The sleepers of straight sections are screwed down to 3/4 by 1/4 inch longitudinals, which help to keep the track straight and prevent the sleepers slipping. Sections should be of the same length and be interchangeable. Make straight sections of the greatest convenient length, to reduce the number of junctions. Sleepers need not be less than 6 inches apart. Fix the sleepers on the longitudinals before hammering the rails into the slots.
A simple method of laying out a semi-circular curve is shown in Fig. 44. Sleepers and longitudinals are replaced by 1/2-inch boards, 8 inches wide. Three pieces, about 32 inches long each, have their ends bevelled off at an angle of 60 degrees, and are laid with their ends touching. Two semi-circles of 24 and 22 inch radius are drawn on the boards to indicate the positions of the rails, and short decapitated brass nails are driven in on each side of a rail, about an inch apart, as it is laid along one of these lines. (See Fig. 44. A.) The inside nails must not project sufficiently to catch the wheel flanges. The spring of the brass will prevent the rail falling out of place, but to make sure, it should be tied in with wire at a few points. The centre rail should on the curves also be 3/8 inch deep, and raised slightly above the bed so as to project above the wheel rails. The method already described of bonding at joints will serve equally well on curves. If the outer rail is super-elevated slightly, there will be less tendency for the rolling stock to jump the track when rounding the curve.
When the rails are in place the boards may be cut with a pad-saw to curves corresponding with the breadth of the track on the straight. If the boards incline to warp, screw some pieces of 1/8-inch strip iron to the under side across the grain, sinking the iron in flush with the wood.
Fig. 42. Details of rails for electric track.
The brass strip for the rails costs about one penny per foot run. Iron strip is much cheaper, but if it rusts, as it is very likely to do, the contact places will need constant brightening.
Fig. 45 shows the manner of laying out a set of points, and connecting up the rails. The outside wheel rails, it will be seen, are continuous, and switching is effected by altering the position of the moving tongues, pivoted at PP, by means of the rod R, which passes through a hole in the continuous rail to a lever or motor of the same reversible type as is used for the locomotive. If a motor is employed, R should be joined to a crank pin on the large driven cog--corresponding to that affixed to the driving wheel (Fig. 47)--by a short rod. The pin is situated at such a distance from the axle of the cog wheel that a quarter of a revolution suffices to move the points over. The points motor must, of course, have its separate connections with the "central station." To show how the points lie, the rod R also operates a semaphore with a double arm (Fig. 46), one end of which is depressed--indicating that the track on that side is open--when the other is horizontal, indicating "blocked." The arms point across the track.
The tongues must be bevelled off to a point on the sides respectively nearest to the continuous rails. The parts AA are bent out at the ends to make guides, which, in combination with the safety rails, will prevent the wheels jumping the track. Care should be taken to insulate centre rail connecting wires where they pass through or under the wheel rails.
It is advisable to lay out a set of points, together with motor and signals, on a separate board.
Fig. 43. Tin chair for centre rail of electric track.
All the wooden parts of an outdoor track should be well creosoted before use.
Fig. 44. Laying out a curve for electric track.
Fig. 45. Points for electric railway.
Fig. 46. Double-armed signal, operated by points.