Ransomes 67978, 67979, 67980, 67981, 67982, 67983 User manual

Brand: Ransomes

Model: 67978, 67979, 67980, 67981, 67982, 67983

Category: Lawnmowers

Type: User manual

4241262-Rev B 6-1

Chapter 6

Hydraulics

Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Test Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Repair Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Hydraulic Hose, Tube, and Fitting General Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

O-Ring Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Hydraulic Hose Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5

Hydraulic Service Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Portable In-Line Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Digital Hydraulic Tester . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

Hydraulic Flow Meter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-6

Digital Pressure Gauge Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Hydraulic Hose Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Hydraulic Test Fitting Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-7

Blocking Disk Set . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Component Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8

Hydraulic Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10

Theory of Operation and Diagnostic Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16

Steering Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-16

Steering Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-17

Raise Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-18

Raise Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-19

Lower Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-20

Lower Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-21

Mow Circuit (On) Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-22

Mow Circuit (On) Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-23

Backlap Circuit Schematic and Theory of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-24

Backlap Circuit Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-25

Field Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26

Preliminary Checks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26

Lift Cylinder Leakage Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-26

Steering Leakage Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-27

Reel Motor Case Drain Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-28

6-2 4241262-Rev B

HYDRAULICS

Instrument Test Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-29

Instrument Test Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-29

Front Cutting Units Circuit Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-30

Front Cutting Units Pump Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-32

Front Reel Valve Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-33

Front Reel Motors Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-35

Rear Cutting Units Circuit Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-38

Rear Cutting Units Pump Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-41

Rear Reel Valve Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-42

Rear Reel Motors Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-44

Lift/Steering Relief Valve Pressure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-46

Lift/Steering Relief Valve Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-48

Lower Relief Valve Pressure Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-49

Lift/Steer Pump Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-50

Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52

Hydraulic Oil Tank—Drain Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52

Gear Pump . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-52

Lift Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-57

Rear Reel Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-60

Front Reel Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-63

Hydraulic Oil Return Filter Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-65

Hydraulic Oil Charge Filter Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-66

Rear Lift Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-67

Center Lift Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-68

Left and Right Front Lift Cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-71

Hydraulic Oil Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-74

Hydraulic Oil Cooler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-76

HYDRAULICS

4241262-Rev B 6-3

Specifications

Test Specifications

Specifications

Front Cutting Units Pump Flow gpm (lpm) 6.8 (25.7) at 3150 rpm

Rear Cutting Units Pump Flow

gpm (lpm) 6.8 (25.7) at 3150 rpm

Lift/Steer Pump Flow

gpm (lpm) 6.8 (25.7) at 3150 rpm

Hydraulic Leakage Percentage Ranges 0–10% = Good

11–20% = Marginal

21% and Beyond = Bad

Lift/Steering Relief Valve Pressure Setting

psi (bar) 1450 ± 10% (100 ± 10%)

Lower Relief Valve Pressure Setting

psi (bar) 450 ± 10% (31 ± 10%)

Reel Motor Forward Relief Valve Pressure Setting

psi (bar) 1167 ± 10% (81 ± 10%)

Reel Motor Reverse Relief Valve Pressure Setting

psi (bar) 1167 ± 10% (81 ± 10%)

Reel Motor Case Drain Rate Less than 1 pint (0.47 L) per minute

6-4 4241262-Rev B

HYDRAULICS

Repair Specifications

Specifications

Gear Pump—Rear Cover-to-Pump Body Bolt Torque lb-ft (N·m) 33 (45)

Gear Pump—Test Fitting Torque

lb-ft (N·m) 32.9 (44.6)

Gear Pump—Tee Fitting Torque

lb-ft (N·m) 55 (74.6)

Gear Pump—Outlet Port Fitting Torque

lb-ft (N·m) 55 (74.6)

Gear Pump—Inlet Port Fitting Torque

lb-ft (N·m) 32.9 (44.6)

Lift Valve—Coil Nut Torque

lb-ft (N·m) 10 (13.5)

Lift Valve—Relief Valve Torque

lb-ft (N·m) 24–26 (32.5–35.3)

