I am looking to open a series of valves in a chamber under 10" of lift(water) ~.36psi which are normally held closed by a very light spring and the constant air pressure. The valves are very light weight and range in surface size from approx 2 to 6 sq inches, or approx .72 to 2.16 lb of initial force to begin opening them. The valves offer the greatest resistance when closed so I need the greatest force to begin opening them but once they start to open the force drops dramatically to mainly the lightweight spring. The weight of the valve at this point actually aids in keeping it open as they are dropping down (hinged at one end). The travel of the free end of the valve surface would be approx 3/8". My thought was to use a very strong permanent magnet situated in direct contact with an electromagnet such that when energized the two magnets would repel each other. This would create a force profile ideally suited to this application as the repelling force would drop as the two magnets moved away from each other and the required force to keep the valve open would also decrease. QUESTION 1: Am I correct in assuming that I can leverage the strong force of the permanent magnet against a relatively weak electromagnet (so as to limit the current/turns required) OR will the repulsive force be closer to the weaker force of the electromagnet? If I cannot leverage the strong force of the permanent magnet this would not be a viable application. QUESTION 2: Can an air core for the electromagnet suffice as the core of the electromagnet, IMO, cannot be iron less the permanent magnet would be so attracted to it as to require excessive current/turns to break that attraction. The requirement for 1000s of these magnets in this application makes it imperative to minimize the current and to a lessor extent the amount of wire for each coil. These coils will have at most a 10% duty cycle and ideally run at approx 12vdc.