SIST-TP CEN/TR 15172-1:2006
(Main)Whole-body vibration - Guidelines for vibration hazards reduction - Part 1: Engineering methods by design of machinery
Whole-body vibration - Guidelines for vibration hazards reduction - Part 1: Engineering methods by design of machinery
This Technical Report provides best practices and methods available for limiting the effects of mechanical whole-body vibration on operators' positions. The guidelines given outline practical ways in which whole-body vibration hazards associated with mobile machinery can be reduced by machinery design. The Technical Report covers four important aspects of the reduction of the effects arising from exposure to hazardous machinery vibration:
a) identification of main sources and operational modes producing vibration that might be hazardous to health and of additional factors worsening the adverse health effects of vibration on the operators;
b) reduction of vibration magnitudes at source;
c) reduction of transmission of vibration from source to the operator;
d) ergonomic adaptation of operators' position: posture, range of vision.
This Technical Report does not provide universal or detailed technical solutions but only a review of engineering methods available. It is not concerned with hand-arm vibration which is covered by CR 1030-1.
This Technical Report is primarily intended as a guideline for people involved in purchasing, using, supplying, marketing or inspecting mobile machinery. It is also intended to be a guidance for writers of type C standards for specific types of machinery.
Ganzkörper-Schwingungen - Leitfaden zur Verringerung der Gefährdung durch Schwingungen - Teil 1: Technische Maßnahmen durch die Gestaltung von Maschinen
Dieser Fachbericht nennt die besten Praktiken und Verfahren zur Begrenzung der Auswirkungen mechanischer Ganzkörper-Schwingungen auf den Platz der Bedienungsperson. Die angegebenen Leitlinien stellen praktische Wege dar, durch die die mit beweglichen Maschinen verbundenen Gefährdungen durch Schwingungen durch die Gestaltung der Maschinen verringert werden können. Der Fachbericht behandelt vier wesentliche Gesichtspunkte zur Verringerung der Auswirkungen, die sich aus der Exposition gegenüber gefährlichen Schwingungen von Maschinen ergeben:
a) Erkennung der Hauptquellen und der Betriebsabläufe, die Schwingungen verursachen, die gesundheitsgefährdend sein können, und zusätzlicher Faktoren, die gesundheitliche Auswirkungen von Schwingungen auf Bedienungspersonen verstärken;
b) Verringerung der Schwingungsintensität am Entstehungsort;
c) Verringerung der Schwingungsübertragung von der Quelle auf Bedienungspersonen;
d) ergonomische Anpassung des Platzes der Bedienungsperson: Körperhaltung, Sichtbereich.
Dieser Fachbericht liefert keine umfassenden oder detaillierten technischen Lösungen, sondern nur einen Überblick über die zur Verfügung stehenden technischen Verfahren. Es befasst sich nicht mit Hand-Arm-Schwingungen; sie werden in CR 1030 1 behandelt.
Dieser Fachbericht stellt hauptsächlich einen Leitfaden für diejenigen dar, die am Erwerb, der Benutzung, der Lieferung, der Vermarktung oder Überprüfung beweglicher Maschinen beteiligt sind. Er dient auch als Leitfaden für Ersteller von maschinenspezifischen Normen (Typ-C-Normen).
Vibrations globales du corps - Guide pour la réduction des risques de vibrations - Partie 1: Mesures techniques lors de la conception des machines
Le présent Rapport technique fournit les meilleures pratiques et méthodes existantes pour réduire les effets
des vibrations mécaniques globales du corps sur des positions d'opérateurs. Les lignes directrices contenues
dans le présent Rapport technique présentent des moyens pratiques permettant de réduire les phénomenes
dangereux de vibrations globales du corps associés aux machines mobiles lors de la conception des
machines. Ce Rapport technique couvre quatre aspects principaux de la réduction des effets provenant de
l'exposition aux vibrations dangereuses des machines :
a) l'identification des principales sources de vibrations et principaux modes de fonctionnement a l'origine de
vibrations pouvant etre dangereuses pour la santé et d'autres facteurs aggravant les effets nocifs des
vibrations sur la santé des opérateurs ;
b) la réduction des niveaux de vibrations a la source ;
c) la réduction de la transmission des vibrations de la source vers l'opérateur ;
d) l'adaptation ergonomique de la position des opérateurs : posture, champ de vision.