Lift Valve—Check Valve Torque

lb-ft (N·m) 19–21 (25.8–28.5)

Lift Valve—Port “P” and Front Side Port “T” Fitting

Torque

lb-ft (N·m) 60 (81.4)

Lift Valve—Port “G” Fitting Torque

lb-ft (N·m) 17 (23)

Lift Valve—Ports “1,” “2,” “3,” “8,” “9,” and “10” Fitting

Torque

lb-ft (N·m) 17 (23)

Lift Valve—Ports “4” and “6” Fitting and One-Way

Restrictor Torque

lb-ft (N·m) 17 (23)

Lift Valve—Rear Side Port “T” Fitting Torque

lb-ft (N·m) 60 (81.4)

Reel Valve—Coil Nut Torque

lb-ft (N·m) 10 (13.5)

Reel Valve—Flow Control Torque

lb-ft (N·m) 24–26 (32.5–35.3)

Reel Valve—Ports “A” and “B” Fitting Torque

lb-ft (N·m) 60 (81.4)

Reel Valve—Port “G” Fitting Torque

lb-ft (N·m) 17 (23)

Reel Valve—Port “P” Elbow Fitting Torque

lb-ft (N·m) 80 (108.5)

Reel Valve—Port “T” Fitting Torque

lb-ft (N·m) 60 (81.4)

Hydraulic Oil Tank Capacity

gal (L) 14 (53)

Center and Rear Lift Cylinder Rod Nut Torque

lb-ft (N·m) 50 (67.8)

Left and Right Front Cylinder Rod Nut Torque

lb-ft (N·m) 50 (67.8)

HYDRAULICS

4241262-Rev B 6-5

Hydraulic Hose, Tube, and

Fitting General Instructions

O-Ring Installation

• Always install new O-rings.

• On hoses with O-ring fittings, make sure O-rings are

properly seated before tightening.

• O-rings should be lubricated with the fluid to be used

in the system prior to assembly.

Boss Fitting O-Ring Installation

O-Ring Seal Kits

• SAE Boss O-Ring Kit Jacobsen PN 5002452

• O-Ring Face Seal (ORS) O-Ring Kit PN 5002454

• Common O-Ring Sizes Kit PN 5002453

Replacement O-Rings for ORS (Face Seal)

Fittings

Replacement O-Rings for O-Ring Boss

Fittings

Hydraulic Hose Installation

Hold the fixed portion of the hose coupling with one

wrench; use a second wrench to tighten or loosen the

hose nut. This will avoid damaging the fitting seal. When

tightening a hose, do not permit the hose to twist; hold

the hose in a normal straight position.

When installing hoses, place fittings at angles to avoid

contact with fixed parts when turning. Make sure hoses

are assembled to proper “A” and “B” ports on

components.

Hydraulic Hose and Tube Torque Values

1 Tubing O.D. or Hose I.D. 2 O-Ring 3 Thread Size

ORS (Face Seal)

Tube Size

ORS (Face Seal)

O-Ring Size

Jacobsen

Part

Number

4 11 339908

6 12 339909

8 14 339910

10 16 339911

12 18 339912

16 21 339913

20 25 339914

24 29 339915

TN4075

TN4097

Tubing O.D.

or Hose I.D.

Thread

Size

Jacobsen Part

Number

1/8 5/16-24 459290

3/16 3/8-24 459291

1/4 7/16-20 339896

5/16 1/2-20 459293

3/8 9/16-18 339897

1/2 3/4-16 339898

5/8 7/8-14 339899

3/4 1-1/16-12 339900

7/8 1-3/16-12 459296

1 1-5/16-12 339901

1-1/4 1-5/8-12 339902

1-1/2 1-7/8-12 339903

2 2-1/2-12 459300

Size lb-ft N·m

Dash Fractional Min Max Min Max

-4 1/4 10121416

-6 3/8 18202427

-8 1/2 32404354

-10 5/8 46 56 60 75

-12 3/4 65 80 90 110

-16 1 92 105 125 240

-20 1-1/4 125 140 170 190

-24 1-1/2 150 180 200 246

6-6 4241262-Rev B

HYDRAULICS

Hydraulic Service Tools

NOTE

The hydraulic service tools listed here can be obtained

from K-Line Industries at http://klineind.com.

