.22 silencer baffle hole....

[Rich]

A properly designed silencer will have the largest chamber nearest the muzzle, that is to say, the first one that receives the air, for the reason air-tech mentions.

I usually build mine with the smallest chamber at the other end.

The length of the chamber governs the frequency where the sound reduction will be at its maximum. Fm = C / (4L) where C is the speed of sound and L is the chamber length, in consistent units of course. The longer chambers give most effect at lower frequencies.

There is a frequency below which this length of chamber will be ineffective. This is the cut-off frequency, or Fc. You can calculate it with reasonable accuracy from the following formula:

Fc = Fm ( 0.003R² – 0.09R + 1.03 ) where R = expansion ratio, ID divided by hole diameter.

There is also a higher frequency at which this length of chamber will be ineffective. That happens at twice the Fm frequency, ie., 2Fm

Using these formulae one can work out the optimum relationship of chamber lengths so that as one chamber tails off in effectiveness the next in size is ramping up to its peak. It turns out to be a Fibonacci sequence, nature's Golden Ratio.

Of course most folk prefer to make the bits and try them out rather than do the maths, it's more fun......

[Rich]

This was one of my most successful designs, fitted to a S200. Yes it's ungainly and no it's not very well finished, I couldn't wait to test it.

http://i.imgur.com/73Pqo4l.jpg

It's a reflex design with four chambers. The overall length is close to 200mm and the OD is 60mm. It's a tube within a tube, the inner tube is 50mm diameter. Air passes along the inner tube and through three baffles. Once it arrives at the last chamber it can escape radially through vent holes in the inner tube and then blow back in the annular void space between the two tubes. You can just see the vent holes at the back.

[rhyslightnin]

This was one of my most successful designs, fitted to a S200. Yes it's ungainly and no it's not very well finished, I couldn't wait to test it.

http://i.imgur.com/73Pqo4l.jpg

It's a reflex design with four chambers. The overall length is close to 200mm and the OD is 60mm. It's a tube within a tube, the inner tube is 50mm diameter. Air passes along the inner tube and through three baffles. Once it arrives at the last chamber it can escape radially through vent holes in the inner tube and then blow back in the annular void space between the two tubes. You can just see the vent holes at the back.

Looks great.. pretty complicated though..
I was thinking about also making a short fat silencer maybe 40mm by 100mm to put on the end and maybe use a wider diameter carbon shroud like a 27mm or a 28mm as the first void....
I've learned now that the barrel under my existing shroud isn't threaded so whatever I do itl be slip on which isn't too much of an issue.
Mmmmmmmmmmmm.... Lots to think about
Thanks all again., Tis very interesting stuff!!
Rhys

Rich you have pm

[bucketboy]

A properly designed silencer will have the largest chamber nearest the muzzle, that is to say, the first one that receives the air, for the reason air-tech mentions.

I usually build mine with the smallest chamber at the other end.

100% opposite to what I have found!


Bb