RAILWAY CONSTRUCTION. 69 



and backed up with earth. This suddenly checks the frame of 

 the waggon, and the body containing the excavated material 

 revolves on its trunnion, tilts up, and shoots out the material 

 well forward, so that the man in charge of the tip head, who 

 also knocks up the "tail-board catch," is able to level off the 

 filling without assistance. The empty waggon is then hauled 

 back, and turned into the siding BC, and another full waggon 

 taken forward and tipped, until all the waggons of the rake are 

 emptied. Ten waggons generally form a rake when the work is 

 pushed forward vigorously, each waggon holding about three 

 tons. The tip-head horse pulls the waggon by a trace-chain 

 having a spring catch at the end, by which the driver releases 

 the horse at the right moment. It is very important that this 

 spring catch should be kept in good order, because occasionally 

 too much impetus is given to a waggon, which, running over the 

 tip head down the slope, would drag the horse with it if the 

 spring catch did not act properly. Good firm foothold must be 

 provided for the tipping horse. 



The tip head should never be carried across culverts or 

 bridges until they have been well backed up, and protected by 

 a thick covering of earth or clay, wheeled in with barrows to an 

 equal height on each side of the masonry, so as to prevent 

 undue side pressure. 



Fig. 59 gives a sketch of one form of end-tipping waggon. 

 In some cases the wheels are made of cast-iron, but as these are 

 readily broken during the rough handling to which earth- 

 waggons are exposed, it is questionable whether the light 

 wrought-iron wheels, with light steel tyres, used on some works, 

 are not more economical in the long run. The framework and 

 body are made of strong undressed timber, well bound and 

 bolted together. The tail-board catch keeps the body of the 

 waggon in its proper horizontal position while loading or 

 running, but when released leaves the body free to tilt up, and 

 to revolve on the front trunnion by means of the circular clip A. 

 The same principle is also applied to side-tipping waggons 

 which are used for the widening of embankments, or formation 

 of platforms and loading-banks. 



The permanent way of these service roads is generally made 

 as simple as possible. A pair of movable rails are used instead 

 of switches, as shown in Fig. 60. These rails are linked together 

 by iron tie-rods, and pulled or pushed over into position for one 