Le présent Rapport technique ne fournit pas de solutions techniques universelles ou détaillées mais
seulement une revue des mesures techniques disponibles. Il ne traite pas des vibrations main-bras qui sont
couvertes par le CR 1030-1.
Le présent Rapport technique est principalement destiné a servir de guide aux personnes concernées par
l’acquisition, l’utilisation, la fourniture, la commercialisation ou le contrôle de machines mobiles. Il est
également destiné a servir de guide aux rédacteurs de normes de type C applicables a des types de
machines spécifiques.
Tresenje celotnega telesa – Smernice za zmanjšanje tveganja zaradi vibracij – 1. del: Inženirske metode pri načrtovanju strojev
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 15172-1:2006
01-julij-2006
7UHVHQMHFHORWQHJDWHOHVD±6PHUQLFH]D]PDQMãDQMHWYHJDQMD]DUDGLYLEUDFLM±
GHO ,QåHQLUVNHPHWRGHSULQDþUWRYDQMXVWURMHY
Whole-body vibration - Guidelines for vibration hazards reduction - Part 1: Engineering
methods by design of machinery
Ganzkörper-Schwingungen - Leitfaden zur Verringerung der Gefährdung durch
Schwingungen - Teil 1: Technische Maßnahmen durch die Gestaltung von Maschinen
Vibrations globales du corps - Guide pour la réduction des risques de vibrations - Partie
1: Mesures techniques lors de la conception des machines
Ta slovenski standard je istoveten z: CEN/TR 15172-1:2005
ICS:
13.160 Vpliv vibracij in udarcev na Vibration and shock with
ljudi respect to human beings
21.020 =QDþLOQRVWLLQQDþUWRYDQMH Characteristics and design of
VWURMHYDSDUDWRYRSUHPH machines, apparatus,
equipment
SIST-TP CEN/TR 15172-1:2006 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TP CEN/TR 15172-1:2006
TECHNICAL REPORT
CEN/TR 15172-1
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
November 2005
ICS 13.160; 17.160
English Version
Whole-body vibration - Guidelines for vibration hazards
reduction - Part 1: Engineering methods by design of machinery
Vibrations globales du corps - Guide pour la réduction des Ganzkörper-Schwingungen - Leitfaden zur Verringerung der
risques de vibrations - Partie 1: Mesures techniques lors de Gefährdung durch Schwingungen - Teil 1: Technische
la conception des machines Maßnahmen durch die Gestaltung von Maschinen
This Technical Report was approved by CEN on 25 July 2005. It has been drawn up by the Technical Committee CEN/TC 231.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 15172-1:2005: E
worldwide for CEN national Members.
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Contents Page
Foreword .3
Introduction.4
1 Scope .5
2 Identification of main sources and operational modes producing vibration that might be
hazardous to health .5
2.1 Identification of main sources and operational modes.5
2.2 Factors that can combine with vibration to increase the likelihood of injury .6
3 Reduction of vibration at source .6
3.1 Travelling on uneven surfaces.6
3.2 Operating of working equipment (tools) .7
3.3 Information from the manufacturer on the use of tools and accessories .7
3.4 Vibrating tools mounted to the machinery.7
3.5 Engine.8
4 Reduction of transmission of vibration from source to the operator .8
4.1 General .8
4.2 Wheel size and tyres.9
4.3 Low-frequency wheel and chassis suspension.10
4.4 Low-frequency cab suspension.10
4.5 Seat suspension and seat design.11
5 Elimination of incorrect posture .11
5.1 General .11
5.2 Improving external cab visibility.12
5.3 Design of cab adapted to the operator dimension and task.13
5.4 Selection of seats adapted to the machine and task.14
6 Summary of questions to be considered when evaluating the design of mobile machinery
in view of protecting operator’s safety and health.15
6.1 General .15
6.2 Visibility .15
6.3 Cabin construction .15
6.4 Selection of seat.16
Annex A (informative) Vibration isolation.17
Bibliography.22
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Foreword
This Technical Report (CEN/TR 15172-1:2005) has been prepared by Technical Committee CEN/TC 231
“Mechanical vibration and shock”, the secretariat of which is held by DIN.
