PHILIPPINE AGRICULTURAL ENGINEERING STANDARD PAES 118: 2001

Agricultural Machinery – Four-Wheel Tractor – Specifications

Foreword

The formulation of this national standard was initiated by the Agricultural Machinery Testing
and Evaluation Center (AMTEC) under the project entitled “Enhancing the Implementation
of AFMA Through Improved Agricultural Engineering Standards” which was funded by the
Bureau of Agricultural Research (BAR) of the Department of Agriculture (DA).

This standard has been technically prepared in accordance with PNS 01-4:1998 (ISO/IEC
Directives Part 3:1997) – Rules for the Structure and Drafting of International Standards. In
compliance with metrication law “Batas Pambansa Bilang 8” enacted on January 1, 1983,
some data are converted to International System of Units (SI).

The word “shall” is used to indicate requirements strictly to be followed in order to conform
to the standard and from which no deviation is permitted.

The word “should” is used to indicate that among several possibilities one is recommended as
particularly suitable, without mentioning or excluding others, or that certain course of action
is preferred but not necessarily required.

In the preparation of this standard, the following documents/publications were considered:

Hunt, Donnel. Farm Power and Machinery Management. 7th Edition. Iowa State University
Press, Ames, Iowa.1977.

Machinery Management Lecture Notes. Wedd, Stephen. University of Sydney, Orange.

November 3, 1999.

American Society of Agricultural Engineers (ASAE) S203.10:1982 Rear Power Take-off for
Agricultural Tractors

American Society of Agricultural Engineers (ASAE) S217.10:1984 Three-point Free-link

Attachment for Hitching Implements to Agricultural Wheel Tractors

International Organization for Standardization (ISO) 500:1979 Agricultural Tractors –

Power-take-off and drawbar – Specification

International Organization for Standardization (ISO) 500:1991 Agricultural Tractors – Rear-

mounted Power-take-off – Types 1, 2 and 3

Regional Network for Agricultural Machinery (RNAM) Test Codes And Procedures for Farm
Machinery. Technical Series No. 12 :1983.

Republic Act No. 7394 otherwise known as “The Consumer Act of the Philippines” enacted
on July 22, 1991.
PHILIPPINE AGRICULTURAL ENGINEERING STANDARD PAES 118: 2001

Agricultural Machinery – Four-Wheel Tractor – Specifications

1 Scope

This standard specifies the requirements for the construction and operation of agricultural
four-wheel tractor.

This is applicable to two-wheel drive and four-wheel drive tractors with a net power range of
4 kW to 400 kW.

2 References

The following normative documents contain provisions, which, through reference in this text,
constitute provisions of this National Standard:

PAES 102:2000, Agricultural Machinery – Operator’s Manual – Content and Presentation

PAES 103:2000, Agricultural Machinery – Method of Sampling

PAES 104:2000, Agricultural Machinery – Location and Method of Operation of Operator’s

Controls – Control for Agricultural Tractors and Machinery

PAES 119:2001, Agricultural Machinery – Four-Wheel Tractor – Methods of Test

ISO 500:1991, Agricultural Tractors – Rear-mounted Power-take-off – Types 1, 2 and 3

ISO 730-1:1994, Rear-mounted three-point linkage – Categories 1, 2, 3 and 4

ISO 6489-3:1992, Agricultural Vehicles – Mechanical Connections on Towing Vehicles –

Part 3: Tractor Drawbar.

ISO 3776:1989, Tractors for Agriculture – Seat Belt Anchorages.

ISO 4253:1993, Agricultural Tractors – Operator’s seating accommodation – Dimensions.

