This invention appears to possess considerable originality as well as ingenuity; but whether it can be made to work on the great scale, as well as we are told it does in the model, is a question upon which great doubts will be entertained, until experience shall decide it. The patentee distinguishes his scheme from all other plans of propulsion on railways by the term Archimedean; and he designates his chief movement the "screw propeller." Both these terms are calculated, in our opinion, to impress an erroneous idea. We should rather describe it as a helix of uniform obliquity, not connected solidly to the axis (as screws are), but with a space of about eight inches between one and the other; the connexion between the two being effected by a series of radiating arms, at about three feet distance apart throughout the entire line of railway. The annexed diagrams will make this construction quite clear.
The above Fig. 1 is an end view of the helical propeller, and Fig. 2 is a side or longitudinal view. In the centre 1 1 is represented the tubular axis; 2, 3, 4, and 5, are the arms of the propeller, and 6 shows the helix, winding round the axis. These parts are very nearly in their true proportion: it is intended to make the propeller in twelve feet lengths, and the diagram shows one of such lengths throughout which the helix makes but a single revolution. Thus every revolution of the screw is designed to propel the train of carriages twelve feet along the rails. Having premised thus much to explain the construction of the "Archimedean screw," we shall avail ourselves of the patentee's specification in our further description, which has reference to the engravings which follow.
"This invention consists in the use and application of a screw, a b c (Fig. 3 subjoined), which is called the "screw propeller," for the purpose of locomotion on railways, and by means of which the moving power is communicated to the trains. This screw is laid down continuously in the middle of the track, and is fixed in the direction of its length, but caused to revolve upon its axis by steam or any other power communicated to it at proper intervals, - say every three miles along the line. This screw may be of any given diameter, say from eighteen to twenty-four inches, formed in lengths of from twelve to fifteen feet each, and consists of a shaft a of cast or rolled iron tubing, four inches in diameter, supporting by means of wrought iron arms b b, keyed on to the shaft, a rolled iron spiral c, whichis bolted to the ends of the arms; the construction is such as to afford perfect confidence in its strength for its intended purpose. The lengths of shafting are connected by couplings, that allow a sufficient play to meet any accidental irregularity in the line, and also to permit them to be laid down on the quickest curves that are allowable on railways, with scarcely any calculable amount of friction: each length rests on turned bearings, in proper metal pedestals e, secured to the cross sleepers of the railway.
The power is communicated to the screw a b c by means of spur wheels, fixed on one end of each line of shafting of one and a half mile in length, which is situated so as to drive two such lines, that is, one in each direction from it, and the gearing is so contrived as gradually to bring the screw propeller into motion, and also to transfer the power from one line to the other without stopping the train.
* Since the above was written, it has been decided to discontinue the use of the ropes, and to substitute locomotive engines for them.
The motion of the screw propeller is communicated to the trains by means of a pair of wheels or rollers g g, so attached to the frame-work of the leading carriage of the train as to bear upon the rim a, spiral rail c, that forms the thread of the screw, one wheel being at either side of the axis of the screw; the position and arrangement of these wheels g g is such, that while one is propelled by being borne against by the thread of the screw, and carries the train forward, the other acts as a check wheel, and prevents the train from moving with an unequal motion, or running forward by acquiring acceleration; and the screw propeller being capable of acting in both directions, when the motion is reversed, that which before acted as a check wheel becomes the propelling wheel, and vice versa.
These wheels g g, which form the only connexion between the trains and the propeller, are perfectly under the control of the conductor, who, by turning the handle h of the vertical screw i, compresses the wheels g g, when he thinks it necessary, with more power upon the screw propeller, or in a moment disengage them from it, and having done so, can instantly apply the break, by continuing the same movement of the vertical screw i, which causes the nut n to press the cross beam m upwards, and bring down the break by means of the suspension rods o o, upon the bearing wheels. Thus, the train may be stopped at any points, without interfering with the motion of the propellor.
In addition to what has been already described, there is a provision in this invention, for dispensing with the flanges on the bearing wheels, and also for conveying intelligence or signals from station to station. This arrangement is shown in the subjoined diagram, Fig. 5; in this case, the bearing saddles e, are triangles the full height of the propeller, and a guide rail k is laid the whole length over the propeller; this rail is made of iron tubing, in lengths equal to the propeller, and fastened or screwed into sockets cast on the apex of the triangular bearing saddle e; against the guide rails, the friction rollers ll run, and the flanges on the bearing wheels are thus dispensed with; the rails may then be reduced to a flat iron bar. It is proposed that signals be conducted through the tube k from station to station.