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Difference between Boyle's law and Pascal's Principle.  

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Difference between Boyle's law and Pascal's Principle.  

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Fluid Power, Fluid Motion and Fluid Mechanics: Pascal, Boyle, Charles and Bernoulli Principle

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Click on all the links at the top of the page.

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Pascal principal: The idea that pressure is transferred though a fluid can be written as an equation: pressure in= pressure out .

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Hydraulics Explanation - Pascal's Principle

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Hydraulics Explanation - Pascal's Principle

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Real-life applications - Pressure - Pascals Principle and the Hydraulic Press, The hydraulic ram

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The three characteristics of fluid pressure described above have a number of implications and applications, among them, what is known as Pascal's principle. Like the SI unit of pressure, Pascal's principle is named after Blaise Pascal (1623-1662), a French mathematician and physicist who formulated the second of the three statements: that the external pressure applied on a fluid is transmitted uniformly throughout the entire body of that fluid.

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Pneumatics vs Hydraulics - The benefits and limitations

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Pneumatics does not have the potential force that hydraulics has to offer. The lifting or moving of heavy loads is not best suited to pneumatics. Hydraulics can smoothly lift and move loads because the hydraulic oil is not compressible, compared to air which can become jerky and spongy as the air pressure fluctuates with cylinder movement or load changes.

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Difference between hydraulics and pneumatics

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Difference between hydraulics and pneumatics

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Hydraulics vs Pneumatics
There are almost no significant differences between hydraulics and and for non-engineers but if you examine further, there are lots of technical uniqueness in each system.

By definition alone, hydraulics is very different from pneumatics because it is used in controlling, transmitting and harnessing power using pressured fluids. The latter is dealing more on studying the impact of pressurized gases and how it influences mechanical movement. Hydraulics is frequently used in the concepts of dams, rivers, turbines and even erosion whereas pneumatics is applied in various fields of dentistry, mining and general construction among others.

The material or substance used differs between the two. In hydraulics, the substance used is an incompressible fluid medium wherein the most common example is oil. Pneumatics, on the contrary, makes use of a very compressible gas like air itself or an appropriate pure gas.

Another difference between the two when applied is the strength of the pressures used in their applications. Hydraulic systems use a greater amount of pressure compared to pneumatic applications. In pneumatics, only 80-100 psi (pounds per square inch) of pressure is used for its industrial applications. Hydraulic-based applications frequently use pressures that range from 1,000-5,000 psi. Nevertheless, other more advanced hydraulic systems even use pressures of up to 10,000 psi. Because of this high power demand, hydraulic systems chiefly use bigger components while pneumatic systems use smaller ones in most applications.

With regard to the control of applications, pneumatic systems are deemed to be simpler and easier to handle than hydraulic systems. Most operators say that using pneumatics is just like the light switch that makes you choose between two simple choices of 'on' or 'off.' This is true because most pneumatics is designed with simple cylinders and standard components only. An exception in the simplicity of either a hydraulic or pneumatic device would come if the entire system is automated.

Summary:
1. By definition, hydraulics is used in controlling or harnessing power with the use of pressurized fluids whereas pneumatics studies how pressurized gases influences mechanical motion or movement.
2. Hydraulics uses an incompressible fluid medium like oil whereas pneumatics uses a compressible gas like air.
3. Hydraulic applications demand greater pressures during operations that reach thousands of pounds per square inch whereas pneumatic applications only require 100 psi pressures more or less.
4. Most hydraulic applications generally use bigger components that pneumatic applications.
5. Hydraulic systems are generally more difficult to operate compared to pneumatic applications.

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Difference Between Hydraulics and Pneumatics

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Hydraulics vs Pneumatics There are almost no significant differences between hydraulics and and for non-engineers but if you examine further, there are lots of technical uniqueness in each system. By definition alone, hydraulics is very different from pneumatics because it is used in controlling, transmitting and harnessing power using pressured fluids.

