2-Liter Bottle Compressor (No Moving Parts)

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Introduction: 2-Liter Bottle Compressor (No Moving Parts)

About: I like making cool stuff and posting it online as a way to share knowledge. Some people will care that I'm also a legit engineer with a bunch of patents and stuff, but I prefer focusing on abilities rather th…

2-Liter bottles are amazing. They weigh almost nothing but can hold well over 100 psi of air or water pressure. In this instructable I use their unique properties to inflate a completely flat car tire without a compressor or electricity!

Supplies

- a bunch of 2-liter bottles (I used eight)

- misc. air fittings

- 1/4" plastic water line (like for ice makers)

- an adapter to connect to a hose bib

Step 1: Collect a Bunch of Empty Bottles

My family drinks sparkling water instead of soda. But each time we finish off a bottle I can't bring myself to toss/recycle such an impressive pressure vessel. It would be nearly impossible to make anything like it at home without metal and a welder but even then it would way 10x more! So for months I've been hoarding 2-Liter bottles not knowing what I would use them for...until now!

Step 2: Design a Manifold

We need something the bottle can screw into with an air-tight seal. I had a number of ideas how to do this. The original cap for the bottle can be drilled and glued/epoxied with various fittings. I've taken the stem from an old bicycle inner-tube, inserted it from inside the cap and used it to inflate a bottle for classroom demos. I could also glue/epoxy the cap into a block of plastic or pvc fitting from the hardware store. Ultimately I decided this project is challenging enough I need it to work the first time, so I'm designing a custom manifold complete with o-ring for sealing. The bottle caps seal on the inside lip of the bottle mouth but the o-ring I chose seats on the tip of the rim.

Step 3: Fabricate Manifolds

This is the most challenging part. Any air leaks will limit the capacity and effectiveness of the compressor. The manifolds could potentially be 3D printed but I want them super robust so they don't crack under pressure. I'm using my mill I've converted to CNC (see my BUILD2 channel for details on that) to "thread mill" a small block of aluminum.

Step 4: Plumb Manifolds Together

I'm attaching the manifolds to a scrap 2x6 board I had lying around. Wood screws work great to pin them down. I threaded the in/out ports with 1/8" NPT on the mill which will fit a variety of fasteners. For convenience I'm using "push connect" fittings that accept 1/4" plastic line. The red tubing came with a Rancho adjustable shock kit I got years ago but the milky white variety works just as well for this and can be found at your local hardware store cheap. However you choose to do it, make sure to check for leaks and minimize them. Also be sure to connect everything in "series" so any air/water that enters from one end has to travel through each bottle to get to the other end.

Step 5: Connect to Hose Bib

The hardware store had plastic connections designed for an outdoor hose bib but they looked like junk to me. I wanted something metal with a pipe thread that would be secure and not leak. Fortunately they had this "Watts" water pressure gauge for pretty cheap and it comes with a nice brass hose bib adapter. Unfortunately that doesn't allow us to do anything other than read the pressure we have available. I purchased the "T" separately and am unscrewing the gauge from the adapter and putting it back together to allow monitoring pressure while using the water. A word of warning, the thread sealant the factory used is REALLY tough. I would have heated it to aid disassembly but that would melt the gauge. Brute force was the answer but it took everything I could muster.

Step 6: Putting It All Together

The exit end depends on what you want to use the compressed air for. I'm inflating a car tire so I'm attaching a valve, gauge and the working end of a broken foot pump. Screw all the bottles into their manifolds, shut the exit valve and stand the whole thing up. That way each bottle will fill before allowing any water into the next bottle. Here's the fun part. Open the hose bib and watch as the water flows in fast at first, then gradually slows down to a stop. My water pressure is kinda high (80 psi) so it can compress the air from all 8 bottles into the last 1.5 bottles at 80 psi. At that point I open the exit valve and let the air flow into the tire, being SURE to shut the valve BEFORE any water leaves the last bottle making its way into the tire. If the tire needs more air you must do the tedious job of unscrewing and emptying all the bottles (I used them to water my lawn) then start the whole process over. Seldom is a tire completely flat but if it is you'll probably need to do this process three or four times. But hey, no electricity or moving parts required!

