mecalac 12 MXT User manual

HANDBOOK OF REPAIR
MANUFACTURER: “MECALAC SAS”

28000 12MXT
M1 1
Contents
1. Safety precautions .........................................................................................................3
2. Description of the machine ...........................................................................................4
2.1 Central joint ......................................................................................................................................4
2.2 Stabilizers .........................................................................................................................................4
2.3 Rear chassis.....................................................................................................................................4
2.4 Transmission ....................................................................................................................................4
2.5 Turntable...........................................................................................................................................4
2.6 Cab ...................................................................................................................................................4
2.7 Controls ............................................................................................................................................4
2.8 Seat ..................................................................................................................................................4
2.9 Equipment ........................................................................................................................................4
2.10 Tool-holder........................................................................................................................................5
3. Technical characteristics ..............................................................................................6
3.1 Turbocharged engine .......................................................................................................................6
3.2 Axles.................................................................................................................................................6
3.3 Capacities.........................................................................................................................................6
3.4 Electrical system...............................................................................................................................6
3.5 Hydraulic system ..............................................................................................................................7
4. Equipment’s travel curves .............................................................................................9
4.1 In back-hoe bucket position .............................................................................................................9
4.2 In loading bucket position...............................................................................................................10
5. Table of stability loads in kg .......................................................................................11
5.1 Lifting and handling in the longitudinal position with standard or telescopic stabilizers.................11
5.2 Lifting and handling in the longitudinal position without stabilizers................................................12
5.3 Lifting and handling in the transverse position with standard stabilizers .......................................13
5.4 Lifting and handling in the transverse position without stabilizers .................................................14
5.5 Lifting and handling in the transverse position with telescopic stabilizers .....................................15
5.6 Lifting and handling in the longitudinal position with stabilizers.....................................................16
5.7 Lifting and handling in the longitudinal position without stabilizers................................................17
5.8 Lifting and handling in the transverse position with stabilizers ......................................................18
5.9 Lifting and handling in the transverse position without stabilizers .................................................19
5.10 Lifting and handling in the transverse position with telescopic stabilizers .....................................20
6. Towing ..........................................................................................................................21
6.1 Disconnection of the hydrostatic travel ..........................................................................................21
6.2 If the turntable is badly oriented.....................................................................................................22
7. Transporting the machine............................................................................................23
7.1 Loading on a trailer ........................................................................................................................23
7.2 Slinging for lifting ............................................................................................................................24
8. Location of the hydraulic components .......................................................................25
9. Hydraulic diagrams ......................................................................................................29
9.1 Travel circuit ...................................................................................................................................29
9.2 Accelerator, main and parking brake circuits .................................................................................30

