SHOCKS FROM WAGONS

Evening Post, Volume CVII, Issue 67, 22 March 1929, Page 19

SHOCKS FROM WAGONS

HOUGH EARTH BY CHAIN

Ono of the unexpected problems which confronted operators of motor vehicles of the heavier type, especially those engaged in the transport, oi' inflammable commodities, was tin: generation and storage within ("lie metal parts of the vehicles of appreciable quantities of electricity. This problem was a serious one for the petrol companies when the bulk distribution of that volatile spirit was commenced, as it was found that the current was frequently discharged in the form of sparks, which caused danger of lire, and the possible combustion of perhaps 000 gallons of petrol in a busy street with appalling consequences became a distinct menace. In the case of vehicles with steel wheels and tires, a safety valve was automatically provided as the current was permitted to return to earth immediately. A rubber-tired vehicle, however, was insulated from this menus of discharge, and became a gigantic storage battery, in which an increasing amount of current was stored until at last it found some outlet. To provide thia outlet, it has become the practice to attach a short length of steel chain to the chassis, one end being permitted to trail on the ground, and by this rough earth connection the dangerous current is discharged.

This matter of electricity in motor wagons appears first to have been brought under notice in England when rubber tires were adopted on steam propelled vehicles. The driver or! one complained on several occasions to the firm which employed him that he had received an electric shock when mounting to his seat. His complaints were not treated seriously until one day the manager of the company tried to get into the driver's seat while the vehicle was stationary, but received a shock which sent him staggering backwards. Con-

vinced that the driver was not suffering from hallucinations by this rough demonstration, the manager set inquiries on foot, and it was established that in the case of steam vehicles the rushing of the steam past the safety valves or through the steam passages had the same effect as that of rubbing sealing wax or amber on silk, and that the storage of electricity followed as a matter of course. Naturally the state of the weather has an influence on this phenomenon. Tho tendency to generate ■electricity is strongest on bright dry days; should the rubber tires be wet they do not insulate the vehicle as perfectly as when dry.