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Facts About Pneumatics | Science with Kids.com

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Learn some facts about pneumatics which is a way of using air pressure to perform work. The history of pneumatics dates back to the 17th century, but the technology is still very relevant today. Modern robotics are now using pneumatics because of the amount of power resulting from less weight than electrical motors.

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Complete the following project on Hydraulics

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Hydraulics is our lifeblood. We know all there is to know about them but we mostly encounter them in heavy machinery through the calibration, repair and installation of rail for example. We also use hydraulics in bolting with hydraulic torque wrenches for example.

But surely it's not just used for lifting trains and tightening bolts? We racked our brains in the office to come up with ideas for where hydraulics are used in everyday life. Here's our list, can you come up with any others?

Gasoline pumps. They make use of hydraulics to draw the fuel from their storage tank to the vehicle.

Cars. A hydraulic brake circuit operates a car's brakes on all four wheels

Vehicle repair and maintenance. A hydraulic system is what makes it possible for a very heavy car to be raised and brought down while being serviced.

Dishwashers. They use hydraulics to increase water pressure for better cleaning. Dishwashers fitted with hydraulics are also generally quieter.

Construction machines. Equipment such as cranes, forklifts, jacks, pumps and fall arrest safety harnesses use hydraulics to lift and lower objects.

Airplanes. They use hydraulic mechanisms to operate their control panels.

Amusement park rides. Hydraulic machines provide and control motion for attractions such as the Ferris Wheel.

Theatrical presentations. Hydraulic power makes it possible for stages to be raised higher and bring them back into place.

Elevators. Some types of elevators use a hydraulic mechanism to power the elevator car's movement and make them stop when needed.

Snowplows. Hydraulic mechanisms allow the plow to move up or down and side to side.

Bakeries. They make use of hydraulics to mass produce breads and pastries, allowing them to be lifted, flipped over and moved along conveyor belts for packaging.

Barber chairs. The pump that the barber steps on uses a hydraulic lift mechanism to adjust the chair's height accordingly.

Office chairs. Hydraulics makes it possible for the chair to rise up or go down, lean backwards or forwards as you adjust its corresponding levers.

The list does not end here as there are a lot of hydraulic machines that also power factories where things ranging from car parts and accessories through to doors, fences and hoses are assembled and fitted.

Imagine if hydraulics had not been invented. Anyone care to go back to using wedges, inclined planes and pulleys and doing manual lifting? In today's biting cold or scorching temperatures?

This entry was posted in Hydraulic Systems. Bookmark the permalink.

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Where are hydraulic systems found in everyday life?

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Hydraulics is our lifeblood. We know all there is to know about them but we mostly encounter them in heavy machinery through the calibration, repair and installation of rail for example. We also use hydraulics in bolting with hydraulic torque wrenches for example. But surely it's not just used for lifting trains and tightening bolts?

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Syringe Hydraulic Arm PDF - Download in PDF Format

Hydraulics is used in many applications we see or use every day. The brakes in an automobile or the lift on the bucket of a tractor are two very common applications. We can experiment with simple hydraulics using plastic syringes for cylinders and small plastic tubing for the hydraulic hose. One definition I read for hydraulics was, "the movement of pressurized liquids through confined spaces".

Like working with gears, pulleys, or levers; a mechanical advantage can be realized by using different size cylinders on the end of the hydraulic connections. By trading distance moved with the amount of force the advantage is realized.

Moving the larger cylinder between 1 mark moved the smaller cylinder 2 marks.

Hydraulic cylinders for lifting and tilting bucket are easily seen in this tractor my father constructed.

The story of my father's company Champall Manufacturing in a 25 minute video. I created this several years ago as a DVD, not the best narration but an interesting story.

