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Compressor Pressure Fluctuations

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  • Member since
    September, 2017
Compressor Pressure Fluctuations
Posted by BlueSprue on Wednesday, September 13, 2017 9:29 PM

Hey all,

Just got back in to modeling as my youngest guy has a keen interest in military machines

I tried out our brand new Iwata Neo brush with it hooked up to my 6 gal Porter-Cable compressor. It has a factory regulator on the compressor which I tried to get down to around 30 psi, but instead with the trigger held, the pressure bumps up and down from 50 psi to zero and back and forth.  No amount of tweaking will change that. With the brush removed from the end of the hose, I can regulate the steady stream of air no problem but when the air tarvels through the brush it bumps up and down in a slow repetitive rise and fall.

Will I need some sort of inline regulator that is more finely adjustable, or is something else wrong?

Thanks!

  • Member since
    August, 2014
  • From: Willamette Valley, Oregon
Posted by goldhammer on Thursday, September 14, 2017 12:01 PM

Try an additional regulator.  You can pick one up from Harbor Freight that has a gauge on it for around $5-6. The gauge runs from 0-200 psi.  I have one that I run with shop air at work, no issues with it.  The regulators on the compressors are meant more for air tools rather than an AB.

  • Member since
    September, 2017
Posted by BlueSprue on Thursday, September 14, 2017 10:20 PM
Thanks goldhammer, I'll try an extra regulator as I figured the ones on the compressors weren't intended to handle such relatively low psi. Is there also possibly a setting on the airbrush that is causing the pressure variations? It's a NEO by Iwata and I'm not entirely certain, but are there adjustable air controls on most dual action airbrushes?
  • Member since
    August, 2014
  • From: Willamette Valley, Oregon
Posted by goldhammer on Friday, September 15, 2017 9:16 AM

I use a NEO as well.  I usually spray at around 15 psi with either MM or Tamiya, thinned at around 50 %.  The DA brush will blow air on the down push and variable material flow getting heavier as you pull back on the trigger.

Play with it to see what suits you as to thinning ratios and psi, you'll find something that you're comfortable with and works for you.  Leave the compressor gauge cranked up and dial it in with the add on one.

  • Member since
    September, 2013
Posted by blackdog62 on Friday, September 15, 2017 9:23 AM

You can purches a inline air valve that fits between the gun and air hose. I'm not sure if will help is the psi is fluctuating.

If your compressuere has a tank try spraying from that with the motor off.

It's also possible that you can have a bad air hose with week tubeing wall that are swelling up and contracting back down with the air pressure.

I sometimes use my 90 gal. Compressuere with the big regulator with no problems. I don't have a neo in my kit but most airbrush don't have a built in air or paint valve hope this info helps you. Good luck.

Jerry.

  • Member since
    July, 2013
Posted by modelmaker66 on Friday, September 15, 2017 1:58 PM

compressor

  • Member since
    September, 2017
Posted by BlueSprue on Friday, September 15, 2017 9:22 PM
Thanks for the suggestions guys. I will try an inline regulator as some of them allow full pressure air from the tank to the inline regulator which steps it down. My setup right now is as simple as possible. A ten foot hose with a 1/4" adapter at the compressor end. The pressure bumps only happen with the airbrush attached and with the trigger pressed. As soon as I let off the trigger, the pressure accumulates and seems to release all at once rather than steadily when the trigger is pressed again. Kind of annoying considering it is coming from a filled tank which is exactly what should prevent this.
  • Member since
    September, 2017
Posted by BlueSprue on Saturday, September 16, 2017 2:11 PM
Update: Still having the same issue. I installed another regulator but the problem seems to be the pressure as it leaves the tank regulator. When the airbrush is off the pressure builds. Then when the trigger is pressed the pressure all comes out at once, regulator drops to zero and goes back and forth slowly from zero to whatever i happen to have set.
  • Member since
    March, 2007
  • From: Northeast WA State
Posted by armornut on Saturday, September 16, 2017 5:31 PM

Air pressure dumps when A/B trigger is pushed.

Air pressure returns when trigger is released.

Able to adjust pressure when hose is open ( no A/B) that is odd because free flowing air will not build pressure until blocked.

Second inline regulator no help.

I would hazard to say you have something hooked up wrong. Inlet to the outlet and or vica versa.

we're modelers it's what we do

  • Member since
    September, 2017
Posted by BlueSprue on Monday, September 25, 2017 5:07 PM

Thanks for the pointers everyone. Turns out it was the cheap regulator on my brand new Porter Cable compressor. When it's dialed down to anything less than max the pressure just fluctuates wildly under any constant demand. 

Went to Canadian Tire and bought a $35 regulator and male/female fitting to hook it up to the quick coupler on the compressor. I now just dial the factory regulator to max and tune the pressure down with the new regulator. Works like a charm and I get several minutes worth of brushing at 30 psi on a single fill!

Thanks again guys!

  • Member since
    March, 2007
  • From: Northeast WA State
Posted by armornut on Monday, September 25, 2017 6:32 PM

Awesome, glad ya have the problem solved. Thanks for reporting your solution as I was concerned ya may have gave up. HAPPY MODELLING!, and airbrushing.

we're modelers it's what we do

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