Homemade silent air compressor

[Dimitris Polychronis]

Hello to all,

I must admit that I have a passion for silent air compressors, simply because you can use them anytime you want without disturbing your neighbors! I built my first compressor 11 years ago using a truck’s brake air tank. Until today I've made 5 silent compressors and I have a 6th one under construction (unknown when it will be finished).

The following video shows the construction of the 5th compressor I’ve made that is actually my first serious built when I started my YouTube channel 6 years ago.

I don’t want to tire you with pictures here (except the necessary ones) because the whole video is actually a slide show with all the info about the built; at the end of the video you will see some photos from the other 4 compressors, but since the time of the video is short I will put these pictures below so you take closer look. I would like to show you more from my previous builds but unfortunately I have only these pictures.

These are the previous 4 compressors I've made.


I have also put one more video showing the basic maintenance of the compressor as well as the replacement of a defective part (non-return valve). I hope that this video will show you a better view of the compressor.

All the best
Dimitris

[Flintlock42003]

Would it be possible to buy one of your silent compressors?

[Sleykin]

How long do the refrigeration compressors last pumping air? What kind of lube do you use in the compressor, and how do you check levels etc.?
They would be perfect for airbrushing or using a pencil die grinder. My shop is plumed for air with the tank and compressor outside in it's own little outhouse. I also have a little pancake compressor for jobs away from the shop. Trouble is, when those guys run everybody hears it...this would be a great addition

[cmarlow]

I am trying to put the pressure and volume in perspective for me. Is .33 cfm at 80 psi about right?

[hemmjo]

I am retired teacher, we used to explore with pneumatics and building automation type devices in class. I built a compressor in the late 80's to run those pneumatic devices and air brushes etc. in my classroom. That compressor is still working. These days it will run my finish nailer as fast as I can cut and fit trim pieces.

I got my compressor from a dehumidifer I picked up along the road on trash day. I get them all the time. I have NEVER found one with a bad compressor. They stop working because the evaporator coils get FILLED with dust from the houses, and they no longer function so people throw them away.

A couple of things I did to ensure longevity is to draw the incoming air through an oil bath air filter. Just a peanut butter jar with oil and a piece of foam filter from a lawn mower type engine. I put an oil separator on the outlet side, between the compressor and the tank. If no oil comes out when you first start the compressor, add little oil until it spits some out. After that keep the separator drained. Read on the appliance where you get your compressor what kind of refrigerant is uses. Then get oil compatible with that.

I used empty "fat boy" propane bottles for the air tank. You can safely remove the center valve core with a home made tool, like you would use for regular valve stem on a tire. It just needs to be longer to reach down into the hole. You have to use a small pick tool to remove the o'ring and small metal collar to access the core. Then fill the bottle with oil to be be sure all of the propane is out. Then drill and tap the hole for 1/8" NPT. Then you can plumb the bottles together with common pipe fittings. My system has 3, just because that is what had around at the time. Each bottle also has its own little pressure relief valve.

The inlet and outlet tubes on most compressors are 1/4" copper tubing, some are steel. I connected to them using a flaring tool. But could just as easily use compression fittings.

Keep in mind that these little compressors are capable of pumping in excess of 500 PSI, be sure you put a safety pressure release valve in your system.

[Dimitris Polychronis]

Thank you very much for your kind offer Flintlock, unfortunately I can't help you for two reasons; first I don't have any of these compressors (they have been sold), except the one you saw on the video that is in used in my shop and second even if I had one available the shipping cost would be extremely high because I live in Greece!

Cheers
Dimitris

[PJs]

Excellent maintenance video, Dimitris and perfect timing for you to display your precision handy work and meticulous attention to detail! Hopefully you can finish your dual compressor one day soon as that would be of interest here also.

Thanks for sharing this timely build with us.

PJ

[Dimitris Polychronis]

Hi Sleykin
As you well said it this type of air compressor is perfect for using an airbrush, a pencil grinder or for a small pneumatic engraver for stone setting or any other art work, this will answers your first question; with proper maintenance they can last for many years because they are made to support tools with low air consumption. Now, the main disadvantage of a fridge compressor is that its motor runs at high rpm transferring motion to a small cylinder inside the housing that increases temperature, meaning that the motor must not work continuously; thankfully all fridge compressors have a thermal switch for protection but it is wise not to reach this limit. The working time of compressor like this is depending on the power of its motor; the motor must stop down equal time with the time of its continuous run.

The rule of thumb is:
A 135 Watt motor must not exceed 15 min. continuous run, after this time must cool down for 15 min. A 280-340W 20 min run - 20 min stop, a 735W 30 min run - 30 min stop

As for lubrication, I use the recommended coolant oil from the manufacturer.


Now checking the oil level is a bit problematic, because fridge compressors haven’t the glass checking window; so the only option is to use a syringe with a hose for sucking the oil from inside the housing and check the quantity and the color of the oil in a measure pot; luckily all reputable manufacturers state the proper oil quantity on the motor’s label.
Fresh oil has transparent pale yellow color, when the color become dark yellow (but still transparent) it's recommended to changed it.

Remember that always small quantities of oil will transferred to the air tank through the cylinder, so it wise to check it every 15-20 hours of total work.

All the best
Dimitris

[Dimitris Polychronis]

Hi cmarlow,
Forgive me, but my knowledge doesn't reach so far. The only that I know is that cfm describes the flow and psi describes pressure and I haven't seen any calculation chart for these two. I'm sorry but I can't help you.

Cheers
Dimitris

[Flintlock42003]

Understand!! Thanks..