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Abstract
A catapult made from thick monofilament can stretch textile-denier filaments at speeds between lOm/sec 150m/sec. The rate of extension can be measured photographically and is found to be uniform, controllable, and reproducible. The catapult is stretched by means of weights between a fixed point and a pulley several metres away. The catapult can be of nylon and of breaking strength about 2 kg. The specimen to be extended is much weaker than the catapult and is only a few centimetres long. It is tied between a point on the catapult near the fixing point, and the fixing point itself. When the catapult is cut between these points, the free end of the catapult moves off at high speed, dragging one end of the specimen with it.
The speed of the catapult tip is found to depend directly on its tension before release, and the conditions can be chosen so that the speed is uniform over a useful distance. The uniform high speed is attained very rapidly: the tip moves at full speed after travelling only a millimetre.
Polypropylene, polyethylene terephthalate, nylon, rubber, and metal wire have been examined as catapult materials, and the textile polymers arc most useful.