Type of External Iron

Computer FEM (finite element magnetics) models suggest the limiting factor for energy transfer is the magnetic saturation of the thin iron nail. This is inherent to the projectile itself, but we can reduce the saturation of the remaining magnetic circuit by adding external iron.

Type of External Iron

This coilgun uses laminated E-core iron salvaged from an ordinary transformer. The transformer was opened and the leaves restacked to complete the magnetic circuit around the nail.

Top View of Iron Laminations

The drawing below shows the dimensions as measured from the transformer core leaves. This is included for documentation purposes, and will become useful if a computer FEM model is later created.

End View of Iron Laminations

The drawing below shows how iron laminations are stacked to form the structure around the coil. The middle layer is made of the E-core sections, pressed tightly around the firing tube. The top and bottom layers are made from the straight iron strips. The existing holes are drilled through to accept the machine screws.

The height of the top and bottom layers is chosen to equal the tube’s diameter. The photograph below shows the finished iron assembly.