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Some technologies are easier to understand
with the help of 3D animation.

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But, what about the 6-Speed 
automatic transmission from Allison.

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To visualize and understand this beautiful
planetary gear set mechanism,

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a 2D animation will be ideal.

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You can consider this 2D drawing as 
a cross section of the 3D model.

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A planetary gear set has 
2 inputs and 1 output.

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If you properly understand 
working of a planetary gear set,

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you can easily understand automatic 
transmissions from the 2D animation.

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The essence of the planetary gear set is that

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just by giving different speeds 
to the ring and sun gears,

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you will be able to get different
speeds at the output.

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The beauty of automatic transmissions lies

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in how these different input 
speeds are transmitted.

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Let's see it in the 2D animation.

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This 3D planetary set 
is represented in 2D as shown.

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In an automatic transmission,

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the input and the output are 
not directly connected.

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They are connected through 
an intermediate shaft as shown.

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Now, a small suggestion before you proceed.

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You will be able to explain 
all seven gears by yourself

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by pausing the video for a moment 
and understanding the mechanism.

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Please try that at every single gear.

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You will be amazed by 
the brilliance of this mechanism.

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If you press clutch C1,

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the input will be connected to the sun gear.

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If you press clutch C5, the output 
ring gear will be stationary.

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This will result in the first gear.

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Now let's add one more gear set.

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Here comes the tricky part.

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The carrier of this set is connected 
to the ring gear of the first set.

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This simply means that

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the output of the second set is 
connected to the input of the first set.

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Think for a moment about what happens
when you apply C1 and C4.

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Since C4 is applied, the ring gear of
the second set will be stationary.

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This makes the carrier turn.

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This carrier is connected to 
the ring gear of the first set.

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So, the ring gear of 
the first set will also turn.

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This, in turn, will increase 
the output speed

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or we will get the second gear.

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To obtain a fourth gear or direct drive,
a rotating clutch module is also used.

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We know that for a direct drive,

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both the sun and the ring gear
should rotate at the input speed.

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If we press C2 and C1 together,
this is what happens.

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In the very same mechanism,

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if you apply C2 and C4 you will 
get very high speed at the output.

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Think for a moment and
try to understand this.

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It is clear that the carrier of the second
set will turn at the input speed.

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However, here the ring gear is stationary.

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This makes the sun gear turn at almost 
three times the speed of the input.

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Eventually,

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a very high output speed is obtained.

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One more gear set is used to obtain 
the remaining gear ratios.

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However, the sun gear of this set 
is not connected to the shaft.

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Instead, it is connected to 
the rotating clutch module.

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So, this sun gear will always turn 
at the input speed.

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And here again,

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the output of the set is connected
to the input of the adjacent set.

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For the remaining gear ratios,
C3 is always applied.

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This means that the brown carrier
or ring gear of the second set

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will turn at one-third of the input speed
for the remaining cases.

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For the third gear, apply C1 as well.

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For the fifth gear, 
apply C2 along with C3.

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The reverse is an interesting mechanism.

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Here, C5 is applied along with C3.

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So here, the carrier of
the second set is stationary.

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This means that the planet gears of
this set will not be able to revolve

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and that they will simply spin.

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This spin is in the same 
direction as the input.

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This planetary spin will make

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the corresponding sun gear spin
in the opposite direction.

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As a result, the output sun gear will
also turn in the opposite direction

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and we will get the the reverse gear.

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We hope that you enjoyed the brilliance
of the Allison transmission mechanism.

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