Heavy commercial vehicles and buses -- Centre of gravity measurements -- Axle lift, tilt-table and stable pendulum test methods

This document describes a standard method for measuring a vehicle's longitudinal and lateral (horizontal plane) centre of gravity (CG) positions and three methods for estimating a vehicle's vertical CG position, the axle lift, tilt-table, and stable pendulum methods. It applies to heavy vehicles, that is commercial vehicles and buses as defined in ISO 3833 (trucks and trailers with maximum weight above 3,5 tonnes and buses and articulated buses with maximum weight above 5 tonnes, according to ECE and EC vehicle classification, categories M3, N2, N3, O3 and O4). CG measurements are performed separately for each single unit.

Véhicules utilitaires lourds et autobus -- Mesure du centre de gravité -- Méthode d'essais du plateau incline, levage d'un essieu et pendule stable

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Status
Published
Publication Date
13-Aug-2019
Current Stage
6060 - International Standard published
Start Date
18-Jul-2019
Completion Date
14-Aug-2019
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INTERNATIONAL ISO
STANDARD 19380
First edition
2019-08
Heavy commercial vehicles
and buses — Centre of gravity
measurements — Axle lift, tilt-table
and stable pendulum test methods
Véhicules utilitaires lourds et autobus — Mesure du centre de gravité —
Méthode d'essais du plateau incline, levage d'un essieu et pendule stable
Reference number
ISO 19380:2019(E)
ISO 2019
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ISO 19380:2019(E)
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© ISO 2019

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Published in Switzerland
ii © ISO 2019 – All rights reserved
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ISO 19380:2019(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principles ..................................................................................................................................................................................................................... 3

5 Variables ....................................................................................................................................................................................................................... 3

5.1 Reference system .................................................................................................................................................................................. 3

5.2 Variables to be measured ............................................................................................................................................................... 3

5.2.1 Variables to be measured for location of x and y coordinates of centre
CG CG

of gravity in horizontal plane ................................................................................................................................ 3

5.2.2 Variables to be measured using the axle lift method for location of z

coordinates ........................................................................................................................................................................... 4

5.2.3 Variables to be measured using the tilt-table method for location of z

coordinates ........................................................................................................................................................................... 4

5.2.4 Variables to be measured using the stable pendulum method for location

of z coordinates ........................................................................................................................................... ................. 4

6 Measuring equipment ..................................................................................................................................................................................... 5

7 Test conditions ....................................................................................................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.2 Ambient conditions ............................................................................................................................................................................. 6

7.3 Test surface ................................................................................................................................................................................................ 6

7.4 Test vehicle ................................................................................................................................................................................................. 6

7.5 Operating and other liquids ......................................................................................................................................................... 6

7.6 Loading conditions, suspension and mechanical parts ....................................................................................... 6

8 Determination of the centre of gravity in the horizontal plane .......................................................................... 7

8.1 General ........................................................................................................................................................................................................... 7

8.2 x position of the centre of gravity in the horizontal plane ........................................................................... 7

8.2.1 Two axle vehicles ............................................................................................................................................................. 7

8.2.2 More than two axles ...................................................................................................................................................... 7

8.3 y position of the centre of gravity in the horizontal plane ........................................................................... 8

8.3.1 Two axle vehicles ............................................................................................................................................................. 8

8.3.2 More than two axles ...................................................................................................................................................... 8

9 Determination of the centre of gravity height ....................................................................................................................... 8

9.1 General ........................................................................................................................................................................................................... 8

9.2 Axle lift method ...................................................................................................................................................................................... 8

9.2.1 General guidance ............................................................................................................................................................. 8

9.2.2 Procedure ............................................................................................................................................................................10

9.2.3 Determination of the axle load and inclination angle ...................................................................11

9.2.4 Location of the centre of gravity above the ground plane with loaded tyre

radius ......................................................................................................................................................................................11

9.3 Tilt-table method ...............................................................................................................................................................................12

9.3.1 General guidance ..........................................................................................................................................................12

9.3.2 Tilt-table procedures.................................................................................................................................................14

9.3.3 Determination of the centre of gravity height z ..........................................................................15

9.3.4 Data presentation .........................................................................................................................................................15

9.4 Stable pendulum method ............................................................................................................................................................15

9.4.1 General guidance ..........................................................................................................................................................15

9.4.2 Stable pendulum procedure ................................................................................................................................17

9.4.3 Determination of platform properties .......................................................................................................17

9.4.4 Determination of the applied torque ...........................................................................................................17

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ISO 19380:2019(E)

9.4.5 Consideration of platform deflection ..........................................................................................................18

9.4.6 Determination of the centre of gravity height, z .........................................................................18

9.4.7 Data Presentation.........................................................................................................................................................18

Annex A (informative) Determination of static loaded radius, r ..................................................................................19

stat

Annex B (informative) Test report — Axle lift method ...................................................................................................................20

Annex C (informative) Test report — Tilt method (up to 3 axles) ......................................................................................23

Annex D (informative) Test report — Stable pendulum method .........................................................................................26

Bibliography .............................................................................................................................................................................................................................29

iv © ISO 2019 – All rights reserved
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ISO 19380:2019(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

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ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/patents).

