There are many equations to determine coil windings on a spool that activate a 430F ferrous armature (solenoid). This electro-magnetic force should have simple equations (inches preferred) that derive forces close enough to use as design starters. 2.00 OD armature x 2.00 long. .050" diameter wires wound on a 2.30 diameter vespel spool. 30 wires per layer and up to 10 layers (300 windings). The armature face is 2.50 square inches. 24 VDC at 3 amps.

 

Dave,

This problem is common in designing valves used in space. I am sure there are some Lockheed engineers who are setting on an Excel sheet that will calculate coil windings and electro-magnet pull forces for you.