CEN/TR 15172 consists of the following parts:
CEN/TR 15172-1, Whole-body vibration — Guidelines for vibration hazards reduction — Part 1: Engineering
methods by design of machinery
CEN/TR 15172-2, Whole-body vibration — Guidelines for vibration hazards reduction — Part 2: Management
measures at the workplace
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Introduction
This Technical Report deals with engineering methods for design of machinery transmitting vibration to the
human body. Guidance on management measures at the workplace is given in CEN/TR 15172-2.
Significant whole-body vibration is mainly related to operators of mobile machinery. Mobile machinery
transmits vibration and shock from the seat for seated operators, from the floor for standing operators, which
may cause adverse health effects, primarily damage to the spine. The effects of vibration depend on its
frequency, direction, intensity, presence of shocks and on the exposure time. They also depend on the
operator's posture. It is important to understand that the design and manufacture of mobile machinery is
complex, requiring extensive technical background.
The EC Directive 98/37/EC on the approximation of the laws of the member states relating to machinery
(Machinery Directive), amended by Directive 98/79/EC, requires that the machinery is so designed and
constructed that risks resulting from vibration produced by the machinery are reduced to the lowest level,
taking account of technical progress and the availability of means of reducing vibration, in particular at source.
Limiting vibration by design is one of the measures that EN ISO 12100-2 suggests machine manufacturers
and designers should consider as part of a strategy to achieve safety by design of machinery in conformity
with European Legislation.
The reduction of vibration by design of machinery can make an important contribution to the effective
protection of people at work from the harmful effects of vibration. In practical situations, however, a
combination of engineering measures and management measures may be necessary.
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1 Scope
This Technical Report provides best practices and methods available for limiting the effects of mechanical
whole-body vibration on operators’ positions. The guidelines given outline practical ways in which whole-body
vibration hazards associated with mobile machinery can be reduced by machinery design. The Technical
Report covers four important aspects of the reduction of the effects arising from exposure to hazardous
machinery vibration:
a) identification of main sources and operational modes producing vibration that might be hazardous to
health and of additional factors worsening the adverse health effects of vibration on the operators;
b) reduction of vibration magnitudes at source;
c) reduction of transmission of vibration from source to the operator;
d) ergonomic adaptation of operators’ position: posture, range of vision.
This Technical Report does not provide universal or detailed technical solutions but only a review of
engineering methods available. It is not concerned with hand-arm vibration which is covered by CR 1030-1.
This Technical Report is primarily intended as a guideline for people involved in purchasing, using, supplying,
marketing or inspecting mobile machinery. It is also intended to be a guidance for writers of type C standards
for specific types of machinery.
2 Identification of main sources and operational modes producing vibration that
might be hazardous to health
2.1 Identification of main sources and operational modes
The machine manufacturer should make a careful investigation of all possible causes of vibration and shock
connected with the full range of likely use of the machinery. In case the machinery is used with tools, the
investigation should include the range of tools likely to be used with the machine.
Internal sources of vibration in mobile machinery are engines, hydraulic devices and transmission.
Normally, the engine is not a problem unless it runs at low speed and has only a small number of cylinders.
Generally, the engine may be a problem in older, poorly maintained machines and in machines where the
user has made changes in the original construction.
Some machinery categories, e.g. vibratory rollers, include intentional vibrating sources. Machinery may also
use vibrating attachment, e.g. separators, rotary snow-ploughs, street-sweeping machines, road milling
machines, refuse collection lorries. Rough braking and handling of gears can cause large vibration and shocks.
The major source of vibration affecting operators of mobile machinery is the contact between wheels and
ground at travelling. The severity is determined by the combination of ground surface, machine dynamics and
travelling speed.
For machinery using tools, the contact between the tool and the material, e.g. in digging, rock drilling, loading,
compaction, is of vital importance. The vibration magnitude depends on the characteristics of the material and
the operator's skill.
Examples where the tools can be the dominant source of vibration are excavators using breakers.
In case of using a trailer, the design of the connection of the trailer to the machine (e.g. truck, lorry) is
important as is the position of the centre of gravity of the trailer.
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Liquids cause vibration when sloshing in tanks. Tanks can be divided into smaller rooms, which will minimise
the vibration.
