In the year 1794, an instrument of this description, upon an improved principle, was invented by Mr. Joseph Kneebone, of Ma-razion, Cornwall, for which the Society for the Encouragement of Arts, etc. in 1795, conferred on him a bounty of twenty guineas.
Description of the Cut of Mr. Joseph Kneebone's Wheel-drag, for two-wheeled Carriages.
This simple contrivance is, on the brow of the hill, applied to the pear wheel, being fastened to the a, a, a, A piece of wrought iron, curved to the exact form of shaft by a chain, to prevent the wheel from passing over it, in case any great obstacles should occur in the road. It answers the purpose of taking off the increased weight, necessarily thrown on the shaft-horse's back when descending any declivities, so effectually that the deep ruts, or loose stones, which frequently occur in roads, do not in any degree impede the descent of the cart. Instead of a loaded carriage running on the heels of the shaft-horse, when descending hills, the drag, by supporting and elevating the wheel, places it on a level, so as to oblige the horse to draw a small burthen. In some instances, it is even necessary to link the chain-horse to the side next the wheel that is dragged; by which means, a weak horse may, without any risk or danger, be placed within the shafts. As soon as the cart arrives at the bottom of the hill, the drag is to be taken off, and secured in the man-ner hereafter to. be described.
a cart-wheel, with the thickest part at b, on which the weight of the cart rests.
1,2,3,4, are shoulders, that keep the wheel within the drag, and should be about 4 inches high. c, Is the wheel, made of solid iron, which is nearly as wide as the drag, 7 inches in diameter; runs on its axis at d; has a strong shoulder; and, as it projects, resists the sudden jolts of rough roads, e, Is the chain to be fastened to the near shaft, in order to keep the drag properly under the wheel, which, from being violently jerked, might be apt to pass over the drag, and leave it behind: this is a necessary precaution, though seldom wanted, if the drag be well constructed.
In the shoulders marked 1, 2, are holes, by which the drag is suspended on hooks beneath the tail of the cart, when it is not employed.
This machine is, doubtless, susceptible of many improvements, especially in the size and construc-• tion of the wheel. By frequent use, the part to which the greatest pressure is applied, will necessarily wear away, and thus injure the drag: to prevent this accident, it ought to be shod, at first, with a plate of iron, or steel, fixed by means of two holes in its bottom; in which, when necessary, a similar piece may be inserted.