Can see we are all mostly gravitating towards the thimble being part of the poppet head and chambers end plug connected to the intake grate while utilizing an external spring.
Can you show a picture of the rest of the valve?Dave
I've been thinking, how much is too much or shall I say how little is too much - what's the maximum reduction in pressure related force keeping the valve closed we can go for? What if we do a full poppet diameter balance chamber and use just a stiff valve spring to keep the valve closed - would it work?
Quote from: rkr on December 26, 2021, 10:42:15 AMI've been thinking, how much is too much or shall I say how little is too much - what's the maximum reduction in pressure related force keeping the valve closed we can go for? What if we do a full poppet diameter balance chamber and use just a stiff valve spring to keep the valve closed - would it work?Maximum reduction? Well, all of it, you just need a soft enough seal.Using springs to close valves is far less efficient than using air, in my experience using very heavy springs make an air gun very inefficient...So that leaves me asking why would you entirely eliminate the greatest, fastest closing force available to your air rifle? Currently in a valve with both spring and valve closing force, air acts as a closing force upon the poppet before the spring is fully compressed, in fact for all we know our valve springs put up a fight, resisting the air flow closing forces due to it containing the residual energy from the hammer strike, if even for a brief moment.I personally don't see a reason to reduce a closing force beyond less than ~100 lbs, unless you design one that temporarily increases its closing force while opened via some unbalancing act.
Valve closing is normal and is the force acting against the area of the valve stem as it is with all poppet valves. The spring is the only thing that keeps the valve closed once it hits the seat and the balance chamber reaches atmospheric pressure in this scenario. What I'm wondering if that's a good or bad thing?
Quote from: rkr on December 26, 2021, 10:42:15 AMI've been thinking, how much is too much or shall I say how little is too much - what's the maximum reduction in pressure related force keeping the valve closed we can go for? What if we do a full poppet diameter balance chamber and use just a stiff valve spring to keep the valve closed - would it work?Just one question, Why? All things have a purpose, why would you need a critically balanced valve with only a spring to keep it shut? I would rather make a piloted valve than critical balanced one. You could open it just by pushin the pilot open. Or by solenoid or very light hammer. And time the valve with fill port size tuning. No point by trying to time it with spring pressure. Marko
Fully balance the valve, use minimum spring rating with a softer material to achieve your seal (this would take trial and error as it depends on material used, sealing surface diameter, and spring used)Then play with larger valve stem sizes, since that is, as you put, primary closing force (which it is in smaller calibers that move little air). If you're talking about a 10-30 fpe rifle with a balance valve, opposed to where they're really needed (150+ fpe rifles), the air movement through the valve is far less, and not as concerning.Essentially, no one has the answer except trial and error. If you have 120 lbs holding a poppet shut right now, and 25 lbs of closing force, your hammer strike is absorbed by both, but no one has a true answer as to what % of that strike is left fighting the 25 lbs of closing force in a very small caliber, probably marginal when compared to the 120 initial #'s holding the valve shut...introducing a larger valve stem diameter thru the valve body would re-introduce hammer strike sensitivity.Is it possible? Sure. Is it practical? Maybe? Does anyone currently have all the answers? No.My 100# recommendation at pressure holding a valve shut is mostly for practical purposes and safety precautions.You also have to consider, if you make a valve open too easily, the hammer strike needed to open it becomes, slow, lazy, weak, and with that more sensitive itself to variation, this is where you find yourself only lightening the hammer itself while keeping the same spring rating, and the end result? A ms or two shaved off hammer lock time which is already in the sub 10 msec range....Also consider, what is the lightest hammer + spring you would want in your rifle. IMO its vital to find the ideal combo here, where the hammer is not too light, nor heavy, and the spring not too stiff, nor too light... I have all the formulas to approximate that personally, which makes it easier to have my perspective. If one wanted to do a lot of work for near nothing, I suppose they could run a short throw, stiffly sprung, light to medium weight hammer to achieve an incredibly low lock time with a near fully balanced valve, seems like a lot of work to me to cut off a few MS of hammer lock time though...so, to me, that is about the only reason to go this route...
MATT,I'm at a loss that your adding OPINION here By your own admission YOU HAVE NEVER EVEN BUILT ONE. Yet alone experienced first hand the cause and effect of the ratios, sealing, sticksion etc etc etc.Now I have no issue with sharing, but to toss out ... Data Says / Read it on the web prior / My feeling are this ... WITHOUT stating you have never actually applied what you think you know.Well ... Lets get real