Portable In-Line Filter

Part Number JAC5097

When hydraulic components fail internally, debris from

the failed component can spread throughout the

hydraulic system and cause additional damage.

This situation can be magnified when dealing with a

closed-loop traction system, where oil is not filtered. In

the event of a traction system component failure, it is

recommended that all traction system components be

disassembled and cleaned, or filtered using a portable

in-line filter available through your Jacobsen Dealer. The

portable in-line filter should also be used when testing

hydraulic systems or after replacing a failed component.

IMPORTANT

Always install the in-line filter so oil flows through

the filter before entering a component. Once filtering

has begun, never reverse the flow of oil, or debris

will re-enter the system.

Digital Hydraulic Tester

Part Number AT40031

Features

• Flow up to 100 gpm (379 lpm)

• Pressure up to 6000 psi (414 bar)

• Temperature up to 250° F (120° C)

• Digital display for flow and temperature

• Analog display for pressure

• Flow accuracy 1% of full scale

Hydraulic Flow Meter

Part Number AT40002

Features

• Glycerin filled pressure gauge

• Precision needle-type load valve

• 4–40 gpm (15–15 lpm) flow range

• Pressure up to 5000 psi (345 bar)

• -12 port size

TN4286

TN4288

TN4287

HYDRAULICS

4241262-Rev B 6-7

Digital Pressure Gauge Kit

Part Number JAC5106

Features

• Quick disconnect fittings

• Pressure up to 5000 psi (345 bar)

• Includes one 5 ft (152 cm) hose

Hydraulic Hose Kit

Part Number JAC5001H

NOTE

This hydraulic hose kit is intended to be used with the

JAC5001A Hydraulic Test Fitting Kit.

Contents

• Two 8 ft (244 cm) 12 ORFS (F) x 10 ORFS (F) hoses

• Four 8 ft (244 cm) 10 ORFS (F) x 10 ORFS (F) hoses

• Two 8 ft (244 cm) 8 ORFS (F) x 10 ORFS (F) hoses

Hydraulic Test Fitting Kit

Part Number JAC5001A

NOTE

For detailed component descriptions and sizes, please

see the K-Line Industries website at http://klineind.com.

Contents

• Twenty ORFS tee fittings in five sizes

• Eight ORFS 90° elbow fittings in four sizes

• Forty ORFS caps in five sizes

• Forty ORFS plugs in five sizes

• Six ORS reducer adapters in three sizes

• Sixteen ORS adapters in four sizes

• Eight blocking disks in four sizes

• Three JIC tee fittings in three sizes

• Three 4 in. (102 mm) jumper hoses in three sizes

• One ORS/male NPTF adapter

• One vented bushing

• One copper tube assembly

Blocking Disk Set

Part Number JAC5001-1

NOTE

This blocking disk set is part of the JAC5001A Hydraulic

Test Fitting Kit.

Contents

• Two -6 blocking disks

• Two -8 blocking disks

• Two -10 blocking disks

• Two -12 blocking disks

• Two -16 blocking disks

TN4290

TN4289

6-8 4241262-Rev B

HYDRAULICS

Component Location

See Figure 6-1.

Figure 6-1: Component Location—Left Side

1 Gear Pump 4 Return Filter Assembly 7 Front Reel Valve 10 Center Lift Cylinder

2 Radiator/Hydraulic Oil Cooler 5 Hydraulic Oil Tank 8 Lift Valve 11 Right Lift Cylinder

3 Charge Pressure Filter 6 Rear Lift Cylinder 9 Left Lift Cylinder 12 Rear Reel Valve

TN3586, TN3628, TN3590, TN3649

HYDRAULICS

4241262-Rev B 6-9

Page Intentionally Blank

6-10 4241262-Rev B

HYDRAULICS

Hydraulic Schematic

See Figures 6-2 through 6-6.

