Ask you technic kaki, do you need to put water into the hydraulic pumps?
In lego technic, there are two types of linear actuators (LA). (sometimes called cylinders)
a) Pneumatic (air operated)
- actuated by means of hand-pressed air pump or;
- actuated by motorized cranked air pump.
- optional compressed air storage so called the 'reservoir'
- air is directed thru flexible rubber hoses.
- flow of air is single direction - no return line required.
b) Mechanical (internal screw operated)
- converts rotary input into linear output.
- complex gearing and shafts are required to direct rotary motion from power source (eg. motor) to the LA.
c) No hydraulic system in Lego so far. (Hydraulic system utilises incompressible liquid as transmission medium)