LOSS OF POWER

Timaru Herald, Volume CXXV, Issue 18617, 12 July 1930, Page 11

LOSS OF POWER

OIL LEVEL IN GEAR-BOX. Perhaps one of the most surprising things in connection with a loss of. power in a motor-car is due to the lubricant in the gear-box, the dominating factor being the level to which the gear-box is filled with oil. But viscosity of the oil,' of course, affects results considerably, but the level of the oil in the gear-box is far and awa: the main factor.

An investigation on this subject was recently carried out in England and the information obtained should not be without interest to the ordinary motorist. It was found that actual friction between the gear-wheel teeth was very small, and varied very little with changes in the nature of viscosity of the oil, and also to be practically unaffected by changes of speed. Another very curious result was that the power loss with an over-full gear-box was found to be greatest on the direct or top gear drive, in which, of course, the Josses due to friction are practically negligible. On the indirect gear ratios efficiency was reduced when the gear-box was over-full, but not to anything like the same extent as on the direct drive. A typical example was given showing that the loss of power on the direct drive was more than six times as great, w’hen an engine running at 100 r.p.m., when the gearbox was four-fifths full than when it

was one-fifth full. It was found that up to powers equivalent to an overload of 250 per cent, there were no signs of the lubrication being inadequate, and the box ran cooler than

when operated in the direct drive position at 1000 r.p.m., when four-fifths

full of oil. Actually the power loss in the first I case was .2 h.p., and in the latter case | 4i h.p. The most interesting discov- ! ery of all was perhaps amazingly high efficiency of the gear-box. When working under its full rated output on the indirect ratios, it gave an efficiency of 9T to 98 per cent., which,' it must be admitted, is an extraordinarily good result. The final conclusions are that an excess of lubricant or too viscous oil, cause excessive loss of power in the direct drive position, that adequate lubrication of the indirect gears is given by sufficient oil just to cover the teeth of at least one of each pair of mating wheels, and that an oil of moderately low,, viscosity gives satisfactory lubrication and minimises churning loss. It would appear from this that in the majority of cases the oil level in the gear-box is too high and is the cause of a considerable loss of power on top gear.