Figure 6-2

10 Micron

Filter

Traction Pump

Suction

Screen

100 Mesh

25 psi

Switch

Hydraulic Tank

25 psi Crack Bypass

10 Micron

Filter

0.50 ci

Forward

Relief Valve

(See Note)

Charge

Filter

Check

Valve

Check

Valve

123

3150 ±50 rpm

Return

Filter

Oil

Cooler

25 psi

Crack

Bypass

Gear

Pump

TN2805

Reverse

Relief Valve

3625 psi

Tow

Valve

0.50 ci 0.50 ci

2.81 ci

Screen

40 Mesh

Charge

Pressure

Relief Valve

315 psi

25 psi

Crack

Bypass

REV

Test

Port

FOW

Test

Port

Control Sleeve

STRG

Test

Port

M1L1

EDC

10 Micron

Filter

Tank Fill Cap

Assembly

0.031 in.

Note:

Forward relief valve pressure is 3625 psi for machines with serial numbers ending 1651 through 2499.

Forward relief valve pressure is 4350 psi for machines with serial numbers ending 2500 and up.

HYDRAULICS

4241262-Rev B 6-11

Hydraulic Schematic,

Continued

Figure 6-3

4WD

Valve

Relief Valve

400 psi

Brake Release

Valve

Left Front

Wheel Motor

TN2806

Reverse

Forward

Brake

Solenoid

Valve

RRF

Check

Valve

Hot Oil

Shuttle

Relief Valve

350 psi

Right Front

Wheel Motor

(See Note)

REV LF

Relief

Valve 400

DRN

0.052

in.

LRF

Check

Valve

RRR LRR

RRF LRF

Right Rear

Wheel Motor

Left Rear

Wheel Motor

11.90 ci 11.90 ci

DRN

Check

Valve

CHG

Brake

Cylinder

Brake

Cylinder

Note:

Front wheel motor displacement is 19.23 ci for machines with serial numbers ending 1651 through 2499.

Front wheel motor displacement is 17.09 ci for machines with serial numbers ending 2500 and up.

(See Note)

6-12 4241262-Rev B

HYDRAULICS

Hydraulic Schematic,

Continued

Figure 6-4

Steering Cylinder

Relief Valve

1450 psi

Steering Unit

Steering Valve

Check

Valve

TN2807

3.90

TEP

HYDRAULICS

4241262-Rev B 6-13

Hydraulic Schematic,

Continued

Figure 6-5

Lift Valve

Solenoid Valve

0.040

in.

Left Front

Cylinder

Center

Cylinder

Left Rear

Cylinder

Right Rear

Cylinder

One-Way Restrictor

TN2808

Lift/Lower

Test Port

Lower

Relief Valve

450 psi

98 6 3 2 4 1

Right Front

Cylinder

0.055 in.

0.040 in.

0.026

in.

Check

Valve

Check

Valve

Check

Valve

0.040

in.

0.040

in.

0.040

in.

0.040

in.

0.040

in.

0.040 in.

6-14 4241262-Rev B

HYDRAULICS

Hydraulic Schematic,

Continued

Figure 6-6

RF Reel Motor

Rear Reel Valve

Solenoid

Valve

Backlap

Valve

Reverse

Relief Valve

1167 psi

TN2809

C Reel Motor LF Reel Motor

• Reel Motor Displacement

LF 550 0.72 ci

LF 570 1.01 ci

• Reel Motor Displacement

LF 550 0.72 ci

LF 570 1.01 ci

RR Reel Motor LR Reel Motor

Rear Reel

Test Port

Check

Valve

Check

Valve

Front Reel

Test Port

Forward

Relief Valve

1167 psi

Reverse

Relief Valve

1167 psi

Check

Valve

Check

Valve

Forward

Relief Valve

1167 psi

Reverse

Relief Valve

1167 psi

Check

Valve

Check

Valve

Forward

Relief Valve

1167 psi

Reverse

Relief Valve

1167 psi

Check

Valve

Check

Valve

Forward

Relief Valve

1167 psi

Reverse

Relief Valve

1167 psi

Check

Valve

Check

Valve

Forward

Relief Valve

1167 psi

Front Reel Valve

Solenoid

Valve

Backlap

Valve

HYDRAULICS

4241262-Rev B 6-15

Page Intentionally Blank

6-16 4241262-Rev B

HYDRAULICS

Theory of Operation and

Diagnostic Information

Steering Circuit Schematic and

Theory of Operation

System Conditions:

