We have a an old Enerpac pump in the lab where the Hydraulic controls were only Forward and Reverse. They were controlled with servovalves that open and close when 110 voltage is applied. I used timer relays to be able to control the load and unload rate of the system. A counter was wired in to count cycles. There was also the option of manual control with the old buttons or to cycle. A pressure relief valve was used to get the same loading every time.
This was used in the research project:
Mid-America Transportation Center
Report # MATC-KU: 36
Performance of Geogrid Reinforced Ballast under Dynamic Loading
Click to access Parsons_363_FINAL_COMBINED.pdf