This is a fully 3D Printed, ejection recovery system for 74mm model rocket fuselages.

It consist of two parts, a tube (fuselage) adapter that connects the lower section to the top and also serves as the cap that will hold the shock coord or string that connects to the piston.

The piston slides freely inside the upper fuselage (the part that holds the nose cone), and connects the shock coord to the lower section, nose cone and parachute.

The design is based on Joe Bernard's piston system (BPS.SPACE) however I am very bad with my hands and don't like cutting so I used a fully 3D printed version. In terms of weight this is lighter than the alternative and the hooks that are 3D printed don't seem to show any sign of wear after 5 consecutive tests.

Print instructions

Print Settings

Printer Brand: Prusa

Printer: I3 MK3S

Rafts: No

Supports: No

Resolution: .20mm

Infill: 10-15%

Filament: Any PLA, PETG
Notes:

You can also try PET-G but careful on the tolerances since materials might change.

Video Demo