Lucas jigs

The Lucas jigs use a ball contact to make and break the electrical circuit which is very effective but, as they have no lateral constraint, are prone to tilting and, hence, can only be used with rings having a large diameter to height ratio. 

One apparatus developed at RAPRA [5) reduc-es operator dependence as far as possible. A load cell is driven onto the jig by a pneumatic ram at the moment when a very small additional compres.sion on the test piece is detected electrically, the ram is automatically stopped, the force reading digitally recorded and the ram reversed. This measuring head can be used with a variety of jig designs including Lucas jigs. 

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