One could presume from the graph that it would be possible to ‘align the stars’ such that you could have unregulated AND a reasonably flat shot string. I know some have had this be the case (my AEA bv is surprisingly flat unregged), my case was kinda by accident and kinda by the fact I can easily change the bv volume externally. Obviously other factors (hammer weight, projectile weight, target velocity, etc) all play into these ‘stats’. Dave
I have a lift limiter in my valve set at the same .09" limitation,
QuoteI have a lift limiter in my valve set at the same .09" limitation,The relationship between lift and dwell does not apply if you have a lift stop, that should be obvious.... The poppet has to be able to coast for it to occur, not have a hard stop....Bob
You made a blanket statement, and I provided the counter-argument.... Hammer energy produces lift, while hammer momentum produces dwell, in a conventional knock-open valve.... Period.... The hammer energy is produced by the spring (average force times travel) and while the hammer velocity changes with weight, the energy does not.... If you change the hammer weight, for the same energy the momentum IS changed, however (heavier hammer more momentum, and vice versa).... Therefore, the relationship between energy and momentum changes as you change the hammer weight.... Note, this only applies if the poppet travel is not artificially limited in some way, and all of the RESIDUAL hammer energy and momentum is not wasted by hitting the back of the valve (or the poppet hitting a stop).... The residual energy, of course, is the energy remaining after the valve cracks from the seat, which removes part of the energy (and momentum) by slowing the hammer.... These relationships are also affected by the closing force on the popper, which is spring force, plus poppet drag (pressure differential across it), and in a balanced valve, any net force provided by the balance chamber.... Again, the relationship between hammer weight and momentum (and hence dwell) for a given hammer energy, is simply dictated by physics.... I presume you are not suggesting those laws are wrong?.... As an aside, don't forget that flow through the valve reaches a limit when the lift equals 1/4 of the diameter, caused by the curtain effect.... Therefore, adding lift after that doees not increase flow.... This occurs at 1/16" lift on a 1/4" throat.... There is no question that the balance chamber in a semi-balanced valve can be made to do virtually anything you want it to.... from blowing the poppet open and dumping the reservoir, to only reducing the cracking force on the poppet, and anything in between.... Before you get all riled up, it would perhaps help to take a deep breath and look at what YOU said, and my response.... Believe it or not, sometimes we can both be right, and a pi$$ing contest is not necessary.... Your experiments are valued, and help all of us understand the complicated dynamics of semi-balance valves.... Let's not lose sight of that, please....Bob
Thank you for destroying a very valuable thread with your rant.... .... I see that your "Watched" label is still required, something I will be requesting....I, Scott, Travis, Lloyd, and many others have built way more custom PCPs, valves and hammers than you could ever hope to achieve, and the relationship between hammer mass and momentum is well documented.... With a conventional valve, if you lighten the hammer (less dwell), you must increase the energy (more spring force and/or travel) to compensate and keep the FPE (area under the lift/dwell curve) unchanged.... The opposite also applies, a heavy hammer can deliver the same FPE with less energy (lift).... The Physics comes into the basic understandings of lift being proportional to energy, while dwell is proportional to momentum (once the energy to crack the valve is subtracted).... As I tried to explain, the flow through the valve, if opened more than 1/4 of its diameter, no longer increases with lift, so for a valve that is ACTUALLY opening that far (easy to measure, but also quite rare in an efficient PCP), all you are left with to change the FPE is a change in dwell with hammer momentum, be that achieved by mass or spring energy.... Just because you happen to disagree is no reason for the rest of us to throw out that valuable piece of information.... or a reason to rant....While there may be certain valve configurations (balanced, semi-balanced, operating with a hammer or poppet stop, etc.) where the lift does not change (because it cannot), the lack of relationship between lift and dwell as you change hammer mass is caused by those other factors, and your statement, if applied only to those situation, may well be correct.... There is your middle ground.... Accept the fact that you are not always right, or leave the Workshop, please....Bob
Thank you for destroying a very valuable thread with your rant.... .... I see that your "Watched" label is still required, something I will be requesting....I, Scott, Travis, Lloyd, and many others have built way more custom PCPs, valves and hammers than you could ever hope to achieve, There is your middle ground.... Accept the fact that you are not always right, or leave the Workshop, please....Bob
Quote from: rsterne on April 17, 2023, 02:34:30 PMThank you for destroying a very valuable thread with your rant.... .... I see that your "Watched" label is still required, something I will be requesting....I, Scott, Travis, Lloyd, and many others have built way more custom PCPs, valves and hammers than you could ever hope to achieve, There is your middle ground.... Accept the fact that you are not always right, or leave the Workshop, please....BobFancy charts, talking louder, slighting others work etc .... THIS THREAD should be LOCKED. If Matt feels he has something to teach us all, Let him create his own thread and then see who contributes or pays attention.