jackssmirkingrevenge wrote:The idea is that once the o-ring is uncompressed, the projectiles needs no effort to go through - though of course the compression itself will take its toll on the component.
More than that - it's not a binary thing, so at some point there's going to be a partially compressed O-ring that the projectile will have enough force to push through.
This is true of any valveless design.
True, but that doesn't mean it's not an argument to be taken into account. I suppose as a technical "can we do this" experiment, valveless is one thing, but in practical terms the question is if any performance benefit is worth the drawbacks of the design. If every projectile needs to be precision engineered, it does need to have a tangible pay-off.
With big enough porting it should be OK.
It's more than just raw area. It's about the smoothness of the flow (ultimately your flow area is limited to that of the barrel) and flow through several small ports is inevitably going to be more turbulent than through one large one.
Not sure I'll build it, but for a pneumatic cartridge type device it would maximize the internal volume while as well as offering burst disk levels of performance while being re-settable.
"Burst disk levels of performance" is a fairly hypothetical bar though. To many people that means "instant", but valve opening time is something of a red herring when it comes to performance, because the fixed variable in the projectile's acceleration is
distance, not time.
A one millisecond valve opening might seem slow when you consider a projectile being in the barrel for 10 ms, but when you consider that (treating it as constant acceleration for the case of simplifying the maths) means the projectile has only swept the first 1% of the barrel (as per
s = ut + 1/2*at^2) by the time the valve is open, valve speed is clearly a case of diminishing returns as far as muzzle energy (being the integral of net force against distance). It doesn't matter if the valve is infinitely fast, that only means an additional 1% performance (so small it'd be lost in shot-to-shot variance).
Flow becomes more important here - and like I mused, I'm not convinced you're going to get clean flow through those ports.