[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.41,0:00:01.73,Default,,0000,0000,0000,,The planetary gear set,
Dialogue: 0,0:00:01.73,0:00:02.72,Default,,0000,0000,0000,,also known as,
Dialogue: 0,0:00:02.72,0:00:04.26,Default,,0000,0000,0000,,the epicyclic gear train
Dialogue: 0,0:00:04.26,0:00:05.35,Default,,0000,0000,0000,,is one of the most
Dialogue: 0,0:00:05.35,0:00:06.41,Default,,0000,0000,0000,,important and interesting
Dialogue: 0,0:00:06.41,0:00:07.95,Default,,0000,0000,0000,,inventions in engineering.
Dialogue: 0,0:00:08.51,0:00:09.49,Default,,0000,0000,0000,,They are great speed \N
Dialogue: 0,0:00:09.49,0:00:10.81,Default,,0000,0000,0000,,variation mechanisms
Dialogue: 0,0:00:10.81,0:00:11.78,Default,,0000,0000,0000,,and are often used in
Dialogue: 0,0:00:11.78,0:00:13.81,Default,,0000,0000,0000,,automobiles as a vital part of
Dialogue: 0,0:00:13.81,0:00:15.23,Default,,0000,0000,0000,,automatic transmissions.
Dialogue: 0,0:00:18.58,0:00:19.97,Default,,0000,0000,0000,,Let's explore the secrets
Dialogue: 0,0:00:19.97,0:00:21.25,Default,,0000,0000,0000,,of the planetary gear set
Dialogue: 0,0:00:21.25,0:00:22.71,Default,,0000,0000,0000,,in this video.
Dialogue: 0,0:00:24.69,0:00:26.04,Default,,0000,0000,0000,,A planetary gear set
Dialogue: 0,0:00:26.04,0:00:27.64,Default,,0000,0000,0000,,has four main parts:
Dialogue: 0,0:00:28.30,0:00:29.87,Default,,0000,0000,0000,,the sun,
Dialogue: 0,0:00:30.60,0:00:32.09,Default,,0000,0000,0000,,planet gears,
Dialogue: 0,0:00:33.03,0:00:34.37,Default,,0000,0000,0000,,ring gear,
Dialogue: 0,0:00:35.75,0:00:36.79,Default,,0000,0000,0000,,and carrier.
Dialogue: 0,0:00:37.42,0:00:38.46,Default,,0000,0000,0000,,You can see
Dialogue: 0,0:00:38.46,0:00:41.19,Default,,0000,0000,0000,,that it sometimes rotates quickly,
Dialogue: 0,0:00:41.87,0:00:43.26,Default,,0000,0000,0000,,sometimes slowly,
Dialogue: 0,0:00:46.21,0:00:47.28,Default,,0000,0000,0000,,and sometimes
Dialogue: 0,0:00:47.28,0:00:48.87,Default,,0000,0000,0000,,even in reverse.
Dialogue: 0,0:00:50.20,0:00:52.56,Default,,0000,0000,0000,,But, how does this happen?
Dialogue: 0,0:00:52.56,0:00:53.47,Default,,0000,0000,0000,,You will be able
Dialogue: 0,0:00:53.47,0:00:54.46,Default,,0000,0000,0000,,to predict the motion\N
Dialogue: 0,0:00:54.46,0:00:55.73,Default,,0000,0000,0000,,of this gear set completely,
Dialogue: 0,0:00:55.73,0:00:56.75,Default,,0000,0000,0000,,if you understand
Dialogue: 0,0:00:56.75,0:00:58.54,Default,,0000,0000,0000,,one simple fact!
Dialogue: 0,0:00:59.37,0:01:01.52,Default,,0000,0000,0000,,When two gears are moving as shown
Dialogue: 0,0:01:01.52,0:01:02.36,Default,,0000,0000,0000,,they should have
Dialogue: 0,0:01:02.36,0:01:05.19,Default,,0000,0000,0000,,the same speed at the interface.
Dialogue: 0,0:01:05.19,0:01:07.44,Default,,0000,0000,0000,,This means that the speed of gear A
Dialogue: 0,0:01:07.44,0:01:09.32,Default,,0000,0000,0000,,should be the same as gear B\N
Dialogue: 0,0:01:09.32,0:01:11.52,Default,,0000,0000,0000,,at their mating point.
Dialogue: 0,0:01:17.18,0:01:19.61,Default,,0000,0000,0000,,The speed has to be the same
Dialogue: 0,0:01:19.61,0:01:20.61,Default,,0000,0000,0000,,otherwise...
Dialogue: 0,0:01:20.61,0:01:21.61,Default,,0000,0000,0000,,the gear teeth will penetrate
Dialogue: 0,0:01:21.61,0:01:22.99,Default,,0000,0000,0000,,each other as shown.
Dialogue: 0,0:01:22.99,0:01:25.81,Default,,0000,0000,0000,,That is an impossible condition.
Dialogue: 0,0:01:27.02,0:01:28.12,Default,,0000,0000,0000,,Just apply this fact
Dialogue: 0,0:01:28.12,0:01:29.63,Default,,0000,0000,0000,,to planetary gear sets,
Dialogue: 0,0:01:29.63,0:01:31.27,Default,,0000,0000,0000,,and you will be able to predict
Dialogue: 0,0:01:31.27,0:01:33.45,Default,,0000,0000,0000,,how speed variation is achieved.
