BS ISO 5721-1:2013 pdf download.Agricultural tractors — Requirements, test procedures and acceptance criteria for the operator’s field of vision Part 1 : Field of vision to the front
4 General provisions for testing
4.1 Measurement accuracy
The equipment and techniques used to make the physical measurements shall be accurate to within ± 2 % of the value measured.
4.2 Eye position The eye position shall be located 680 mm above and 20 mm in front of the seat index point when determined in accordance with ISO 5353 (see Figure 1). 5 Requirements, test procedures and acceptance criteria
5.1 Requirements
5.1.1 General
The tractor shall be constructed and equipped in such a way that, in road traffic and in farm use, the driver has an adequate field of vision, under all the usual conditions pertaining to highway use and to work undertaken in fields. The field of vision is adequate when the driver has at least a partial view of each front tyre or fender when in the straight ahead position and at track width appropriate for the overall width of single tyres not to exceed 2,55 m.
5.1.2 Masking effects
Masking effects shall not exceed 700 mm. Masking effects due to adjacent structural components over 80 mm in width shall be so configured that there is an interval of not less than 2 200 mm – measured as a chord of the semi-circle of vision to the front – between the centres of two masking effects.
There shall be no more than six masking effects in the semi-circle of vision to the front and no more than two inside the sector of vision to the front defined in 3.5. For the purpose of determining the masking effects in the sector of vision to the front, the masking effects due to the frame of the windscreen and to any other obstacle may be considered as a single effect, provided that the distance between the outermost points of this masking effect does not exceed 700 mm. Outside the sector of vision to the front, masking effects exceeding 700 mm but not exceeding 1 500 mm are, however, permissible if the components causing them cannot be redesigned or relocated: on each side there may be a total of either two such masking effects, one not exceeding 700 mm and the other not exceeding 1 500 mm, or two such masking effects, neither exceeding 1 200 mm.
5.1.3 Blind spots Blind spots caused by rear-view mirrors shall be disregarded if the design of these mirrors is such that they cannot be installed in any other way.
5.1.4 Windscreen wipers Tractors fitted with windscreens shall be equipped with power-driven windscreen wipers and the area swept by these wipers shall ensure an unobstructed forward view corresponding to a chord of the semi- circle of vision to the front at least 8 m long within the sector of vision to the front. The rate of operation of the windscreen wipers shall have at least one setting that provides a minimum of 20 cycles per minute.
5.1.5 Equivalent requirements The requirements of ISO 5006:2006 are considered equivalent for the purpose of this International Standard.
5.2 Test procedures
5.2.1 Checking of the field of vision The tractor shall be placed on a horizontal surface as shown in Figure 2. On a horizontal support level with the reference point, there shall be mounted two point sources of light, e.g. two × 150 W, 12 V, 65 mm apart and symmetrically located with respect to the reference point. The support shall be pivotable at its centre point about a vertical axis passing through the reference point. For the purpose of measuring the masking effects, the support shall be so aligned that the line joining the two light sources is perpendicular to the line joining the masking component and the reference point. The silhouette (deepest shadow) overlaps projected on to the semi-circle of vision to the front by the masking component when the light sources are switched on simultaneously or alternately shall be measured in accordance with 3.4 (Figure 3).BS ISO 5721-1 pdf download.ISO 5721-1-2013 pdf download
