So normally I don't post in these sorts of threads, positive or negative, however I've now gotten several messages asking more or less the same handful of questions so I figured I'd poke my head in and clear the air.
First I feel I should explain why I'm doing this. I do this moderator research because I find it fun, interesting, and very VERY challenging. I've been doing it for years. For a while my day job was designing suppressors on firearms. Constraints though in that industry meant I could never truly scratch my itch for certain exotic architectures. When my wife bought me an FX Crown which was louder than my tastes, and I noticed airgun moderators were widely legal in the US, I picked this back up. I publish the research because I've met some genuinely amazing human beings doing similar in the past, people way smarter and more interesting than I, who've become great friends. I started offering them for sale because said people started banging on my door wanting to get their hands on my research. At first I gave them away for free, but they're too expensive and time consuming to make to just give away, so the obvious solution was to charge money but also try and hide the designs away so the general public wouldn't get their hands on them. And that leads me to my first important point: in case it wasn't crystal clear let me just say it again these are all EXPERIMENTAL. These are meant for enthusiasts who want to play with cutting edge experimental moderator technology. If that doesn't describe you, please purchase one of the many alternatives on the market. qball I'm very specifically looking at you saying this, these are very clearly not what you're looking for.
Second I want to hit the point of durability. I don't have some secret test rig in the back room made to break moderators, my research is basically all published out there for people to read. If you want to hit one of my designs harder than I have, by all means since all this is an experiment, but know you're in uncharted territory. I do engineer safety factors into the designs, That safety factor is >3, that is to say every design is rated to handle greater than three times the output pressure of the test rig (in this case my 80FPE FX Crown). Just to give some context, safety factors vary widely depending on industry. Orbital launch vehicles for example (rocket ships) tend to have a safety factor between 1.1 and 1.3. Structural members in buildings are usually 2. Usually the most extreme safety factors you'll see on equipment is 10. Most high pressure air vessels, such as the bottles in the airgun industry, have a safety factor of around 3-4 depending on how you rate/test them.
So why did Trinitymaker's core fail? While I haven't examined it yet, I suspect it is a simple case of exceeding the pressure the design was built for. FPE is NOT the determining factor for what sort of abuse you're going to subject a moderator to, it is just a very rough way of guestimating it without doing any real math. Pressure and volume are related, and so if you substantially reduce that expansion volume, you're going to correspondingly increase the operating pressure. Based on a little napkin math and the ideal gas law, the shroud on my Crown alone is likely reducing the operating pressure of any moderator attached to it by a factor of over 6. Add a little more, again very rough, napkin math for that heavily modified Condor and you're probably somewhere north of 10x what that poor little Gladius was designed for. Not only am I not surprised it failed, I'm quite pleased to hear it survived ~20 shots. The point is the air pressure and volume at the muzzle are the real factors, but that is a much more complex thing and it something not well understood. Pressure transducer experiments in moderators is something I'd like to get into, but that poses a whole suite of challenges and I'm just not there yet.
Why don't I publish outputs in decibels? This is something I've covered before with ackuric who seems to have either not seen it or ignored it. I responded more comprehensively and technically to your claims that a cell phone with an app is a good way to measure sound output from airguns in a different thread, which anyone interested in the more technical elements can/should revisit. Let me cover it again briefly since you brought it up.
I have never seen a single test of airgun moderators with a sound meter capable of reading the peak output, that is to say the "uncorking" peak produced when the pellet clears the moderator muzzle. The cell phone app sound meters ackuric has repeatedly recommended simply can not do it. Even the respectable Extech 407730 used by AEAC, which is much better than most of the other airgun tests I've seen, isn't capable of it. The peak uncorking event is over in less than one ten thousandth of a second. If you go to page 3 of the manual for the Extech, you can clearly see that this meter's fast response time is .125 seconds or approximately four orders of magnitude too slow. If you have an example of someone who has used an impact sound meter, which is a VERY different device from a typical sound meter, to measure airgun moderators I would love very much to read their research. They probably have much more valuable things to say than I do. So please, don't hold out on us, if you have a link to such research or have done it yourself PLEASE share it.
That said, if you want an apples to apples comparison, decibels to decibels, you need three things:
1) An impact sound meter capable of reading the actual peak (not capturing some random unknown post-peak sample)
2) That sound meter needs to be calibrated. The firearms industry standard is a Brüel & Kjær which needs to be calibrated every 6 months if memory serves.
3) Said research/data needs to be published so we all can see it and compare.
I don't have all three. I've got a meter capable of reading the peak, but it does not have a recent enough certificate of calibration, meaning it is effectively "uncalibrated" therefore the db conversions are not valid. So while I have a conversion to decibels, I don't publish it because I don't want to create a pool of garbage data. It also wouldn't mean anything to most people because there is nothing out there to compare it to.
I hope that makes it clear why I don't publish decibel conversions, instead providing raw outputs. Believe me, I would love to get burst disc calibrations on a regular basis not only to make my data potentially more useful to someone else in the future who has an impact meter as well, but also to fight any potential for drift of the meter itself over time. But I don't, so here we are. I do the best I can with what I've got, and you kinda have to make up your own mind to take it or leave it I guess. After all, even if I published the converted data, I'd just be another crazy guy on the internet.
I share all this because I find the research fun, and I cherish some of the friendships I've made doing this. They tend to start with the same sort of email "hey, I loved your research, but I'd like to try out one of your designs. Is there any way I can get my hands on one?" They are why I do this, what makes it worthwhile. If its not your cup of tea, no biggie. I try to avoid getting sucked into these forum fracas specifically because they're no fun at all, but I wanted to try explaining a couple important technical issues people had brought up, and so I hope this helps.
And, with that, I'm going to take a bit of a break from the forum. Cheers everyone!
