Excavators The Marvels of Mechanical Engineering - Sabin Mechanical Engineering

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00:00Excavators contain many unique engineering mechanisms within them.

00:04When a driver's skill is combined with the amazing engineering of excavators, miracles happen.

00:10Here is one example.

00:12This excavator driver is struggling to unload the material from a wagon.

00:16The best solution here is to keep the excavator on this raised platform.

00:21In this new elevated position, the excavator does its job perfectly.

00:25However, the question is, how can we make the excavator climb up such big steps?

00:31As humans, when we want to climb up a big step, what do we usually do?

00:36We fix our arms on the step and climb it as shown.

00:39The excavator must do the same thing.

00:42Fixing the arm allows it to climb up effortlessly.

00:45Obviously, this action does not occur exactly as is demonstrated in these visuals.

00:50The excavator is not a superman.

00:53Let's first see how the arm is fixed to the platform properly.

00:58The arm is controlled by these joysticks.

01:01When the driver moves the left joystick forward,

01:04high-pressure fluid enters the cylinder of the arm.

01:07When this happens, the arm rolls out.

01:11Now, it's time to make the bucket curl downwards.

01:15To do this, simply activate the right joystick.

01:18You can see how this beautiful mechanism is activated by the piston movement and moves the bucket downwards.

01:26As you probably noticed, the excavator's arm has one more piston cylinder arrangement.

01:32This cylinder is known as the boom cylinder.

01:36To activate this cylinder, the driver uses the right lever again.

01:40However, this time, it's moved in a perpendicular direction.

01:44It's pretty easy to guess what will happen if you activate the boom cylinder.

01:48The boom of the excavator will come down and the bucket will press properly against the platform.

01:54This produces a tremendous frictional force between the bucket and the platform.

01:59As a result, the bucket is locked to the platform when the boom cylinder is activated.

02:04We can consider the bucket as a strong arm grip.

02:08What will happen if the excavator driver further increases the pressure in the piston?

02:14The boom will not be able to go down any further.

02:17It's stuck.

02:18Consider pausing the video here to take a moment to think about what you believe will happen in this case.

02:24The pressurized fluid also applies a force on the cylinder.

02:28Since the piston is stuck, the cylinder will move up relative to the piston.

02:35Let's pan the camera out to get a different perspective of this operation.

02:39The cylinder is connected to the front of the excavator body.

02:43This means the excavator body will tilt up as shown.

02:48Let's repeat this animation so you can observe everything carefully.

02:52Along with this body tilt, the track is also rotated to move the body forward.

02:57Eventually, the excavator body can rest on the edge of the platform in a stable position.

03:03Once the excavator rests on the edge of the platform, the arm can be removed from the platform.

03:09Next, we can observe the wonder behind the excavator's swing motor.

03:13The swing motor is hydraulically powered and can rotate the excavator's body 360 degrees.

03:19When the driver operates the swing motor, the excavator body spins.

03:24From this position, spin the excavator body by 180 degrees.

03:30In this new position, the bucket is once again pressed against the ground, forming a fixed point.

03:37What do you think the driver should do?

03:39Should they increase or decrease the length of the boom cylinder?

03:43If you said they should decrease the length, you are right.

03:49The excavator body stands horizontal now.

03:52The remaining operation is simple.

03:54Just move the excavator backward.

03:57Since there is one more step to climb, the driver will have to repeat all the operations once again.

04:04From this elevated position, the excavator can do its task quite efficiently.

04:09Have you ever seen or been curious about what is inside this track geometry?

04:14If you remove this cover, you will come across this beautiful and crucial engineering device.

04:19A hydraulic motor.

04:21The hydraulic motor runs a sprocket, which runs the track.

04:25Interestingly, this motor does not run on electricity, but on high pressure fluid.

04:31The way a high pressure fluid rotates the hydraulic motor is illustrated here.

04:37The high pressure fluid in the bottom region wants to move the piston towards the left.

04:43Similarly, the low pressure fluid in the top region wants to move the piston towards the right.

04:49Unfortunately, both these motions are not possible because the swash plate cannot swivel as shown.

04:56However, if this disc rotates, both piston motions are satisfied.

05:03Doesn't that sound wild?

05:06How can a few axial pistons rotate a disc?

05:10Recall that we already explained the logic behind this motion.

05:13This is how the track motor works.

05:16This rotation is transferred to a planetary gearbox arrangement.