Some information on methodologies for identification of vibration and shock during various operational modes
can be found in EN 1032 and EN 14253.
2.2 Factors that can combine with vibration to increase the likelihood of injury
It is probably the combination of the stresses from poor position and vibration that causes back pain. The
machinery manufacturer should make a careful investigation of all possible causes which might force the
operator to adopt poor posture.
The ergonomic design should support a driving posture that minimises the adverse effects of the vibration
transmitted to the body (primarily to the spine). An upright driving position is important.
Outside visibility always comes first. Even if it is detrimental to his posture, an operator will compensate to
overcome the lack of good visibility essential for safe machine operation. Driving a counterbalance truck with a
high load, cutting the grass with a tractor along the merge of a road are examples where the operators might
bend forwards or backwards or twist the body in order to increase the visibility at travelling or operating of
equipment.
When the vertical seat adjustment is insufficient, some operators can have difficulty to reach the floor pan or
pedals with the feet. In fork lift trucks tall operators have to drive in bent position in order to avoid the head to
get in contact with the overhead guard.
On some vehicles the operator’s legs cannot slip easily under the steering wheel. When this is the case, the
operator might push his seat back to allow his thigh room to move and as a result he has to lean forward to
operate the machine controls and steering wheel.
The adverse health effects of vibration can increase when the machine is operated on slopes and side slopes
due to effects on operator’s posture, on efficiency of cab and seat suspension.
Jumping from machines could cause significant shock loads to the body. To minimise this risk, a well
designed machine access system (including suitably placed hand holds and slip resistant steps) should be
provided and the operator should be encouraged to use the access system instead of jumping from the
machine. Machine specific standards for access systems should be used, such as EN ISO 2867 for earth-
moving machines or EN 1553 agricultural machinery. When no machine specific access system standard is
available, general guidelines for access systems can be obtained from the EN ISO 14122 series.
3 Reduction of vibration at source
3.1 Travelling on uneven surfaces
The vibration affecting the operator when travelling depends on the mechanical design of the machine. It also
depends on the ergonomic design (e.g. visibility) that can help the operator to avoid excessive vibration, e.g.
by choosing speed and route around obstacles.
It should be observed that also small obstacles may lead to high vibration levels for machines with small-size
wheels, hard tyres, a short wheelbase or less suspension.
The vibration and shock caused by the contact between the machinery and the ground when travelling is
affected by the design and dimensions of the wheels. Designers should aim at a low centre of gravity, located
close to the cross point of the diagonal lines between the wheels. In some cases the centre of gravity can
move when travelling, e.g. machinery carrying a tool such as a suspended boom. This movement should be
taken into account.
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Working equipment and tools mounted to the machinery might cause excessive vibration at travelling due to
change of the centre of gravity. An example of avoiding this is the use of special suspension devices, e.g.
hydraulic accumulators for boom suspension in earth-moving machinery. The manufacturer should give
information on limitation of tools and the effects on the vibration by the use of tools.
3.2 Operating of working equipment (tools)
Examples of working equipment are:
buckets of excavators,
ploughs, balers or powered cultivators;
cranes and processors (cutting devices) of forestry machines;
grading devices of graders;
drilling devices of mining machines;
milling devices of road milling machines.
Generally, soft movements should be aimed at in the design of working equipment and its integration in the
machine. Vibration should not be transmitted from the tool to the operator's position.
Hydraulic functions should be carefully adapted to provide soft operation.
Linkages should be correctly balanced and excessive play avoided. Accessories and loads can change the
centre of gravity, changing the vibration characteristics when moving.
The controls of the tools should be placed so that the operator will maintain an upright position and avoid
unnecessary twisting of the body when using the tools.
3.3 Information from the manufacturer on the use of tools and accessories
One important factor is to provide the right tool for the job. The machinery manufacturer should give good
guidance on what tools to use and how to operate the tools in order to minimise the vibration without losing
efficiency. Also the tool maintenance instructions are important.
The manufacturer should provide information on limitation of application of tools and the effects on vibration
by use of tools. The manufacturer should also provide information on limitation of slope, limitation of loads,
speed, etc.
Often problems occur when the machine and tool have been produced by different manufacturers.
