Friday, September 22, 2017

Portable 3D-Printed Railgun

The railgun uses 6 300J, 350V, 5500uF capacitors which combined weigh 20lbs and can deliver >1050V and 1.8kJ of energy to the projectile.

Capacitors are first wired in parallel with flexible busbars inside of a 3d-printed housing

Busbars were custom made and are flexible 4AWG equivalent.

All 3 pairs of 2 capacitors.

Caps are held together in a 3d printed frame

The frame includes the emergency discharge SCR, power resistor and button to discharge any leftover energy in the caps after a shot.

The capacitor bank all wired up.

Compared to the rest of the railgun.

The railgun's electronics are based around an Arduino Uno R3 which monitors the capacitor voltage, amperage, temperature and battery voltage to ensure even charging and operation./

The 12V LiPo battery is first stepped up to 120V using a micro-inverter, then stepped up to 1550V through a transformer before being rectified.  The high voltage rectifier gets quite hot so a heatsink was mounted on the outside.

Here, the 900psi injector system can be seen along with the high voltage transformer (the grey box under the green tube).

Attaching the handle which contains the pressure regulators.  The pnumatic system in the handle steps the CO2 down from a paintball tank into a compressed gas tank located in the center of the body.

The railgun is capable of firing copper plated tungsten, aluminum, carbon and teflon/plasma.  Here we have copper plated tungsten armatures.

The injector system accelerates the armatures from rest in the breach loader to 100 m/s before contacting the rails.

After the first test, the pressure broke a steel bolt in the injector and a piece of weak 3d-printed PLA which held the bolt in place.  A new polycarbonate injector piece and nylon bolt plate were printed and the problem never happened again.

The finished rails.  The rails consist of a set of outer and inner rails.  The outer rails are non-replacable and made of aluminum.  They never contact the armature so they never experience rail erosion.  The inner rails are copper and are designed to be periodically replaced.  They are held in place by the polycarbonate muzzle break and the polypropylene injector and are free to slide in and out once the muzzle break is removed.

The rails are modular and can be removed and replaced easily even after the railgun is assembled. 

After the second shot.  The outer rails were later modified to prevent further damage after I realized the extent of the problem.

Here the muzzle break is removed to see the full profile of the inner and outer rails as well as the teflon insulators.

CAD design of the railgun.  Everything in grey was 3d-printed.

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