Garden Sprayer Bottle for Air Pressure

[mojorising]

The title says it all....

 

All the air brush threads talk about buying a compressor.

 

Just wondering why modelling spray guns apparently do not use simple manually pumped pressure bottles to provide spray pressure since only a tiny volume of air is required to sustain the spray.

 

I have a 5 litre sprayer for the garden with a hand pump on top. You pump air into the bottle manually and it provides sustained pressure for some time and that is spraying large volumes of glyphosate in the garden.

 

If it was hooked up to a model spray gun surely it would provide enough air pressure to last for hours I would guess given the relatively tiny volumes of paint being sprayed compared with weedkiller in the garden.

 

[Parabat]

I think it would be difficult to regulate the pressure, but it could be done. With a small compressor you have consistent pressure that you can alter if needed.

[Corsairfoxfouruncle]

Many years ago i had a friend that used a 10 gallon air tank meant for filling tires. He converted it to airbrush by adding the water trap/regulator and correct hose. He would go to the service station fill it up and air brush when he needed to paint quietly. He had a standard compressor for when he wasnt being quiet. The only downfall to the airtank idea as there is no warning when the air started to run out. And you'd be spraying then sputtering paint. So it is possible just has some drawbacks. 

[Robbyrockett]

Well you could use it, you could even use a regulator. But you'll get about 30 seconds out of each pump up.

 

 

 When you pump up the sprayer and use it to discharge a liquid the compressed air is only expanding by the volume of liquid lost so your total expansion is at best 1 liters to 5 liters , a loss of 4 liters of volume.

1 liter at 50psi can expand to 2 liters and be 25psi, 2 liters at 25 can expand almost to 4 liters before hitting atmospheric. So pumping to the max pressure (45 for most of these)

Can just about empty all the fluid no matter what the fluids flow rate is.

 

Now pump the sprayer up empty and pull the trigger, it will lose pressure in seconds because you are simply venting the air to atmosphere.

You will be doing the same thing with the airbrush but an average airbrush discharges 15 lpm.

 

So assuming that you can pump the sprayer to 45 psi and your airbrush needs 20 to operate correctly and you have a normal 14.7psi atmospheric your useable pressure differential is 25psi

(25psi)(5l)=(14.7)(x)

 

Solve for x

You have 8.5 liters total useable air. Spray time would total about .56 minutes in a perfect world.

But youd lose some air to the regulator dumping high side excess pressure when the brush was not spraying.

 

 

The 10 gallon tank... 38 liters at 120 psi

20 solid minutes of spray time.

 

 

 

 

 

 

[John R]

When I started using an airbrush one air supply that I tried was a car tyre for which you could (maybe you still can) get a clip-on adapter. It was not a success. I found that the only way to go was to get a compressor.

[Rob G]

Waaaay back when, I too used a car tyre to power an airbrush. I made up a T-piece so that I could plug a cheap 12V compressor onto the tyre and have it running while I used a Badger tyre adapator to run the airbrush - it worked well enough until funds were sufficient for me to acquire something a bit less dodgy.

 

Note that to use a spare tyre for airbrushing, you MUST have a tube in the tyre, or it won't work. Which is a bit of a PITA, as tubed tyres are almost a thing of the past.

 

Note also that I recommend not buying that new Tamifujigawa kit and instead buying a compressor- even if it's only a mains powered cheap, noisy Chinese-made auto supply store (Supercheap, Harbor Freight, whatever chain you've got in your bit of the world) type, it'll be a lot less frustrating than any other air source. The one I bought nigh on 20 years ago is still choochin', I used it yesterday to blow out a motorcycle carb I was rebuilding- value for money if you ask me.

[blanco77]

Lol. Thats a great idea! I can only too well imagine the reaction from my significant other discovering a car tyre and series of tubing in the bathroom!

[Artie]

I use a compressor made from a fridge engine. No noise at all, just hear the air flowing from the airbrush.....add a pressure regulator and a damp filter, and there you are, an absolutely silent machine...quite similar to this one:

[blanco77]

Hi Artie,

 

Somewhere in the labyrinth of my Dads ME workshop is a compressor. I know this question has been asked before but as of today, what is the airbrush gun to buy on a budget, but not badger budget? Those brushes with the large silver bowl type to hold your paint would be great. I work 1.72 scale, hand painted many many models but apart from rattle cans to prime and tamiya tape, i need a decent piece of kit. Dads compressor sounds like a sonic boom from memory, and very likely to have mum screaming at me

 

Appreciate if you can point me in the right direction, both brush and compressor to do stuff like under shading and acheiving flawless top coats.

 

Thanks,

 

S

[blanco77]

On 31/05/2018 at 18:58, mojorising said:

The title says it all....

 

All the air brush threads talk about buying a compressor.

 

Just wondering why modelling spray guns apparently do not use simple manually pumped pressure bottles to provide spray pressure since only a tiny volume of air is required to sustain the spray.

 

I have a 5 litre sprayer for the garden with a hand pump on top. You pump air into the bottle manually and it provides sustained pressure for some time and that is spraying large volumes of glyphosate in the garden.

 

If it was hooked up to a model spray gun surely it would provide enough air pressure to last for hours I would guess given the relatively tiny volumes of paint being sprayed compared with weedkiller in the garden.

 

After painting War hammer 40k miniatures from Games Workshop, I still love you!! at hideous prices for 30 years im sceptical, I would say manufacturers dont want this.

 

How would you regulate air flow, some sort of valve, scratch build? New project? I am on the hunt for a decent kit brush and silent compressor. Being a newbie to the spray world. Your idea would be earth friendly too. I really hope you could make something like this. S

[Robbyrockett]

On 8/6/2018 at 3:19 AM, Artie said:

I use a compressor made from a fridge engine. No noise at all, just hear the air flowing from the airbrush.....add a pressure regulator and a damp filter, and there you are, an absolutely silent machine...quite similar to this one:

Only issue with the fridge compressor conversions is this;

The fridges let lubricating oil circulate through the lines. These type silent compressors have a provision for circulating the oil within the pump and also an internal heat exchanger for the oil.

Funny thing is most fridge compressors have the same provision internally but it has been blocked off or doesnt have the heat exchanger installed to make it work, so on a conversion it will slowly pump all of its oil into the air supply and overheat more often even when they have oil and so they dont tend to last too long.

 

Edited August 31, 2018 by Robbyrockett

[Robbyrockett]

An italian company in the late 40's called cesco made a foot powered pump with roughly the same stroke and capacity as a garden sprayer. Same deal 3 minutes to pump it...30 seconds of spraytime all while dealing with rapidly dropping pressure. They werent very popular 

Edited August 31, 2018 by Robbyrockett

[Steve Noble]

A decent compressor will provide clean, dry air all day long. Many are as quiet as a mouse. There really isn't a magic, cheap way to get a decent air source for airbrushing. I feel a compressor is the only real way to achieve this...

[stringbag]

A friend of mine uses CO2 bottles. Lasts him about 2 years and refills cost less than £20 a pop.  It's quiet (obviously). No moisture trap required either, and the initial cost was less than he would have spent on a compressor.

 

Chris.

[Mike]

1 hour ago, Steve Noble said:

Many are as quiet as a mouse.

My silent compressor (Silair 30D) must have been based on a slightly asthmatic mouse cos you can just about hear it.  When you turn on the spray booth fan though, it pales into insignificance.  A silent spray booth would be a real find!