PET & Sigg bottle pneumatic air tank adapters for fischertechnik

Turn PET soda bottles or Sigg water bottles into air tanks for fischertechnik pneumatic applications
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updated January 27, 2025

Description

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Turn PET soda bottles or Sigg water bottles into air tanks for fischertechnik pneumatic applications.

Both kinds of bottles are suited for compressed air up to at least 1 bar, the Sigg metal bottles are perfect for vacuums. The PET adapter is suited for caps marked with "cr-cap".

Fittings

Both PET and Sigg adapters come in versions with two or three fittings, the latter is useful for directly connecting a gauge like this one.

There are versions for two types of fttings, the Sigg design only supports the second one:

  • all-in-one printed fittings (see last image middle of bottom row). It's a bit harder to print those air tight, and they are less flexible than the second solution:
  • with 5 mm holes for external M5 threaded pneumatic fittings with matching silicone/NBR o-rings. There are plenty of variants like M5-AU, M5-ALU, M5-PB, M5-SL with valve etc., e.g. on aliexpress or you can use one of my printed desings (see last image).

Note that the printed holes are not threaded. Use a M5 machine screw to cut the threads (see last image). Make sure that the outer surface remains clean and flat, as it is here that the fitting's small O-ring will need to seal things air tight.

Gaskets

As gaskets you can use 28x4mm silicone O-rings for the PET bottles and original spare parts for the Sigg bottles (I got mine here).

Alternatively, both will work with gasket rings cut from rubber sheets, even old bicycle tubes can work. Stencils for cutting those to size are included for both adapters. Try two layers if one does not work and make sure they are perfectly clean and dust free.

Print Settings

Printer:

Creality Ender 3 v2

Rafts:

No

Supports:

No

Resolution:

.1 - .2 mm

Infill:

15%

Filament:

any PLA/PETG

any


Notes:

Print all adapters bottom/open side up, of course.

For airtight printing the general wisdom is to
  • increase number of walls (I use 5)
  • lower print speed
  • increase extruder temperature
  • decrease fan speed
  • decrease layer height
  • smooth critical surfaces (those that have contact with O-rings)
  • avoid quality deteriorating printing problems, particularly stringing and oozing

Do not increase flow rate as this will make the fischertechnik connectors too tight.

Category: Construction Toys

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Model origin

The author marked this model as their own original creation. Imported from Thingiverse.

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