9.3 Steering and slewing circuits..........................................................................................................31
9.4 Turntable supply and return circuit .................................................................................................32
9.5 Equipment pump, stabilizers, Oscillation lock and cooling circuits ................................................33
9.6 Boom, intermediate boom, dipper, offset and additional functions ................................................34
9.7 Bucket circuit ..................................................................................................................................35
9.8 Spool valve (A / Down - B / Upper) ................................................................................................36
9.9 Additional hydraulic equipment for fitting of the hammer return on the equipment (option) ..........37
9.10 Tool-holder circuit (option) ..............................................................................................................38
9.11 Air conditioning circuit (option) .......................................................................................................39
9.12 Telescopic stabilizers (option) ........................................................................................................40
9.13 Safety valves (option).....................................................................................................................41
9.14 Manual accelerator (option)............................................................................................................42
9.15 Volvo tool-holder (option) ...............................................................................................................43
9.16 Additional hydraulic, electrical control of the additional function (option) ......................................44
10. Parts list of the hydraulic diagram .............................................................................45
11. Installation of the electric bundles .............................................................................47
12. Location of the electric components ..........................................................................49
12.1 Solenoid-operated valves...............................................................................................................49
12.2 A relay plate (under the cab seat) ..................................................................................................53
12.3 B relay plate (under the cab seat)..................................................................................................55
12.5 Air conditioning relay box (option) (under the cab floor) ................................................................56
12.4 Relay box (on fuel tank) .................................................................................................................56
13. Parts list of the electric diagram ................................................................................57
14. Adjustment procedure..................................................................................................59
14.1 Adjustment procedure for the heat engine.....................................................................................59
14.2 Hydraulic adjustment procedure for the gears ...............................................................................61
14.3 Direction adjustment procedure .....................................................................................................68
14.4 Hydraulic adjustment of the equipment..........................................................................................70
15. Control Sheet................................................................................................................79
16. Tools .............................................................................................................................81
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28000 12MXT
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1. Safety precautions
Throughout this book the symbol is used to draw your
attention to areas where special care is required, to prevent
accidents and injury.
• Construction sites are busy places, often with wet, muddy
ground, conditions which impede other workers ability to
avoid carelessly driven machinery. Skid-steers are designed
to be highly manoeuvrable and compact in operation. They
are rugged and can be operated under a variety of
conditions, and the operator may be presented with hazards
associated with operating this machine.
•Be vigilant and “think safety”.
•DO NOT operate this machine unless you have been
properly instructed on its control and safe operation.
• These operating instructions are designed to familiarise the
user with the machine and its designated use. The instruction
manual contains important information on how to operate the
machine safely, properly and most efficiently. Observing
these instructions help to avoid danger, to reduce repair
costs and down-time and to increase the reliability and life of
the machine.
• The operating instructions must always be available
wherever the machine is in use. These operating instructions
must be read and applied by any person in charge of carrying
out work with and on the machine, such as:
–care and disposal of fuels and consumables.
–maintenance (servicing, inspection, repair) and/or
transport.
• In addition to the operating instructions and to the mandatory
rules and regulations for accident prevention and
environmental protection in the country and place of use of
the machine, the general recognised technical rules for safe
and proper working must also be observed.

