ok , you almost have it.
you need 2 of the (e) items.
so that you will have 4 pistons in the center.
ie...
ea,eb,ec,ed
ea and eb cannot be allowed to apply pressure on each other.
likewise
ec and ed cannot be allowed to apply pressure on each other.
because the pressure in tanks (B) and (D) will be higher than the pressure in tanks (C) and (A) and this higher pressure
will equalize with the tanks (A) and (C) and when these tanks equalize then you will no longer have the ability to have exact fluid velocity of water and mercury.
there must be a partition between ea and eb in the picture.
there must be a partition between ec and ed in the picture.
like this
tank A <------eb | ea------> tank B
tank C <------ed | ec------> tank D
you will have 4 hydraulic systems that are independent
of each other yet are controlled by a central pressure
apparatus ( the 4 pistons in the center ).
draw another picture with the changes above and post it.
