6.1 The machine shall be of the pendulum type shown schematically in Fig. 1 and Fig. 2.
The base and suspending frame shall be of sufficiently rigid and massive construction to prevent or minimize energy losses to or through the base and frame.
The position of the pendulum holding and releasing mechanism shall be such that the vertical height of fall of the striker shall be 610 6 2 mm (24.0 6 0.1 in.).
This will produce a velocity of the striker at the moment of impact of approximately 3.5 m (11.4 ft)/second. The mechanism shall be so constructed and operated that it will release the pendulum without imparting additional acceleration or vibration.