The locking synchronisation has to produce synchronisation between the pre-meshing of the gear wheel and the sliding clutch. As long as this synchronisation is not achieved, it should close the sliding clutch to prevent the pre-meshing. This saves mechanical damage to the components and prevents ugly noises when changing gear.
Shown in the above animation are, on the left, the (running freely on the shaft) gear wheel with the pre-meshing and on the right the synchronizer linked with the shaft and the (blue) sliding clutch. At differing RPMs, the (red) synchronizer of the sliding clutch positions itself in the way, because with differing RPMs, it is offset by around half a tooth. It does not allow connection with the synchronizer if there is more than half a tooth of offset per rotary direction.
The stronger the driver now presses against the gearshift, the more the synchronising ring is pressed into the cone of the gear wheel. Both have, in this case, roughly the
function of an oil bath clutch. One can, by using more pressure, force synchronisation. However, the abrasion also increases between synchronising ring and the gear wheel cone, and with it excessive wear and tear. In any event, the driver is responsible for the premature wearing out of the synchronisation. Particularly unfavourable is downshifting too quickly.
Apart from the synchronisation shown here, there are various possibilities to generate friction between the synchronising ring and the gear wheel. To increase the service life of the friction pair, there can be, e.g., two or three friction surfaces inserted, one after the other. 08/15