Does air hose I.D matter? - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-05-2009, 06:44 AM
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For reference.

The 3/8" hole is twice the area of a 1/4" hole.

The hose will cause resistance. A long hose with 1/4" couplers will cause a significant pressure (flow rate) drop. This is a two fold problem as the 1/4" couplers can flow less air and there is friction loss from the long hose.

My experience with my HVLP guns all Devilbiss (mid range gun and a GFG) was a pressure loss when I was using the 1/4". The bumper demon does not need as much air. This gave me very inconsistent results as I would have the pressure and flow for testing and the start. Once the static pressure in the hose dropped the gun did not spray as well since the 1/4" fittings could not flow enough air to supply the gun properly.

Since switching over to all 3/8 couplers I have found all my other tools are more consistent.

Keep in mind I only have 3/8" hose, that is the most common hose and is likely what you already have.

I have also found that the gun regulators may not be able to supply enough flow rate to work on a big gun. Only the better regulators can give you the flow rate. The common ones you find work well on the small guns such as the Bumper Demon.

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  #17 (permalink)  
Old 08-05-2009, 09:48 AM
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What type of compressor do you use, what is the airflow stated on the compressor. With a small compressor it will not put out the volume needed to fill a larger diameter hose, that may be why you're getting a higher reading with the 1/4in hose.
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Old 08-05-2009, 10:48 AM
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I switched to 3/8" couplers and it made a huge difference.
A larger hose than 3/8" made no difference.
It's the couplers that are the bottle-neck.
Look inside a 1/4" female quick disconnect and you'll see the actual
passage for air is choked down more than half.
the hole is only about 1/8" dia.
That's the restriction, switching to a 3/8" disconnect doubles
that opening. Still not as big as a 3/8" hose but more than twice
the volume of air can pass by than a 1/4" disconnect.



I made this and adjust my air at the wall until I get the right amount
at the gun, then I remove it.
Most regulators restrict air flow,
This is truely what I get when set.
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Old 08-05-2009, 01:03 PM
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Quote:
Originally Posted by acquadigio79
When I switched to 1/4" air hose my guns work very good....

So are you saying that your system works better with the 1/4" hose? There is absolutely no way the 1/4" hose would work as good as a PROPERLY working 3/8" hose. Either you have changed some of the fittings along with the hose and eliminated the obstruction or that 3/8" hose was plugged up somewhere along it's length. Like Shine said 1/4" hose is for airbrushes you need that 3/8" hose along with the proper high flow fittings.
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