Synchromesh Mechanism

The synchromesh mechanism shown in the figure performs as follows:
As the synchromesh sleeve is moved into engagement with the dog teeth of the gearwheel for 2nd gear, for instance, the internal cone of the sleeve will first come into contact with the spring-loaded baulk ring which is in engagement with the dog teeth of the gearwheel. At its outermost position, the baulk ring can turn about half a tooth pitch in relation to the gearwheel. If 2nd gearwheel is running at a different speed from that of the output shaft at the instant when 2nd gear is to be engaged and the sleeve begins to move in the direction towards 2nd gear position, the sleeve will be restrained by the teeth on the baulk ring which will have turned in relation to the dog teeth on the gearwheel. The friction between the conical faces of the sleeve and baulk ring will ensure that the sleeve and gearwheel are running at the same speed. The torque on the baulk ring will then be reduced, so that dog teeth of the baulk ring and sleeve can be slid into engagement with the dog teeth of the gearwheel.





1. Synchromesh sleeve
2. Baulk ring
3. Spring
4. 1st speed gearwheel
5. 2nd speed gearwheel





The gearbox is equipped with a brake which ensures smoother engagement of reverse gear. The brake consists of a spring mounted on the selector rod. When reverse gear is selected, the spring applies slight pressure to the 1st / 2nd selector fork, thus braking the gears by means of the 1st synchromesh mechanism.