BS EN ISO 7096:2020 pdf download – Earth-moving machinery – Laboratory evaluation of operator seat vibration
5.3 Test seat
5.3.1 General The operator seat for the test shall be representative of series-produced models, with regard to construction, static and vibration characteristics and other features which can affect the vibration test result.
5.3.2 Run-in Before the test, the suspension seats shall be run-in under conditions stipulated by the manufacturer. If the manufacturer does not state such conditions, then the seat shall be run-in for 5 000 cycles, with measurements at 1 000 cycle intervals. For this purpose, the seat shall be loaded with an inert mass of 75 kg and adjusted to the mass in accordance with the manufacturer’s instructions. The seat and suspension shall be mounted on the platform of a vibrator, and a sinusoidal input vibration shall be applied to the platform at approximately the suspension natural frequency. This input vibration shall have a peak to peak displacement sufficient to cause movement of the seat suspension over approximately 75 % of its stroke. A platform peak to peak displacement of approximately 40 % of the seat suspension stroke is likely to achieve this. Care should be taken to ensure against overheating of the suspension damper during the running-in, for which forced cooling is acceptable. The seat shall be considered to have been run-in if the value for the vertical transmissibility remains within a tolerance of ±5 % when three successive measurements are performed under the condition described above. The time interval between two measurements shall be half an hour, or 1 000 cycles (whichever is less), with the seat being constantly run-in.
5.3.3 Seat adjustment
The seat shall be adjusted to the weight of the test person in accordance with the manufacturer’s instructions. With seats where the suspension stroke available is unaffected by the adjustment for seat height or test person weight, testing shall be performed with the seat adjusted to the centre of the stroke. With seats where the suspension stroke available is affected by the adjustment of the seat height or by test person weight, testing shall be performed in the lowest position which provides the full working suspension stroke as specified by the seat manufacturer. When the inclination of the backrest is adjustable, it shall be set approximately upright, inclined slightly backwards (approximately 10° ± 5°).
5.4 Test person and posture The posture of the test person during the testing shall be in accordance with Figure 1.
NOTE 1 See ISO 10326-1:2016, 8.2.
NOTE 2 The differences in the posture of the test person can cause a 10 % difference between test results. For this reason, recommended angles of knees and ankles have been specified in Figure 1. The simulated input vibration test shall be performed with two persons. The light person shall have a total mass of 52 kg to 55 kg, of which not more than 5 kg may be carried in a belt around the waist. The heavy person shall have a total mass of 110 kg to 115 kg, of which not more than 12 kg may be carried in a belt around the waist.
5.5 Input vibration
5.5.1 Simulated input vibration test to evaluate the SEAT factor
This document specifies the input vibration in nine input spectral classes (EM 1 through EM 9) for earth-moving machinery for the purpose of determining the SEAT factor.
In accordance with ISO 10326-1:2016, 10.2.2, the SEAT factor is defined as
The simulated input vibration used to determine the SEAT factor is defined in accordance with ISO 10326-1:2016, 9.2, but the frequency weighting shall be in accordance with ISO 2631-1:1997/Amd 1:2010.
The test input for each class is defined by a power spectral density, G* P (f), of the vertical (Z axis) acceleration of the vibrating platform, and by the unweighted rms vertical accelerations on that platform (a* P12 , a* P34 ). The vibration characteristics for each input spectral class EM 1 through EM 9 are shown in Figures 2 through 10, respectively. Formulae for the acceleration power spectral density curves of Figures 2 to 10 are included in Table 2. The curves defined by these equations are the target values to be produced at the base of the seat for the simulated input vibration test of 5.6.2.