This section is from the "Modern Machine Shop Construction, Equipment, And Management" book, by Oscar E. Perrigo. Also see Amazon: Modern Machine Shop Construction, Equipment, And Management.
All curves are of 12 feet radius to the inside rail of the curve, and it would be better to make them 14 feet if possible, as the longer the radius the easier the cars will go around the curves, no matter what system of construction of cars is used. For switches the plan will be as shown in Fig. 133. Special castings are constructed as shown at A, B, and C, and to these the curved and the straight track will be joined as shown. Of course, these special castings must be made for right and left switches, necessitating two patterns of each piece. A shifting tongue to the switch need not necessarily be provided for cars carrying light loads, as it is a comparatively easy matter to guide them as desired. These yard tracks are laid upon timbers which are bedded in flush with the top of the ground. For the straight track they are 3 × 4 inches and secured, as shown, by cross pieces and through and through bolts ⅝ inch in diameter. For the curves 3 x 10 inch timbers are needed, and they are similarly fastened. In attaching the straight sections to each other the timbers are lapped and bolted as shown. On the curves, switches, and similar places, iron straps fastened by bolts or lag screws are used to connect them, as shown in the drawing.
In laying the track, the frogs and crossings of the switches should be first put in place and connected with the straight pieces of track, which may be easily cut to length on the power hack-saw. Such curves as are necessary to connect the switches to the straight track are then put down, care being taken to have the proper pieces of curved track to connect with the straight track so as to properly fit the groove in it. It will be necessary to have a gage by which to locate the second track, after the first line of rails has been put down and correctly lined up.
Another form of track is shown in Fig. 138, for the straight yard track. It has the advantage of having no groove where water, snow, or ice may find a lodgment and impair the usefulness of the system. This form of track may also be constructed for the curves, by placing it the proper distance apart to permit the wheels to run up on their largest diameter on the outside rail and their smallest diameter on the inside rail. Grooved track will be needed at the switches.
Fig. 134. Cross Section of Straight Track when Laid.
Fig. 135. Cross Section of Curved Track when Laid.
In fastening down these tracks heavy, flat-head wood screws are used for track having a groove, and lag screws for track constructed as shown in Fig. 138.
In Fig. 139 is shown another form of track for shop floors, letting the rails in flush with the top of the floor. The sides of the track are square with its lower surface, so as to have it fit up to the edges of the floor planks without cutting them to an angle. Curved track is similarly made, the groove being wider but the edges of the track vertical, as shown.
It will be noticed that all this track is of cast iron, as being a cheap and convenient material. Steel rails laid on ties may be used for the straight track if desired, and cast iron rails for the curves and the switches, but the expense will be considerably more, and the additional outlay is not necessary if light loads, say under two tons, are to be carried.
Fig. 140 shows a plan and cross-section of a turntable. It is composed of two castings; the lower one, or bedplate, being, for convenience, made of octagonal form, and having formed in it a proper recess for receiving the turntable proper, which is journaled or pivoted upon a center pin cast upon the bedplate. Two annular bearing surfaces are provided, in addition to the boss around the pivot pin. At the ends of the track grooves are formed suitable pockets for receiving the ends of the track and holding them in line with the turntable grooves. At one side is shown a simple and convenient latch, A, pivoted flush with the top of the bedplate in the projections, B. Four recesses are formed in the top of the turntable proper, into any one of which this latch may be dropped as desired. For heavy loads the annular bearing surfaces are sometimes provided with grooves and hardened steel balls introduced to eliminate a large percentage of the friction, but in this case the additional expense is hardly necessary, if the bearing surfaces are kept well slushed with a thick grease. It will be better to face up the bearing surfaces in a large lathe that they may be true and evenly bearing surfaces, but this may be omitted if castings can be had which are straight and true. Where these turntables are used in yards, holes should be left in the bedplate casting to permit the water to run through, and thus avoid as much as possible the danger of their freezing up. The bedplate should be supported by 3 x 5 inch timbers placed directly beneath the tracks in both directions, these being usually used in connection with tracks at right angles to each other.
Fig. 136. Cross Section of Straight Track.
Fig. 137. Cross Section of Track on Curves.
Fig. 138. Cross Section of Straight Yard Track.
Fig. 139. Cross Section of Straight Shop Track.
Fig. 140. Plan and Cross Section of Turntable.
It will be noticed that all of this track work is so simple and plain that the work of laying it may be done by any good carpenter; and that the effort is made to have all the arrangements of both track and cars of the most simple and inexpensive character consistent with utility and durability.