Dunlop pendulum

Figure 9-6. Rebound resilience apparatus, (a) Lupke pendulum (b) Schob pendulum (c) Dunlop pendulum (d) Goodyear-Healey pendulum (e) tripsometer (m = off-centre mass) (f)...

The British standard, BS 903 Part A89, is not identical because it also specifies the Dunlop tripsometer. A previous version additionally included the Dunlop pendulum which is a compound pendulum shaped to ensure high rigidity, attached by a spindle and ball races to a massive structure. The indentor is 2.5 cm diameter and the test piece a 50 mm square block 25 mm thick. The ISO method is included, but in different format, as Method B and two appendices. 

The Dunlop tripsometer is an unusual design of pendulum consisting of a 42 cm diameter steel disc mounted on bearings and with an out of balance mass in the form of a bracket carrying the 4 mm diameter indentor attached to its periphery. It operates at considerably higher strain energy density than the ISO method but is claimed to have high accuracy and can be used with a relatively small test piece. Compared to the Lupke pendulum, it is also a very compact apparatus. 

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