CARS AND SHOCK

Hawke's Bay Tribune, Volume XXV, Issue 79, 16 March 1935, Page 13

CARS AND SHOCK

Powers of Resistance One of the essential features of a j motor ear component must be its re- ' sistance to shock. This is especially the case in regard to items such as 1 steering knuckles and axle beams, which bear the brunt of the often ' violent shocks transmitted by road i surface irregularities. It is interest- j mg to note, therefore, that the Morris ■ organisation manufactures such com- I ponents from special steel, heat-treat- I ed to give the greatest possible resistance to these repeated blows. Each consignment of imported com- [ ponents is carefully checked tor resistance to impact (in addition to I other tests) by means of the Izod Test, j A sample is taken, cut into a convent- ' ent length, and machined to a defin- . its diameter A standard V” shape no*?h is then made at a pre-detrrm-J

ined distance from one end, and the test piece is ready for breaking in the Izod machine. The actual test is very simple. The specimen is fixed in a vice in the base of the machine, and the pendulum of standard weight is allowed to fall a definite distance, the shaft on which the pendulum is pivoted being directly over the test piece. The work done by the pendulum in breaking the test piece is recorded on a scale. It there were no specimen in the vice, the pendulum would swing through the same arc beyond the centre of gravity that it has fallen; if it is impeded in any way, work is absorbed and the pendulum will swing through a smaller arc due to energy absorbed. Therefore, the decrease in the arc described after breaking the test piece is a measure of the impact I resistance

One of the best means of tracking j down a persistent squeak or rattle is ! to take the car to the top of a long lull and allow it to freewheel down with the engine switched off. Without mechanical noises, it is much easier to Eaten, attentively, and in th’- way it is usually possible io ascertain roughly in what part of the car the trouble lies. _ i