The Locomotive Of Today

100 The Engine : Valve S etting. riinning- is eventually done; this is usually less than half the full distance from the central position of the lever, and it is here that the motion should be most accurately adjusted. The wheels are slowly revolved by the apparatus described above and known as a “jigger,” it being particularly observed that they are turned the proper way—that is, forward when the lever is in fore gear, and backward when it is in back gear. The spindles are “ blacked ” by having soot from a torch lamp deposited upon them at those portions about to be marked by the trammel, to enable the marks to be easily cliscerned. As the extreme travel of the spindle is approached, the long end of the trammel is placed in the pop upon the cylinder or motion plate, and the shorter point is continually passed across and across the spindle, removing the lamp black, this process being continuecl until the spindle com- mences to return ; thus, the point of extreme travel beyond the point of cut-off may be taken from these indications by a small pair of dividers from the original small pop upon the valve spindle, and a plate is then marked with this distance. The wheels are turned until the other dead centre of the valve spindle is reached, and the point taken as before, and the two being marked upon the plate, the differ- ence can be measured, and the rod lengthened or shortened as required, it being usual to leave the rods a little short, about of an inch, to allow for the expansion of the spindles, etc., when heated, and also for the settling of the engine upon the springs, especially when the cylinders are inclined. After adjustment the rods are fitted up again and tried over, both in forward and backward gear, and any error that cannot be entirely eliminated is usually divided to reduce its effect as far as possible. The pistons and rods having been placed in position and the cylinder covers put on, the pistons are pushed to each end of the cylinder to get the extreme points to which the pistons can be forced, the slide bars being marked from the crossheads at these points. Then the connecting rods are put on and coupled up, and the wheels revolved to get the extreme points of travel, and thus ascertain the amount of clearance between the pistons and covers at each end of the cylinders. To obtain the dead centres a pair of compasses and a trammel are required, and a “pop” is made in the slide bar, in a convenient place, into which one leg of the compasses is placed, whilst with the other the crosshead is scribed, the wheels being stopped for this purpose when a point near the end of the stroke is reached. The trammel is next used to mark the tyre also at this point, one end of it being placed in a pop on