ISO/DIS 8082:2001, Roll-over Protective Structures (ROPS) – Laboratory tests and

Performance Requirements.
 PAES 118: 2001

3 Definitions

For the purpose of this standard, the following definitions shall apply:

3.1
drawbar
bar at the rear of a tractor to which implements are hitched

3.2
drawbar power
power available at the drawbar sustainable over a distance of at least 20 meters

3.3
four-wheel tractor
self-propelled, wheeled vehicle having two axles designed to carry, pull or propel agricultural
implements and machines

3.3.1
four-wheel drive
type of four-wheel tractor where power is transmitted to all wheels

3.3.2
two-wheel drive
type of four-wheel tractor where power is transmitted to rear wheels with small front wheels
being pushed along

3.4
linchpin
retaining pin used in the hitch pins or studs

3.5
lower hitch point tire clearance
clearance (x) expressed as a radial dimension from the lower hitch point to the outside
diameter of the tire with the implement in raised position and all side sway removed from the
links (see Figure 1a)

3.6
lower hitch point tractor clearance
horizontal dimension (z) between the rearmost parts of the tractor in the area between the two
lower links and the horizontal line through the two lower hitch points throughout the range of
vertical movement of the hitch points (see Figure 1b)
NOTE The power-take-off master shield may be removed, if necessary to meet this
dimension.

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a) Tire clearance b) Tractor clearance

Figure 1 – Lower Hitch Point Tire and Tractor Clearance

3.7
power-take-off (PTO) shaft
external shaft usually at the rear of the tractor providing rotational power to implements and
machines

3.8
PTO output power
power measured at the PTO shaft

3.9
roll-over protective structure (ROPS)
roll-over protective device (ROPD)
safety frame
two- or four-post structural frames primarily used to protect a seat-belted operator from being
crushed in case the machine rolls over

3.10
three-point linkage
combination of one upper link and two lower links, each articulated to the tractor and the
implement at opposite ends in order to connect the implement to the tractor (see Figure 2)

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Upper link

Leveling adjustment Detail "A"

Hitch point

Link point

PTO shaft
Detail "A"
Lower link

Figure 2 – Three-point Linkage and its Components

3.10.1
hitch point
articulated connection between a link and the implement (see Figure 2)

NOTE For geometrical analysis, the hitch point is established as the center of the articulated
connection between a link and the implement.

3.10.2
leveling adjustment
adjustment of the right lower link so that the hitch point may be moved vertically with
respect to the left lower hitch point to provide an inclination of the implement (see Figure 2)

3.10.3
link point
articulated connection between a link and the tractor (see Figure 2)

NOTE For geometrical analysis, the link point is established as the center of the articulated
connection between a link and the tractor.

3.10.4
upper hitch pin
pin that connects the upper link to the implement (see Figure 2)

3.10.5
upper link pin
pin that connects the upper link to the tractor (see Figure 2)

3.11
wheel tread
center to center distance between two front or rear wheels

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4 Classification

4.1 two-wheel drive

Figure 3. Two-wheel drive tractor

4.2 four-wheel drive

Figure 4. Four-wheel drive tractor

5 Construction Requirements

5.1 Materials

The tractor shall be generally made of cast iron and steel materials.

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5.2 Controls

The various controls of the tractor as shown in Figure 5 shall be located and operated in
accordance with PAES 104.

Work light switch (front)

1000 2000

Glow plug 0
Work light switch (rear)
indicator
3000

Light switch

Starter switch

Engine stop knob

Hazard light switch

Steering wheel

Main gear shift lever

Dual speed-shift
switch
Parking brake Foot throttle
lever Hydraulic draft lever
Hydraulic position lever
Clutch pedal
Hand throttle lever

Synchro-shuttle
shift lever Remote control valve lever

Auxiliary gear
shift lever

Front wheel Hydraulic select lever

drive lever Brake
pedal PTO clutch control lever

Differential lock pedal Hydraulic lowering speed knob

Figure 5. Typical controls of a four-wheel tractor

5.3 Hydraulic Three-point Linkage System

5.3.1 The tractor shall be equipped with position and/or draft implement controls.

5.3.2 The dimensions of three-point linkage shall be based on the following categories to
enable implements to be attached to all makes of tractors. Each category covers tractor power
ranges as shown in Table 1.
Table 1 – Three-point Linkage Categories
Maximum Drawbar Power
Category
kW
1 15 – 35
2 30 – 75
3 60 – 168
4 135 – 300
Source: ASAE Standard 209, Agricultural Tractor Test Code.

