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In the following year, 1812, Messrs. William Chapman, of Durham, and E. W. Chapman, of Wallsend, Northumberland, took out a patent for "a method or methods of facilitating the means, and reducing the expense, of carriage on railways and other roads;" which they describe as chiefly consisting in the use of a chain, or other flexible and continuous substance stretched along the road to be travelled, properly secured at each end, and at suitable intervals; and in the application of this chain round, or partially round a grooved barrel or wheel, in such manner as not to slip when this grooved wheel, which is fixed upon, before, or behind a carriage containing the motive power, shall be put in motion by that power, so that by the revolution of the grooved barrel round its axis, either one way or the other, it shall necessarily draw the said carriage, and any others which may be attached to it, within its power of action.
As the carriage containing the motive power, when thus loaded, may be too heavy in some instances for the existing iron or wooden rails, if it rested on four wheels only, Messrs. Chapman proposed to use six or eight wheels, in order that they might more freely move round curves in the road, and that the weight might be more distributed thereon; the pressure being thus reduced upon each bearing point, in the inverse proportion of the number of wheels.
The means adopted by the patentees for carrying their invention into effect, are described at considerable length, with explanatory drawings, in their specification; but as Mr. Wood informs us that the application of it failed at the Heaton Colliery, where it was for a time put into practical operation, and as the details of it would occupy too large a space in our pages, if inserted, we shall refer the reader to the enrolled document for them.
The cause of the failure just mentioned is stated to have been owing to the waste of power arising from the excessive friction of the chain. There are one or two incidental observations in the specification which ought not perhaps to pass unnoticed. Allusion is made to the possibility of employing inflammable gas as the motive power, which, most of our readers are aware, was a few years ago carried into effect by the ingenious Samuel Brown, and which we propose to describe in the course of this article.
We also remark, although it is of little moment, that the specification contains the first proposition we have met with for employing the common winnowing machine to force a current of air under the fire-place.
The annexed engraving exhibits an elevation of one of the locomotive engines of Messrs. Chapman, which was employed on the Heaton Colliery. The boiler consists of a large cylinder, of the Trevithick kind, with the furnace and a double or return flue passing through it to the chimney, situate on one side of the fire door; opposite to which is a chest containing the fuel of supply.
The steam chamber is a large vertical cylinder, from which proceeds laterally a pipe to conduct the steam to two vertical cylinders, fixed on either side of the boiler. The motion of the piston rods actuated two vibrating beams, to which were appended two connecting rods, whose lower extremities worked two revolving cranks, carrying on their axis, spur gear, which, through the medians of a train of toothed wheels, shown, gave simultaneous motion to all the running wheels.
The weight of this engine, with its water and fuel, we are informed was six tons; and it was set to work in December 1812, upon the railway leading from Mr. J. G. Lambton's collieries to the river Wear. It drew after it 18 loaded coal waggons, weighing 54 tons, up a gentle ascent rising 5/16ths of an inch to a yard (or 46 feet in a mile) at the rate of four miles an hour. The power of the engine was applied to the running wheels as already described; and it was found that their resistance to slipping upon the rails was the utmost power it could exert in drawing waggons after it, which in this instance was carried to the extreme; for although the friction was equal to the drawing forward the train of eighteen waggons, after they were fairly in motion, it did not overcome their ‘vis inertia’ until after a considerable slipping of the wheels of the carriage.
We have introduced this notice of the earliest experiment made with the engine of the Messrs. Chapman, because it exemplifies, in the cleanest manner, that precise inclination of the plane upon which the smooth wheels of a carriage, bearing a certain weight, will slip round, without advancing the machine. It also proves the necessity in such cases of increasing the friction of the opposing surfaces, either by augmenting the weight, or by some contrivance resembling those suggested by Trevithick in his specifications, which Dr. Lardner repeatedly in the course of his work treats as an absurd attempt to remedy an "imaginary difficulty."