## 4 Discussion
### Calculation of Overturning and Stabilizing Moments
\(M_{O2}=5593.28\) N--is the moment resulting from the product of the manual force--dynamic \(M=400\) N acting on the arm \(r_{2}\) equal to 12.71 m. The minimum value for the manual force \(M\) is taken as 400 N for the scissor lift designed to carry more than one person (Table 1), applied at the height of 1.1 m above the work platform floor. The manual force--dynamic \(M\) is taken to be dynamic forces with factor 1.1 (Table 7). Taking the above data into account, condition (5) is as follows:  
\[M_{S}=47,679.82\;\text{Nm}>M_{O}=13,091.01\;\text{Nm}, \tag{8}\]  
and conclude that the condition for the stability of the scissor lift is satisfied. Calculation of Overturning and Stabilizing Moments with Used to Aerodynamic Coefficients Obtained from Experiment and CFD  
The obtained values of aerodynamic coefficients from the experiment and from the CFD simulation are used to determine forces \(F_{X}\), and \(F_{Y}\) acting relative to the tipping line of the scissor lift of the real object of investigation. \[F_{X}=F_{x}\cos(\beta),\;\;\;F_{Y}=F_{y}\sin(\beta), \tag{9}\]  
Next, we determined the reduced value of force \(F_{rd}\) and moment \(M_{rd}\) acting relative to the tipping line of the scissor lift as a function of the angle of wind attack \(\beta\). \[F_{rd}=\sqrt{\left(F_{X}\right)^{2}+\left(F_{Y}\right)^{2}},\;\;\;M_{rd}= \sqrt{\left(M_{F_{rd}}\right)^{2}+\left(M_{2}\right)^{2}},\;\;M_{F_{rd}}=F_{rd }.h_{1}. \tag{10}\]  
The moment \(M_{rd}\) is taken to be dynamic moment with factor 1.1. Finally, the sum overturning moments from experiment \(M_{Oexp}\) and CFD simulation \(M_{O\;CFD}\) due to wind direction was determined:  
\[M_{Oexp}=M_{rd\;exp}+M_{O2},\;\;\;\;\;\;M_{O\;CFD}=M_{rd\;CFD}+M_{O2}, \tag{11}\]  
and the comparison of the results for three different wind speeds acting on the scissor lift is shown in Figures 14-16. Taking the above discussed results into account, the characteristics of the overturning moment as a function of wind speed for the angle of 15\({}^{\circ}\) can be determined (Figure 17). According to Figure 17, the scissor lift will be overturned at approximately 21.95 m/s (76.825 km/h). Note, however, that according to the standard and manufacturer's data, the maximum wind speed is 12.5 m/s (45 km/h). Figure 14: Comparison of the overturning and stabilizing moments received from the experimental and numerical tests with the calculation based on [17] for the wind speed \(V=12.5\) m/s (config. 1). Calculation of Overturning and Stabilizing Moments with Used to Aerodynamic Coefficients Obtained CFD  
Figure 18a shows the values of the moment coefficients \(C_{\text{M}c}\), which could cause the overturning of the investigated scissor lift as a function of the wind direction described by angle \(\beta\) together with the assumed schema of the acting loads. Figure 16: Comparison of the overturning and stabilizing moments received from the experimental and numerical tests with the calculation based on [17] for the wind speed \(V=25\) m/s (config. 1). Figure 17: Comparison of the overturning and stabilizing moments received from the experimental and numerical tests for 15\({}^{\circ}\) angle of wind attack with the calculation based on standard EN280 for the wind speed \(V=12.5\)–\(25\) m/s. Figure 15: Comparison of the overturning and stabilizing moments received from the experimental and numerical tests with the calculation based on [17] for the wind speed \(V=20\) m/s (config. 1). As can be observed, the most dangerous situation is when the wind blows along the direction, which creates the angle \(\beta\) = 30\({}^{\circ}\) with the \(X\)-axis of the coordinate system shown in Figure 3 for configurations 1 st and 2 nd. In the case of configuration 3 rd, the most dangerous wind direction is equal to \(\beta\) = 15\({}^{\circ}\). It is worth noting that the extended movable deck has no significant impact on the moment M induced by the wind.