PRODUCTIVITY SERIES HYDRAULICS Table of Contents – Page 1 of 2 ABOUT THIS MANUAL SAFETY INFORMATION INTRODUCTION WHAT'S IN THIS BOOK? WHY SHOULD I READ THIS BOOK? THE BASIC PRINCIPLE OF HYDRAULICS BENEFITS OF HYDRAULICS HOW WE USE HYDRAULICS TERMS AND COMPONENTS HYDRAULIC TERMS - HYDRAULICS / HYDRODYNAMICS / HYDROSTATICS WORK POWER PRESSURE FLOW EFFICIENCY HYDRAULIC COMPONENTS - RESERVOIR FILTER PUMP - FUNCTION PUMPS - BY TYPE VALVE--FUNCTION VALVES--BY NAME ACTUATOR ACTUATORS--BY TYPE REVIEW SECTION #1 UND
PRODUCTIVITY SERIES HYDRAULICS Table of Contents – Page 2 of 2 SPECIFICATIONS - Continued HYDRO-GEAR BDP 10 ROSS MF SERIES WHEEL MOTOR SUNDSTRAND SERIES 15 TUFF TORQ K61A PROBLEM SOLVING STEP 1: ASK THE OPERATOR STEP 2: STUDY THE AVAILABLE INFORMATION STEP 3: INSPECT THE MACHINE STEP 4: OPERATE THE MACHINE TO VERIFY STEP 5: LIST THE POSSIBLE CAUSES STEP 6: TEST POSSIBLE CAUSES TEST EQUIPMENT INLET/OUTLET HOSE PRESSURE GAUGE FLOW METER/LOAD VALVE TEST EQUIPMENT NEEDS REVIEW SECTION # 3 REVIEW SECTION ANSWERS
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INTRODUCTION In What’s Why Should I Read This Book?.............................. 3 3 The Basic Principle of Hydraulics ............................ 4 Benefits of Hydraulics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 ................................... 5 How We Use Hydraulics TERMS AND COMPONENTS HYDRAULIC TERMS Hydraulics Hydrodynamics Hydrostatics ..................... Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
REVIEW SECTION# 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 SPECIFICATIONS Eaton Model ........................................... 7 23 EatonModel11 .......................................... 23 EatonModel781 ......................................... Hydro-Gear316.0500 ..................................... 24 24 ..................................... Hydro-Gear BDP 10 ...................................... Ross MF Series Wheel Motor ...............................
What's In This Book? This publicationis designed to familiarize the reader with basic hydraulics.It starts by defining common terms and components used with hydraulics. The components are then put together to show how they function in a hydraulic circuit. Once you are familiar with the basics, the book will review some of the systems that are used on Toro(R) equipment. A section on problem solving covers whatto do when you encounter a problem.
The Basic Principleof Hydraulics Hydraulics referto the useof liquids to transmit energy. In hydrostatic systems, mechanical energy from an external source is converted into hydraulic pressure. The pressure is then transferred through a circuit and re-converted into mechanical energy. In our products, the mechanical energy is supplied by an engine and the liquid used to transfer energyis oil.
How We Use Hydraulics Applications for hydraulics are diverse throughout industry. With lawn and garden equipment, the main uses are to: 1. Propeltheunit 2. Lift implements attached to the unit 1.1311.
The first stepin becoming comfortable with hydraulics is to learn the language. This section provides descriptions and examples of common hydraulic terms and components. We will first define some of the common terms used when working with hydraulics. Then we will describe the components which are included in many of the hydraulic systems you encounter. of the chapter will The review section at the end test your knowledge of the terms and components.
I HYDRAULIC TERMS (cont’d) Horsepower Power is done or Power is the rate at which work energy is transferred. Power is measured in foot pounds per second(ftlbs/sec). Power Work Time One horsepower is equalto 550 ftlbs/sec. Moving 55 pounds 10 feet in one second takes one horsepower. 55 Ibs In hydraulics,to transmit powertwo factors must be present; pressure and flow. 1 second Power Pressure X Flow Pressure Pressure provides the potential to transmit energy.
Heat Rise Efficiency Efficiency describes the amount of power output from the hydraulic system as compared to theamount of power putinto it. Most hydraulic pumps and motors operate between 80% to 90% efficiency. The loss of power is made up by leakage and fluid friction. This friction causes a heat rise in the system. As a pump or motor wears internally, it becomes less efficient and the operating temperature increases.
HYDRAULIC COMPONENTS (cont’d) Pump Function A pump is a device that transfers fluids by either suction, pressure or both.A pump converts mechanical energy into hydraulic pressure and flow. Pumps can either be fixed or variable displacement. HYDRAULIC A fixed (constant) displacement pump transfers a set amount of fluid during each revolution. To change the output, the speed at which the pump operates must be changed. A variable displacement pumpcan changeits output per revolution.
