The projectile’s starting position is critical. The position must be repeatable, adjustable in small increments, and provide positive retention with low separation force.
This coilgun does not need a magazine loader; manual loading is acceptable for my purposes of coilgun demonstration.
A lightly magnetized bolt satisfies all the requirements. The threads allow easy adjustment in small well-defined amounts. A small permanent magnet placed at the head end provides a small but sufficient force on the projectile. No glue is needed; the magnetization holds it securely in place.
This carriage bolt is approximately 3” by ½”, it has a thread pitch of 18 turns per inch. It can be adjusted by 0.0555 inches (1.411 mm) with each turn.
A small rectangular magnet at the end away from the projectile was found to work very well in lightly magnetizing the bolt.
Last update June 25, 2007 by Barry Hansen ©2007