Manufacturers should provide instructions on how accessories and loads should be carried in specific
operating modes to minimise vibration, e.g. for earth-moving machinery, the boom should be raised when
travelling (use of accumulators).
3.4 Vibrating tools mounted to the machinery
If a machine is equipped with optional vibrating hydraulic tools, e.g. hydraulic hammers, cutter crushers or
screening buckets, this could contribute to the vibration of the operator. As a minimum, the operating
frequency and level of excitation force of the tool needs to be known and the influence from this tool should be
evaluated together with the vibration isolation systems of the main machine in order to minimise the vibration
exposure of the operator.
The tools may be boom mounted or three-point linked.
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In the case of machinery including vibration exciters, e.g. vibratory rollers, it is important that the frequency
selected for the excitation is as high as feasible with regard to the work efficiency in order to enable an
efficient isolation of the operator from the source. It is also important to avoid a conflict between this frequency
and its harmonics and the resonance frequencies of the machine structure.
3.5 Engine
Vibration produced by the engine is unlikely to be of a magnitude that could cause a health risk, presumed
that the engine is well balanced and resiliently mounted to the structure. For one-cylinder reciprocating
engines, where balancing is not normally feasible, extra care needs to be taken in the mounting of the engine.
It is of primary importance to avoid with good margins a coincidence between n times the rotational speed of
the engine and resonance frequencies of the engine suspension and of the engine mounting structure (n is an
integer).
4 Reduction of transmission of vibration from source to the operator
4.1 General
Reduction of transmission of vibration from source to the operator often includes use of resilient mounts,
either by separating the source of vibration (e.g. engine) from the machine structure or by separating the
operator from the vibration source or vibrating structure (vibration and shock isolation of wheels, chassis,
operator's cab, seat).
Methods for vibration and shock isolation are well described in the literature and handbooks. It is important
that the designer of resilient suspension systems and their integration in the machine has good knowledge of
structural dynamics. The designer needs to know how to optimise the system with regard to resonance
frequencies, internal damping in the isolating elements, and location and directivity of elements in relation to
the centre of gravity of the part to be isolated.
Some general considerations in selection of vibration and shock isolating devices can be found in EN 1299.
Transmission of vibration and shocks from the contact between the ground and tyres to the operator can be
reduced by means of vibration isolation elements (resilient suspension systems) positioned at different key
points (see Figure 1):
Tyres;
wheels and chassis (vehicle body);
cab;
seat.
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Key
1 vehicle body 5 cab suspension
2 seat 6 body suspension
3 cab 7 tyres
4 seat suspension
Figure 1 — Schematic presentation of possible suspensions
When resilient suspension systems are designed and selected, it is important that prevention from both shock
and vibration is taken into account. Ideally, a resilient suspension should be designed so that its highest cut-
off frequency is significantly less than the dominant input frequency. Suspension travel should be sufficient to
prevent bottoming or topping on end-stops. The lower the input and the cut-off frequency, the larger the
required travel. A compromise should be developed for the specific machine between the capacity of reducing
long-term low-level vibration and occasionally occurring high-level vibration and shock. Internal damping in the
suspension system has a positive effect on vibration transmission at the resonance frequency of the
suspension system, but insignificant effect on the reduction of occasional shocks or bumps.
Use of several resilient suspension systems in a suspension chain, e.g. simultaneous use of soft pneumatic
tyres, resilient chassis suspension, resilient cab suspension and resilient seat suspension, requires high
technical skill, due to the complex interaction of the suspension systems. It is also important that the
characteristics of the suspension systems do not change over long periods of time (this is especially a
problem for systems based on organic materials). The manufacturer should provide recommendations on
replacement of the suspension system elements. It is important that such recommendations are followed.
Basic concepts of suspension systems are given in Annex A.
4.2 Wheel size and tyres
Tyres are normally selected according to their rolling resistance, grip, stability, cost, resistance to collision
damage, etc.
The machinery manufacturer should carefully investigate the vibration generation characteristics of the tyres
and recommend tyres and inflating pressures that minimise the vibration in the particular machine. Information
should be provided on the appropriate selection of tyres for different use of the machine.
Small-dimension wheels will cause excessive vibration also when travelling over small ground irregularities. It
is therefore important that the wheel size is selected for the typical travelling conditions of the machine.
