How Transmission or Motorcycle Transmission works

What is the use of gearning?

The transmission or gearbox of a vehicle allows us to modify the rotation ratio between the engine crankshaft and the rear wheel. This relationship has the name of "ratio" and, to understand it in a simple way, it works in the same way as the change of a bicycle with marches: with the small dish and the large pinion we obtain a lot of strength (torque) but little speed, what That allows us to climb slopes with little effort and, in the same way, with a large dish and a small pinion we get more speed for each pedal turn, but we must exert more effort to accelerate.

Pandora's box

The gearbox allows us, therefore, to adapt the force of the motor (torque) and its speed (RPM) to the different conduction conditions, modifying the change ratio, thus retaining the power.

In large displacement motorcycles, the most used change is the mechanical change of constant taking (sequential constant mesh gearbox). Its activation is manual, generally with the foot and is sequential because to go up or go down the intermediates (1-N-2-3-4-5-6) must always go through intermediates.

Although it is one of the devices with the greatest mechanical complexity of the motorcycle, we will try to explain its operation in a very simple and simplified way.

Everything is reduced to two axes

The gearbox consists of 2 axes: the primary axis, which receives the movement of the engine crankshaft through the clutch, and the secondary, which receives the movement of the primary axis and transmits it to the rear wheel, through the Correa or secondary chain.

Both axes have gears (marches) that go from higher to lower size (such as bicycle pine nuts) and constantly faced and engaged between them (hence their constant or constant -tap name.

The trick is that only some of these gears rotate solidarity with each axis, the others are "loose" that is, they do not turn, although the axis does. These gears have the peculiarity that they can slide laterally on the axis and in doing so they fit some outgoing with free gears, forcing them to turn with them (and with the axis).

Changing march

When the change is in neutral, the primary axis rotates, but since there are no connected gears on the secondary axis, it does not rotate. When introducing the first speed, what happens is that the “C” gear moves towards the “B” gear, inserting in it. As the “B” gear is constantly moved by the “A” gear, this movement is transmitted to the secondary axis, moving the chain and the wheel.

In another similar example, if we introduce the second speed, the “C” gear returns to its initial position and at the same time the “Z” gear moves and fits with the “Y” gear. As this gear is constantly moved by the “X” gear, the motor movement passes from the primary axis to the “X” gear, then to the “y” connected to the “Z”, which transmits it to the secondary axis and the wheel.

It is important that you remember that all blue gears rotate free, without contact with the axis, and red gears move laterally, but are constantly united with the axis.

The drum marks the rhythm

The gear displacement movement is done through the change drum, which has channels through which the tetones of the exchange forks move, which in turn move the red gears.

The change drum revolves through a “carraca” mechanism driven by the change lever, moved by our foot. The drum has a star -shaped machining so that the marches remain in place helped by a dock. In this star there is a specific cleft for the dead point.

Frank Burguera

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