NOTE For more detailed specifications of three-point linkage refer to ISO 730-1.

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5.3.3 The dimensions associated with the tractor is given in Table 2 and shown in Figure 6.

Table 2 – Dimensions Associated with the Tractor under the three-point linkage categories

Figure 6 – Dimensions Associated with the Tractor

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5.4 Drawbar

5.4.1 Types of drawbar

a) fixed drawbar b) swinging drawbar c) link drawbar

Figure 7 –Drawbar types

5.4.2 The drawbar shall be situated in the longitudinal mid-plane of the tractor. The
−0
diameter of the hole in the drawbar should be 33 + 0.5 mm. The thickness of the drawbar
shall be not more than 32 mm. (see Figure 8)

NOTE For more detailed specification of drawbar refer to ISO 6489-3.

32 mm

33 mm

Figure 8 – Clevis-type drawbar hole diameter and thickness

5.4.3 Mechanism for drawbar height adjustment shall be provided, as this can be useful for
setting up the implement for the most efficient output.

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5.5 Transmission systems

5.5.1 Main clutch and PTO clutch

5.5.1.1 Dry type single-plate clutch

The clutch is engaged when the driven plate is gripped firmly between the flywheel and
pressure plate by the force of the pressure spring causing the rotary motion of the flywheel to
be transmitted through driven plate to main drive shaft. (see Figure 9a)

Applying a stepping force on the clutch pedal causes the rod to move in the direction of the
arrow accompanying the leftward movement of the release bearing so that the lower end of
the release lever is pushed in the same direction. The pressure plate is shifted toward the right
against the force of the pressure spring removing the pressure from the driven plate so that
transmission of the revolution of the flywheel to the driven plate is cut bringing the main
shaft to a halt. (see Figure 9b)
Pressure Plate
Pressure Spring
Release Bearing Driven Plate

Free Travel

Drive Shaft

Power From Engine

Clearance
Release Lever Power Flow
Pressure Spring
Flywheel
Pin
a) Clutch engaged

Release Bearing

Release Lever
Clearance
Clearance
b) Clutch disengaged

Figure 9 – Dry Type Single-plate Clutch

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5.5.1.2 Dual clutch

When both the main clutch and dual clutch parts are both engaged, the main clutch disc and
PTO clutch disc are transmitting power to the main driving shaft and PTO driving shaft,
respectively. (see Figure 10a)

The first stage of stepping on the clutch pedal causes the pin to move in the direction of the
arrow, but the original space between the pin (2) and the pressure plate (1) is wide enough to
prevent the pin (2) from pulling the pressure plate. However, the pin (1) pushes the pressure
plate towards the flywheel side until it comes apart from the main clutch disc. Thus, the first
stage recession of the clutch pedal disengages the main clutch part while the PTO clutch is
still engaged. (see Figure 10b)

The second stage of stepping on the clutch pedal deeper down causes the pin (2) to pull the
pressure plate (1) away from the PTO clutch disc making both the PTO clutch and main
clutch disengaged. (see Figure 10c)
Pin (2)
Clearance
Pin (1)

Release Lever

Flywheel Release Bearing

Running Drive Shaft

Clutch Pedal

PTO
Drive Shaft
Pressure Spring

PTO Clutch Disc

Clutch Rod
Pressure Plate (1)
Main Running Clutch Disc
Pressure Plate (2)

a) Both are engaged

No Clearance

b) Main clutch is disengaged c) Both are disengaged

but PTO clutch engaged

Figure 10 – Construction and Function of Dual Clutch

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5.5.2 Transmission gears

The transmission gears shall be classified based on the following:

5.5.2.1 Sliding mesh gears

Gears on the main shaft are meshed with the other gears on the counter shaft selectively by
sliding them along the splined part of the gear. (see Figure 11)

