The driver operates the gearchange by the selection of the gear required on a quadrant similar to an auto box selector but marked...... R (reverse) N (neutral) 1 2 3 4
The basic idea is FIRST you move the gear lever to the next desired gear, and THEN when you wish to change you operate the pedal.
To start off from stationary first (second in some cases) is selected and the change gear pedal depressed. As soon as the change gear pedal has been released the next gear can be selected.
With the engine speed increased -
The centrifugal clutch bites by means of bob weights which fly out and cause pressure plates to close on twin clutch plates..
A fluid flywheel acheives this by the transfer of fluid to the outside or periphery of the flywheel.
http://en.wikipedia.org/wiki/Presele...x#Use_in_buses