Soft Airvalve spring and air pressure

busanga

Double Actioner
if you put a soft spring in doesnt the air forcing the valve up negate the soft spring once you reache a certain air pressure. The air pressure will be forcing the valve closed not the spring and the spring is there onlt to keep valve closed before air pressure takes over.

so i ssume the soft springs only really work on brushes using a low air pressure..

on my Eclipse CS for eg, i doubt would make any difference as can spray up to 30 /35 psi and i can actually feel the difference that makes to pressing the trigger down compared to when the air is off..

caveat...i havent tried a soft spring so not sure of effect it would have on hgher pressures
 
Even at higher air pressures ? i would have thought the hgh air pressure would keep the valve closed and require more force o open it.?

i would like to try one, where can i get one ?
 
No.
There are 2 different springs. The needle chuck tension spring will dictate how much force you need to do to pull the needle back with the trigger. That's a common spring that is modified, usually to be softer. Usually called "soft springs". That has nothing to do with air pressure.
The other spring is the air valve spring. Changing it will dictate how much pressure you put down in the trigger for air to flow.
Air pressure will not close the valve. You are just diverting air around it. The pressure will not fight the spring. At least not at the pressures we are working.

Thanks,
Ismael
 
No.
There are 2 different springs. The needle chuck tension spring will dictate how much force you need to do to pull the needle back with the trigger. That's a common spring that is modified, usually to be softer. Usually called "soft springs". That has nothing to do with air pressure.
The other spring is the air valve spring. Changing it will dictate how much pressure you put down in the trigger for air to flow.
Air pressure will not close the valve. You are just diverting air around it. The pressure will not fight the spring. At least not at the pressures we are working.

Thanks,
Ismael
but when i increase the air pressure on my compressor i can feel it get harder to press down on the trigger (i am talkig about the airvalve, not pull back for paint) this is because the air is pressing the valve stem with the tiny O ring harder against the opening thus requiring more force to push it down... that is waht i am assuming anyway , based on the feel. and when i disconnect the air then the trigger is easy to push down so the air is affecting the force required to push down... as i only have to overcome the force of the spring and not the air
 
I would guess it would become an issue at very high pressures but I've seen T-shirt guys using 50-60 psi with no issues. That means the spring is still the dominant force.
 
One more thing, I accidentally assembled an air valve without the spring a while ago, and I couldn't get it to stop the flow of air. So the air pressure did not close it.
 
i think what is the issue is the initial force to press it down, when i am running 30 psi is almost like a switch to click it down because the valve is sealed and needs to be cracked open against the air, but when i switch air off, it pushes down easily, obviously when the valve has opened then the spring takes over as the air by passes the valve now
 
One more thing, I accidentally assembled an air valve without the spring a while ago, and I couldn't get it to stop the flow of air. So the air pressure did not close it.
like i mentioned in OP the spring is there to keep airvalve closed initially otherwise air will just flow past it, but as it is sealed by spring, the air increases the force on the seal the higher the psi... is basically just like a prssure cooker valve

And since the airvalve is basically (especially for beginners) an on off switch the spring will make no difference to use, as i press it all the way down anyway, those who are more experienced would be able to regulate air volume by pressing against the spring just sligtly...so like a MAC valve...then a soft spring would be ideal
 
ah i have just realized my mistake... once i have overcome the initial air pressure (clicked trigger down) then air passs by and spring takes over,,,thus if it is a soft spring i can easily hold it down compared t a stiff spring....got it now ! phew !! :)

As i dont paint for hours it most probably wont affect memuch at ths point to hold down the standard spring, though i do find that sometimes i inadvertently let the trigger up as i am manipulating the trigger back and forth, maybe this is where the soft spring would help me.

would like to try one
 
found this...gives some figures... how accurate, who knows ??

Designed from Prof. Zsolt Kovacs and the University of Brescia (italy), this Air Valve Spring is the most effective add-on for every Iwata airbrushes.

Made of austenitic stainless steel, Zsolt’s spring needs about 75grams to open the air flux (@0 air pressure), the original CM-B spring needs 160grams, while the HP-B needs 320grams. The air is perfectly closed up to 4bars . The finger fatigue won’t be a problem anymore. Giving more softness to the trigger will result in more feeling with the airbrush and less ergonomics problems.


As you can see he is talking about at 0 air pressure, because the air pressure would have an affect on the initial opening,,,after that it is down to the spring...so easier to keep down a soft spring
 
Pressures are not really high enough, nor is there enough surface area of the valve head exposed to the pressure to make a whole lot of difference in opening force. There is only @ .0122" sq.in. of valve head exposed to pressure (maybe +/-0.04psi? @ 35psi set pressure). If we were talking a few 1000psi, there would be something to talk about.

The needle chuck tension spring will dictate how much force you need to do to pull the needle back with the trigger. That's a common spring that is modified, usually to be softer. Usually called "soft springs".

This may be correct among the modeling community, but in the art/illustration community the "soft spring" is in reference to the trigger/air valve spring, and is a very common mod.

I wind my own springs so I can set the rate myself. There are gobs of places to find springs from...
 
I may have gotten the math wrong, (been a while). I think the force on the valve head would be @ 0.5psi at a 35psi working pressure.
 
i can feel the difference easily, when the air is on at 30 psi it takes a click to push valve down, (not to keep it down but to initially open it) but when i unplug air there is hardly any force required to push down and open the valve.... this is hinted at here....

QUOTE:

Zsolt’s spring needs about 75grams to open the air flux (@0 air pressure), the original CM-B spring needs 160grams, while the HP-B needs 320grams.

END QUOTE

this infers that at Anything more than 0 air pressure it would require more grams...and i can actually feel that on my brush... it takes more to initially open the valve due to the air pressure..

strangely when i look for soft springs i keep coming up with just Blair spring, which is crazy at 30USD... i will make my own too . i have played with fork spring rates and spacers in my motorbike forks, is not rocket science :)
 
Thanks Dave! That was my impression from the very few times it was mentioned in the modeling forums, but I could be wrong altogether.
 
yes, 0.5psi is more than 0psi. You are right, it isn't rocket science - it is straight physics. Lets use 35psi... which is 35 pounds per square inch. Half a square inch would be exposed to half the pressure, so @ 17.5psi, right? A valve stem has a total surface area of @ 0.0145 square inches.

I have a digital force gauge, so just tested a Micron Takumi. At 0psi i got a stock reading of 0.45lbs to break the seal. At @35psi I got a reading of 0.95lbs to break seal. So, I think I got the math right in the corrected post - at @35psi set pressure the air will add @0.5lbs to the force required to press the trigger.
 
Sounds about right about half a pound ,plus possibly some 'sticking / inertia ' of the O ring as it is pressed harder into the brass before it breaks loose. I can def feel the difference as I crank up the air.. is not a huge difference in 'feel', but feel it I can.

i was referring to the making of the springs is not rocket science , should be easy enough to modify some springs I can find around. Maybe some click pen springs ? Will have a fiddle around
 
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