Figure 11 – Sliding Mesh Type Transmission Gears

5.5.2.2 Constant mesh gears

A gear on the counter shaft and an idler on the main shaft are kept in constant mesh, while
the sliding clutch (1) and (2) on the splined part of the main shaft are connected with the
gears by sliding them along to drive the main shaft. To attain the main shaft’s maximum
speed, the drive shaft shall be directly connected to the main shaft by sliding clutch (1) to the
left. If the mating clutch (1) is shifted to the right connecting it to gear 2, the main shaft will
assume the same speed as the gear 2. Similarly, when the mating clutch (2) is shifted to the
left connecting it with gear 3, the main shaft’s revolution will be reversed. (see Figure 12)
Mating Clutch (1) Mating Clutch (2)
1 2 1 2

Main Shaft

Counter Shaft

Reverse Gear
Figure 12 – Constant mesh type transmission gears

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5.5.2.3 Synchronous mesh gears

5.5.2.3.1 Constant load type

Cone clutches are formed between the inner part of the hub and the mating gears (1) and (2).
Mating of the clutch is done by moving the sleeve axially which gives sliding motion to the
hub via the steel balls along the main shaft. By mating of the friction clutch, the revolution of
the gear and the main shaft are made uniform.

If the sleeve is pushed further after giving same revolution to the gear and the main shaft, the
steel balls are displaced from the grooves causing the sleeve to slide on the hub resulting in
smooth meshing between the clutching gear and interval splines of the sleeve. (see Figure
13a)

5.5.2.3.2 Inertia lock type

The clutch is engaged when the sliding ring is moved by shift lever, the fixed collar moves
together by spring force and its end face presses against the cone. Differential revolution
speed, if any, between the gears (1) and (2) and the main shaft causes the cone to rotate in
one way until it halts by the side face of the fixed collar. And the more the sliding ring of the
teeth of the cone are pressed, the more the cone is pressed by cam lift generating frictional
torque in the cone clutch which result in the synchronizing action. When the speed of the
main shaft and the gear (1) or (2) is equalized, the torque given by cone clutch to rotate the
cone is lifted and the sliding ring returns the cone to its neutral position passes the teeth and
meshes with the clutching teeth of the gear (1) or (2). (see Figure 13b)
Spring Steel Ball
Main Shaft Sliding Link
Sleeve Fixed Collar
Gear (1) Gear (2) Spring Main Shaft
Cone
Hub

Gear (1)
Hub Gear (2)

a) Constant load type b) Inertia lock type

Figure 13 – Synchronous Mesh Type Transmission Gears

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5.5.2.4 Planetary gears

It is composed of the sun gear fixed on the driving shaft; the planetary gear which is meshed
with it; the carrier fixed on the driving shaft which supports them; the ring gear on the
internal side of which the planetary gears are in mesh; and the brake for locking the ring gear.

When the ring gear is locked and the sun gear is driven by the driving shaft, the planetary
gears will rotate around the sun gear, at the same time, spinning by themselves, and the
carrier rotates in the same direction. (see Figure 14)
Brake

Sun Gear Carrier

Carrier

Planetary
Gear Planetary
Sun Gear Gear

Ring Gear
Brake

Figure 14 – Principles of Planetary Speed Change Gears

5.5.2.5 Fluid coupler and transmission

In hydrostatic transmission (HST), the plunger or gear pump delivers liquid to the hydraulic
motor which is similar to the pump in construction (see Figure 15). The HST makes use of a
small volume of liquid at high pressure for power transmission.

Wheel

Pump Motor
Engine

Figure 15 – Hydrostatic Transmission (HST)

5.5.2.6 Tractors may have “on-the-go” shifts and/or shuttle gears which enable quick forward
and reverse selection in each gear.

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5.5.3 Differential gears

When the tractor is turning (see Figure 16a), the resistance against the inner wheel becomes
greater than the resistance against the outer wheel, the difference of which is reflected to the
differential side gear as a corresponding differential resistance. This differential resistance
causes the differential pinions to turn giving different rotating speeds to the differential side
gear, resulting to different rotating speeds of the right and left driving wheels. (see Figure
16b)