• Engine running

• Steering wheel turned to the right or left (left turn

shown)

Oil Supply to Steering Unit

Hydraulic oil is drawn from the hydraulic oil tank by

section 1 of the gear pump assembly. Before entering the

gear pump assembly, the inlet oil is filtered by a

100-mesh screen to remove any debris. Operating

pressure oil from section 1 of the three-section gear

pump is routed to port “P” of the steering unit.

Steering Circuit

Operating pressure oil enters the steering unit at port “P,”

and is routed to the pilot line of the 1450 psi (100 bar)

relief valve, against the relief valve and check valve, and

to the steering valve.

With the steering wheel in the neutral (straight ahead)

position, the steering valve routes all of the operating

pressure oil out of the steering unit through port “E,”

supplying operating pressure oil to the lift valve.

With the steering wheel turned to the left, the steering

valve is moved, allowing oil to flow through the valve to

the gerotor metering section. Oil is then routed through

port “L” of the steering unit to the piston side of the

steering cylinder, extending the rod, and moving the rear

wheels in the desired direction.

Oil from the rod end of the steering cylinder flows back

into the steering unit through port “R,” through the

steering valve, and through port “T.” Oil exiting the

steering unit is routed through the lift valve and then

returns to the hydraulic tank.

Oil from the rod end of the steering cylinder is also routed

to port “ST” of the park brake release valve. When the

park brake release valve (lever) is in the normal position,

oil is blocked.

Circuit Relief

The steering system is protected by the 1450 psi (100

bar) relief valve. If the pressure on the pilot line of the

relief valve reaches 1450 psi (100 bar), the valve will

open, dumping operating pressure oil through port “T” of

the lift valve to the hydraulic tank.

HYDRAULICS

4241262-Rev B 6-17

Steering Circuit Schematic

See Figure 6-7.

Figure 6-7

1 Operating Pressure Oil from Gear Pump (Section 1) 3 Return Oil to Lift Valve (Port T)

2 Operating Pressure Oil to Lift Valve (Port P) 4 Return Oil to Park Brake Release Valve (Port ST)

TN2862

Steering Cylinder

Relief Valve

1450 psi

Steering Unit

Steering Valve

Check

Valve

3.90

TEP

Operating Pressure Oil

Return Oil

Metered Oil

6-18 4241262-Rev B

HYDRAULICS

Raise Circuit Schematic and Theory

of Operation

System Conditions:

• Engine running at fast idle

• Mower raise/lower switch in the raise position

NOTE

The cutting unit motors will automatically shut off as the

cutting units are raised.

Oil Supply to the Lift Valve

Hydraulic oil is drawn from the hydraulic oil tank by

section 1 of the gear pump assembly. Before entering the

gear pump assembly, the inlet oil is filtered by a

100-mesh screen to remove any debris. Operating

pressure oil from section 1 of the gear pump is routed

through the steering unit. The steering unit will supply oil

flow to the lift valve via port “E.”

Raise Circuit

Operating pressure oil supplied by section 1 of the gear

pump enters the lift valve at port “P.” The oil flows

through the solenoid valve, check valves, and 0.040 in. (1

mm) orifices to the rod side of the front and center lift

cylinders. Oil also flows unrestricted through the 0.026 in.

(0.66 mm) one-way restrictor to the rod side of the rear lift

cylinders. Oil flow to the rod side of the lift cylinders

raises the cutting units.

