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The mandrel is held in place by 2 3D printed end caps. The aft mandrel fits over the casting tube and can be taped in place to seal that end. The foam mandrel is epoxied into the aft cap. The forward mandrel cap slides inside the liner tube and is designed to sit flush against the propellant. The mandrel slides through it. The forward cap contains captive nuts to allow it to be pulled out of place. Both of the caps were 3D printed from ABS plastic to allow them to be dissolved with Acetone should other extraction techniques fail. Both caps are designed to be an appropriate thickness so that the nozzle and seal disk can seat fully in the liner. Future improvements might include printing the aft cap to allow the propellant to match the taper of the nozzle converging section, or machining these from aluminum to make them more robust and extractable.
Nozzle End Madrel Cover.SLDPRT
Cutting the Liner to Length
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