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expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso

.org/iso/foreword .html.

This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 33,

Vehicle dynamics and chassis components.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/members .html.
© ISO 2019 – All rights reserved v
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ISO 19380:2019(E)
Introduction

Methods are presented for measuring the location of the centre of gravity of an individual vehicle unit

in the horizontal, lateral and vertical planes. Location of the longitudinal and lateral centre of gravity

positions are obtained through successive use of wheel or platform scales. Three different methods

are described for measurement of the vertical centre of gravity – the axle lift method, the tilt-table

method, and the stable pendulum method. The selection of the method to use depends on the facility

and resource availability, as well as constraints imposed by the vehicle design. Knowledge of a vehicle

unit’s centre of gravity supports vehicle modelling work, design validation and planning for other

dynamic tests yet to be performed.
vi © ISO 2019 – All rights reserved
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INTERNATIONAL STANDARD ISO 19380:2019(E)
Heavy commercial vehicles and buses — Centre of gravity
measurements — Axle lift, tilt-table and stable pendulum
test methods
1 Scope

This document describes a standard method for measuring a vehicle’s longitudinal and lateral

(horizontal plane) centre of gravity (CG) positions and three methods for estimating a vehicle’s vertical

CG position, the axle lift, tilt-table, and stable pendulum methods. It applies to heavy vehicles, that

is commercial vehicles and buses as defined in ISO 3833 (trucks and trailers with maximum weight

above 3,5 tonnes and buses and articulated buses with maximum weight above 5 tonnes, according to

ECE and EC vehicle classification, categories M3, N2, N3, O3 and O4). CG measurements are performed

separately for each single unit.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 612, Road vehicles — Dimensions of motor vehicles and towed vehicles — Terms and definitions

ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ISO 15037-2, Road vehicles — Vehicle dynamics test methods — Part 2: General conditions for heavy

vehicles and buses
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 8855, ISO 15037-2 and the

following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
3.1
scale

instrument or device used to measure total vehicle, axle, track or individual wheel weights

3.2
crane
device used to lift one end of the test vehicle, with sufficient lift capacity
3.3
load cell
device for measuring force along a single axis
3.4
axle hoist

device used to lift an individual axle with the crane (3.2) and safety provisions to prevent the axle from

leaving the hoist once lifted
© ISO 2019 – All rights reserved 1
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ISO 19380:2019(E)
3.5
tilt-table

apparatus for supporting a vehicle on a nominally planar surface and for tilting the vehicle in roll by

rotating that surface about an axis nominally parallel to the x-axis of the vehicle

Note 1 to entry: A tilt-table is composed of (1) a single structure supporting all tyres of the vehicle on a contiguous

surface, or (2) multiple structures supporting one or more axles on separated, but nominally coplanar surfaces.

3.6
wheel dummy
surrogate solid wheel used to remove tyre compliance
3.7
trip rail

rail or kerb fixed to the tilt-table (3.5) surface and oriented longitudinally beside the low-side wheel

dummies to prevent the vehicle from sliding sideways
3.8
tilt angle

angle between the ground plane and a vector that is in the plane of the tilt-table (3.5) surface and is

perpendicular to the tilt axis
3.9
tilt angle variance

differences between the tilt angles (3.8) observed at each vehicle axle due to tilt-table (3.5) compliance,

twist or misalignment of multi-platform tilt-tables
3.10
critical wheel lift

first moment when one or more wheels lifts from the table surface, following which stable roll

equilibrium of the vehicle cannot be maintained
3.11
critical tilt angle
tilt angle at critical wheel lift (3.10)
3.12
tilt-table ratio
TTR
tan (Φ ), as shown in Formula (1)
TTR=tan(Φ ) (1)

Note 1 to entry: It can also be expressed as tan (Φ ) at the occurrence of critical wheel lift (3.10).

