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From: "George Lendich" <lendich@aanet.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-3646826@logan.com>
Subject: Re: [FlyRotary] Re: Phonic Band gap filter
Date: Wed, 20 May 2009 07:44:13 +1000
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Ernest,
Certainly interested any results either good or bad,
George (down under)
> George Lendich wrote:
>> Al,
>> I would off- set the tubes, the idea is to not have a direct path for the 
>> sound waves to travel in a direct line, front to back (path of least 
>> resistance) make them stainless and of a reasonable thickness.
>> George (down under)
> George, we're skinning a different cat here.  We can actually have a 
> completely see-through muffler.  The idea is to control interference 
> patterns so that certain frequencies are canceled.  The dimensions are 
> critical to determining what frequencies are canceled, and the depth and 
> width of the band gap is heavily influenced by the difference in Young's 
> Modulus between the two materials.  The greater the difference, the more 
> pronounced the effect.
>
> My ultimate goal is a stainless box using .050" material.  It takes about 
> 10ft of tube to make what you saw in the pictures.  I think the technique 
> will be to make a box, then drill the hole pattern all the way through. 
> Push a tube into each hole, and then weld the tube to the box on both 
> sides.  With this constructions, air can flow through the tubes to keep 
> the steel strong and help cool the exhaust.
>
> I did just think of something.  My experiment wasn't as valid as it could 
> have been.  I should have run a test with just the filter box in place. 
> That is, the wooden box with the filter elements removed.  It could have 
> been the box had more to do with the results than the filter elements. 
> I'll update you when I've run another test.
>
> -- 
>
> http://www.ernest.isa-geek.org
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>
>
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