I Made Mini Air Compressor

I have been wanting to do this project for a long time, but it took me a while to get parts such as a fire extinguisher and a compressor that runs on 12 volts / a small compressor that is used to pump tires on cars.

In order to make the project as cheap as possible I bought most things second-hand, i.e. at the local market, where you can find a lot of things that are cheaper but defective or used.

The idea is to make a small compressor that I can keep in my workshop so that I can use it to blow out computer components or, for example, for drying, when I clean something with isopropyl alcohol.

I decided to use the smallest fire extinguisher that could be found (max 16.5 bar intake), so that it would not be too big, because there is not much space in the workshop.

Ideal to combine with small car compressor (12V 18bar max), which is great but still limited in its capabilities, (for example) if I had found, a larger air tank, it would have overheated while filling it.

The project turned out really cheap, I'm even happy with how it turned out.

When I do some things like that, I try to make a project to be multifunctional, that is, to have a certain modularity of use, so I will try to do that in this version as well.

• Fire extinguisher (preferably used or empty).
• Tyre Inflator Air Compressor, Car Pump 12Volt.
• Compressed air hose with 1/4” BSP female and male quick connectors.
• Air Blow Gun with Extension Nozzle.
• Compressor hose.
• Teflon tape.
• O-Ring Seal Gasket / Rubber Washer Seals.
• Hose clamp / fitting.
• 1/4” BSP female and male quick connectors.
• Rubber valve for car tires.
• Power source which can be like large battery or computer power supply.

To open Compressor is not a problem, a couple of screws and that's it. I have three of them.

All three are the same, at least on their stickers they say that they are 12V and that their maximum pressure is 18 bars (250psi).

How they work? Well It's mostly very simple and for that reason they are not expensive, at least those that are made with, let's call it, bad tolerances.

In case we have a DC motor that drives the piston in the cylinder via gears. As the piston moves, we have a small non-return valve and pressure is created.

Everything looks fine in this one, but it was very dirty.

Speaking of which, we can mention the other two that are faulty ... one had the plastic gear was worn out and only the engine was spinning,

While on the other the cylinder cracked, fell apart basically.

It is also very important to note that they are not made to work for a long time because they overheat. Especially if they do more pressure / more amps used on motor.

After I cleaned everything, I tried to reduce some tolerances by placing the washer, but I quickly realized that this was a bad idea because the gears were so stiff that it couldn't turn at all.

So I put everything back to how it was, I just lubricated the whole mechanism first. I use here bearing grease because I didn't have silicone grease (white grease) at the time, which is the best for plastic and rubber, i.e. it doesn't affect them like peroilum-based grease does.

I need to connect something to it so that i can test everything, so the next thing is to fix the end of the hose on compressor. An old car valve connector can even be reused, which is a press fit on the hose, basically it is easily removed. I cut off the damaged part of the hose, put a hose clamp on it and tightened it well. I'm lucky because often the hose can't be repaired it becomes very stiff and breaks.

After putting it together I tried it and now it seems ok, it now works as it should, making pressure. I tried to block the end of the hose and it is already consuming 4 A, which is very close to the maximum of my power supply.

Since I now have pressure, I should store that somewhere, so now is the time for air thank from fire extinguisher which can take maximum of 16.5 bars. 

Ideally it would be empty and It is quite easy to disassemble it, to open it.

This one was empty but I had to blow it out a bit with a compressed air to make it clean. The material from which it is made is aluminum, which is great if there is condensation.

As you saw I have 3 pieces, but I chose this one mainly because of its nozzle.

Others had a conical tip. This one has a flat tip with no angle, so I thought it would be easier for me to mount the fitting on it. I didn't have such a big thread to cut in, so I tried with a smaller one that i had and tried to forced it to screw in ... because it's plastic after all, but nothing worked.

So I used fire.

I have a small kitchen burner and I didn't even have to hold it for a long time and the connector went in perfectly, but I wasn't really prepared, of course when everything sits down you need to cool the connector, so I got the idea to slowly cool it with air but ... everything went sideways literally.