Note 2 to entry: See Figure 5.
3.13
central axis

axis defined as the intersection of the longitudinal median plane of the vehicle, Xv-Zv, and the ground plane

3.14
stable pendulum

pendulum apparatus for supporting a vehicle on a nominally planar surface where the combined vehicle

and pendulum centre of gravity is below the pivot point
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ISO 19380:2019(E)
3.15
unstable pendulum

pendulum apparatus for supporting a vehicle on a nominally planar surface where the combined vehicle

and pendulum centre of gravity is above the pivot point
3.16
platform

nominally planar surface of the pendulum on which the vehicle unit or trailer is parked

3.17
vehicle restraint

means to constrain the vehicle unit or trailer in the longitudinal direction on the pendulum platform (3.16)

4 Principles

This document specifies a method to determine the longitudinal and lateral centre of gravity coordinates

in the horizontal plane and three common methods to determine the vertical centre of gravity

coordinate. The longitudinal and lateral centre of gravity coordinates, x and y , are determined in

CG CG

the horizontal plane using scales. Individual scales can be used at each wheel or axle location, or the

vehicle wheels or axles can be moved across a single scale successively. The vertical centre of gravity

coordinate (z ) is determined using either the axle lift, tilt-table or stable pendulum method.

The accuracy of the vertical centre of gravity measurements is dependent on the vehicle condition

during measurement, measurement equipment accuracy and potential movement of heavy sprung or

unsprung masses within the vehicle – such as engine and transmission assemblies and suspensions

–, during the measurement process. Methods involving tilting the vehicle or lifting the vehicle axles

are prone to movement of suspended components. Consequently, the required accuracy of the vertical

centre of gravity measurement should be considered when selecting a measurement method. In general,

the pendulum method results in less movement of suspended components, and does not require that

the suspension be locked-out vertically.
5 Variables
5.1 Reference system
The reference system specified in ISO 15037-2 shall apply.
5.2 Variables to be measured

5.2.1 Variables to be measured for location of x and y coordinates of centre of gravity in

CG CG
horizontal plane

With the vehicle at rest on the ground plane and prepared with the load condition specified for the test,

the following shall be measured and recorded in accordance with the dimensions given in ISO 612 and

ISO 8855.
— F the total vehicle load (or weight);
— n number of axles;
— F i axle load (F is the front axle load);
zi z1
— F i axle, left wheel track load;
zi,left
— F i axle, right wheel track load;
zi,right
— F total left track load;
z,left
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ISO 19380:2019(E)
— F total right track load;
z,right
— l vehicle average wheelbase of 2-axle vehicle;
— l right track wheelbase of 2-axle vehicle;
right
— l left track wheelbase of 2-axle vehicle;
left
— l average axle distance (left and right track) from front axle to axle i;
i-1
— b i axle track (b is at the front axle).
i 1

5.2.2 Variables to be measured using the axle lift method for location of z coordinates

In addition to the relevant variables listed above, measure and record the following.

— F ’ i axle load after lifting is initiated;
— F ’ left track axle load on the i axle after lifting is initiated;
zi ,left
— F ’ right track axle load on the i axle after lifting is initiated;
zi ,right

— θ vehicle pitch angle change in the X Z plane, relative to the initial orientation on the

ground plane before lifting occurs;
— r average static loaded radius of all tyres; see Annex A;
stat
— r the average static loaded radius on the i axle; see Annex A.
stat i

5.2.3 Variables to be measured using the tilt-table method for location of z coordinates

In addition to the relevant variables listed above, measure and record the following.

— l longitudinal distance between the contact centres of the two axles contacting the

trip rail;
— y half-width across wheel dummy trip edges on i axle;
— r average static radius of the wheel dummies;
stat, dummy
— Φ critical tilt angle;
— Z height of the centre of gravity with the wheel dummies.
NOTE See Figure 7 for a description.

5.2.4 Variables to be measured using the stable pendulum method for location of z

coordinates

In addition to the relevant variables listed above, measure and record the following.

— h pivot height from the platform surface;
— h platform's CG distance below the pivot axis;
— W load of the platform including the restraint components;
— W applied load;
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ISO 19380:2019(E)

— θ tilt angle of the platform relative to the gravity vector (positive for the front of the

vehicle pitched down);

— X longitudinal displacement of the vehicle relative to the platform (positive for forward

vehicle displacement);
— h vertical distance from the pivot axis to the location of the applied load;

— l horizontal distance from the pivot axis to the location of the applied load.

NOTE See Figure 8 for a description.
6 Measuring equipment

The measuring equipment, transducer installation and data processing shall be in accordance with

ISO 15037-2.

Typical operating ranges of the variables to be determined for this document are shown in Tables 1 and

2 and in ISO 15037-2.

