1020
THEORY AND PRACTICE OF ENGINEERING.
Rook II.
Fig. 1549.
RAILWAY WAGGON.
of the wheels is about 1 inch deep, slightly bevelled off from the inner side to the outer, sothat when the wheel is running in a straight direction, the edge of the flanch is kept aboutan inch clear of the rail, or from coming in direct contact with it: this is effected by makingthe tire, which is 4 inches broad, slightly conical, the inclination being about one part inseven or eight. Where the flanches are not bevelled or are too shallow, the carriages arevery apt to run off the rails, andshould they come in contact with adefective joint in a rail the sameevil is likely to occur.
Waggons 6 feet in length and2 feet deep are found convenient onrailways for carrying earth and bal-last, as well as the other materialsrequired whilst the works are inprogress. The plan shows the un-der side of the framing, consisting oftwo stout longitudinal timbers toreceive the iron axles, upon whichthe wheels turn. The bottom ofthe waggon is further strengthenedby iron plates, and a three quarterround iron bar passes from one sideof the frame to the other, to holdthem together in the middle, and toassist in supporting the load at thebottom. The uprights at the sidesare mortised into the bearer atbottom as well as the top rail, andat each angle is an iron bolt thatscrews the whole together in thedirection of its height. The endsare movable, sometimes sliding ingrooves, at others merely pinned intheir place.
In the construction of all kinds ofrailway carriages great attentionshould be paid to the centre ofgravity of the load, for if too high their oscillation is considerably increased, which frequentlyoccasions them to be thrown off the rails, even where the wheels have the proper depth offlanch : the revolving parts of the machinery in a carriage should be always so balancedthat a smooth and equable motion can always be maintained.
In Italy carts of a different character are used for ordinary purposes, mounted above fourcast-iron wheels, in such a manner that they can be tilted on one side, but the body beingabove the top of the wheels is objectionable.
Fig. 1550.
PLaN of waggon.
Fig.1552.
Fig. 1551.
CARTS
Another method is sometimes adopted where low wheels are used, which only requires astout block to be placed over one half the axle : the waggon or cart is hung upon the edge,which allows of its being tilted sideways foT unloading. The side is hung either upon pivotsor a strap hinge, so that it can be let down to accommodate the throwing out the earth orballast it may contain: when the carriage is level, it is maintained in that position by acouple of irons, attached to the opposite side to that which inclines: these either hold withinan eye or fasten upon a loop by means of a pin.