History of Champall Manufacturing - Link to YouTube video

Testimonial to Popularity of the Project

Sandy Gady 7th and 8th grade Math,Science, Design and Engineering teacher

"I have done the hydraulic arms with the syringes, they are so cool it's beyond description. I used to do them when I taught 6th grade in a small town. We had lots of retired people with saws, so they would cut up the wood we needed. I then enlisted several of them to come into the classroom and we taught kids how to use drills, screwdrivers and hammers to assemble the finished project. In the end, they had a hydraulic arm that moved in three directions. I've had contact with some of these students since, and many of them still have their hydraulic arms 20 years later. They still beam with pride when they talk about them. Cost of materials, about $5.00. Educational value, priceless".

FuelMyBrain kids built a slightly different version of the hydraulic arm.

Large flat container was used to hold water to fill the hydraulic arms.

Jump Down to Additional Syringe Experiment

The tubing I used was the type used for
aquarium airlines. Fuel line for model glow engines would work but is more expensive. There could be medical sources also. Then I found
1/8″ ID x 3/16″ OD tubing at a Fleet Farm
store which is a tight fit.

Syringes can be purchased where farm supplies are sold. I used the 12cc size as the pump and the 6cc size as the actuator cylinder.

I used one flat washer on the pivot point of the gripper part of the arm, not sure it is needed.

8/32 Machine screws were used to hold clamps on and for pivot points.

The base can be made from scrap boards also, best to pick out the better boards as some are warped. This board was labeled as 1" x 6" but true dimension was smaller.

Making Up the Parts
Normally I am making up kits for a class, so I will get all the parts fabricated first. That way few tools are needed to complete the project and it is safer for them not having to use saws or drills.

Cut 1" from both ends of craft stick, the ends are used for building gripper parts and the center is used to connect syringe to pushrods.

Construction

Drilling the two holes on boom to mount the actuator (syringe). There is also a hole at the far right that is
the pivot for this portion of the arm.

Drilling hole at end for gripper assembly, this is drilled 90 degrees from the other holes.

Plastic tubing to be used at a bearing for the wire pushrod can be
cut from the tubing in a pen.
Putting it Together
It is at this point that the students would start assembling the parts
that had been fabricated.

To position the two craft sticks that will be part of
arm bearing make sure that the arm will come down to where the actuator is almost pushed in.

Also make sure the arm can swing upwards without the binding at the hinge location.

Syringe actuator in extended position should lift arm above horizontal position.

Note washer on the bolt at the pivot point should help the wood parts move easier. Do not tighten the head of the bolt down too tight, the parts must be free to move easily.

The wood piece with plastic tubes is glued
to the end of the syringe actuator. Hot glue holds fairly well or you can use small wood screws to attach the wood to the end of the syringe.

Bring the gripper plates together, pull the actuator out to almost full extension, and insert the pushrod ends with the 90 degree bends into the small holes.

Push the tubing on the syringe where the needle would normally attach. If the fit of the tubing is too loose, stretch the
ends of the tubing while heating it
will shrink the tubing at the ends.
Too much heat is not good, just
enough to shrink the tube slightly for
a tighter fit on the syringe.

Actuator for gripper attached to boom. It must be placed at the correct spot so amount of travel is correct for the gripper.

Either 3/16″ OD plastic or aluminum tubes can
fit over the end of syringe to make a tight
connection with clear tubing if using 3/16″ ID tubing.

With the tubes on the end of the syringes the
clear tubing fits tight.

Filling the Cylinders

Part of the key to success with this project is getting as many of the air bubbles out of the lines as possible. In automobile brake lines this is known as "bleeding the brakes". I am not sure I have the best procedure for this
but I will give some suggestions.

Bring the actuator cylinder plunger down, pull the line off and pull in some water into the line with the larger cylinder. Put the line back on the small cylinder and push water into it. When it is full, turn the actuator cylinder upside down so the water does not drain out.

The next steps are to pull water into the large syringe
and line, repeating this until the air bubbles are gone.
No doubt it will take several strokes of pulling water through and pushing some of it out until the bubbles
are gone.

