Groom (door closer)

This device was originally designed with a spiral spring as the actuator (stl file attached).

However, due to the viscoelastic characteristics of PLA, this spring loses its effectiveness very quickly.

I had to look for another type of actuator and I opted to use bicycle inner tube.

A piece of inner tube (700x20 to 23 mm for road or racing bike) about 900 mm long makes the spring.

This inner tube is installed in double thickness in the system. The two ends are fixed in the hub and the central fold on the drive cleat. The winding is done in a spiral on the rollers (see pictures). To avoid the accumulation of residual air, a hole must be drilled in the central part of the air chamber.

Fixing is done by creating a loop that is inserted into the housing and then a pin is placed in this loop.

The tension can be adjusted by varying the length of the inner tube piece and/or the angular offset of the arms. The "useful" stroke is at an angle of approximately 120°.

The design of the spring box was made for a door whose axis of rotation is to the left when pushing. For the other direction, the parts marked "sym" in their file name must be made.

Pins and bores should be lightly sanded and lubricated (Teflon grease ....).

See the mounting dimensions in the attached document.

Do not exert significant torque without placing the spring box cover.

You will need TTPC20 type screws.

If possible, axes and bores should be printed vertically for best quality.

All parts are printed with a wall thickness of 1.2 mm and a filling of 20% except:

• the tray which has a 40% fill

• the spring " for those who want to try.... "for info, the direction of the spring must be such that its diameter increases with the torque exerted. The thickness of the outer walls should be more than 2.4 mm.