ISO 28981:2009

INTERNATIONAL ISO
STANDARD 28981
First edition
2009-11-01
Mopeds — Methods for setting the
running resistance on a chassis
dynamometer
Cyclomoteurs — Méthodes pour fixer la résistance à l'avancement sur
un banc dynamométrique
Reference number
©
ISO 2009
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©  ISO 2009
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ii © ISO 2009 – All rights reserved

Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms and definitions .1
4 Symbols.2
5 Test moped, chassis dynamometer and instruments .3
6 Required accuracy of measurements .4
7 Road test .4
7.1 Requirement for road .4
7.2 Ambient conditions for the road test .4
7.3 Reference speed.5
7.4 Specified speed .5
7.5 Coastdown starting speed.5
7.6 Coastdown time measurement beginning speed and ending speed.5
7.7 Preparation of test moped.5
7.8 Rider and riding position.6
7.9 Measurement of coastdown time.6
8 Data processing.8
8.1 Calculation of running resistance force.8
8.2 Running resistance curve fitting .8
8.3 Target running resistance force for chassis dynamometer setting.8
9 Chassis dynamometer setting derived from on-road coastdown measurements .8
9.1 Requirements for the equipment .8
9.2 Inertia mass setting.9
9.3 Warming up of chassis dynamometer .9
9.4 Adjustment of tyre pressures .9
9.5 Moped warming up.9
9.6 Procedures for setting chassis dynamometer .9
9.7 Verification of chassis dynamometer.12
10 Chassis dynamometer setting using the running resistance table .12
10.1 Applicability .12
10.2 Requirements for the equipment .12
10.3 Setting the running resistance force on the chassis dynamometer.14
10.4 The specified speed for the chassis dynamometer.14
10.5 Verification of chassis dynamometer.14
Annex A (normative) Moped description.16
Annex B (normative) Chassis dynamometer and instruments description .18
Annex C (informative) Record of coastdown time and chassis dynamometer setting .20
Bibliography.23

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 committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 28981 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 23, Mopeds.

iv © ISO 2009 – All rights reserved

Introduction
[6]
This International Standard is based on ISO 11486:2006 , which specifies the measurement method(s) for
determining motorcycle running resistance on the road, but adapted to the different vehicle category of
[6]
mopeds. The most significant difference between this International Standard and ISO 11486:2006 is that
use of chassis dynamometers with a fixed load curve is permitted and a specific verification method is
specified.
INTERNATIONAL STANDARD ISO 28981:2009(E)

Mopeds — Methods for setting the running resistance on a
chassis dynamometer
1 Scope
This International Standard specifies the measurement method for determining the moped running resistance
on the road, and two methods of setting the chassis dynamometer with the moped running resistance. It is
applicable to mopeds as defined in ISO 3833.
2 Normative references
The following referenced documents are indispensable for the application 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 3833, Road vehicles — Types — Terms and definitions
ISO 7116, Mopeds — Measurement method for maximum speed
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
running resistance
F
total force resistant to a running moped which, when measured by the coastdown method, includes the friction
forces in the drive-train
3.2
reference speed
v
moped speed at which the running resistance of the moped is calculated and then used for setting the chassis
dynamometer
3.3
specified speed
v
moped speed at which the running resistance on the road is measured to determine the running resistance
curve
3.4
moped kerb mass
m
k
moped dry mass to which is added the mass of the following:
⎯ fuel: tank filled at least to 90 % of the capacity specified by the manufacturer;
⎯ oils and coolant: filled as specified by the manufacturer;
⎯ auxiliary equipment usually supplied by the manufacturer in addition to that necessary for normal
operation [tool-kit, carrier(s), windscreen(s), protective equipment, etc.]
3.5
moped reference mass
m
ref
kerb mass of the moped increased by a uniform figure of 75 kg which represents the mass of a rider
4 Symbols
For the purposes of this document, the symbols in Table 1 apply.
Table 1 — Symbols
Symbols Definition Unit
a The coefficient of polygonal function —
b The coefficient of polygonal function —
c The coefficient of polygonal function —
a The rolling resistance force of front wheel N
T
b The coefficient of aerodynamic N/(km/h)
T
d The relative air density under test conditions —
T
d The standard ambient relative air density —
F The running resistance force N
F The set running resistance force on the chassis dynamometer N
E
F (v ) The set running resistance force at the reference speed on the chassis dynamometer N
E 0
F (v ) The set running resistance force at the specified speed on the chassis dynamometer N
E i
F The total friction loss N
f
F (v ) The total friction loss at the reference speed N
f 0
F The running resistance force N
j
F (v ) The running resistance force at the reference speed N
j 0
F The braking force of the power absorbing unit N
pau
F (v ) The braking force of the power absorbing unit at the specified speed N
pau j
F (v ) The braking force of the power absorbing unit at the reference speed N
pau 0
F The running resistance force obtained from the running resistance table N
T
*
F The target running resistance force N
*
F The target running resistance force at the specified speed N
j
*
F (v ) The target running resistance force at the reference speed on the chassis dynamometer N
*
F (v ) The target running resistance force at the specified speed on the chassis dynamometer N
i
f The rolling resistance N
*
f The corrected rolling resistance in the standard ambient conditions N
f The coefficient of aerodynamic drag N/(km/h)
* 2
f The corrected coefficient of aerodynamic drag in the standard ambient conditions N/(km/h)
K The temperature correction factor for rolling resistance —
2 © ISO 2009 – All rights reserved

Table 1 (continued)
Symbols Definition Unit
m The test moped mass kg
m The actual mass of the test moped kg
a
m The equivalent inertia mass kg
i
m The flywheel equivalent inertia mass kg
fi
m The moped kerb mass kg
k
m The equivalent inertia mass of all the wheels kg
r
m The moped reference mass kg
ref
m The rider mass kg
rid
m The rotating mass of the front wheel kg
rf
m The equivalent inertia mass of the rear wheel and the moped parts rotating with the wheel kg
r1
p The standard ambient pressure kPa
p The mean ambient pressure during the test kPa
T
T The mean ambient temperature during the test K
T
T The standard ambient temperature K
v The specified speed km/h
v The specified speeds which are selected for coastdown time measurement km/h
j
v The reference speed km/h
v The speed at which the measurement of the coastdown time begins km/h
v The speed at which the measurement of the coastdown time ends km/h
∆T The corrected coastdown time at the inertia mass (m + m) s
E i r1
∆T The average coastdown time at the specified speed s
i
∆T The average coastdown time of the two tests s
j
∆T The target coastdown time s
road
∆t The coastdown time s
∆t The mean coastdown time o
...