20 Silencer Test

[Cableaddict]

For a tuned mass damper to be added to an existing structure (barrel) one would need to add the extra mass and a separate spring on which the mass is suspended. If all you do is add a mass to the existing barrel, all you are doing is changing the frequency of the existing spring-mass system (the barrel stiffness and distributed mass). This frequency change can be effective in changing the spread on target. Tuned mass dampers take some analysis to be effective since you need to design in both the frequency and the location.

i believe this is correct. 

However, it's also probable that simply changing the overall frequency will help (or hurt) accuracy, at least to a small extent. The reason is the same as with room acoustics:  Certain frequencies are reinforced / amplified whlie other frequencies are nulled because of the length of the room dimensions (or in this case, the length of the barrel) in conjunction with the wavelength of each frequency.  So, adding a moderator changes both the resonant frequency of the barrel AND the effective length, at least somewhat.   It should be noted, however, that when two objects which have different resonant frequencies (such as a steel barrel and an aluminum moderator) are mechanically joined, they tend to minimize each other's resonance.  (This is an actual, known thing.) So, my guess is that MOST of the time, adding a moderator will help, more often than hurt

Still,  if one gets negative results, one solution might be to add a carbon fiber sleeve to the barrel,  compression-fit to the breech as the moderator is screwed on. (See the two recent,  in-depth threads about this.)

-------------------------

Another very important note:

As I have mentioned before,  my stock DonnyFL Shogun made a very noticeable pinging sound when I first put it on.  I was practically stunned.
I didn't do any accuracy tests, sadly,  but surely that was going to cause extra movement beside the extra noise. I simply wrapped the Shogun in duct tape, and the problem went away.

[WhatUPSbox?]

The point of my earlier post was not to discourage people from attempting to use mass to change the response of their barrel. It was just that the tuned mass damper terminology sends you into a different technique and Google results may be confusing.

I tried to do some accel based measurements at the tail end of the Titan thread https://www.gatewaytoairguns.org/GTA/index.php?topic=176445.msg156150612#msg156150612 The results can be challenging to interpret and most people are much better off just using on target improvement as their guide.

[subscriber]

I tried to do some accel based measurements at the tail end of the Titan thread https://www.gatewaytoairguns.org/GTA/index.php?topic=176445.msg156150612#msg156150612 The results can be challenging to interpret and most people are much better off just using on target improvement as their guide.

Thanks for posting the link, Stan.  Your timing with reminding me about that thread is perfect. 

Your data and chart annotations seem easy enough to understand.   Your work should help make sense of a POI shift with different pellet weights, shot from a springer.  So I pointed to your post in this new thread:  https://www.gatewaytoairguns.org/GTA/index.php?topic=196622.msg156290196#msg156290196

[WhatUPSbox?]

The problem with the testing in that Titan thread is that it is just a teaser of what is going on. It is a difficult problem to partition into simpler tests and results. I did get a second accel module so that may help. Need to think of some test configurations that would produce useful results.

[subscriber]

Stan,

Any test data that helps GTA members better understand what is going on when they fire their airgun is appreciated. 

Each one of us has an idea of the real value carried by a given data set.  For me, a long time constant sound measurement device is not worth as much as the subjective opinion of the person doing the "test" (or preferably an unbiased witness).  Some might even call such sound measurement devices "worthless" for LDC evaluation. 

Certainly, if the person collecting the data is putting a lot of time and money into the rest of the hardware, they should not be using a hammer to drive screws.  So, when Charlie was using "the wrong" sound meter type, rather than heckle him, I offered to buy him a "fast" peak hold meter, that I thought would increase the value of his results significantly.   Not lab quality, but then my generosity tops out at $100.  He got the message and bought his own.

I am not overly concerned about one sound meter reading 3 dB different from another (or about their absolute calibration, as long as they do not drift).  Proving they rank different airgun and moderators in the same order; by the same spread.  That said, seeing people casually place sound meters near a muzzle suggests they are unaware of the inverse square, sound to distance relationship.  They used an "expensive" instrument, "so the data must be valuable". 

I accept non-standard meter placement, as long as it is declared and consistent in a comparison test.   Pyramyd Air seem to place their sound measurement instrument "near the muzzle".   They don't seem to appreciate that the difference absolute sound levels, when measured casually somewhere between what looks like 18 to 24" from the muzzle, turns their data into gibberish.   Never mind that the mic is sometimes a little ahead of the muzzle, and sometimes behind.   Much less laughable to measure at 20 feet +- 1 foot.  And not near the trap, else that is the dominant sound.   

