BRITISH CARS.

Greymouth Evening Star, 19 February 1937, Page 9

BRITISH CARS.

A TECHNICAL REVIEW. ■ On the surface the car engine is not. [much changed, but in detail work [many improvements have been includ- ■ cd, states the “-Autocar.’’ London, in la review of the British cars shown at I the Olympia Exhibition. Crankshafts jure even larger in size and are often i made of a special kind of east iron; (new roller bearing liners, and aluminjium, bronze or silver cadmium alloy ■ bearings are coming into use. ; Connecting rods are stiffer at the 'big end, and there is a general ten- | deucy to simplify the auxiliary drives, I usually in favour of employing a belt or belts. The situation regarding [valves remains much as it was—some i prefer side valves, other overhead, and a few the overhead camshaft, too. Hardened inserts are sometimes used for valve seats. High clearance, harmonic cams are widely in use. Gear boxes seem to have settled down to synchromesh types first, selfchanging second, and mixed varieties next. Silence is not always secured, but the lack of it is frequently due to the design of the case rather than to the gear cutting. Considerable improvements have been made in synchromesh mechanism, and on some a quick, resolute' change can be made without causing a noise, though on many a slow, gentle movement'of the lever is necessary. Epicyclic gears give the perfect change, but are heavy, and tend to become noisy, especially when idling, unless provided with an automatic clutch or fluid flywheel.

i SYNCHROMESH GEARS. ! The dry single-plate clutch with I cushioned centre nas become almost universal. Synchromesh gears give a good, simple solution to the inexpert driver’s difficulties and their arrival has probably caused a postponement of the development of automatic varI fable gears. There are very many of these in process of evolution. The overdrive, such as is fitted on many American cars, has not yet come into practice on British cars, although it may do so when -we get our overdue high-speed roads. It is, of course, an old notion revived in silent form. Free wheels are still popular with some motorists, though few 1937 cars are equipped with them as standard. Open propeller shafts are almost niversal. They are getting stronger, and needle roller bearings are normally used for the universal joints. These bearings are also finding a way into the gear box construction and other parts of the car. Steel rear axle cases of the banjo type are almost universal, as is the spiral bevel final drive. The worm final drive continues its hold, but the hypoid bevel has gained ground, partly due to the desire of designers to provide a low floor line. As regards lubrication of the car generally, the dipstick is the most usual method of measuring the contents of the engine oil sump. It is not popular with owners because it is a messy thing to use, the handle is often in a dirty position, and the stick itself has to be wiped and replaced before it is removed a second time and read. We could do with something better, for. the dipstick encourages neglect, and some people actually wait until the engine rattles before they replenish the oil. Dipsticks are now being provided for the gear box and for the axle oil level checking, for which purpose they are well suited. Chassis lubrication is now much simpified, and w’hat with oilless bushes and automatic lubrication systems there is much less work for the owner, or his garage service station, to do.

IMPROVED BRAKES. Considerable improvements have been made in braking, not only to secure increased efficiency, but also to obtain as good a result with a much lighter pedal pressure. There are vacuum-assisted brakes in use to-day which require no more pressure than the accelerator pedal, and which are sensitive and progressive in action. There has been a distinct change over to fully compensated brakes with easy adjustment, and with linkage in which friction and springiness are reduced to a minimum. Hydraulically operated brakes, wheih also have these virtues, continue to stand very high in general estimation, and have made headway. In detail brakes have benefited by the use of chromidium cast iron drums, and by a notable improvement in the efficiency and the more regular quality of brake linings. The near future may see the adoption of differential four wheel braking, that is. braking which uses a certain proportion of power between front and rear wheels under light application, but increases the proportion on the I rout wheels as the braking effort is. increased. If four wheel brakes are arranged so that 60 per cent of the effect is on the front, wheels and 40 per cent on the rear, a good brake is obtained, but the front shoes wear their linings out before those on the back wheels. With differential braking the normal effect may be 50-50. rising to 75 per cent, front and 25 per cent rear under emergency stopping conditions.

Hand brakes are now being tucked away more conveniently between the front seats, or even under the scuttle, so that, they do not impede entry into the driver’s seat from the right or left doer, mil some are not as efficient as they might be.