Table 1 — Variables, typical operating ranges and recommended maximum errors of variables

not listed in ISO 15037-2 for the longitudinal and lateral centre of gravity measurements

Recommended maximum
errors of the combined
Variable Typical operating range
transducer and recorder
system
Vehicle, axle or track load: Up to 40 000 kg (392 400 N) 0,2 %
≤2 000 mm ±1 mm
Distance:
>2 000 mm ±0,05 %

Table 2 — Variables, typical operating ranges and recommended maximum errors of variables

not listed in ISO 15037-2 for the vertical centre of gravity measurement
Recommended maximum
errors of the combined
Method Variable Typical operating range
transducer and recorder
system
All Suspension air-spring inflation 500–1 000 kPa 15 kPa
pressure:
Vehicle, axle or track load: Up to 40 000 kg (392 400 N) 0,2 %
Distance: ≤2 000 mm ±1 mm
>2 000 mm ±0,02 %
Axle Lift Angles: ±30° ±0,05°
Tilt-table Angles: ±60° ±0,1°
Tilt angle variance: ±0,2° ±0,05°
Heading angle error: ±1,0° ±0,05°
Tilt rate: Up to 0,1°/s 0,2 %
Lateral deflections: ±50 mm ±1 mm
Stable Angles: ±7° ±0,01°
Pendulum
Applied mass (weight): Up to 2 500 kg ±0,2 %
(24 525 N)
Distance X: ±20 mm ±1,0 mm
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ISO 19380:2019(E)
7 Test conditions
7.1 General

The limits and specifications indicated below shall be maintained during the test. Any deviations shall

be identified in the test report.
7.2 Ambient conditions

The surface shall be clean and dry, especially if the test is performed outdoors, and the ambient

wind speed is recommended to be less than 1 m/s. Since in certain cases the temperature of vehicle

components may influence test results, the ambient temperature shall be reported.

7.3 Test surface

The test surface, when applicable, should be in accordance with ISO 15037-2 and the surface should be

hard enough to avoid surface deformation when measuring the vehicle.
7.4 Test vehicle

The load condition shall be reported as described in ISO 15037-2. Tyre pressures and the suspension

setting (if applicable) shall be recorded.

On vehicles with multiple adjustable seats or other device such as beds, adjust the items to a mid-

travel position (longitudinal and vertical) and adjust the seat back torso angle to the manufacturers’

designated specification or as close as possible to 15°. The positions shall be reported.

On vehicles with steering wheel reach and rake, the position shall be reported.
7.5 Operating and other liquids

The fuel tanks shall be completely full or empty, including the urea tanks. Fuel motion within an unfilled

fuel tank can have an adverse effect on the results. If the displacement of other liquids carried on the

vehicle (operating and otherwise), such as engine oil, is expected to influence the results, precautions

should be taken to fill the fluid tanks, drain the fluids or note the potential issue. Tank conditions

(empty or full) and locations shall be reported. Occurrences of leaking fluid when the vehicle is inclined

should be noted.
7.6 Loading conditions, suspension and mechanical parts

Vehicle payload shall be held in place to avoid displacement due to inclination of the vehicle.

If the vehicle has a suspended cab or semi-suspended cab, the cab shall be locked at its standard height

when the vehicle is in a horizontal plane with no driver in the cab. Once the vehicle payload is set,

the wheel suspension shall be locked or constrained to avoid deflection during vehicle inclination or

pitching. Other components with flexible mounting may need to be constrained as well, if deflection

will adversely influence the results. It may not be necessary to lock out these components if the stable

pendulum method is used to measure the vertical centre of gravity.

Immediately prior to each test event, all self-regulating suspensions shall be adjusted such that they are

at the proper ride height or, in the case of the suspensions for certain auxiliary axles, at the prescribed

inflation pressure. The initial ride height of each suspension shall be reported.

When lifting or inclining the vehicle during the axle lift method test, the gearbox shall be in neutral,

any lockable differential shall be released, and the parking-brake shall be released with no longitudinal

constraints applied. Any steerable wheel shall be steered straight ahead.
6 © ISO 2019 – All rights reserved
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ISO 19380:2019(E)

Tyre condition and pressure shall be in accordance with the vehicle manufacturer’s recommendations

and ISO 15037-2. In case a range is specified for tyre pressure, the highest pressure value should be

selected to minimize tyre deflection.

Suspended components such as the engine, gearbox and axles can move laterally and/or longitudinally

when lifting or tilting the vehicle. Such displacements can influence measurement accuracy and should

be noted accordingly.
8 Determination of the centre of gravity in the horizontal plane
8.1 General

When using scales for wheel and axle load measurements, care should be taken to ensure scales are

used in a common plane with an inclination less than 1 % grade within the wheelbase of the vehicle.

Permissible deviation of any scale from the common plane is based on engineering judgement to

minimize measurement error. Consid
...

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