# Analysis of Different Guide Elements' Designs in Hydraulic Cylinders
## 4 Results
### Guidance with Hydrostatic Seal  
The measured frictional forces for design with hydrostatic bearing are shown and reported separately for each pressure used in Figures 16-18. At a pressure of 20 bar (Figure 16), the frictional force at velocities below 0.1 m/s increases with increasing radial load (from 0 kg to 50 kg), being 736 N at 0 kg and 1760 N at 50 kg. In addition, the frictional force decreases rapidly with increasing velocity and reaches its lowest value (10 N at 50 kg) at 0.21 m/s. A further increase in velocity leads to a slight increase in frictional force, which reaches values between 100 N and 200 N at velocities above 0.5 m/s. At a pressure of 120 bar (Figure 17), the trend of the curves is similar to that for 0 bar (see Figure 16). At velocities below 0.1 m/s, the frictional force increases with increasing radial load, being 700 N at 0 kg and 1430 N at 50 kg. Furthermore, the frictional force decreases rapidly with increasing velocity and reaches its lowest value (30 N at 50 kg) at 0.23 m/s. A further increase in velocity leads to a slight increase in frictional force (approx. 50 N per 0.1 m/s). At a pressure of 240 bar (Figure 18), the trend of the curves is similar to that for 0 bar and 120 bar of pressure (see Figures 16 and 17). At velocities below 0.1 m/s, the frictional force increases with increasing radial load, being 740 N at 0 kg and 1450 N at 50 kg. Furthermore, the frictional force decreases rapidly with increasing velocity and reaches its lowest value (50 N at 50 kg) at 0.21 m/s. A further increase in velocity leads to a slightly greater increase in frictional force than at 120 bar, reaching a maximum value of 530 N at 10 kg at a velocity of 0.6 m/s. The violet curve represents the measurement without orifice (flow restrictor). The initial values of the frictional force are almost the same as for the measurements with the orifice, but reach better minimum values (10 N) at 0.23 m/s. A further increase in velocity leads to an increase in the frictional force, which reaches a maximum of 580 N at 0.58 m/s. The graphs in Figures 16-18 show that the pressure reduces the initial frictional forces, especially at higher radial loads. Figure 18 shows a measurement without the use of orifices (restrictors). It can be seen that the curve does not deviate significantly from the other measurements.  
Figure 15: Measured friction force in relation to velocity at a pressure of 240 bar, for design with labyrinth seals.  
Figure 19 shows the measurement results of three different guide elements at a pressure of 240 bar and a radial load of 50 kg. This is the pressure that normally occurs in hydraulic systems. Such high radial loads are not desirable in hydraulic systems, but in our case the radial load of 50 kg was used to test how different components (especially guide elements) work and how robust they are. Guide rings (GRs) have the highest initial frictional force (approx. 1800 N), followed by hydrostatic bearing (HB), with approx. 1450 N frictional force; the lowest is the labyrinth seal (LS), with approx. 902 N frictional force. Furthermore, the frictional force decreases with increasing velocity. The minimum value for GR is 690 N at 0.18 m/s, 210 N at 0.23 N for LS, and 50 N at 0.21 m/s for HB. A further increase in velocity leads to an increase in frictional force. The gradient is steepest for HB, followed by GR, and is most constant for LS. The steeper the curve, the greater the increase in frictional force.  
Figure 16: Measured friction force in relation to velocity at a pressure of 20 bar, for design with hydrostatic bearing.  
Figure 17: Measured friction force in relation to velocity at a pressure of 120 bar, for design with hydrostatic bearing.