OF
A MACHINE,
For propelling Boats, on narrow Canals, without disturbing the Water.
The application of steam-power, to the motion of boats on narrow canals, is, I believe, much impeded by the consideration that the agitation of the water injures their banks, and would finally destroy them. On the other hand, it is known, that to drive a vessel, by acting on a fleeting medium, such as water, we must, at once, submit to lose about one half of the whole power employed—that is, the power, armed with energy enough to produce the required velocity, must go through twice the space that constitutes the way or progress of the vessel. This depends, however, on the size of the floats or paddles employed, compared with the section of the boat, as modified by the form of the prow; but it is difficult to employ a paddle so large as to suffer more resistance from the water than the boat itself; and, if they are found just equal, the loss of power is exactly one half of the whole. These, then, are the two difficulties which I hoped to avoid, by the method now to be exhibited.
The idea is this—To have a large and heavy wheel A connected with a long shaft B, reaching from the boat to the shore, and, turning that wheel in the boat, to propel the latter, by means of it’s rolling motion, on the bank or track-way; or, in some cases, on a proper rack, placed there for that purpose.
The Machine itself is represented in [figs. 3 and 4], of [Plate 31]; [fig. 3] being a stern-view, and [fig. 4] a side-view, both of the machine and the vessel. C is an axis, placed along the vessel, and turned by any convenient power—as a horse, a steam-engine, &c. On this axis, considered as the first motion, are fixed the two bevil wheels b c, from which the long shaft B A of the rolling wheel takes it’s motion. The use of the two wheels b c, is to drive the boat in the same direction on whichever side of the boat the wheel A may be placed; for this, of course, must follow the track-way, which is sometimes to the right and sometimes to the left of the vessel.—Between the two wheels c b, is a sliding block (or catch-box) d, in which the shaft A B of the large wheel has it’s lower pivot, and by which it’s wheel B is almost instantaneously shifted from one to the other of the vertical wheels b c: the catch-box d being itself worked by a lever, of which the end only is seen at e, [fig. 4]. In [fig. 3], there is further shewn a rope or stay f, which, fastened to the socket s, of the rolling wheel A, and fixed in the middle of the boat, at the greatest possible distance from it, serves to keep that shaft at or near an angle of 90 degrees with the boat’s side: so that (the vessel being long) it becomes easy by means of the rudder, assisted, perhaps, by lee-boards to keep the way of the boat in a line parallel to the shore, notwithstanding the tendency to veer outward, given by the wheel A, while acting on a point so far from the body of the vessel.
I further observe, that, in order to shift the apparatus, with a certain facility, from one side of the boat to the other, there is a mast M placed ahead of the mechanism just described, which rises as high as the length of the main-shaft (but can be lowered to pass a bridge, &c.), and to the top of which is fixed the block g, through which a rope passes from the foot of the mast to the above-mentioned socket of the wheel A. By this rope the wheel is hauled up till nearly ready to fall over the centre; when a push from below will complete that passage; and the wheel A, being afterwards lowered by the rope h i, will soon find it’s proper position on the other side of the boat, as before anticipated. Where, it should also be remembered, that this shaft must have a joint and socket, to permit it’s being bent, to pass a bridge, &c.
Hitherto we have supposed this rolling wheel to act on the bank or track-way solely by it’s weight; but this is not our only resource; for this wheel might be made of a moderate weight, and be pressed down by a brace reaching along the boat, toward the head and stern (see k l, [fig. 3.]), and hauled taught through an eye of the socket s; by which manœuvre (the points k l being lower than the centre A of the wheel) the latter will be pressed forcibly downward, and cause that cohesion there, from which the boat is ultimately to take her motion.