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HYDRAULICSSTUDENT INFORMATION

Area of Study: Energy/Power

Objectives: Students will discover the basic principles of hydraulics. Students will comprehend where hydraulics are utilized in our world.

Related Careers:

AircraftEquipmentMechanicsandTechnicians perform scheduled maintenance, make repairs, and complete inspections required by

the Federal Aviation Administration to keep aircraft in peak operating condition,

ConstructionEquipmentOperators use machinery to move construction materials, soil, and other materials and to apply

asphalt and concrete to roads. They work in all weather conditions.

ElevatorInstallersandRepairers install and repair elevators, escalators, dumbwaiters, & moving sidewalks. Elevator

installers & repairers must have knowledge of electronics, electricity, & hydraulics.

HeavyVehicleandMobileEquipmentServiceTechniciansandMechanics repair and maintain engines and hydraulic, transmission, and electrical systems

powering farm equipment, cranes, bulldozers, and railcars. Key Words and Definitions:

1.Cylinder: A hollow shape. It is a round container with straight parallel sides.

2. Energy: The ability to do work.

3. Incompressible:Incapable of or resistant to compression. 4.MechanicalAdvantage: An increase in force or speed by the use of a machine.

5. MechanicalEnergy: The energy of motion.

6. p.s.i.: Pounds per square inch. 7. Piston: A cylindrical-shaped object moved by pressure.

8. Power:The amount of work done1.

1. Thode, B., Thode, T. A farmer moved a hay bale with hydraulics on a loader.

Mike Breen Photo

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HYDRAULICSOccupational Choices

Focus: Heavy Vehicle Service Technicians & Mechanics

AfterHighSchool:Applied Technology Center or Community College - 1 to 2 years to earn a certificate of completion or an Associates degree in Diesel or Heavy Equipment mechanics. Most places that employ will require on the job training.

A Heavy Vehicle Service Technician or Mechanic is usually considered fully qualified after 3 or 4 years of on the job training.

TheWork:Employment of heavy vehicle service technicians and mechanics will be needed to perform routine maintenance on diesel engines, examine hydraulic equipment for leaks, diagnose electrical problems, and occasionally weld broken structural parts. They may work in a shop indoors or have to go to the job site to repair the equipment as it may be to difficult to bring it into the shop. A shop may have individual specialists in major engine repair, transmission work, electrical systems, and suspension or brake systems. Farm machinery, cranes, bulldozers, and railcars are all examples of heavy vehicles that require such service.

EmploymentOpportunities•Federal Government• State and Local Governments• Construction Industries• Agriculture Industries• Mining Industries• Railroad Industries

•Auto •Electronics •Math •Technology & Engineering •Computer Science •Chemistry •Physics •English •Social Studies

ClassestotakeinSchool:

Earnings:According to a 2010 survey, people employed as a Mobile Heavy Vehicle Mechanic had an median salary of $46,140. In Utah, the wage was higher coming in at $48,600.

In 2010, Farm Equipment Mechanics and Service Technicians earned average yearly wages of $34,680.

In 2010, Mobile Heavy Vehicle Mechanics’ earnings ranged from $29,710to$64,850. Earnings vary by experience and location.

PersonalCharacteristics•Good Communications skills• Excellent Math Skills• Computer skills to test & analyze • Ability to read service manuals• Ability to read technical reports

Source: Occupational Outlook Handbook 2010 -2011 Edition & Career One Stop

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Energy and Power

Energy is the ability to do work. Energy comes in many different forms. When you turn on a light switch, drive in a car, or mow the lawn, you are using energy. To use energy you must be able to control it. In the simple example of turning on a light switch, you are controlling the energy.

Power is the amount of work done during the use of the controlled energy. It is a measurement of how much energy was used in accomplishing a certain task.

Fluid Power

In this unit of study, we are going to apply these ideas to one way of controlling energy. The method of controlling energy that will be focused on is probably one that you will not be familiar with. It is called fluid power. This brings up ideas of using the power of water to move a water wheels to grind grain to make flour as shown in the picture at the right. However, fluid power is not about water wheels.

Fluidpower is the use of pressurized fluids (liquids and gasses) to control and transmit power. Fluid power is broken down into two areas and these are pneumatics (moving gases) and hydraulics (moving liquids). This document will concentrate on the branch of fluid power known as hydraulics.

Hydraulics - What is it?

Hydraulic systems are a fundamental part of today’s work environment. Hydraulics is the science of liquids, such as, water or oil. In hydraulic systems, pressure can be exerted through liquids, and that pressure can transmit motion from one place to another.

Hydraulic Principles

Motion can be transmitted because liquids are incompressible; that is, they cannot be compressed to a smaller volume. Figure 1 shows two pistons in a cylinder with a liquid between them. When the applying piston is moved into the cylinder 8 inches, the output piston would be pushed along the cylinder the same distance.

The pastoral pond-side Hameau has a mill with a water wheel. It was built in 1783 for the Queen of France, Marie Antoinette.

Mike Breen Photo

Fluids can transmit motion.Figure 1

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In figure 2, the force applied to a liquid is transmitted by the liquid in all directions and to every part of the liquid. As a result, when a piston with 1 square inch of area applies a force of 100 pounds on a liquid, the pressure will be registered throughout the entire hydraulic system. No matter how big the chamber or how wide the tubing in this example, the force will be 100 pounds per square inch (p.s.i.). The force applied is transmitted equally in all directions.

