Connect PET Bottles, Make TrussFab Structures

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About: We believe that computer science and mechanical engineering are about to unite. In the future, users will solve mechanical problems by digitizing the involved objects using 3D scanners, solving the problem i...

Intro: Connect PET Bottles, Make TrussFab Structures

Hi, this is guide for preparing bottle pairs for constructing TrussFab structures.

TrussFab is a plugin for SketchUp that allows you to fabricate large scale structures that are sturdy enough to carry human weight. TrussFab achieves the large scale by complementing 3D print with plastic bottles. TrussFab considers bottles not as “bricks”, but as beams that form structurally sound node link structures also known as trusses.

Find more about the project: https://hpi.de/en/baudisch/projects/trussfab.html

Here we describe three different techniques to form truss members from PET bottles:

1) Inflating (with dry ice or liquid nitrogen) - thanks PETMAT for the idea

2) screwing

3) taping

If you are interested in tryingout our TrussFab plugin for SketchUp (research prototype for non commercial use), just drop us an email!
contact author: robert.kovacs@hpi.de

You can also download our demo models from Thingiverse.

IMPORTANT: before you start your design, make sure that you have tested your bottles, adjusted the bottle lengths in the software to match the actual lengths, and test the print the connectors to see if everything fits well together.

Step 1: Connecting Bottles Using Dry Ice

Take tree bottles of the same type, possibly with a long cylindrical bottom part.

Step 2:

Cut one of them open and preserve the long cylindrical part. Make it as long as possible.

Step 3:

Crease the other two bottles and insert them into the previously cut cylinder. Don't worry if they are getting crumpled, we will inflate them.

Step 4:

Put a small spoon of dry ice into the bottles, close them and shake them until they blow up.

Take care: if you put too much dry ice, the bottle can explode. Make some experiments before you do this step. If the pressure is to high, open the lid for a second.

Alternatively you can also use liquid nitrogen for this step.

Step 5:

If you choose the right type of bottles, they will fit inside so well that they won't come apart easily.

Maybe you'll need to try out different bottle types for this method. Also it might help if you place a bit of double-sticky tape on the inside of the cut cylinder. This will secure them even more.

Step 6: Connecting Using Wood Screw (you Can't Inflate)

Alternatively you can choose this technique:

(1) You can use regular wood screws and an extra long screw driver. Drill small holes in the bottoms before screwing.

(2) Use dowel screws (double sided screw) and simply screw them into each other.

For this technique choose bottles which fit well together with their bottoms (they are not wobbling). Also try to use stiffer bottles, because you cant inflate these ones to increase stability.

Step 7: Use Any Kind of Wide Tape or Shrinking Tube

This method is probably less strong or long lasting, but very easy to do and you can achieve additional strength by inflating the bottles using dry ice.

For this technique choose bottles which fit well together with their bottoms (they are not wobbling).

Step 8: Now, Use TrussFab to Design Your Structure, Generate the 3D Printed Hubs and Build Your Thing:)

Step 9: Special Thanks to Everyone Who Contributed to This Project

Robert Kovacs, Anna Seufert, Ludwig Wall, Hsiang-Ting Chen, Florian Meinel, Willi Müller, Si-jing You, Maximilian Brehm, Jonathan Striebel, Yannis Kommana, Alexander Popiak, Thomas Bläsius, Tim Oesterreich, Dominik Meier, Melvin Witte, Tobias Arndt, Nico Ring, Lukas Fritsche, Thijs Roumen, Alexandra Ion, Oliver Schneider, Perdo Lopes, Mirela Alistar, Lung-Pan Cheng, Sebastian Marwecki, Arthur Silber, and Patrick Baudisch

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    23 Discussions

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    joaquini5HCIHPI

    Reply 7 months ago

    this is such an awesome idea!! Where can i find the plugin?

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    HCIHPIjoaquini5

    Reply 7 months ago

    Thanks. Just drop me an email on robert.kovacs[at]hpi.de and I'll send it to you.

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    PascalJHCIHPI

    Reply 8 months ago

    Yes. The magic here is the custom angles for the connector hubs.

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    vinstruct3vinstruct3

    Reply 11 months ago

    Does this mean that if I can't 3D print or laser cut the key component I can't make these, i.e there are no commercially available connectors?

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    HCIHPIvinstruct3

    Reply 11 months ago

    You can also order the connector pieces form one of the online 3D printing services, like 3Dhubs.

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    MatiasG11vinstruct3

    Reply 11 months ago

    Just ask anyone with printer for printing thith things for you.

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    rxxannevinstruct3

    Reply 11 months ago

    The connectors are explained in the link near the start of the article.

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    StuartK15

    10 months ago

    I would think a shot of expanding foam inside the bottle would do to inflate and help increase strength. May also work to connect bases - especially if you sleeve the joint with foam inside. I would think a heat gun would also shrink the cut bottle sleeve to make tight on two inflated bottles - much like the actual heat shrink tubing. OR you could try to inflate the entire truss - add small diameter holes through centers of connector's, add small holes in bases of bottles that you join air tight (heat shrunk). You could add an air inflation fitting (3/8" NPT Female Thread ?) to one of the base connections. THEN assemble and inflate the entire truss - you could even monitor the inflation at the far end with another fitting and a pressure gauge...

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    ericCycles

    11 months ago

    If you just need the liquid nitrogen/dry ice to reinflate the bottles so that they fill the sleeve, I would look a a bottle cap outfitted with a bicycle tire valve.

    3 replies
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    HCIHPIericCycles

    Reply 11 months ago

    Cool idea! How would you do it?

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    ericCyclesHCIHPI

    Reply 11 months ago

    You get a presta bike valve from an old bike tire,
    drill a hold in a bottle cap for the bike valve,
    insert the end of the bike through the hole,
    add a nut and washers and teflon gas tape to either side.
    Then attach your bike pump and pump away.

    The air cannon/pop bottle rocket projects have lots of alternative designs for inflating a pop bottle using a bike pump.

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    HCIHPIericCycles

    Reply 11 months ago

    Yes, this would be super useful, but to do this for couple of hundreds of bottles is a bit tidies work... I have made an other type of bottle inflating device, which inflates them using a compressor and then tightens the cap. It works, but have to work on the usability a bit more. If you are interested write me an email and I can send you the files. Rob

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    padilla8888

    11 months ago

    How about the connection of the three or more bottles,joining the top of the bottles?

    1 reply
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    HCIHPIpadilla8888

    Reply 11 months ago

    That is happening using the 3D printed hubs, generated by the trussFab software.

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    mrwonton

    11 months ago

    AMAZING!

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    JamesA41

    11 months ago

    Awesome way to re-use waste where recycling isn't available or if user wants to. There used to be links online with someone, I want to say in Mexico since may relate to Mexico City once being a lake where floating gardens and waste merged into land covering the lake, making a houseboat also with yard area on top of bags/nets of plastic bottles. I've never seen anything like this. If you fill them with fluid you could store heat and also to equillibriate your environment slower. My Dad would do that with the hoop houses, green houses and in the basement.

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    Copymutt

    11 months ago

    you lost me at "tack them" and then proceeded to inflate them.

    Jim

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    sitearm

    11 months ago

    No fair that boat oar should be made with trussfab too LOL. Nice work! : )