Driving Wheels

Higher Revolution of
Outer Wheel
Lower Revolution of
Inner Wheel
Driving
Wheels

a) Function

Differential Case Differential

Pinion Shaft
Spiral Bevel Gear
Differential
Side Gears
Rear Axle

Driving Shaft Final Drive Gears

Spiral Bevel Differential

Pinion Gear Yoke Shaft
Differential
Pinion Gears

b) Construction

Figure 16 – Function and Construction of Differential Gears

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5.5.4 Differential lock

The differential lock is a device by which a restraining force is applied to the differential
gears in case one of the wheels go into an idle spin, so that the differential yoke shafts are
rotated together as one unit. (see Figure 17)
Differential
Pinion Gears

Shift Fork Shift Fork

Differential Lock
(pin type) Differential Lock
(mating clutch type)
Differential Differential
Yoke Shaft Yoke Shaft

Differential
Side Gears

a) Pin type b) Mating clutch type

Figure 17 – Types of Differential Locks

5.5.6 PTO shaft

The main characteristics of the three types of PTO shafts shall be as specified in Table 3.

Table 3 – Characteristics of PTO Types

PTO Nominal Number and Type PTO Rated

Type Diameter of Splines Speed PTO Shaft Profile
mm rpm

Straight spline

1 35 6 straight splines 540

21 involute
2 35 1000 Involute spline
splines

20 involute
3 45 1000
splines

NOTE For more detailed specifications of the PTO, refer to ISO 500.

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 PAES 118: 2001

5.6 Wheel tread adjustment

Mechanism for wheel tread adjustment shall be provided, as this can be useful for allowing
the wheel tread to be matched with implements.

5.6.1 Front tread

The length of the front axle itself shall be adjusted by changing set bolt positions as shown in
Figure 18a. The length of the tie-rod shall be adjusted accordingly. For four-wheel drive
tractors, the front tread shall be adjusted by inverting the disc or changing the position of the
wheel hub along the shaft as shown in Figure 18b.

5.6.2 Rear tread

For two-wheel and four-wheel drive tractors, the rear tread shall be adjusted by inverting the
disc, since the shaft length is not changeable. Or, it shall be adjusted by changing the position
of the wheel hub along the shaft. (see Figure 18b)
Center pivot

Front axle
A

Bolt
A and B is of the
Tie rod same pitch

a) Tread adjustment of front wheel

Axle
Disc
Rim Bolt

Tire

1 2 3 4

5 6 7 8
b) Tread adjustment of rear wheels

Figure 18 – Examples of Wheel Tread Adjustment

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5.7 Brake system

The brake system shall be classified according to:

5.7.1 manner of applying braking force

5.7.1.1 internal expansion type

The motion of the brake cam in the direction of the arrow makes the brake shoes open
outward until the brake linings are pressed hard against the brake drum for braking
(see Figure 19 a).

5.7.1.2 external contraction type

The motion of the link arm in the direction of the arrow makes the brake band tightly in
contact with the brake drum for braking (see Figure 19 b).

5.7.1.3 disc type

The steel balls between the two actuating discs pushed them outward until they are pressed
hard against the brake discs for braking (see Figure 19 c).

Adjusting Anchor
Brake lining Cam (or Hydraulic slave cylinder) yokes
Brake pedal
Axle Brake drum Brake lining

Retracting spring

Brake shoes Link arm

Brake band Brake drum

Adjusting screw

a) internal expansion type b) external contraction type

Brake discs
Steel ball

Actuating disc
Pull rod

Actuating arm

c) disc type

Figure 19 – Types of Brake based on Brake Force Application

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5.7.2 manner of transmitting the force from the control

5.7.2.1 mechanical brake

The motion of the brake rod in the direction of the arrow is transmitted through the brake
lever to rotate the brake cam for braking. (see Figure 20a)

5.7.2.2 hydraulic brake

The stepping force on the brake pedal is converted to hydraulic forces by the master cylinder
and then transmitted through the pipe to the wheel cylinder. (see Figure 20b)

Brake pedal

Brake rod

Brake lever
Brake cam

a) mechanical brake

Brake pedal
Brake oil

Wheel cylinder

Master cylinder

b) hydraulic brake

Figure 20 – Types of Brake based on Brake Force Transmission

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6 Performance Requirements

6.1 The drawbar power and field performance shall be tested in accordance with
PAES 119.

6.2 The allowable wheel slip for maximum efficiency is shown in Table 4.
Table 4 – Acceptable Level of Wheel slip

Tractor type Firm Soil Tilled or Soft Soil

% %
Two-wheel drive 7 – 11 10 – 15

Four-wheel drive 6 – 10 8 – 13
Source: Machinery Management Notes #1 – Traction.

