SYNCROMESH GEAR.

Ellesmere Guardian, Volume LVI, Issue 80, 22 October 1935, Page 2

SYNCROMESH GEAR.

TYPES IN CARS AND MOTOR CYCLES.

Motor cyclists rather brag" about the fact that they have had constant mesh gearboxes for years, and that it is only recently that car drivers have been able to experience this joy. In a sense the motor cyclist is right, although there is a difference between constant mesh and synchromesh. In the former type all the gears I are constantly in mesh and changing is made easy by a comparatively small clutch compared with the car clutch, which takes some little time to "slow down."

Several kinds of synchromesh are in use-on cars to-day, but the general principle of the system is that small cones are brought into frictional contact before the teeth of a dog clutch are engaged. Those parts which might otherwise clash are thereby brought to synchronised speeds before direct engagement. The control is the same, but instead of double declutching it is actually better to move the level firmly through from one position to another with just a normal declutch.

In some gearboxes a positive check is included that prevents the gear teeth from meshing until the cones have fully completed their work of lining up the teeth. With others this is omitted, so that too forcible a use of the gear lever may result in a clash. With this type a slight delay in the shift is advisable. Some cars apply synchromesh to the two top gears of a four-speed gearbox. As these are the most used gears, the absence of the synchro system for the two lower gears is not so much missed. Other cars use I the system for all gears. j The exact operation of synchro box! |is as follows:—Having declutched in j the normal manner, the driver moves [the levers from top toward second.. As a result of this, a sleeve is moved rearward, carrying with it a slider (splined to the mainshaft of the box) in which an internal cone is formed. This cone makes contact with an external cone situated on the second gear. The latter rides freely on the mainshaft and is, of course, turning at a lower speed. The action of the two cones described is to synchronise the speeds of the gear and the shaft, which means that there is no clash on engagement as the speeds are "lined jup" correctly. After the speeds have | been synchronised the movement of the gear lever shifts the sleeve along until the cogs engage, connecting the gear to the shaft. The inner slide is left behind, but by now all is well and the gear is correctly home, and although the entire operation sounds complicated and to the layman undoubtedly is, it takes no time and cannot go wrong.

Motor cyclists can no longer brag about their gearboxes, for now any owner of a modern car can whip his gears through and so enjoy those swift changes he has admired in the past. Synchromesh is quite different from self-changing, pre - selectors, clutchless changes, and other modern developments, but it is perhaps the; most widely used type of box on modern cars. f