Dialogue: 0,0:01:36.03,0:01:37.49,Default,,0000,0000,0000,,Assume that the ring gear
Dialogue: 0,0:01:37.49,0:01:41.04,Default,,0000,0000,0000,,is held stationary
Dialogue: 0,0:01:41.17,0:01:44.13,Default,,0000,0000,0000,,and we rotate the sun gear.
Dialogue: 0,0:01:44.13,0:01:46.74,Default,,0000,0000,0000,,Think of what happens to the planet gears:
Dialogue: 0,0:01:48.44,0:01:51.75,Default,,0000,0000,0000,,At point A the planet gear should\Nhave a certain speed
Dialogue: 0,0:01:51.75,0:01:56.56,Default,,0000,0000,0000,,and at point B the speed should be \Nzero as the ring gear is stationary.
Dialogue: 0,0:01:57.16,0:02:01.16,Default,,0000,0000,0000,,However, how are both of these conditions\Npossible at the same time?
Dialogue: 0,0:02:01.96,0:02:07.16,Default,,0000,0000,0000,,There is only one way the planet gear should spin as well as turn
Dialogue: 0,0:02:07.77,0:02:13.60,Default,,0000,0000,0000,,The spinning will produce velocities in opposite [directions] at the top and bottom points as shown
Dialogue: 0,0:02:13.94,0:02:17.70,Default,,0000,0000,0000,,Whereas the turning Produces unidirectional velocities
Dialogue: 0,0:02:19.07,0:02:26.14,Default,,0000,0000,0000,,at the top the spinning and turning velocities are in opposite directions, so the velocity [of] point B is zero.
Dialogue: 0,0:02:26.82,0:02:29.23,Default,,0000,0000,0000,,at The bottom they get added up
Dialogue: 0,0:02:30.08,0:02:36.38,Default,,0000,0000,0000,,in short the Planet gears are forced to turn in order to satisfy the condition of velocity.
Dialogue: 0,0:02:36.54,0:02:41.81,Default,,0000,0000,0000,,as The carrier is attached to the planet gear it will turn along with the planet Gears
Dialogue: 0,0:02:42.82,0:02:48.37,Default,,0000,0000,0000,,Now let's see what happens when the sun gear is held stationary and the ring gear is rotated
Dialogue: 0,0:02:50.40,0:02:55.64,Default,,0000,0000,0000,,This is the exact opposite to the previous case at the inner point of the planet gear
Dialogue: 0,0:02:55.64,0:03:01.04,Default,,0000,0000,0000,,the Velocity should be zero and the outer points should have the speed of the ring gear.
Dialogue: 0,0:03:01.04,0:03:06.70,Default,,0000,0000,0000,,in This case the planetary Spin will reverse in order to satisfy the speed conditions
Dialogue: 0,0:03:08.100,0:03:11.74,Default,,0000,0000,0000,,However this case has one more difference
Dialogue: 0,0:03:12.29,0:03:17.55,Default,,0000,0000,0000,,The speed of point B. Will be higher than [the] speed of point A in the previous case
Dialogue: 0,0:03:18.21,0:03:21.77,Default,,0000,0000,0000,,This is obvious as the ring gear radius is higher
Dialogue: 0,0:03:26.16,0:03:33.76,Default,,0000,0000,0000,,This will make the planet gear spin and turn at a higher speed thus the carrier will turn at a higher speed
Dialogue: 0,0:03:36.57,0:03:40.37,Default,,0000,0000,0000,,Let's now explore this reverse mechanism of Planet Gears
Dialogue: 0,0:03:42.58,0:03:46.69,Default,,0000,0000,0000,,For this what you have to do is just arrest the motion of the carrier
Dialogue: 0,0:03:47.100,0:03:53.15,Default,,0000,0000,0000,,This means the Planet gears are not allowed to turn and can only spin
Dialogue: 0,0:03:55.02,0:03:58.44,Default,,0000,0000,0000,,This Spin will be opposite to the rotation of the sun gear
Dialogue: 0,0:03:59.63,0:04:04.28,Default,,0000,0000,0000,,This spinning Planet Gear will make the ring gear rotate in the same Direction
Dialogue: 0,0:04:04.62,0:04:12.02,Default,,0000,0000,0000,,In short the direction of rotation of the ring Gear will be the opposite to the sun gear thus we will get the reverse gear
Dialogue: 0,0:04:15.37,0:04:22.63,Default,,0000,0000,0000,,Here you can note that in order to achieve different speeds the input must be given to different parts of the planetary gearset
Dialogue: 0,0:04:22.63,0:04:25.70,Default,,0000,0000,0000,,This is practically difficult in an actual mechanism
Dialogue: 0,0:04:26.53,0:04:29.08,Default,,0000,0000,0000,,in an automatic transmission [to] achieve this
Dialogue: 0,0:04:29.08,0:04:35.21,Default,,0000,0000,0000,,Three planetary gear sets are connected in series as shown with coaxial Shafts
Dialogue: 0,0:04:35.70,0:04:41.82,Default,,0000,0000,0000,,To understand how this arrangement effectively transfers the input rotation to different parts of the planetary gearset
Dialogue: 0,0:04:41.82,0:04:44.66,Default,,0000,0000,0000,,Watch our video on automatic transmission
Dialogue: 0,0:04:45.61,0:04:49.61,Default,,0000,0000,0000,,Your support on patreon.com is greatly appreciated to make our educational service sustainable. Thank you