is controlled by electricity. Mounted over the trough are two control rooms, one at either end. From here the speed of the lifting motors is controlled and the trough brought to rest at the correct level. The vertical speed is 4 inches a second.
In practice, however, the building of this lift was not so easy. Engineers had no precedent on which to work and no assurance that even the most modern materials might not collapse under the huge weights involved.
Work started on the scheme in 1926 and went on steadily for eight years before the system was opened in 1934. The first step was to build two access channels which would short-circuit the existing lock system and lead to the high- and low-level sites of the proposed lift. On the Berlin, or higher side the access channel left the old canal some hundreds of yards before the locks were reached. Giant steam shovels, each capable of taking 20 tons of earth in one bite, made short work of the new stretch. At its end it opened out into a wide basin where ascending and descending barges could pass. Here the canal stopped, the ground in front of it sloping down in a miniature precipice to the low level which the lift would serve.
To carry the new stretch of canal to the site of the lift it had to be taken out over the “precipice” in the form of a giant aqueduct, unsupported by the earth but resting on a massive latticework of steel and concrete. This aqueduct had to carry the immense weight of steel, concrete and water which formed this canal above the level of the ground.
The ground which had to bear this weight was far from firm and ordinary foundations would have given under the stress. Months of calculation and of tests with large-scale models followed, before the engineers got to work on the site. Models were thoroughly tested and delicate instruments recorded the stresses and strains in different parts. Then, forearmed with positive information, the engineers drove the first piles into position.
These piles were among the largest that have ever been used. To find firm support they had to be driven over 60 feet below the water level of the subsoil.
Heavy concrete piers, each composed of hundreds of tons of heavily reinforced concrete, were sunk scores of feet below the surface. As each pile and pier was completed it was tested with weights far heavier than those it would have to bear in ordinary use. By the time the upper work was under way the ground site was almost a solid block of steel and concrete.
Then began the task of building the aqueduct. On the piers and piles there grew up a forest of lattice girders, connected and interconnected for strength. Along the top of this forest the skeleton of the mid-air canal began to grow. Forty feet wide, so as to accommodate the broadest barge, it ran for nearly 200 yards from the hilltop. It was a massively built cradle of steel lined with concrete several feet thick.
Meanwhile the site was being prepared for the even heavier structure of the giant lift itself. Experts had worked out that the lift would weigh upwards of 20,000 tons, or as much as a big transatlantic liner. As the slightest subsidence would throw the whole system out of truth and make the work useless, the engineers were faced with building what are among the most solid and immovable foundations known.
Thousands of piles were first sunk into the bottom of the excavated site, and on them a vast concrete “raft” was built. This consisted of a solid block of concrete, reinforced with steel rods up to 2 inches thick. The raft was 367 feet long, 103 feet wide and 26 feet deep. Weighing thousands of tons, it was one of the biggest masses of concrete ever poured. The mere transport of the concrete involved the use of hundreds of freight trains, and months were occupied in mixing and placing the semi-liquid material. Special precautions were taken to cool this great mass, so that the heat generated in drying should not cause cracks to appear and weaken the whole structure. Expansion joints were provided to take up the forces produced by heat and cold. Finally, supported by piles and by nine massive concrete piers which went 70 feet down into the subsoil, the great concrete platform stood immovable and solid.
THE LOWER APPROACH to the Niederfinow Barge Lift. Barges enter the trough and the gates are shut after them, completely sealing the tank. The lift motors then come into operation, and the barges are raised 116 feet vertically. In about fifteen minutes they are in the aqueduct extending from the hilltop in the background.
Then began the building of the lift itself, a towering structure nearly 200 feet high, 308 feet long and 88 feet wide, which dominated the countryside for miles and sent the local peasants into ecstasies of mirth and incredulity.
The most important section of the whole lift was the “trough” or cage which would hold the barges. This was 278 feet long and 40 feet wide; it had a depth of 8 ft. 6 in. of water. It was built of the highest quality steel and weighed about 4,200 tons.
To lift such a weight unaided would have been beyond the power of any lift gear; so an ingenious system of counterweights was evolved to balance the tremendous pull of gravity. The engineers knew that the total weight of trough, water and barge would always remain constant, for when a barge crept slowly into the trough it displaced a quantity of water exactly equal to her own weight.
The weights used were huge blocks of solid concrete, each 24 feet long. These were arranged in groups of six, stacked in a strong metal framework which would act as a support if a rope were to break. This was a necessary precaution, as the sudden breaking of a rope might otherwise have sent the heavy trough, barge and all, hurtling down the shaft, to bring the whole great structure to earth in a tangle of steel. A total of 256 thick steel ropes, 128 of them on either side, connected the trough and the counterweights. Though each rope would have to take a weight of only 22 tons, each of them was capable of holding 150 tons without danger of a break. The ropes ran over double-channel sheaves, huge steel wheels with a diameter of 10 ft. 4 in.
As the thick ropes weighed many tons, it was necessary to compensate for their weight when the trough was at the top of the shaft. Four heavy lengths of chain, each weighing 22½ tons, were slung from the counterweights to the bottom of the trough. When the trough moved up these chains exactly balanced the pull of the wire ropes and reduced the amount of power necessary by hundreds of horse-power.