Small actuator cylinder with water to top of syringe end when positioned upside down.

I found that even after shrinking the ends of the tubing, some people were pulling the syringes off so I am taping the connections after the line is full of water.

If glue is not holding the small piece of wood to the end the syringe, two small wood screws into the plastic should hold.

Now using large wood screw countersunk to hold arm to base.

College for Kids class built 12 of this project.

One addition that could be added is a way
to limit the upward travel as there is not
enough support for the plunger when it
pushes out to the extreme causing
arm to bind at the very top.

Syringe Hydraulic Arm was a Big Hit at my Booth
for STEM Day at MN State Fair

Note: some of the hydraulic kits are on sale right now.
Syringe Arms College for Kids 2014
Ram feature added to this arm.
Additional Experiments
I have been working on building a simulator to demonstrate Pascal's Principle of fluids using syringes and plastic tubing.

"Pascal's Principle states that when there is an increase in pressure at any point in a confined fluid, there is an equal increase at every other point in the container."

What exactly does this mean in practice? For the simulator I used a large syringe that has a piston cross section diameter of 34 mm and small syringe with cross section diameter of 13 mm. Like other mechanical systems there is a mechanical advantage where distance moved and force tradeoff. When the smaller piston is pushed with a force, that force is distributed equally across the larger piston cross section causing a greater net force. For the fluid to be spread across the larger cross section more fluid volume must be moved from the smaller cylinder.

For my first experiment I worked from the other direction and pushed the large cylinder a short distance of 8 mm which extended the small cylinder a much longer distance of around 60 mm until it could not move any farther. I calculated this also which was off the first time but repeated trial proved that calculated and observed were very close.

For calculations we need the formula for the area of a circle :

Area of Circle = π x radius²

Large Piston cross section area = 3.14 x (34/2)² = 907 sq mm

Small Piston cross section area = 3.14 x (13/2)² = 133 sq mm

Moving the large piston 8 mm will displace amount fluid = cross section x length of movement

Fluid Displaced = 907 sq mm x 8 mm = 7256 cu mm

The movement of the small cylinder should be the fluid displaced / cross section area of small cylinder.

7256 / 133 = 54.6 mm movement of small cylinder

Actual movement was recorded at 60 mm or 6 centimeters. My calculations included some rounding errors and measurement of piston might not have been accurate.

I have not checked the amount of force generated but did check the amount required just to move the opposite cylinder. Moving the small cylinder with the large cylinder took a large amount of force, 1250 grams or around 12 newtons. This is like pushing down on the short end of a lever. Pushing the small cylinder took very little force.
Air Powered Model Car
I built the OWIKit Air Racer kit which uses compressed air to power the car much like how a steam engine functions. It is a rather difficult kit to build with so many pieces and the tiny O-rings. Blog article on building OWIKit Air Powered Racer.

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Syringe Hydraulic Arm PDF - Download in PDF Format Hydraulics is used in many applications we see or use every day. The brakes in an automobile or the lift on the bucket of a tractor are two very common applications. We can experiment with simple hydraulics using plastic syringes for cylinders and small plastic tubing for the hydraulic hose.

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by Chris Woodford. Last updated: April 26, 2018.

What's the connection between a water pistol and this gigantic crane? On the face of it, no connection at all. But think about the science behind them and you'll reach a surprising conclusion: water pistols and cranes use the power of moving liquids in a very similar way. This technology is called hydraulics and it's used to power everything from car brakes and garbage trucks to motorboat steering and garage jacks. Let's take a closer look at how it works!

Photo: This crane raises its giant boom into the air using a hydraulic ram. Can you spot the ram here? The main one is shining silver in the sunlight in the center of the picture. There are also rams supporting the stabilizers ("outriggers"): feet that extend out near the wheels to support the crane at the base when the boom is extended (they're highlighted with yellow and black warning stripes).

