Ijaw Dictionary Online

How Automobiles Work


In motorcycles, the torque and rpm of a
wheel is controlled by manually shifting gear levers up or down with our left
foot. Motorcycle gear box comprises of a series of different gear steps which can
be switched according to the requirement. The gear lever is connected to a shifter
shaft, and the other end of the shifter shaft is connected to a ratchet
mechanism. This ratchet mechanism activates as shown in the animation. The
purpose of this ratchet mechanism is to rotate the shifting drum at specific
angles. The shifting drum has special shaped channels cut into it. Special
attachments known as shifting forks fit into these channels. Gears known as gear
dogs or dog clutches fit into these shifting forks. As the shifting drum
rotates, the shifting fork along with gear dogs slides sideways as shown in
the animation. The purpose of sliding dog clutches will be explained shortly. First
let’s understand the arrangement of different gears in gearbox. There’s an
input shaft and an output shaft. The gears are arranged with their axes
aligned to their respective shafts. Some gears are internally splined.
These splines perfectly mesh with external splines of their respective
shafts. These splines allow gears to slide from side to side while
maintaining the same angular speed as the shaft. All gears which are shown here
in red color are splined. Some gears are freewheeling gears. These gears can freely spin about their axes but cannot slide sideways along the
shaft. gears shown in blue color are
freewheeling gears. The remaining gear is a static gear which is attached to the
input shaft. Let’s number all these gears from one to five for better
visualization. Please note that all freewheeling gears
adjacent to dog clutches have recesses. The dog teeth can slide into these
recesses and lock these two gears with each other. Now let’s see how power is
transferred with different gear ratios in a gear box. One thing you can observe
here is that every splined gear is meshed with a freewheeling gear. In this
condition, if we spin the input shaft, no power has transferred to the output
shaft. This is the neutral position of the motorcycle. To change into first gear, the gear dog
number five in the output side slides toward the freewheeling gear number one
and locks with it. Since the gear number five is splined the output shaft will
now spin with this gear. This is the first gear. When we change to second gear the gear dog number five in output shaft returns to neutral position and gear dog
number four slides toward number two gear and locks with it. The technique is
similar when we shift to third gear. The fourth gear. And the fifth gear. Please
note here that before shifting from one gear to the other the previously locked
gear dog returns to neutral position first, only then it slides into another
recess to achieve power transmission. This is why there is a neutral
in-between every successive gear. But in real life, we find the neutral
position only in between first and second gears. To understand how this
happens, let’s go back to our ratchet mechanism. A star shift detent mechanism
is responsible for proper shifting of gears. As we can see the star plate has
ridges and valleys. A spring biased roller rolls on to these ridges and
valleys. The position of the roller at each Ridge of the star corresponds to
neutral condition. As we can visualize, the roller cannot rest on the ridges of
the star and immediately disposes to the appropriate valley, preventing the
shifting drum to stop at neutral position. But one of the ridges of this
plate is ground off as we can see here. This is done in between first and second
gears so that the roller can briefly rest on this ground off surface, thus
enabling the shifter drum to stop at neutral position instead of shifting
directly to second gear. The transmission system we showed here
is known as constant mesh transmission system because all gears remain engaged
with each corresponding gear mates at all times. In conventional sliding mesh
transmission, gear shifting is done by completely disengaging a gear with one
year and re-engaging it with another. It involves complex mechanisms and drivers
need tremendous skill to operate them. In addition, imperfect meshing causes
gear teeth to grind and wear. The constant mesh transmission completely
eliminates this problem. As you might have noticed that some gears
are only partially engaged sometimes. But this is not a problem because they are
not transmitting power at this moment. Only those gears which are transmitting
power need to be fully engaged at that instant We hope you learned something today.
Thanks for watching.

9 thoughts on “How a motorcycle transmission works (Animation)

  1. Motorcycle is one of the best transport in all over country i loved it engine of motorcycle i had bazaz which was good but now i sold it

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