05:20The output of the gearbox is transferred to a sprocket, which drives the track.

05:26The other track also has a similar but independent hydraulic motor arrangement.

05:31Here's another interesting question for you.

05:34How can an excavator execute a turn?

05:37By rotating the hydraulic motors at different speeds, the turn can be achieved easily.

05:43The swing motor we saw earlier also runs with the help of a similar hydraulic motor.

05:48Here, in addition to the motor there, should be a big slewing ring as well.

05:53In short, an excavator needs high pressure fluid for its arm operation, track rotation, and operating the swing motor.

06:02This high pressure fluid is supplied by a set of axial piston pumps.

06:07Although they look very similar to the hydraulic motor we saw earlier,

06:11this device specifically acts as a pump.

06:14The pump is driven by a huge diesel engine.

06:17These two pumps act as the heart of an excavator,

06:22essentially supplying the stream of blood responsible for keeping the excavator alive.

06:27Interestingly, just by adjusting the angle of the swash plate,

06:31the axial pump can vary the output pressure it's producing.

06:36Please have a look at this boom raise example.

06:39We know that, in order to raise the boom,

06:42the high pressure fluid must reach this side of the piston.

06:46Let's now see how all these amazing technologies logically work together

06:50when high pressure fluid reaches the piston as a result of the driver moving the joystick.

06:55When the driver moves the joystick,

06:57this movement sends an electrical signal to the excavator's brain,

07:02to an electronic control unit.

07:04At this point, it's the ECU's duty to make the high pressure fluid from the axial pump reach the cylinder of the boom.

07:11This is why this fluid valve is used.

07:14Can you tell what would happen to the fluid flow if the spool was moved to the right side?

07:19It's quite obvious that the high pressure fluid will easily enter the piston's bottom region,

07:24and low pressure fluid from the top of the piston will escape through the same valve.

07:30This will result in upward motion of the piston, or the boom rising up.

07:35If you want to lower the boom, just move the spool towards the left.

07:39By following the fluid flow arrows, you'll be able to explain this motion as well.

07:45You can see how drastically the connection of the fluid flow is modified due to the movement of the spool valves.

07:51At this stage, the only question that remains is how high to move the spool right and left.

07:57This right and left movement is achieved again with the help of fluid pressure.

08:02The pressurized fluid required for the spool movement comes from a different pump, a small gear pump.

08:08A simple solenoid valve controls this fluid motion.

08:12As you can see, when the solenoid valve of the left side is activated,

08:16the solenoid valve spool moves up,

08:19and pressurized fluid from the gear pump moves the spool of fluid valves towards the right.

08:24If you want to move the spool of the fluid valve to the left, just activate the other solenoid valve.

08:31In short, when you move the joystick, the ECU sends a signal to the solenoid valve.

08:37The solenoid valve then releases pressurized fluid to control the fluid valve.

08:42You already know how the fluid valve controls the boom cylinder

08:45by properly channeling the high pressure fluid from the axial pump.

08:49In reality, the solenoid and main valves sit together as shown.

08:56Now that you've learned many of the fascinating technologies behind excavators,

09:00here's a small challenge for you.

09:02This excavator has to climb down, but the drop is incredibly steep.

09:07How can you get this excavator to climb down safely?

09:10This is what will happen if you try to climb down the excavator directly.

09:15Oh my god, a big accident.

09:18Now, let's see the real operation of climbing down an excavator.

09:22The first stage in excavator climb down operation.

09:25Touch this bucket to the ground and move the excavator body forward.

09:31You can see the excavator body is always remaining horizontal since the bucket is supporting that.

09:39And this is the maximum distance the excavator can come forward in this stage.

09:43It's looking amazing, right?

09:45Now, for the second stage, you have to activate this cylinder and press down the bucket always down.

09:53And at this stage, move the excavator body further forward.

09:59Wow!

10:00You can see the angle got reduced here and the excavator is still horizontal.

10:04Now, the last stage, activate this cylinder and make the body touch the ground like this.

10:11Wow!

10:13Perfect!

10:14We are almost done with the operation.

10:16Remaining stage is quite simple.

10:18Just make the excavator body move forward.

10:22And we are done with it.

10:24Such an easy and efficient operation to climb down an excavator.

10:28You may be aware that this channel is surviving.

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10:33So, before leaving this video, if you can support our channel, I will be so grateful.

10:37Thank you for watching the video.

10:38Take care.

10:39Bye-bye.

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