50-TON BUCKTON MACHINE. 57 



weight of beam, poise weight, and fittings. The two knife 

 edges, one of which (D) points upwards, and the other (B) 

 downwards, are so placed that when the beam is in its 

 normal position these two edges lie in a horizontal plane, 

 which also should contain the centre of gravity of the 

 beam and poise weight. 



The poise weight, marked C in the figure, weighs 1 ton, 

 and consists of two solid cast-iron discs joined by a con- 

 necting piece at the top, and it hangs, saddle fashion, over 

 the beam. It rests on the beam through four small wheels 

 or rollers, which traverse pathways on each side of the 

 beam. In this way the weight can be moved from end to 

 end of the beam. Its movement and position is controlled 

 by a screw running the whole length of the beam, and 

 rotated by gearing. The traversing of the weight can be 

 effected by the movement of a hand wheel, but in many 

 instances a belt connection is made, so that the weight can 

 be traversed by power by the simple movement of a lever. 

 This is especially useful for rapid testing, and is almost 

 indispensable for bringing the weight back to its zero 

 position when a test has been completed. 



When there is no pull on the specimen, and the beam 

 is perfectly balanced, the poise weight C is in the position 

 shown, to the left of the knife edges. It has been said 

 that the knife edges and the centre of gravity of the beam 

 lie in a horizontal plane. This position of the centre of 

 gravity can be adjusted by means of a small balance 

 weight, which is capable of being raised or lowered ; by 

 bringing the centre of gravity into the same horizontal 

 plane as the knife edges a condition of neutral equilibrium 

 is obtained, which is necessary for accurate testing. The 

 plan of having the poise weight at the negative end of the 

 steelyard, when the machine is in equilibrium, is quite a 

 distinctive feature of the Buckton single-lever machine. 

 In order to increase or measure the load upon a 

 specimen held in the clips it is only necessary to rotate 

 the hand wheel E either by hand or power, and so cause 

 the poise weight C to move upon its rollers towards the 

 right-hand end of the lever. This throws the whole system 

 out of balance, and causes a load to come upon the 

 specimen. As the poise weight is 1 ton, and the distance 

 between the knife edge B and the knife edge D, 3 in., for 

 every 3 in. traversed by the weight in moving along the 

 beam in the direction of the long end, an additional load 

 of 1 ton is put upon the specimen in the jaws. The extent 



