Overdrive Gear

Poverty Bay Herald, Volume LXV, Issue 19803, 3 December 1938, Page 13

Overdrive Gear

[MOST motorists are by now familiar * with that excellent fitting founr on many cars to-day, the overdrive gear. Tests have shown that wher. it is engaged, fuel consumtpion is reduced by a gratifying margin, while the quieter running of the comparatively slowly revolving engine is distinctly pleasant to driver and passengers.

There is one small fault in the by easing the accelerator back at about 45 miles an hour, and it wiil stay in engagement until the speed drops to about 30 rn.p.h., when it automatically engages itself, and the normal ton gear ratio is resumed. There is one small foult in the overdrive. There are occasions when the car is hill-climbing with the overdrive in use, and the greater power of the normal ratio is required. That involves slowing down the car to 30 rn.p.h; or thereabouts, so that the overdrive will drop out of engagement. But that in turn often means a read soeed so low that the engine canot pick up its revolutions again* and the gar either struggles to the top or a change' 1 to second has to be - made; " If it were nosible to disengage the overdrive at any speed, that troubl'd' \oould not arise. The manufacturers of one of the best-known overdrive gears, according to an American report, have recentlv modified the design so that by pressing the accelerator pedal a little beyond the full throttle position the overdrive can be disengaged. This is quite a good arrangement, because any driver wishing to change down to normal ton would already have the throttle wide open. It is unlikely that he would want to resume the normal drive when cruising with a small throttle nooning on love’ country unless he suddenly required better acceleration, when again the downward movement of the accelerator is a nerfectlv natural one.

The mechanism, which has been devised to obtain the desired result is a simple arrangement of an elec-tric-solenoid, and the extra pressure off the accelerator closes the operating switch.