From the Journal of the Franklin Institute, July 1836
REPORT ON MESSRS. GARRETT AND EASTWICK'S LOCOMOTIVE STEAM ENGINES.
The Committee on Science and the Arts, constituted by the Franklin Institute of the State of Pennsylvania for the promotion of the Mechanic Arts, to whom was referred for examination, the Locomotive Engines made by Messrs. Garrett and Eastwick, report:
That they have examined one of these engines now in progress of construction, at the shop of Messrs. Garrett and Eastwick, and witnessed the performance of another which has been completed and placed on the Philadelphia and Trenton Railroad for trial.
They are constricted upon the principle of outside connections, the general arrangement being similar to that adopted by Mr. M. W. Baldwin with some modifications, however, of sufficient importance to give them a distinct original character. The most striking peculiarity is in the manner of reversing. This operation is performed in the different engines heretofore in use, by various contrivances, all of which involve the necessity of ungearing the connection of the eccentric rods with the rock shafts; consequently their action depends upon the contingency of throwing these parts again into gear, which can be effected only at particular points in the revolution of the eccentrics.
In the engines under consideration, the reversing is performed by means of moveable valve seats, which are placed between the slides and the true seats, and connected with hand levers by rods passing through stuffing boxes in the steam chest.
In each moveable seat are five passages, four of which are steam ways and one for the exhaust; two of the steam ways and the exhaust opening pass directly through the seat, the other two steam ways pass only about one-third through, and communicate with chambers which form oblique passages from one end of the seat to the other, so that the steam which enters the upper opening at one end of the seat, escapes by the lower opening at the opposite end.
When the moveable seat is so adjusted that the direct passages coincide with the openings in the true seat, the action of the valve is similar to the common short slide; but if the seat be shifted, so that the communication shall be through the oblique passages, the course of the steam to the cylinder will be reversed without any change in the motion of the slide. This arrangement possesses the merit of simplicity in a high degree, and as its action does not depend upon any contingency, the engine can be reversed with certainty and precision. A small loss of steam results from the increased thickness of the valve seat, but it is believed the amount will not be sufficient to produce any appreciable effect upon the power of the engine. It has been suggested that the inequality of wear to which the movable seat will be subjected in its different positions, must render its surface irregular, and impair the tightness of the valve; some inconvenience may arise from this source, the extent of which can be determined only be experience; it is not apprehended, however, that the evil will be of a serious nature.
The situation of the cylinders and driving wheels in engines, with outside connections, allows a leverage to the working strain, which very much increase the wear between the driving axles and their boxes, and also twists the frame out of its proper form. Messrs. Garrett and Eastwick have endeavored to guard against the injury resulting from this cause by some slight changes in the parts most exposed to its effects.
Instead of turning down the bearings of the driving axle to obtain a shoulder for preventing lateral motion in the axle, they leave the axle its full size throughout, and provide against lateral motion by facing the hubs of the wheels, so as to form shoulders which bear against the outer ends of the boxes. The increased extent of bearing surface which is thus obtained both within the boxes and at their ends, enables them to resist more effectually, the thrust of the engine and adds to their durability.
The firmness of the whole machine has been increased by bracing the cylinders to the firebox, and bolting to the under side of the frame a strong plate of iron, which passes entirely around it and is secured to the pull bar.
The Committee have been informed that the engine which is upon the Trenton Road, has given entire satisfaction during a trial of several weeks constant service; the exhibition of its performance witnessed by them was highly gratifying, and they feel themselves warranted in saying that these engines afford evidence of ability to manufacture locomotives equal to any in the country for excellence of workmanship and general finish.
By order of the Committee.
WILLIAM HAMILTON, Actuary
July 14, 1836