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Although bogies are mainly used in trailers due to their better load carrying capacity, they will also generally
improve the situation on vibration and shock because the trailer climbs over the obstacles smoother than a
single-axle construction would do.
The vibration transmission characteristics of the tyres, chassis suspension, cab suspension and seat
suspension should be combined in a manner to minimise the transfer of vibration from the contact between
the wheels and the ground to the operator.
It should be noted that excessively soft tyres induce low-frequency motions that can cause severe pitching.
Most mobile machinery is fitted with pneumatic tyres. Exceptions are off-road machinery fitted with tracks and
industrial trucks that are often fitted with solid tyres for stability reasons and for puncture resistance. Solid
tyres should only be used on smooth ground.
In case of tracked machinery, the track division is important. Here, the excitation frequencies related to the
normal speed and track division should not be close to the resonance frequencies of structure and
suspensions.
4.3 Low-frequency wheel and chassis suspension
Low-frequency wheel and chassis suspension is typically used for cars and lorries. It is also used in some
agricultural tractors. Low-frequency wheel suspension is not useful in cases of low resonance frequency of the
tyres.
When wheel or chassis suspension is used, it is important that they are designed so that they don't enforce
tipping or rocking and rolling movements. It may be especially harmful and unpleasant when tipping and
rolling results in the operator being thrown forwards and backwards or sideways when travelling over rough
surfaces. Means to minimise pitching and rolling include internal damping in the suspension system and
localising the suspending elements so that the cross point of the diagonal lines between the elements is as
close as possible to the rotational centre of the rigid-body motion of the machine.
The use of tilting cabs with forwards, backwards and sideways movement could be a way to minimise the
effects of pitching and rolling on the operator.
A disadvantage of using resilient mounts in the wheel plane of the machine is that the cross point of the
diagonal lines between the damping elements is below the centre of gravity of the machine and therefore
creates rocking, pitching and rolling problems. This effect can be partly reduced by using unidirectional
elements pointing to the centre of gravity.
4.4 Low-frequency cab suspension
Low-frequency cab suspension can be used to ensure vibration isolation in all directions. The advantage
compared to rigid cab mounting combined with vibration isolation of the seat is that the operator is protected
with respect to several degrees of freedom. Another advantage is that the isolated part includes a larger mass
and therefore less displacement at the suspension resonance frequencies for a given excitation force and less
space required for avoiding topping and bottoming.
Since the mass of the cab is large, it is very important to make sure that the vibration isolating elements are
mounted to a rigid structure of sufficiently high impedance.
Experience of use of vibration isolated lorry cabs with very low isolation resonance frequencies (1 Hz to 2 Hz)
show potential problems with motion sickness and drowsiness.
Similar considerations as for low-frequency chassis suspension apply to the localisation of the vibration
isolation elements.
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Cab suspension will reduce vibration in the steering wheel and controls, and the noise will also be reduced.
Cab suspension is useful for reducing continuous vibration. Suspension of the seat needs normally to be
added in order to take care of shock. Technical skill is needed in combining cab and seat suspension.
4.5 Seat suspension and seat design
The seat suspension should be designed with regard to the characteristics of the vibration to which it will be
exposed. Low-magnitude vibration without pronounced shocks and high-magnitude vibration containing
shocks create different demands on the seat suspension.
The seat suspension should be designed according to the dynamic characteristics of the machinery and with
respect to the frequency content of the driving forces. Important parameters to take into account are
resonance frequencies of the machinery and of the seat, and the characteristics of the suspension at the top
and bottom positions of the stroke.
In EN ISO 7096 there are, for a number of earth-moving machinery, maximum values for the seat effective
amplitude transmissibility (SEAT) as well as minimum requirements for the damping performance. Test codes
for agricultural tractors and industrial trucks are given in ISO 5007 and EN 13490, respectively.
In certain machines, e.g. forestry forwarders and harvesters, automatic self-levelling seats can be used to
compensate movements due to ground irregularities.
The seat should be designed with regard to the nature of the machine operation, it should be robust, have as
little backlash as possible and be firmly fixed to the structure of the machine. Where appropriate, it should be
designed for prolonged periods
...
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