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
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