116 Feet in Five Minutes
No great power is necessary to lift and lower the trough, with its 1,000-tons burden; for weight and counterweight are so exactly balanced that scarcely any lifting force is necessary. Four electric motors, each of 75 horsepower, are mounted on the supporting structure, one at each corner, and these drive the trough through pinions and racks. These motors are all designed to run at exactly the same speed, through synchronizing apparatus, so that there shall be no jamming or slewing. They are also interconnected electrically, so that, should one of them break down, the other three will take up the load between them without distress.
To raise such a tremendous mass is a slow business, and the 116-feet journey takes about five minutes. But it is necessary only to compare this time with the two hours required for the old trip through four locks to realize the full value of the barge lift.
The electrical energy for the main working of the lift is taken from the ordinary trunk mains at a pressure of 10,000 volts and is stepped down to about 380 volts by transformers installed in a substation near the lift. Lest the public supply should fail - and threaten to halt the lift halfway up the shaft - three 150 horse-power emergency diesel generators can be switched in. This substation is controlled by experts sitting before instrument panels in a big switch-house near the lower approach canal. From here a supply is given to the lifting motors, to the electrically worked steel gates on the trough and to those at the entrances of the approach canals.
THE SHAFT OF THE BARGE LIFT. The trough weighs 4,200 tons, and is balanced by huge concrete counterweights connected with the trough by 256 thick steel ropes. These are arranged in groups of six in a strong metal framework. The end of the aqueduct leading to the upper section of the canal is shown at the top of the shaft.
Mounted over the trough itself are two control rooms, one at either end of the long “pool”. From here the speed of the lifting motors can be controlled and the trough itself brought to rest at exactly the right level to coincide precisely with the level of the approach channel that it is serving.
The electrical equipment in these trough control rooms is supplied through four copper rails, running vertically up the main shaft structure. Forty sliding “shoes” attached to the trough make contact with these rails. Similar connexions are fitted at either end of the trough so that its gates can, if necessary, be opened and closed from the shore control rooms.
The trough is started by pressing the appropriate button; it then automatically accelerates for about twenty seconds until it reaches its operating vertical speed of 4 in. a second. This is not a high speed for an ordinary lift, but is fast in consideration of the load moved.
Every effort has been made to eliminate the human element as much as possible. As the trough approaches its final position it automatically operates a switch which brings a regulator motor into action and reduces the speed to about one-third of an inch a second. At this slow speed it can easily be stopped in the right position by pressing the “stop” button, but even for this simple job a “mechanical brain” has been perfected. This consists of a photoelectric cell which actuates a relay and stops the motors when a beam of light shining upon it is broken.
At the entrance to either approach canal is set a big scale, on which a pointer connected with floats indicates the varying level of the canal water. This pointer is connected with a metal diaphragm which interrupts the beam of light playing on the cell as the slow-moving trough reaches exactly the right position. This ensures that, when the connecting gates between canal and trough are opened, the level will be equal and no surge of water will be caused. Two more safety switches are installed to guard against failure of the first stop switch. Either of these will automatically cut out the motors and stop the lift, should it pass the right position.
When a big 1,000-tons barge arrives at the end of the lower approach channel on its way, say, to Berlin, if the trough is at the bottom of the shaft, but not connected to the canal, the lock-master’s first job is to go to the control board by the banks of the canal and unlock the main switch with a key. This throws the main circuit into life. Without the carefully guarded key not one motor could be turned on.
Signal lamps now glow out to indicate that the panel is “alive”, and other lamps indicate the positions of the various gates and equipment. The lock-master then presses several other buttons. First he fills the space between trough and canal gates with water at the touch of one button. Then he raises the two heavy steel gates, so that trough and canal become one stretch of continuous water. The various buttons are so arranged on the panel that they are automatically pressed in the right order. As a safeguard against any unauthorized movement of the gates, which might possibly lead to the flooding of the whole works, special keys are fitted to the gate control buttons.
As each operation is completed, appropriately coloured lamps glow on the indicator board. If all has gone smoothly about 108 seconds will pass before the barge is ready to move into the trough. Special haulage gear then warps the heavy barge into the trough and the tow ropes are cast off, a job which occupies at most another five minutes.
The gates, on trough and canal end, are lowered. The water in the small intervening space is pumped out again. Catches and locks which fix the trough into position are released and the lift is ready to go. Again, the pressing of a few buttons and an interval of 98 seconds suffice for these operations.
The lock-master now moves to the control panel which is mounted on the trough itself. Here the same master key is used to undo the interlocking gear.
The pressing of another button sets the lifting motors running and speeds the lift up to its determined pace. During the upward journey the lock-master walks to the control room at the other end to supervise the exact levelling off between trough and upper canal. Once again he presses buttons to fill the space between gates with water and finally to raise them out of the way. The barge then goes on her way, 116 feet higher than she was a few minutes before.
A TOWERING STRUCTURE OF STEEL, nearly 200 feet high, 308 feet long and 88 feet wide, contains the trough in which barges weighing up to 1,000 tons are raised from the lower level of the Hohenzollern Canal. A huge aqueduct joins the upper section of the canal to the lift.