2. Description of the machine
The excavator is made up of a front chassis section, a rear chassis section, a turntable, a cab and equipment
consisting of four elements.
2.1 Central joint
The ground contact of the four wheels is provided by the oscillation of the rear axle. The ground contact
of the four wheels is provided by the oscillation of the rear axle.
2.2 Stabilizers
Two independently-controlled stabilizers combined with the oscillation lock stabilize the machine during
operation.
2.3 Rear chassis
The rear chassis section is equipped with a water-cooled 4 in-line-cylinder engine.
- The engine drives two variable displacement pumps which perform the following functions:
• Transfer movement pump: coupled in a closed circuit with a variable displacement motor, the
assembly forming a hydrostatic transmission.
• Equipment pump: movements of the rams, power-assistance of the controls and associated
functions.
- The engine also drives a fixed displacement pump which performs the machine’s steering and slewing
movements.
2.4 Transmission
The transmission is of the permanent 4x4 type, with a limited-slip differential on both axles.
2.5 Turntable
The turntable is connected to the front chassis section by a slewing crown wheel. The turntable supports
the operator’s cab, the excavator’s equipment and the counterweight.
The slewing internal crown wheel is driven by a hydraulic motor equipped with a negative brake in the
event of a power-assistance pressure fault.
2.6 Cab
The monocoque cab is closed and heated. It is “FOPS” and “ROPS” approved (falling objects and roll-over
protective structure).
2.7 Controls
The cross position of the equipment controls makes it possible to combine the various actions flexibly and
efficiently.
2.8 Seat
The seat is sprung, dampened, height-adjustable and adjustable lengthwise.
2.9 Equipment
The equipment is in the centre of the machine. It is made up of four elements: the boom, the intermediate
boom, the coupling and the dipper.
The boom is controlled by the parallelogram formed by the boom ram, the braces and the boom
connecting rods. This gives it the advantage of a 140° travel.
The equipment can be offset on both sides by means of a hydraulic ram.
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2.10 Tool-holder
At the end of the dipper is the tool-holder permitting the instant changing of the bucket or tool from the cab
without manual intervention. Buckets or tools are taken up automatically. Only their unlocking requires
hydraulic energy.
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12MXT 28000
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3. Technical characteristics
3.1 Turbocharged engine
- Type:.........................................................................................................................CUMMINS 4BT4.5C
- Diesel: ......................................................................................................................... 4 in-line cylinders
- Net horsepower at flywheel (DIN 70020 / ECE-R2403): ........................................ 74 kW at 2,200 rpm
- Maximum net torque at flywheel (DIN 70020 / ECE-R2403): ............................. 414 N.m at 1,500 rpm
- Cubic capacity: ........................................................................................................................ 4506 cm3
- Bore x stroke: ........................................................................................................... 102 mm x 138 mm
- Cooling by: ................................................................................................................................... coolant
- Air filter: ......................................................................................................... with dry cyclonic cartridge
3.2 Axles
- Rigid axle on the front chassis section: .................................................................. DANA 112 / 132
Gear ratios:
• Bevel gear: ............................................................................................................................. 11 / 35
• Epicyclic wheel reducer, 4 planet wheels: .................................................................................. 1 / 6
- Oscillating axle on the rear chassis section: ................................................. DANA 311 / 112 / 102
With transfer box:.................................................................................................................... DANA 311
Gear ratios:
• Coupled transfer box: ............................................................................................................ 1 / 1,77
• Bevel gear: ............................................................................................................................. 11 / 35
• Epicyclic wheel reducer, 4 planet wheels: .................................................................................. 1 / 6
- Self-blocking differential: ........................................................................................... limited slip 45%
- Integrated oil-bath disc brakes: ............................................................................ 6 discs at the front
:............................................................................. 6 discs at the rear
3.3 Capacities
- Hydraulic oil tank: .............................................................................................................................. 82 l
- Total capacity of the hydraulic circuit: ............................................................................................. 135 l
- Front and rear axle housing, each: .................................................................................................. 6.8 l
- Transfer box on the rear axle: ....................................................................................................... 0.75 l
- Wheel reducer: .............................................................................................................................. 0.75 l
- Diesel engine, Sump: ........................................................................................................................ 11 l
- Diesel fuel tank: .............................................................................................................................. 130 l
- Cooling system: ................................................................................................................................ 14 l
3.4 Electrical system
- Battery: ................................................................................................................................ 12 V 175 Ah
- Starter: ............................................................................................................................. 12 V - 2.7 KW
- Alternator: ........................................................................................................................... 12 V - 62 Ah
- Alternator (air conditioning option): .................................................................................... 12 V - 95 Ah
- Battery cut-out.
- Track rotating commutator, all of whose wires (white) are marked with a number.
- Engine shut-off device which works by cutting off the diesel fuel supply.
- Lighting and signalling complying with the highway code.
- Relay / fuse box (under the cab seat).
- Wiring harnesses with waterproof connectors.
- Negative pole to the chassis.