You can't squash a liquid!

Gases are easy to squash: everyone knows how easy it is to squeeze a balloon. Solids are just the opposite. If you've ever tried squeezing a block of metal or a lump of wood, with nothing but your fingers, you'll know it's pretty much impossible. But what about liquids? Where do they fit in? You probably know that liquids are an in-between state, a bit like solids in some ways and a bit like gases in others. Now, since liquids easily flow from place to place, you might think they'd behave like gases when you tired to squeeze them. In fact, liquids are virtually incompressible-much like solids. This is the reason a belly flop hurts if you mess up your dive into a swimming pool. When your body smacks into the pool, it's because the water can't squeeze downwards (like a mattress or a trampoline would) or move out of the way quickly enough. That's also why jumping off bridges into rivers can be very dangerous. Unless you dive correctly, jumping off a bridge into water is almost like jumping onto concrete. (Find out more about solids, liquids, and gases.)

Photo: Why does water squirt so fast from a syringe? You can't really compress a liquid at all, so if you force the water up through the wide part of the syringe by pushing hard on the plunger at the bottom, where's that water going to go? It has to escape through the top. Since the top is much narrower than the bottom, the water emerges in a high-speed jet. Hydraulics runs this process in reverse to produce lower speed but more force, which is used to power heavy-duty machines. It's exactly the same in a water pistol, which is effectively just a syringe shaped like a gun.

The fact that liquids don't compress easily is incredibly useful. If you've ever fired a water pistol (or a squeezy washing-up liquid bottle filled with water), you've used this idea already. You've probably noticed that it takes some effort to press the trigger of a water pistol (or to squeeze water from a washing-up bottle). When you press the trigger (or squeeze the bottle), you're having to work quite hard to force the water out through a narrow nozzle. You're actually putting pressure on the water-and that's why it squirts out at a much higher speed than you move the trigger. If water weren't incompressible, water pistols wouldn't work properly. You'd squeeze the trigger and the water inside would simply squash up into a smaller space-it wouldn't shoot out of the nozzle as you'd expect.

If water pistols (and squeezy bottles) can change force and speed, that means (in strict scientific terms) they work just like tools and machines. In fact, the science of water pistols powers some of the world's biggest machines-cranes, tipper trucks, and diggers.

Hydraulics in theory

Turn a water pistol on its end and this is (crudely simplified) what's going on inside:

When you press on the trigger (shown in red), you apply a relatively large force that moves the trigger a short distance. Because the water won't squeeze into a smaller space, it gets forced through the body of the pistol to the narrow nozzle and squirts out with less force but more speed.

Now suppose we could make a water pistol work in reverse. If we could shoot liquid into the nozzle at high speed, the water would flow the opposite way and we'd generate a large upward force on the trigger. If we scaled our water pistol up many times, we could generate a big enough force to lift things. This is exactly how a hydraulic ram or jack works. If you squirt fluid through a narrow tube at one end, you can make a plunger rise slowly, but with a lot of force, at the other end:

The science behind hydraulics is called Pascal's principle. Essentially, because the liquid in the pipe is incompressible, the pressure must stay constant all the way through it, even when you're pushing it hard at one end or the other. Now pressure is defined as the force acting per unit of area. So if we press down with a small force on a small area, at the narrow end of the tube on the left, there must be a large force acting upward on the larger area piston on the right to keep the pressure equal. That's how the force becomes magnified.

What about energy?

Another way to understand hydraulics is by thinking about energy.

We've already seen that hydraulic rams can give us more force or speed, but they can't do both at the same time-and that's because of energy. Look again at the water pistol graphic up above. If you press down quickly on the narrow pipe (with a little bit of force), the plunger on the wide pipe rises slowly (with a lot of force). Why would that be? A basic law of physics called the law of conservation of energy says we can't make energy out of thin air. The amount of energy you use to move the plunger is equal to the force you use times the distance you move it. If our water pistol produces twice as much force at the wide end as we supply at the narrow end, it can only move half as far. That's because the energy we supply by pushing down is carried right around the pipe to the other end. If the same amount of energy now has to move twice the force, it can only move it half the distance in the same time. That's why the wider end moves more slowly than the narrow end.