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    29 Comments

    0
    spacewarewolf
    spacewarewolf

    2 years ago on Step 6

    This might be useful for a classroom.
    I'm guessing your tires take a little less than 3 bar and that's 43.5113213 pounds per square inch. And that's what you put in the last cycle. Unsafe.
    Then there's the volume of air you need to reach that pressure. How many times did you cycle to get to a pressure enough to get to a service station? Unpractical.
    And the wasted water. Unethical.
    Just buy a portable compressor that plugs to to the car lighter😉

    0
    definingsound
    definingsound

    2 years ago

    Can te technique of using tap water pressure be used with a single bottle, to make a rocket bottle launcher that doesn’t require an air pump?

    Just mount the rocket, turn on the tap, launch!

    0
    haroun
    haroun

    2 years ago

    I can't help but think about how heavy a SodaStream bottle is compared to a disposable soda bottle & think there is a real risk of blowing up one of your bottles. It's the same sort of thing with using an old propane grill bottle for an air tank, the metal isn't as thick as that on a tank built to be refilled at around 120psi, likewise the plaastic soda bottle is a single use design. Certainly folks reuse them for various things but they do have an inherent flaw that may allow for failure which if the bottle has water in it is not so bad but if it's filled with air it could be plastic shrapnel flying all over.

    0
    QuintBUILDs
    QuintBUILDs

    Reply 2 years ago

    Bursting is a concern but a minimal one. I built a semi-automated water rocket launcher that has launched the same bottle 60+ times pressurized to 120+ psi each time with no issues. Plus watch the burst tests online of the cutting edge water rocket crowd and they get 200+ psi before bursting. Plastic bottles are impressive!

    0
    definingsound
    definingsound

    Reply 2 years ago

    Soda stream bottles Safely contain 800 psi of co2!

    0
    NeilRG
    NeilRG

    2 years ago

    I respectfully challenge the assertion that a 2 liter soda bottle can withstand 80 psi much less 100psi repeatedly. How do we know that all soda bottles are made to the same quality standard? A Soda Stream bottle is MUCH thicker and even it carries warnings about pressure and life expectancy. This has to do with liability concerns of the manufacturer no doubt.

    0
    definingsound
    definingsound

    Reply 2 years ago

    A soda stream bottle contains the pressure of liquid CO2 at room temperature: over 800 psi (vapour pressure of liquid co2 at 22°C).

    A 2L bottle is at least 10% as strong as a soda stream bottle. So a 2L bottle can safely contain 80 psi.

    A 2L bottle is normally charged to about 3 atm (44 psi) by a soda bottler. This project does exceed that pressure but by less than double.

    0
    mtairymd
    mtairymd

    2 years ago

    I love geeky stuff like this. Nice job!

    0
    macaroni555
    macaroni555

    2 years ago on Step 6

    Great project to demonstrate real world physics in a simpler science project way. Great teaching method that is doable with the help of an adult. The only thing I wish this instructable had was a video showing each step. For me I was curious to see the cnc drill out the screw lip on the inside of the metal piece and then the final project in use. Good job!

    0
    QuintBUILDs
    QuintBUILDs

    Reply 2 years ago

    Have I got a treat for you sir... I remembered I used the fabrication of the blocks as the subject of a separate video on my engineering GD&T channel. If you don't work on design of manufactured parts you'll have no interest in any of the videos on that channel (pretty boring stuff otherwise) but you may get something out of the one that shows the blocks being made. Here's the link:

    0
    QuintBUILDs
    QuintBUILDs

    Reply 2 years ago

    Thanks. I never know how much fabrication footage to show. I've included a lot more machining in my "rain gutter power" videos.

    0
    jott_1
    jott_1

    Question 2 years ago

    What software did you use to design the manifold? Are the files available?

    0
    QuintBUILDs
    QuintBUILDs

    Answer 2 years ago

    Fusion360. What format would be most useful to you?

    0
    jott_1
    jott_1

    Reply 2 years ago

    DWG or DXF.

    0
    QuintBUILDs
    QuintBUILDs

    Reply 2 years ago

    Good, I made a basic print already. Let me dig it up and I'll post it somewhere and give you the link. Or tell me an email address and I'll send it.

    0
    crimes
    crimes

    2 years ago

    Yeh it is just good thinking and smart, we need more people like you. Thank you for the science of things and something very practical. Nice work!

    0
    The Lightning Stalker

    No electricity or moving parts required except for the electricity powering the well pump and the pump itself or the municipality's pumps if you have city water.