Determining Pressure on a Fluid To determine the amount of pressure put on the fluid a mathematical formula will be used. FORCE applied (in pounds) dividedby the pistons’s UNITAREA (in Square Inches) will equal the PRESSURE in p.s.i. . Figure 3 illustrates this idea. Looking at the cylinder on the left side of the diagram, the cylinder has a 1 square inch piston and a force of 100 lb. is exerted. If the mathematical formula is applied, the 1 inch piston is divided into the 100 lb. of applying force which results in 100 p.s.i. on the fluid. The cylinder on the right side of the diagram has a piston of 2 square inches and a force of 100 pounds was exerted. If 2 is divided into 100 lb., then mathematically the pressure on the liquid will be 50 pounds per square inch.

Why is the hydraulic pressure in the system determined by dividing? If you have ever tried to run through a swimming pool filled with a few feet of water, you understand that water is denser than air and it takes more work for you to run through the pool of water. With this correlation, it may be easier to see why we divide to determine the amount of pressure on the fluid. In this case, there is a bigger mass and we are moving it through a fluid which is denser than air so it is going to take more work to move it. Pressure on the fluid = Applying Force / Size of Piston (P=F/UA)

Figure 3

Pressure applied to a liquid is transmitted equally.Figure 2

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Determining Cylinder Force With an input-out-put system, we can determine the force applied to any output piston by multiplying the pressure in pounds per square inch (p.s.i) by the area of the output piston in square inches. For example, the pressure shown in the system in figure 4 is 100 p.s.i. The output piston to the left has an area of 0.5 square inches. Therefore, the output force on this piston is 100 times 0.5 which equals 50 p.s.i.. The center piston has an area of 1 square inch, and its output force will be 100 p.s.i. (100 x 1). The right hand piston has an area of 2 square inches, and its output force will be 200 p.s.i. (100 x 2). The bigger the output piston, the greater the output force. This is stated mathematically by taking the PRESSURE on the fluid in p.s.i. and multiplying by the output pistons’s UNITAREA (in Square Inches) will equal the output FORCE in p.s.i..

STOP for the Demonstration

Even very simple fluid power systems require mechanical input. As we push on the syringe, we have taken mechanicalenergy and exerted it on the fluid. This changes the energy into fluid power. This fluid power is used to transmit the energy to the syringe at the other end which changes the power back to the moving output syringe. This output is called mechanicalpower which is the movement of the syringe that lifted the 6 kilogram weight. When we use mechanical energy to do work, it becomes mechanical power.2 In this case, we also have a mechanicaladvantage which is an increase in force that allows us to lift the weight painlessly. Hydraulics are not used by themselves, but in a combination of other electrical and mechanical systems to do the work that they are designed for.

2 Bohn, C., Fales, J., Kuetemeyer, V., MacDonald, A.

Cylinder Force = Pressure in the system x Size of Output Piston.Figure 4

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Hydraulics and Impacts on Society

By the pushing of a button or throwing a switch, many people use hydraulics in their everyday jobs. Many designers and engineers have put fluid power to work for us. Hydraulics are used in conjunction with mechanical and electrical systems to make many tasks possible that would be impossible for us to do physically by ourselves. Most of us are not even aware of all the uses of hydraulics. The impact of this technology has been tremendous, and it has been seamlessly integrated in our society. We use this technology everyday. Hydraulics are used in several places in vehicles. One of them has to do with stopping the car. When the brake pedal on a car is pressed down, the driver’s foot is pushing a piston that is forcing fluid back to activate the brake drum that actually stops the car. Without hydraulic brakes, your trip to school today could have been much more frightening!

A few other uses of hydraulics are:

1. Firemen use a tool called the “Jaws of Life” to rescue people trapped in automobiles and buildings.

2. Hydraulically operated machinery in the form of bulldozers, backhoes, fork lifts and cranes used during construction. 3. Farmers use hydraulics in farm equipment to aide in planting and harvesting and feeding cattle.

4. Many elevators use hydraulics to operate.

5. Every week a truck stops and picks up the garbage from your house. It uses hydraulics pick up the garbage can and to compress the garbage once it is in the truck.

6. Hydraulics operate the landing gear on airplanes.

7. Some car service centers lift cars using a hydraulic lift so the vehicle can be worked on underneath.

8. Some museums and amusement parks have animated dinosaurs that move and growl. The movements of many of these machines are hydraulic.

Can you think of others?

Hydraulic Spreaders (Jaws of Life)Firehouse19 Photo

A “bobcat” skid loader uses hydraulics.Mike Breen Photo

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HYDRAULICSStudent Work Sheet

Name:________________________________________ Period: ____ Date: __________

Directions:In the blank on the left, write the correct answer to the statement or question.

1. _____________________ _________ is the ability to do work.

2. _____________________ Fluid power is the use of ___________ fluids to control and transmit power.

3. _____________________ _________ is the science of liquids.

4. _____________________ Motion can be transmitted because liquids are _________.

5. _____________________ In illustration 1, if piston A moves 12 inches, how far will piston B move?

6. _____________________ In illustration 2, tell how many p.s.i. the diagram on the left will show.

7. _____________________ The reading on the needle will be ____ p.s.i..

8. ______________________ In illustration 2, tell how many p.s.i. the diagram on the right will show.

9. ______________________ The reading on the needle will be ______ps.i..

10. _______________________

11. _______________________ (10.&11.) List two machines or devices that use hydraulics.

Illustration1

Illustration2

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12. ______________________ Calculate the pressure on each gauge. Write the answer in the blank and draw it on each gauge in illustration 3.

Calculate the output force in p.s.i for each of the following output pistons in illustration 4.

13. ______________________ output force for 1 sq. in piston

14. _____________________ output force for 2 sq in piston

15. _____________________ output force for 3 sq in piston

Illustration3

Illustration4