what is the purpose of load-pacing gear? describe one form of the load pacing gear and explain the principle of its operation ?

equipment built into the same valve body is used for long- and and for removing loads. period holding and for load cycling. Load-Pacing When testing non-metallic materials, it is often necessary to apply the load at a predetermined rate. permit the rate of application of the load to be adjusted within close limits. However, some indication that the load is being applied at the Gear The normal controls of the machine correct rate is deirable. This is done by an indicating accessory known as 'load-pacing gear', fitted to the machine illustrated in Fig 4.1. Concentric with the chart there is a disc with a dotted pattern (as shown in Fig 4.3) on the inside of the third ring of graduations. This disc is driven by motor-operated driving gear which is capable of rotating it in either direction at an infinitely variable speed. of the disc is adjustable by means of a control knob, s in Fig 4.1, The speed of rotation giving a range of 1 to 25 minutes for one chart sweep; this is indicated on a graduated scale immediately above the knob. To carry out a test at a specified loading rate, the required rate is divided by the chart range in use, and the resulting figure is set on the The pacing-gear switcht pacing-speed indicator by rotating knob s. is then switched on, causing the pacing disc to rotate. the load is applied at the required rate, the load pointer is set (by manual adjustment of the loading control valve o) to move at the same To ensure that speed as one of the dots on the pacing disc. Sometimes, a means of automatically controlling the load without the operator's constant attention is desirable. Automatic Another indicating Load Control