The front and back coils are the motor of the machine. When power comes into the circuit the coils pull the armature bar down, (with magnetism) disconnecting the contact screw from the front contact spring, this opens the circuit and causes the coils to lose magnetic force returning the armature bar back to its original position; the contact screw and front contact spring reconnect closing the circuit. Thus returning power to the coils creating a rapid loop of the circuit opening and closing.
Why are there 2 coils?
If the frame is made of a material that facilitates this i.e., (iron.) Then you will not need a machine part called a, “yoke” to connect the two magnets. This is done to increase the magnetic force by directing both magnetic poles towards the armature bar.
There are a lot of tweaks and custom set ups for coils but the 3 basic sizes you will see are: 8 layer, 10 layer, and 12 layer. And bigger does not mean better.
The number represents how many times the coil core has been completely wound up and down the surface of the core. What is the difference in layers? The more layers the stronger the magnet. But that is not the only thing that will affect the coils behavior. Wire gauge, wind direction, wire composition, how tight the wire is wound, the material the core is made from, surface area of the armature bar, surface area of the top of the cores, if the core is properly insulated, and the capacitor paired with the coil/coils will all affect the behavior.
The more layers a coil has the more voltage will be needed to power the coil and the harder it will, “hit” bring the armature bar down. Bigger coils mean more force and more voltage to run. More force equals more trauma to the skin and more voltage equates to more heat; use the right components to get the job done.
You always want to make sure your coils are wound in phase. In phase simply means the coils are both wound in the same direction. This way the north and south poles of the magnetic fields will sync up.
The basic materials to build a coil are:
A cover for the finished outside of the coil i.e., (shrink wrap tubing, coated in sealant, or other type of custom cover.)