6.3 The tractor equipped with three-point linkage shall have the minimum hydraulic lift
force capacity available throughout the power range, at a distance of 610 mm beyond the
lower hitch points (without external assist hydraulic cylinders) as shown in Table 5.
Table 5 – Hydraulic Lift Force Capacity
Maximum drawbar power Lift force per drawbar power*
kW kN/kW
65 and below 0.31
20.15 plus 0.155 kN/kW for the succeeding drawbar
Above 65
power
Source: ASAE Standard S217.10,Three-point Free-link Attachment for Hitching Implements to Agricultural Wheel Tractors

6.4 Tractor speed during field operations

The tractor shall be able to pull field implements up to 8 km/h.

7 Safety Requirements

7.7.1 When the PTO is in use, a cover or casing that protects the sides of the PTO shaft
shall be fitted. An additional non-rotating casing shall also be provided when the PTO is not
in use. This casing shall enclose the PTO shaft completely and be fixed to the tractor body.

7.7.2 A seat shall be provided which will adequately support the operator in all working
and operating modes. Adequate and comfortable support and protection for the feet shall be
provided.

NOTE For more detailed specification of seat and ROPS refer to ISO 4253 and
ISO/DIS 8082, respectively.

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 PAES 118: 2001

7.7.3 All tractors powered by 15 kW engines or higher shall be equipped with ROPS and
seat belts.
NOTE For more detailed specification of seat belt refer to ISO 3776.

7.7.4 The noise emitted by the tractor measured 50 mm away from the operator’s ear level
shall not be more than 92 db (A). *

8 Other Requirement

8.1 The engine of the tractor shall be equipped with cooling system suitable for tropical
operations.

8.2 Mechanism that minimize/reduce vibration shall be provided.

9 Workmanship and Finish

9.1 The tractor shall be free from manufacturing defects that may be detrimental to its
operation.

9.2 Any uncoated metallic surface shall be free from rust and shall be painted properly.

9.3 The tractor shall be free from sharp edges and surfaces that may injure the operator.

10 Warranty for Construction and Durability

10.1 Warranty against defective materials and workmanship shall be provided for parts and
services except for consumable maintenance parts (i.e. fan belts, oil filter, fuel filter, etc.)
within six (6) months from the purchase of the tractor.

10.2 The construction shall be rigid and durable without breakdown of its major
components (i.e. transmission, cooling, lubrication systems, etc) within six (6) months from
purchase by the first buyer.

11 Maintenance and Operation

11.1 Each tractor unit shall be provided with the following minimum quantity of basic
hand tools: three (3) pieces open wrenches, one (1) piece each of Philips and flat screw
driver, one (1) pair of mechanical pliers, one (1) piece adjustable wrench, one (1) piece
grease gun, one (1) piece of tire wrench and one (1) piece of lifting jack.

_________________________
*
Allowable noise level for six (6) hours of continuous exposure based on Occupational Safety and Health Standards,
Ministry of Labor, Philippines. 1983.

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PAES 118: 2001

11.2 An instruction manual, which conforms to PAES 102, shall be provided.

11.3 All components that require regular maintenance, servicing and adjustment should be
easily accessible.

12 Sampling

The tractor shall be sampled for testing in accordance with PAES 103.

13 Testing

The sampled tractor shall be tested in accordance with PAES 119.

14 Marking and Labeling

Each tractor shall be marked in English language with the following information using a
plate, stencil or by directly punching it at the most conspicuous place:

14.1 Registered trademark of the manufacturer

14.2 Brand

14.3 Model

14.4 Serial number

14.5 Name and address of manufacturer

14.6 Name and address of importer (optional)

14.7 Country of manufacture

14.8 Safety/precautionary markings

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