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Author Topic: Underground silencer version 2.0  (Read 8544 times)
stephendv
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« on: February 01, 2010, 10:42:06 AM »

Improved the undergound silencer by using a series of sand filled block baffles, works REALLY well and has completely eliminated the deep bass boom of the engine.  The loudest noise now is valve clatter  Grin





More photos here: http://www.casanogaldelasbrujas.com/blog/2010/01/26/exhaust-silencer-version-2-0/

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frotter
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« Reply #1 on: February 01, 2010, 02:01:27 PM »

Nice one!
An exhaust Pit o Doom is a joyous thing indeed....   Smiley





 bike
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  HE WHO CONTROLS THE LARD - CONTROLS THE UNIVERSE!!   Its me, incidentally..
knighty
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« Reply #2 on: February 01, 2010, 09:46:59 PM »

how's the generator running ?  any problems with it ?  any other usefull info ?

(I'm always nozy when it comes to CHP!)

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stephendv
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« Reply #3 on: February 01, 2010, 10:07:25 PM »

Nice one!
An exhaust Pit o Doom is a joyous thing indeed....   Smiley

Hehe, yours has skewed baffles too!  When I heard of the famous pit o doom, I thought it was just a plain old pit, not an uber-sophisticated baffle system  Grin

knighty, the generator's running fine now, finally.  After replacing the radiator fan, and the electronics and fixing the starter motor...  starts every time now (touch wood).
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noelsquibb
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« Reply #4 on: February 01, 2010, 10:19:39 PM »

the only thing missing is the water filled snake to grab that last little bit of heat ?

careful what metals you use though  stir
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mmmmm,  gravy
Ivan
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« Reply #5 on: February 01, 2010, 10:43:31 PM »

Here's my pit of doom. The baffles are carefully positioned centrally, so that the slightly longer path along one side of the baffle, cancels the sound of the exhaust gases travelling along the other side. If only I could get the thing started, I could test the theory.

P.S. Stephendv, Did you find that the sand is important in reducing the sound to your new improved low level?


* ivans_pit.JPG (44.67 KB, 343x458 - viewed 1606 times.)
« Last Edit: February 01, 2010, 10:45:20 PM by Ivan » Logged
stephendv
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« Reply #6 on: February 02, 2010, 08:33:44 AM »

They're all coming out of the woodwork now!  No idea how important the sand is, the original design was basically a vertical expansion chamber with 3/4 buried and a hole in the top (I later covered the other 2 holes):


was a bit silly to begin with as it really didn't help much with the sound.  I think the biggest influence is that the whole structure is underground, I'd like to think that the sand helps a bit as it can be compacted so should absorb some of the shockwaves, in theory anyway.  Maybe it would be a good idea for yours since I'm guessing that your lister makes more of a boom than my 1500 rpm'er.
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jotec
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« Reply #7 on: February 02, 2010, 09:45:18 AM »

I want one.
This is next on the list after getting it generating well. Any advice on size of depth?
D ick
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stephendv
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« Reply #8 on: February 02, 2010, 02:00:22 PM »

Due to some freak coincidence it seems frotter's, ivan's and my chambers all have 3 baffle bricks - and it seems to work fine.  Mine is a 12Hp single cylinder engine, if yours is bigger then you might need a few more.  The roof of the chamber is about 40cm underground.
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daftlad
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« Reply #9 on: February 02, 2010, 02:08:43 PM »

Due to some freak coincidence it seems frotter's, ivan's and my chambers all have 3 baffle bricks -

Great minds obviously think alike.
ta ta
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Ivan
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« Reply #10 on: February 06, 2010, 11:54:49 PM »

Nope, it's more like 'Lazy minds copy'.... in my case, I simply copied Frotter's design.
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KenB
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« Reply #11 on: March 04, 2010, 05:13:07 PM »

Guys,

Looks like I'm being left behind here - obviously spent too much time poncing around central London for a year and not getting real stuff done. Plenty time for than now - till I have to get a proper job.

I do however have a stainless steel washing machine drum cast into the block that the Startomatic sits on. A sort of concrete entombed expansion chamber which will percolate the water vapours into the subsoil.

It's about 600mm below ground with a lot of concrete on top of it.

With my new hat on, a 25 gallon drum of woodchips make an excellent noise abatement system for even the most discerning exhaust. 

Wood is going to be the new lard for 2010.  You can cook with it, and the rats won't eat it.



Ken


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Paulh_Boats
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« Reply #12 on: March 04, 2010, 09:52:52 PM »

Slighty off topic - when I was mad keen about tuning up cars as a student I read all the Uni books I could find about engine performance. One of the important exhaust features is the expansion box...it allows the gases to expand and lose their energy. Less energy = less noise.

It looks like you all have the ideal expansion thingy - so well done chaps!

-Paul
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