GEAR BOX OIL

Hawera Star, Volume L, 21 February 1931, Page 12

GEAR BOX OIL

Perhaps one of the most surprising things m connection with a loss of power in an automobile is due to the lubricant in the gearbox; the dominating factor being the level to which the gearbox is filled with oil. The viscosity of the oil, of course, affects results considerably, but the level of the oil in the gearbox is far and away 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 the actual friction between the gear wheel teeth was very small, and to vary 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 gearbox was found to be greatest on the direct or top gear drive, in which, of course, the losses 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 (with the engine running at 100!) r.p.m.) when the gear-box 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 case was 2 li.p. and in the latter case 4J h.p. The most amazing discovery of all perhaps was the amazingly high efficiency of the gear-box. When working under its full rated output on the indirect gear ratios, it gave an efficiency of 97 to 98 per cent., which,

it must be admitted, is an extraordinarily good result. The final conclusions are that an excess of, or too viscous a, lubricant causes excessive loss of power in the direct drive position; the adequate lubrication of the indirect gears is given by sufficient oil just to cover the teeth of at least one of each P aia of matmg w’heeis; and that an oh of moderately low viscosity gives satisfactorv lubrication and minimises churning loss. It would appear from this that iu the majority of cases the oil level in the gearbox is too high and is the cause of a considerable loss of power on top gear.