But I didn't give up, I decided to make it and then I saw that I had window cleaner on hand and with that I cooled everything and decided to test the tank before deciding what to do next, like to cut this part or use other one that i have.

The first test did not go well. Something is blocking the air outlet.

I tried unscrewing the fitting and it was even easy. But I found a problem, as I pushed the hot metal into the plastic, a plug eventually formed, I easily removed it and before I went to test again I decided to put Teflon tape on threads of the fitting just in case so that there would be no air leakage.

The handle creaked a bit, but I lubricated it with silicone oil spray.

Test number two went without a hitch. The tank can be filled through the fitted fitting,

but since I will use it to blow out the air, I have to put something for the intake and I will put a Rubber Tyre Valve. I measured the thickness of the valve because the hole must be smaller than it. for the position, I decided on the upper part that is flat so that the valve could sit as well as possible. After drilling, it is very important to clean the hole thoroughly so that the rubber on it is not damaged during mounting and that it fits as well as possible.

The valve is inserted from the inside and will pull itself until you hear it sit down. and that's it, it's easy to install and easy to change if ever needed.

The tank fills without problems no air is released i just need a little stronger power supply, my lab power supply can't handle the amperage when the pressure builds up to 3 bar.

Next I'll try to fix a few things so that I have something to connect to it. I start with the Air blow gun.

My previous repair with tape didn't work :) so I decided to punch out the broken part and solder the two broken parts together. Since I didn't manage to break it out, I didn't want to damage anything, I tried to drill through the broken part, and then I realized that the top was screwed in before, so I decided to screw in instead of soldering.

I cleaned the thread on the main part and tapped the thread on the tubular part.

And just like that, that part was fixed. I added some Teflon tape and I changed the rubber seal just in case, I've had this air blow gun sitting for a long time,

and for the that reason I did clean it inside because it started to oxidize. I cleaned top and bottom end and lubricated it with oil for pneumatic tools.

The only thing I'm still missing is a hose and i have one that I saved because I hoped it can be repaired. It is broken at the end, and since I can see that the end is metal, I decided to take it apart, cut off the damaged hose and put it back together.

In the end I realized that I should have tried to fix some things sooner because in a short time fixing I managed to have a little compressor set.

But I'm still missing a shorter hose and I have some hardware I can use from one that was eaten by a dog.

I heated one end of the hose that i had and expanded it, the other end fits without problem and evrything is fixed with hose clamps. And now I have also a shorter hose that is easier to use and it will come in handy when I need it to be compact or easier to transport.

I recently bought a 3D printer, but I'm not good at designing and printing on it, so I took the opportunity to learn and

make legs that will hold everything together and also enable easy separation of the tank from the compressor.

The design was simple, I started with the shape of the Greek letter omega and then extruded it to a thickness of 2 cm.

It is important to measure the container correctly because it will not work if the holder is too narrow or too wide.

I'm very pleased with how it turned out.

The idea is that the container can be taken anywhere to be used and then refilled, so that I have more options, such as being able to hold everything horizontally or vertically, connecting it to different compressor etc.

What I learned with testing is that it does matter what power source I use.

For example, the laboratory power supply was ok until it was necessary to make a bigger pressure than 2-3 bars, because its maximum is 5 Amps. The compressor would slowly slow down until he came to a complete stop.

The car battery was ideal and charged without any problems, and the consumption was around 6-7Amps (at 6-8bar pressure), but since it is quite bulky, I decided to try the PC power supply.

I had problems with it, but only because I used a thinner wire, when the amperage increases, the compressor slows down a lot and the wire gets very hot, by increasing the thickness of the wire there were no more problems.

It is also important that the compressor itself does not run for too long because there is a possibility that it will overheat, it is written on the housing that it should not run for more than 6 minutes

In the end It is important to remember that this is a small compressor and it is not realistic to expect any big results from it. For what it was designed and what all the combinations are possible ... it is perfect.