An Internal Gear (Gerotor) pump uses two gears to provide a constant output of oil per revolution. The inner gear is offset from the pump’s center and is driven by the input shaft. A or rotor surrounds larger internal toothed gear the inner gear, providing a rotating mesh point to trap oil. True internal gear pumps usea crescent seal which provides a sealing area between both gears . Gerotor pumps utilize rounded teeth which do not requirea crescent for sealing.
HYDRAULIC COMPONENTS(cont'd) A Charge Pump is a small constant displacement pump whichis driven by the input shaft. It provides a base circuit pressure and flow which can be used for the following functions: & Transferring oil from the reservoirto the hydrostatic pump & 4 Pushing oil through a system filter Supplying oilto remote lift cylinders - Valve Function Valves are usedto provide controlin a hydraulic system.
Directional Valvesare usedto control the direction or pathof fluid flowin a hydraulic system. This may consist ofa check valve preventing backflow through a line or a spool valve diverting the fluid’s path to a remote cylinder. 3.4297.4 Flow Control valves are usedto regulate flow into or out ofa hydraulic component. With a lift cylinder, a flow control valve can control the rate at which oil enters or leaves the cylinder. This allows the speed at which the cylinder extends or retracts to be regulated.
HYDRAULIC COMPONENTS(cont’d) - Check Valve A check valve can be used for pressure control or directional control. It usually consists of a ball andseat area. A spring may be used to hold the ball on the seat. Some check valves are adjustable. This is accomplished by using a spring with a different rate, shimming the existing spring or compressing the spring with a threaded adjuster. I I I 3.4297.4111 Push Valve - A push valveis a flow control valve usedto open a pump/motor circuit.
Spool Valve A spool valveis a directional valve usedto control oil flow. There aretwo types of spool valves: open center and closed center. Both types allowoil flow to be diverted to a remote circuit when the spool is not centered. A closed center spool valve stops flow from the pump when it is centered. This typeof valve is not used with a positive displacement pump. OPEN CENTER An open center spool valve allows oil from the pump to pass through the valve when the spool is centered. CLOSED CENTER 3.
HYDRAULIC COMPONENTS (cont’d) Hydraulic Cylinder A hydraulic cylinder converts hydraulic pressure and flow into linear mechanical energy. I t consists of a sealed chamber, piston, and piston rod. Cylinders can be either single action or dual action. CHAMBER PISTON PISTON ROD 3.4297.417 Single Action Cylinder Single action cylinders can only be powered in one direction. Gravity or spring pressureis used to retract the cylinder after extension. These cylinders comein two different styles.
1 . In hydraulic systems, .- energy from an external source is converted into hydraulic and flow. 2. As the load onhydraulic a system 3. is increased, the operating increases. refer to hydraulic systems which primarily use fluid pressure transfer to energy. 4. Work is the application of a force through a 5. Power is the rate at which 6. Flow is usually measured 7. external An gear pump is done or energy in is a is transferred. per displacement pump. 8.
Properties Of Liquids A liquid has noshape, it always assumes the shape of its container. Unlike air, liquids compress only slightly under pressure. A force applied to a contained liquid will exert equal pressurein all directions within the container. 3.4297.420 Force Magnification To gain a mechanical advantage, the sizeof the ends of the container canbe varied. Example::The pump hasan area of 1 square 10 square inch. The cylinder has an area of inches.
The flaws can be corrected by installing a reservoir and two check valves. One check valve will keep oil from being forced back into the reservoir and the second will keep oil the under the cylinder when the pump handle is raised. When the pump armis raised, the surface area of the chamber between the check valves increases. As the area increases, pressure acting on the surfaces inside the chamber decreases.
Building A Basic Circuit (Cont’d) This cycleis repeated until the cylinder ram is fully extended. Notice in the simplifiedsystem, To accomplish this, the ram can not be let down. we need to add a second valve under the cylinder. This valve should not open unless the pressure capacityof the systemis met or it is A manually opened to let the cylinder ram down. return line will direct the oil from the cylinder back to the reservoir. 3.4297.
When the spool valveis offset, oil is directed into the bottom end of the cylinder and the piston rodis extended. Notice thatoil from the opposite sideof the piston also passes through the spool valve and back to the reservoir. I 3.4297.4:29 When the pressurein the cylinder reaches the setting of the pressure relief valve, the valve opens and directs the oil flow backto the reservoir. This happens when a high resistance is met, such as the cylinder reaching the end of its”stroke. I I 3.4297.
Building ASystem Drive Let’s replace the cylinder with another type of actuator a fixed displacement hydraulic motor. With the motorin place, this system will provide the continuous mechanical energy output needed to propel lawn and garden equipment. This system can reverse the direction of travel by changing the spool offset and reversing the oil flow through the motor. Notice that there is nothing in this system that will allow the output speed to be changed.
1. Under load, which pressure gauge(A or B) below will indicate the most pressure? 2. If both circuits below have the same amountof pressure applied to them, which circuit(A or B) is capable of lifting more weight? 3.
