Barry's Coilguns

External Iron

Computer models (FEM) suggest the limiting factor in efficiency 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.

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.

This diagram shows how E-cores are arranged in pairs, facing the coil. Although the extra opening could accept another coil, this design only uses a single stage and the extra material was removed.

Transformer E-core arranged around firing tube

The goal is to obtain as much magnetic flux as possible through the firing tube and nail. The next figure illustrates the flux path in the magnetic core material.

Sketch of magnetic flux in transformer core

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