As I am more interested in not spooking people much further away than one meter, the standard protocol used to measure "hearing safe" suppressors on firearms is not the standard I insist on.   I do insist on repeatable and reproduceable.  And that requires a "test plan", however informal.

I assume that the module you would attach to an airgun to measure vibration would have very low mass, so as not to influence the result ("too much").  That said, one uses the equipment that is available to you.  Even if attaching the test equipment, induces a shift in natural frequency; that may not null out the trends and dependencies you are attempting to capture and demonstrate.  Please carry on.

[subscriber]

The problem with the testing in that Titan thread is that it is just a teaser of what is going on.

Your standard may be too high.  And I mean that in the best possible way.

Which reminds me of the old adage: 
The relentless pursuit of perfection is the enemy of achieving good enough. 
Or words to that effect:  https://en.wikipedia.org/wiki/Perfect_is_the_enemy_of_good

[WhatUPSbox?]

Yeah, it may be worthwhile to start a couple of threads in the engineering gate on test methods and data expectations for both the noise and the barrel harmonics topics. Kick around what is possible given the constraints of a hobby.

[Goldwing]

I got one of Charles Wong moderators and very impressed with it performance, slightly beating out my beloved Huggett Snipe and at half the price too!
Thanks again
Dan

[mwgm2020]

I got one of Charles Wong moderators and very impressed with it performance, slightly beating out my beloved Huggett Snipe and at half the price too!
Thanks again
Dan

I’ve not heard of Charles Wong moderators. Do you have a link to them?

[subscriber]

I’ve not heard of Charles Wong moderators. Do you have a link to them?

https://www.gatewaytoairguns.org/GTA/index.php?topic=182312.msg156076642#msg156076642

[Jshooter71]

I’ve not heard of Charles Wong moderators. Do you have a link to them?

https://www.gatewaytoairguns.org/GTA/index.php?topic=182312.msg156076642#msg156076642

I think he meant a link, as in how to obtain one.

[subscriber]

I think he meant a link, as in how to obtain one.

Unfortunately Charlie is not making those anymore.  If you PM Charlie (OP of this thread) he might know of a spare one somewhere.  Or, someone reading this thread might know, and pipe up.

[Rick67]

I think he meant a link, as in how to obtain one.

Unfortunately Charlie is not making those anymore.  If you PM Charlie (OP of this thread) he might know of a spare one somewhere.  Or, someone reading this thread might know, and pipe up.

They were available for a long time and for so cheap a price ($67 shipped) and yet people hesitated   

It is a very nice piece and the 1/2 threads are better than my Donny FL Tantos'.

[Goldwing]

Sorry for the confusion, quote from a PM from Charles, should clear it up

Thanks for the post! Especially about it being quiet like the Snipe.

Just to add one detail, I myself don’t actually construct those AUO silencers, it’s a couple of guys whose names prefer not to be mentioned that I try to help out.

I don’t mind being mentioned as having them available, I just don’t want ppl thinking I’m actually making the silencers.

Thanks again!

[subscriber]

Sorry, Charlie

Correction:  The guys Charlie knew are not making those LDCs anymore.  Or, are they still in business?

[Rick67]

Sorry, Charlie

Correction:  The guys Charlie knew are not making those LDCs anymore.  Or, are they still in business?

If so, I'd want a mini one this time 

[subscriber]

I have a very simplistic way of thinking:  When an unambiguous statement is made, it stands, until it is replaced by another unambiguous statement.  I bolded the unambiguous part of Charlie's statement in the quote below.

My attribution to Charlie as the source was not because he made the LDCs, but because he was the contact person on the forum to obtain one.

Thanks sir Richard, truth is they are down to their last 20 units or so with no plans to make any more.

[Goldwing]

Also I was told I was at my own risk shooting a 25cal through it, but it works perfect, even though its made for 22cal without any damage

[Rick67]

Also I was told I was at my own rick shooting a 25cal through it, but it works perfect, even though its made for 22cal without any damage

They look nice sheathed in a foam grip 

[mwgm2020]

I got one of Charles Wong moderators and very impressed with it performance, slightly beating out my beloved Huggett Snipe and at half the price too!
Thanks again
Dan

I’ve not heard of Charles Wong moderators. Do you have a link to them?

AHHH!  The AUO's!  Why didn't you just say that?!?