Plan of the St. Maurice Canal, showing Cable Traction.
During the year 1888, experiments were carried out on the Saint Maurice canal with a system of cable haulage introduced by M. Levy, which seems to be of some value. An endless cable, supported by pulleys on posts along the banks of the canal, is set in motion by a hauling engine situated at some convenient point, and the barges which are attached to this cable are thus drawn along. On one side of the canal the cable runs in one direction, and on the other side it runs in the opposite direction, so as to accommodate both up and down traffic. Notwithstanding the extreme simplicity of the idea, there occur considerable difficulties in its practical application, the most formidable of these being the danger that, by the oblique pull from the barges, the cable may be thrown off its supporting pulleys into the water, especially where there occurs a bend in the canal. To prevent the cable from leaving the pulleys, the latter are provided with deep flanges; but as these would prevent the easy passage of the oblique hauling rope, some special provision had to be made for this purpose. The flange on the water side of each pulley has two gaps, as shown in the drawings ([pp. 405-406]), and as the cable with its hauling rope passes into the groove, one or the other of these gaps engages the oblique rope, but not the cable which passes on in a straight line. The rope passing through the gap is thus shunted out of the groove, and passes clear of the pulley. The attachment of the rope to the cable is shown at 3. At certain intervals along the cable are attached ferrules, between which is a shackle A, which can freely revolve. Through this shackle is passed the hauling rope, made fast upon itself by an easily detachable clamp D, from which a line is taken on board. By a pull at this line the clamp is unfastened, and the hauling rope is slipped through the shackle, so that the man in charge of the barge can at any moment disconnect the latter from the cable. The speed of the cable is from 2¼ to 2½ miles per hour, and with this speed no difficulty was experienced in making the attachment. The difficulty, however, was to impart motion to the barge without unnecessarily straining the cable. It will be easily understood that when a weight of 200 tons to 300 tons has to be set in motion, even at a comparatively slow speed, the acceleration must not be too great, otherwise the strain on the cable and hauling rope would be excessive. The attachment must therefore not be an absolutely rigid one, and, to give time for the gradual starting of the barge, the hauling rope is taken round a brake drum, and allowed to slip at first, so that the barge may be gradually set in motion; the brake is then locked, and the only further attention required is the steering. At the end of the length of canal served by the rope, the bargeman simply pulls the line, and the momentum of the barge is sufficient to carry it on to the next section, where it would be similarly attached to a running cable.
Cable Traction on the St. Maurice Canal.
The illustration on [p. 404], reproduced from Industries, shows the engine house by the side of the canal bank: and a plan of the experimental installation as at present carried out is shown on [p. 405.] The results have been so encouraging, that it is intended to equip about 6½ miles of canal with this system. Compared with horse haulage, there is said to be a considerable gain in speed; and, as far as can be judged at present, the cost of haulage is reduced from 10 to 30 per cent.
FOOTNOTES
CHAPTER XXVIII
[266] ‘Monthly Magazine,’ vol. iv. p. 75.
[267] Ibid., vol. xi. p. 195.
[268] ‘Agricultural Magazine,’ vol. vii. p. 152.