Lucas apparatus

The force measuring head, together with provision for applying the extra compression. can be a beam balance, as used in the well-known Lucas apparatu.s. a universal tensile machine, or a specially designed electronic load cell unit [4]. The point at which the small amount of extra compression has been applied can be detected by breaking an electrical circuit. An early apparatus used a load cell attached to an arbor pre,ss. The operator manually lowered the pre.ss until the break in the electrical circuit was indicated visually by the extinction of a light. The Lucas apparatus has a similar detection system the balance weights are adjusted manually until the force exerted by the beam just overcomes the force exerted by the test piece. Both of these approaches involve a somewhat... 

Apparatus, such as that developed at RAPRA13, has been designed to reduce as far as possible operator dependence. A load cell is driven onto the jig by a pneumatic ram at the moment when a very small additional compression on the test piece is detected electrically, the ram is automatically stopped, the force reading digitally recorded and the ram reversed. The Rapra measuring head can be used with a variety of jig designs including Lucas. 

KR1 Kramer-Lucas, H., Sehenek, H., and Wolf, B.A., Influenee of shear on the demixing of polymer solutions. 1. Apparatus and experimental results, Ma ro io/. Chem., 189, 1613, 1988. 

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