## 2 Materials and Methods
### Experimental Setup  
For experimental research in the aerodynamic tunnel, the model of the investigated scissor lift with an approximate scale of 1:14 is prepared. Due to the specificity of the research, it is important to maintain the geometric dimensions of the model in relation to the real object, while some elements were simplified or omitted. Simplifications used in the model: (a) Arms of the scissor mechanism made of full profiles (originally an open rectangular profile), (b) connections of the scissor mechanism members made with the use of screws and bushings (originally pins), (c) stabilizing supports permanently integrated with the chassis (in the original it is possible to disassemble), (d) rigidly mounted road wheels, (e) elements of the platform and covers of the engine and hydraulic system made of 3 mm thick PVC.  
Making the scissor mechanism from full profiles and the use of PVC with a thickness inconsistent with the scale of the model is reasonable because the overall dimensions have been preserved, and thus the reference surface, which is needed to determine the force and moment coefficients. Moreover, the whole described simplifications of the scaled model do not affect the surface in the orthogonal projection. The scaled model with the geometrical dimensions is shown in Figure 2.  
\begin{table}
\begin{tabular}{l c} \hline \hline
**Technical Data** & **Value** \\ \hline Platform Height [mm] & 12,500 \\ Stowed Height (Top Guardrail) [mm] & 3000 \\ Platform Entry Height [mm] & 1880 \\ Overall length [mm] & 3660 \\ Overall length with outriggers [mm] & 4570 \\ Width [mm] & 2310 \\ Platform length extended [mm] & 4570 \\ Platform length retracted [mm] & 3350 \\ Lift capacity [kg] & 454 \\ Roll-out deck capacity [kg] & 227 \\ Self-weight \(Q\) [kg] & 4400 \\ Maximal number of persons on the platform & 4 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Selected technical data and geometrical dimensions of the scissor lift MEC 4191 RT [52].  
The experimental tests are carried out for three configurations of the scissor lift, namely:  
* configuration 1, where the work platform of the model is positioned 891 mm from the floor level (height measured to the top guardrail, as is shown in Figure 2 with extended roll-out deck),
* configuration 2, the configuration of the scissor lifts the same as in the case of variant 1, but the roll-out deck is retracted, and finally,
* configuration 3, where the work platform is positioned 450 mm from the tunnel floor level to the top guardrail with retracted roll-out deck.  
In all mentioned cases, it is assumed that the wind direction varies from 0\({}^{\circ}\) to 180\({}^{\circ}\) with an increment equal to 15\({}^{\circ}\). At this stage of analysis, the presence of workers on the platform is not considered. The impact of the presence of people will be studied further.  
The assumed coordinate system and the way the angle of wind direction is defined are shown in Figure 3. For the tested model of the scissor lift, the aerodynamic moment \(M_{z}\) and aerodynamic forces \(F_{x}\) and \(F_{y}\) are measured using the three-component aerodynamic balance based on the electric resistance strain gauges [54]. The orientation of the fixed coordinate system \(x\), \(y\), \(z\) is as follows: \(x\)--along wind direction, \(y\)--across wind direction, \(z\)--vertical direction.  
The sensitivity of the aerodynamic balance in the range of 0 to 2 N in increments of 0.1 N is 89.4%, in the range of 2 to 10 N in increments of 2 N is 92.9%, and in the range of 10 to 50 N in increments of 10 N is 99.7% [54]. A similar topic, including research in a wind tunnel, was described in [55; 56; 57].