3.5 Hydraulic system
Three completely independent circuits: hydrostatic transmission, equipment circuit, and steering and
slewing circuit.
3.5.1 Hydrostatic transmission
Reversible closed circuit, with declutching bypass valves in case towing is necessary.
- Transfer movement pump: ............................................................................................. 71 cm3
- Transfer movement engine:........................................................................................... 140 cm3
- Axial piston engine and pump:
Variable displacement and axial piston motor and pump permitting the continuous variation of the
transmission ratio over the machine’s entire speed range. Automatic adjustment of the optimum
transmission ratio to suit the motion resistance and accelerator setpoint of the diesel engine: it
is automobile control.
- Selection of direction of travel:
(F) “forward” or (R) “reverse” by electric control on the steering ”Commodo”, without being
obliged to stop.
- Two speeds:
For both directions of travel selected by the “Commodo” steering electric control:
•(L) “site” (between 0 and 6 kph).
•(H) “road” (between 0 and 26 kph).
Possibility of control in “loader mode” (L) or (H) and (F) or (R) using the right manipulator.
- Inching” slow approach control:
Allows reducing the displacement speed at a constant engine regime and therefore applying a
constant power to the wheels in both front / reverse directions.
- Handbrake (parking and emergency):
It works by lack of pressure on the integrated discs on the front axle.
- Hydrostatic foot brake:
Foot-operated control with Inching device, main brake function and working brake function.
- Main brake:
In the initial part of its travel, it reduces the machine’s travel speed by means of the valve (Inching
function), then if the braking pressure exceeds 13 bar it acts simultaneously on the integrated
discs on the front and rear axles (main brake function). This system increases the service life of
the brake discs.
- Working brake:
A switch locks the foot-operated control in the braked position and makes it possible to work by
releasing the brake pedal while at the same time having the brakes locked.
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3.5.2 Equipment circuit:
- Variable displacement, axial piston pump:
• Cubic capacity: .............................................................................................................. 63 cm3
• Maximum delivery: .................................................................................................... 140 l/min
- Associated functions by solenoid-operated valves:
• Low pressure: ............................................................................................................. ~ 35 bar
- Accelerator.
- Oscillation lock.
- Seat pivoting console safety device.
• High pressure: .......................................................................................................... ~ 280 bar
- Stabilizers.
- Tool unlocking.
- Offset.
- Combined SX14 “LUDV” valve block:
• Five elements of proportional Load Sensing function with individual balancing for each
element: boom, intermediate boom, dipper, bucket and auxiliary.
• One input element.
• One open-centre element for slewing with separate supply.
• Proportionality of the functions always complied with irrespective of each element’s pressure
level.
• Anti-cavitation pressure relief valve on each element.
• Hydraulical-assisted proportional function controls, by manipulators or foot-operated controls
supplied at low pressure with standby accumulator.
3.5.3 Slewing and hydrostatic steering circuit:
- Hydrostatic steering:
Double-acting ram controlled by a ORBITROL unit, protected by two anti-shock valves
• Fixed displacement gear pump:
- Cubic capacity: ........................................................................................................ 19 cm3
- Maximum delivery: ............................................................................................. ~ 43 l/min
- Maximum pressure: ............................................................................................... 175 bar
- Slewing:
• Hydraulic motor: .................................................................................. MSE05 with brake F07
- Maximum pressure: ............................................................................................... 230 bar
- Cubic capacity: ...................................................................................................... 750 cm3
• Slewing internal (balls) crown wheel with remote greasing.
• Rotation speed: .............................................................................................................. 8 rpm
- Hydraulic filtration:
• on return circuit for the equipment (10 µ).
• on booster pump circuit for travel (10 µ).
- Paint:
• Polyurethane paint: ................................................................................ Grey VOLVO 80BR3
• Polyurethane paint: .............................................................................. Yellow VOLVO 80BR3
• Solidifying agent: .............................................................................................................. DT6
• Thinner (diluent): ............................................................................................................. X400
- Basic mixture ratios: 100 parts color to 30 parts solidifying agent, with 5 to 15 % thinner
for total.
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4. Equipment’s travel curves
4.1 In back-hoe bucket position
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
2 m
3 m
4 m
0 m 1 m 1 m 2 m2 m 3 m 3 m 4 m 5 m 6 m 7 m
7560
5580
3720
6860
6740
2500

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4.2 In loading bucket position
0 m 1 m 1 m 2 m2 m 3 m 3 m 4 m 5 m 6 m 7 m
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
2 m
3 m
4 m
3620 7450
6100
6735
6620

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M1 11
5.1 Lifting and handling in the longitudinal position
with standard or telescopic stabilizers
Working conditions:
- On wheels with the stabilizers.
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Without any tool (bucket, loader, etc.) with handling plate +
hook.
Stability loads and hydraulic limits according
to standard ISO 10567.
5. Table of stability loads in kg
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
2 m
3 m
4 m
0 m 1 m 1 m 2 m2 m 3 m 3 m 4 m 5 m 6 m 7 m
2400
1700 1300
2000
1400
3200
3200
1900
1300
1200
2000 1750
1450
2700