We use several different hydraulic systems across our product line. Allof these systems are made from the basic components described earlier and operateby using the fundamental principles of hydraulics. Eaton Model 7 This hydrostatic transmission has a variable radial-ball pistonpump and fixed displacement radial-ball motor.Maximum pump outputis 0.465 cu. in.(7.62cc) per revolution. The motor output is 0.767 cu.in (12.57 cc) per revolution.It does not use a charge pump.
Eaton Model 781 This transaxleis used as a pair(RH & LH) to make up a complete drive system. It has a variable radial-ball pistonpump and fixed displacement radial-ball motor. Maximum pump output is 0.465 cu.in.(7.62cc) per revolution. The motor outputis 0.767 cu. in. (12.57 cc) per A revolution. It does not use a charge pump. remote expansion tankis used for a reservoir with a fine screen at the bottom of the inlet line providing the filtrationof incoming oil.
Hydro-Gear BDP 10 This pump is a variable output axial piston design with a maximum output of 0.61 cu. in. (10 cc) per revolution. This pump uses a gerotor charge pump to pre-charge the system. This is usedin a separated pump and wheel motor system. Hydraulic lines connect the pump with a wheel motor. Ross MF Series Wheel Motor The Ross wheel motor is an internal gear (gerotor) design. The displacementis 12 cu. in./rev (196.7cc/rev. A separate pumpis used to provide the pressure and flow to this motor.
Tuff Torq K61A This transaxleis completely self-contained andhas its own differential. It utilizes a variable axial a fixed displacement axial piston pump and with piston'motor. An internal spring assists in returning the control arm to neutral. A dampening pistonis used on the motion control input arm to smooth directional changes. 1.1311.
Using a systematic approach makes hydraulic troubleshooting easy. By following a process which narrows down the possible causes, a problem can be pinpointed and confirmed. Step 1 : Ask the Operator Step 2: Study the Available Information Step 3: Inspect the Machine Step 4: Operate the Machine to Verify Problem Step 5: List the Possible Causes Step 6: Test Possible Causes Step 1:Ask The Operator A detailed problem description is a valuable diagnostic tool during troubleshooting.
Inspection Results Oil is fairly clean- no signs of water or overheating Spool valve works smooth Hydro is clean Hoses appear in good shape Does not apply- unit drives great so the problemis in thelift circuit. Drive operationOK Engine runsOK. Lift system does not work. Seems like it tries to raise deck. Noisy when spool valveis off center. Step 3: Inspect The Machine Its now timeto collect physicalevidence. Again, take notes on what you see. Inspect the the oilin the unit.
Step 5: List The Possible Causes Make a listof the possible causes for this problem. Use your notes to support your conclusions. Which causes best match the description of the be easily verified? problem? Which causes can Step 6: Test Possible Causes Using the technical information and the proper test equipment, test the possible causes to verify your conclusions. Start with the items on your list which are the easiest to check.
To properly troubleshoot many hydraulic systems, it is necessary to measure the pressure andor flow at various pointsin the system. This can only be done by using the proper test equipment. if there Service and repair manuals will indicate are specific tests which can be performed aon specific hydraulic system. The amount of pressure andor flow the system should be generating will determine the size and type of the equipment needed.
Flow Meter Load Valve Flow Meters are usedto measure the actual flow in a circuit during operation. The meter is placed inline and will indicate flow in gallons per minute (gpm). A Load Valveis a flow control valve which can be used during testingto simulate a load.As the flow is restricted, a higher loadis simulated. Load valves are usually used in combination with a flow meter. 1.1311.16 Test Equipment Needs The type of test equipment you need depends on the typeof equipment being servicedin your shop.
1. The first step in problem solving is to: A. Study the available information B. List the possible causes C. Inspect the machine D. Ask the operator E. Operate the machine to verify the problem 2. Oil which looks milkyis most likely contaminated with: A. Milk 8. Dirt C. Water D. Transmissionfluid E. Nothing 3. An indicator of an overheated hydraulic system is: A. Burnt smelling fluid B. Oil loss in the system C. Loss of power as the system warms D. Air bubbles in the reservoir E. Black colored oil 4.
Review Section 1 1. mechanical,pressure 2. pressure 3. Hydrostatics 4. distance 5. work 6. gallons,minute 7. fixedconstant 8. Pressure Control, DirectionOf Flow, Volume Of Flow 9. mechanicalenergy 10.single action Review Section# 2 1. Both gauges will read the same amount of pressure because they arein the same circuit. 2. Circuit A - Force is equal to pressure times the area on which it is acting. The pressure is the same in both circuits.
f- This Productivity Series Manual was written as a training guide for service technicians. Learning the fundamentals of a subject is a necessary step in becoming an expertin any area. This publicationis designed to increase the readers knowledge on hydraulics. The Toro Company has made every effort to make the informationin this manual complete and correct. We are hopeful that you will find this manual a valuable addition to your service shop.