Oil from the piston end of the front and center lift

cylinders flows through the 0.040 in. (1 mm) orifices and

back to the return filter, oil cooler, then hydraulic tank. Oil

from the piston end of the rear lift cylinders flows through

the 0.055 in. (1.4 mm) orifice and back to the hydraulic

tank. The orifice restricts the flow of oil, dampening the

reaction of the cylinder retraction.

Circuit Relief

The lift system is protected by the 1450 psi (100 bar)

relief valve in the steering unit. If the pressure on the pilot

line of the relief valve reaches 1450 psi (100 bar), the

valve will open, dumping operating pressure oil through

port “T” of the lift valve to the return filter, oil cooler, and

then the hydraulic tank.

HYDRAULICS

4241262-Rev B 6-19

Raise Circuit Schematic

See Figure 6-8.

Figure 6-8

1 Operating Pressure Oil from Steering Unit (Port E) 3 Return Oil to Hydraulic Tank

2 Return Oil from Steering Unit (Port T)

TN2863

Lift Valve

Solenoid Valve

0.040

in.

Left Front

Cylinder

Center

Cylinder

Left Rear

Cylinder

Right Rear

Cylinder

One-Way Restrictor

Lift/Lower

Test Port

Lower

Relief Valve

450 psi

98 6 3 2 4 1

Right Front

Cylinder

0.055 in.

0.040 in.

0.026

in.

Check

Valve

Check

Valve

Check

Valve

0.040

in.

0.040

in.

0.040

in.

0.040

in.

0.040

in.

0.040 in.

Operating Pressure Oil

Return Oil

Metered Oil

6-20 4241262-Rev B

HYDRAULICS

Lower Circuit Schematic and Theory

of Operation

System Conditions:

• Engine running

• Mower raise/lower switch in the lower position

Oil Supply to Lift Valve

Hydraulic oil is drawn from the hydraulic oil tank by

section 1 of the gear pump assembly. Before entering the

gear pump assembly, the inlet oil is filtered by a

100-mesh screen to remove any debris. Operating

pressure oil from section 1 of the gear pump is routed

through the steering unit. The steering unit will supply oil

flow to the lift valve via port “E.”

Lower Circuit

Operating pressure oil supplied by section 1 of the gear

pump enters the lift valve at port “P.” The oil flows

through the solenoid valve to the pilot lines of the check

valves, the 450 psi (31 bar) relief valve, and through the

0.040 in. (1 mm) orifices to the piston side of the front

and center lift cylinders. Oil also flows through the 0.055

in. (1.4 mm) orifice to the piston side of the rear lift

cylinders. The 450 psi (31 bar) relief valve allows

sufficient pressure to build up to unseat the check valves.

Once that pressure is satisfied, the relief valve will shift,

dumping excess oil to the return filter, oil cooler, and then

the hydraulic tank.

With operating pressure oil at the pilot lines of the check

valves, the check valves open. Gravity allows the cutting

units to lower, pulling against the lift cylinders. Oil from

the rod end of the front and center lift cylinders flows

through the 0.040 in. (1 mm) orifices, which dampen the

lowering of the reels to prevent damage to the cutting

units, and then flows through the check valves, and back

to the hydraulic tank. Oil from the rod end of the rear lift

cylinders flows through the 0.026 in. (0.66 mm) one-way

restrictor, which lowers the rear cutting units at a slightly

slower rate than the front cutting units, then flows through

the check valve, and back to the hydraulic tank.

Circuit Relief

The lower system is protected by the 450 psi (31 bar)

relief valve. If the pressure on the pilot line of the relief

valve reaches 450 psi (31 bar), the valve will open,

dumping operating pressure oil through port “T” of the lift

valve to the hydraulic tank.

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Ransomes 67978, 67979, 67980, 67981, 67982, 67983 User manual

Brand: Ransomes

Model: 67978, 67979, 67980, 67981, 67982, 67983

Category: Lawnmowers

Type: User manual

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Ransomes 67978, 67979, 67980, 67981, 67982, 67983 User manual

Ransomes 67978, 67979, 67980, 67981, 67982, 67983 User manual

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