12MXT 28000
12 M1
5.2 Lifting and handling in the longitudinal position
without stabilizers
Working conditions:
- On wheels without the stabilizers.
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Without any tool (bucket, loader, etc.) with handling plate +
hook.
Stability loads and hydraulic limits according
to standard ISO 10567.
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
2 m
3 m
4 m
0 m 1 m 1 m 2 m2 m 3 m 3 m 4 m 5 m 6 m 7 m
2000
900
750
1400
850
3200
3200
1900
1200
900
2000 1650
1200
2700

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M1 13
5.3 Lifting and handling in the transverse position
with standard stabilizers
Working conditions:
- On wheels with the stabilizers.
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Rear axle oscillation locked.
- Without any tool (bucket, loader, etc.) with handling plate +
hook.
Stability loads and hydraulic limits according
to standard ISO 10567.
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
2 m
3 m
4 m
0 m 1 m 1 m 2 m2 m 3 m 3 m 4 m 5 m 6 m 7 m
2700
2000
1600 1000
2200 1400
950
800 700
3200
3200 1900 1300
950

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14 M1
5.4 Lifting and handling in the transverse position
without stabilizers
Working conditions:
- On wheels without the stabilizers.
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Rear axle oscillation locked.
- Without any tool (bucket, loader, etc.) with handling plate +
hook.
Stability loads and hydraulic limits according
to standard ISO 10567.
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
2 m
3 m
4 m
0 m 1 m 1 m 2 m2 m 3 m 3 m 4 m 5 m 6 m 7 m
2700
2000
1300
900
1800 1150
800
650 600
3200
3200 1700 1100
800

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M1 15
5.5 Lifting and handling in the transverse position
with telescopic stabilizers
Working conditions:
- On wheels with the telescopic stabilizers fully extended.
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Rear axle oscillation locked.
- Without any tool (bucket, loader, etc.) with handling plate +
hook.
Stability loads and hydraulic limits according
to standard ISO 10567.
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
2 m
3 m
4 m
0 m 1 m 1 m 2 m2 m 3 m 3 m 4 m 5 m 6 m 7 m
2700
2000
1600 1350
2200 1800
1300 1150 1000
3200
3200 1900 1300 1100

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16 M1
5.6 Lifting and handling in the longitudinal position
with stabilizers
Working conditions:
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Without any tool (bucket, loader, etc.).
-Bucket ram always full extended with hook fixed on tool-
holder rod.
Stability loads and hydraulic limits according
to standard ISO 10567.
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
0 m 1 m 2 m 3 m 4 m 5 m 6 m 7 m
2500
2000
1750 1450
1450
2400
2000
1400
1150
1300
1700
1800
2500
ZONE A
ZONE B
ZONE A: Bucket is necessary
ZONE B: With bucket, deduct 300 kg from table values

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M1 17
5.7 Lifting and handling in the longitudinal position
without stabilizers
Working conditions:
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Without any tool (bucket, loader, etc.).
-Bucket ram always full extended with hook fixed on tool-
holder rod.
Stability loads and hydraulic limits according
to standard ISO 10567.
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
0 m 1 m 2 m 3 m 4 m 5 m 6 m 7 m
2500
2000
1750 1450
1200
2000
1400
850
1150
750
900
1800
2500
ZONE A
ZONE B
ZONE A: Bucket is necessary
ZONE B: With bucket, deduct 300 kg from table values

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5.8 Lifting and handling in the transverse position
with stabilizers
Working conditions:
- On level, compact ground.
- Equipment used without any offset.
- Front and rear chassis sections aligned.
- Rear axle oscillation locked.
- Without any tool (bucket, loader, etc.).
-Bucket ram always full extended with hook fixed on tool-
holder rod.
Stability loads and hydraulic limits according
to standard ISO 10567.
7 m
6 m
5 m
4 m
3 m
2 m
1 m
0 m
1 m
0 m 1 m 2 m 3 m 4 m 5 m 6 m 7 m
2500
2000
1600 1300
1000
2200
1400
800
700
700
950
1800
2500
ZONE A
ZONE B
ZONE A: Bucket is necessary
ZONE B: With bucket, deduct 300 kg from table values