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Warning Compressed Air Can Be Dangerous!
We don’t suggest or encourage anyone to try this for themselves. Careful research and appropriate safety precautions were taken at all times.
Air is highly compressible and when held under pressure it can contain a lot of energy. Plastic drinks bottles are not intended to hold high pressures, they can also become brittle and weak due to age or exposure to light. If a bottle under pressure fails suddenly it can cause physical harm.
The pressure in the system I discuss here never exceeds 40psi.
With this in mind let’s see what’s in this episode.
- Why Add a Coke Bottle to my Compressor?
- The Theory
- Attaching the Bottle
- Fixing Leaks
- T Connector
- Getting a bit Moist
Mostly because I have a need to tinker, a desire to upgrade my airbrush equipment and no money to do so. However there are some performance benefits too. The airflow should be more consistent, the compressor should run less of the time and stay cooler and I could remove the water trap and bleed valve from the airbrush. Removing these parts was important to me as I find it a bit cumbersome. Something I’m still unsure of but should point out is what the status of my warranty is on the compressor after making this mod.
Inspired by this youtube video I felt I could make something similar. My compressor already had an automatic cut off/on (pressostat) built in but no regulator. So the plan was to use a T-connector to attach the bottle between the compressor and regulator. The compressor should then control the pressure in the bottle and the regulator should control the pressure in the airbrush.
I have no experience with pneumatic equipment or plumbing so researching and finding the components was a bit of a challenge and since I’d be ordering online I wouldn’t know if anything would work until it arrived.
The starting point was obvious as I already own a Sparmax ARSIM compressor. The specs tell me the output connector is 1/8 BSP so I need parts that will marry up to that. The T-connector has 3 female ‘swivel connectors’ which mean I can put the connector at the angle I want.
The regulator was as cheap as I could find and came with 2 adaptors to change the 1/4 BSP female outputs to the 1/8 BSP male I needed. To get everything sealed I also got some PTFE tape.
To attach the bottle I went with a 1/8 BSP male to male connector but in hindsight a banjo bolt with extra nut may have been a better choice. I also picked up some washers with rubber seal installed.
From my RC collection I ended up using some diff o-rings and green slime grease to help seal some parts.
Attaching the Bottle
Empty, wash and clean the bottle. Remove the cap and make the smallest hole you can to start threading the connector in, I used an RC body shell reamer. Now was a tricky part because of the way the swivel connector works on the T there had to be enough thread showing through the cap. I ended up using 1 washer and an oring. Everything has to be done up nice and tight here. I could have done with a socket here but since I didn’t need the threads I used some mulgrips to get the job done.
That’s the ‘complex’ part of the build done everything else should screw on from here. The only other thing would be to note the direction of the arrow on the regulator and hook it up the right way round.
Nothing’s ever that easy! Pretty much everything leaked on my system when I first tested it. The regulator was the worst as both adaptors and the pressure gauge were leaking. I found the leaks using soapy water and a brush, I could only find one leak at a time and after sealing it the next would appear. So I had to be patient and rebuild most things a few times and keep testing until it was all sealed up.
The only joints which didn’t leak were the compressor output, airbrush hose and perhaps surprisingly the bottle fitting. Everything, that could, had a few wraps of PTFE tape on it to start with.
Both output adaptors leaked, the threads into the regulator weren’t nice. I eventually solved with plenty of PTFE tape, an o-ring and some grease. The pressure gauge fitting also leaked and I solved this with some extra PTFE tape.
Due to the way this works the nuts had to be done up quite tight to prevent leaks. The challenging one here was the one for the bottle as it depended on the thread showing through the bottle cap. Altering the stack to use 1 washer inside the bottle and an o-ring outside did the trick.
After the initial build I held onto my airbrush and switch the compressor on. I then stood back and waited for the compressor to stop which it did after a short while. I could see the needle on the pressure gauge was dropping but nothing had moved. I let everything sit and allowed the air to seep out until I was confident to approach the system.
During the process of fixing leaks the system was filled and emptied a number of times, once everything was sealed I tested another 3 or 4 times and let the bottle sit at pressure for an hour or so.
The next day I had a stack of models ready for priming so I set about it to see how this all now worked in practice.
It actually worked a lot better than I expected. The regulator seemed to bed in and by the end of the session held a nice steady pressure. I discovered the cut off for the ARISM compressor is 40 psi and cut in is at 25 psi. So I can use nice consistent pressures under 25 psi. Even at this pressure the tank lasts longer than I thought and the compressor is powerful enough to top it up as I paint and pretty much whenever I stopped painting for a few moments to change model or clean the tip it would fill the tank entirely ready to go again.
I tried some lower pressures and things lasted longer but I prime at 25 psi so I didn’t do much. Lower pressure results will have to come when it’s time to do some colour.
After I had finished priming the compressor wasn’t as warm as it normally gets so hopefully I can paint for longer now without things getting too toasty! Overall I’m very happy, a great fun project and performance boost, success!
However there’s always room for improvement so I’d prefer it if I could support the regulator as everything is hanging off the compressor output connector but it seems OK. I also now have to put it on a box as the regulator sits lower than the bottom of the compressor. Well at least I found a use for my cleaning kit! The only other thing I’d prefer is a pressure gauge that doesn’t go so high so it’s possible to set the spraying pressure more accurately.
Getting a bit Moist
After the first session the last thing I did was to remove the bottle and let the moisture out. This shouldn’t be a problem as the tank won’t corrode and we have a moisture trap to stop anything getting to the airbrush. The bottle also shouldn’t let much moisture out due to the way it collects on the sides.
Thanks for reading and I hope you enjoyed this slightly special article, I had a lot of fun. You can let us know what you think in the comments below and follow us on Facebook.Thanks for reading and we hope you enjoy these articles. You can let us know what you think in the comments below and follow us on Facebook. We also earn a little towards our paint if you shop with Element Games through us. Use code VIN016 at checkout to earn double crystals on any order.