Hydraulics in practice

You can see hydraulics at work in this digger. When the driver pulls a handle, the digger's engine pumps fluid into the narrow pipes and cables (shown in blue), forcing the hydraulic rams (shown in red) to extend. The rams look a bit like bicycle pumps working in reverse. If you put several rams together, you can make a digger's arm extend and move much like a person's-only with far greater force. The hydraulic rams are effectively the digger's muscles:

Each ram is working like a diesel-powered water pistol in reverse:

The engine is pumping hydraulic fluid through one of the thin pipes to move the thicker ram out with much greater force, like this:

You might be wondering how a hydraulic ram can move both inward and outward if the hydraulic fluid is always pushing it from one direction. The answer is that the fluid doesn't always push the same way. Each ram is fed from opposite sides by two separate pipes. Depending on which way the fluid moves, the ram pushes either inward or outward, very slowly and smoothly, as this little animation makes clear:

Next time you're out and about, see how many hydraulic machines you can spot. You might be surprised just how many trucks, cranes, diggers, dumpers, excavators, and bulldozers use them. Here's another example: a hydraulic hedge-cutter on the back of a tractor. The cutting head needs to be sturdy and heavy to slash through hedges and trees and there's no way the driver could lift or position it by hand. Fortunately, the hydraulic controls do all that automatically: with several hydraulic joints, a bit like a shoulder, elbow, and wrist, the cutter moves with as much flexibility as a human arm:

Hidden hydraulics

Not all hydraulic machines are so obvious, however; sometimes their hydraulic rams are hidden out of sight. Elevators ("lifts") keep their workings well hidden, so it's not always apparent whether they're working in the traditional way (pulled up and down by a cable attached to a motor) or using hydraulics instead. Smaller elevators often use simple hydraulic rams mounted directly underneath or alongside the lift shaft. They're simpler and cheaper than traditional elevators, but can use quite a bit more power.

Motors are another example where hydraulics can be hidden from view. Traditional electric motors use electromagnetism: when an electric current flows through coils inside them, it creates a temporary magnetic force that pushes against a ring of permanent magnets, making the motor shaft rotate. Hydraulic motors are more like pumps working in reverse. In one example, called a hydraulic gear motor, the fluid flows into the motor through a pipe, making a pair of closely meshing gears rotate, before flowing back out through another pipe. One of the gears is connected to the motor shaft that drives whatever the motor is powering, while the other ("the idler") simply turns freely to make the mechanism complete. Where a traditional hydraulic ram uses the power of a pumped fluid to push the ram back and forth a limited distance, a hydraulic motor uses continuously flowing fluid to turn the shaft for as long as necessary.

Artwork: A simplified hydraulic gear motor. The fluid (yellow) flows in from the left, spins the two gears, and flows out to the right. One of the gears (red) powers the output shaft (black) and the machine to which the motor is connected. The other gear (blue) is an idler.

Why would you use a hydraulic motor instead of an electric one? Where a powerful electric motor generally needs to be really big, a hydraulic motor just as powerful can be smaller and more compact, because it's getting its power from a pump some distance away. You can also use hydraulic motors in places where electricity might not be viable or safe-for example, underwater, or where there's a risk of electric sparks creating a fire or explosion. (Another option, in that case, is to use pneumatics -the power of compressed air.)

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How hydraulics works | Science of hydraulics

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by Chris Woodford. Last updated: April 26, 2018. What's the connection between a water pistol and this gigantic crane? On the face of it, no connection at all. But think about the science behind them and you'll reach a surprising conclusion: water pistols and cranes use the power of moving liquids in a very similar way.