## 3 Results and Discussion
### Pallet Behavior  
Table 5 shows the acceleration, duration, and delta velocity responses registered in the pallets for each shock event in the study. The peak acceleration measured on the pallet was, on average, 13.15 G. The data has a coefficient of variation of 40%, with the lowest peak acceleration value of 3.7 G in the reach truck and the highest acceleration value of 19.51 G measured in the gas forklift. The impact event duration was 12 ms with a coefficient of variation of 37%. Impacts to the pallet show an average change in speed of 0.73 m/s, with values as low as 0.23 m/s measured in the reach truck and as high as 1.35 m/s measured in the gas forklift. The coefficient of variation for delta velocity was 42%.  
Figure 5: Interaction plot for Forklift Peak Acceleration response.  
The \(p\)-values obtained in the analysis show that the main factors, including forklift type, entry speed, and top load, significantly affect the peak acceleration response measured on the pallet (\(p<0.05\)). Significant two-way interactions were found in the combinations of forklift type and entry speed, forklift type and top load, and pallet design and top load. The three-way interaction between pallet design, entry speed, and top load is also significant in the model (\(p=0.001\)).  
The effect of the main variables on the peak pallet acceleration response was investigated with a main effects plot (Figure 6). The forklift type plot shows an increase of 16% in peak pallet acceleration response due to changes in forklift type. The acceleration response change seems to be affected by the weight of the forklifts. No significant differences were found in pallet impact event duration for the different forklifts (Appendix A).  
\begin{table}
\begin{tabular}{c c c c c c} \hline
The entry speed plot shows a 14% peak pallet acceleration increase when the speed was 0.45 m/s. Similar to the forklift type plot, there was no change in the duration response for the increasing levels of speed. The effect of the top load shows a significant increase in peak pallet acceleration for the 227 kg top load (13.8%). The Tukey pairwise comparison shows no significant differences between the responses for the change of top load from 680 kg to 1134 kg.  
Significant two-way interactions are shown in Figure 7. Significant differences were evaluated with the Tukey pairwise comparison method.  
The measured accelerations obtained by forklift type is dependent on the entry speed. At lower speeds, there are differences between the forklifts. The reach truck presented the lowest acceleration response. This behavior could be explained by the reach mechanism of this forklift, which could act as a cushion during impacts. At higher speeds, the greatest acceleration was measured on the gas forklift.  
The acceleration obtained with the different forklift types is also dependent on the top load of the pallet. High differences in behavior are seen for each type of forklift depending  
Figure 6: Main effects plot for pallet peak acceleration. Tukey pairwise comparison indicates means that do not share a letter are significantly different at \(\alpha=0.05\).  
Figure 7: Interaction plot for pallet peak acceleration response.  
on the top load. The greatest acceleration was measured in the gas forklift carrying a 227 kg top load.  
Pallet design affects the acceleration values obtained for each top load combination. The greatest acceleration response was recorded for the plastic design using a 227 kg top load. This increase in acceleration could be caused by the plastic pallet sliding around more easily when it is impacted by the forklift.