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Author Topic: Silent Lister exhaust  (Read 17324 times)
bottleveg
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« on: May 19, 2010, 10:19:16 PM »

In my quest to achieve a completely silent exhaust Im planning to build a breezeblock chimneystack 40 wide, 10 deep and probably 6 or 7 feet tall. The standard 2 Lister pipe would first go through a Lister cast iron damper and then enter the base of the chimney.
So far I can see two possible options: -
 I could construct a series of horizontal corridors that would be 5x 8 sq, so the gasses would travel along one corridor, turn a corner and travel along a second corridor, on the same level, before passing up into the same construction above. A square spiral, if there is such a thing?
The second option is to have a series of chambers, 5x 8x 12, one above another and the gas would pass through a 6 hole from one to another.
My thinking is that the first option would allow the gases to run out of energy before they reach the top. The second option would give continues expansion chambers.
What do you think? Anyone tried this sort of idea?
Digging a large sump in the ground is not really an option due to tree roots. If Im not 100% successful I still have the option of passing the gases several metres from the top of the chimney through soil pipe. But, as always money is limited so, at the moment, thought is cheaper than action.
My ultimate goal would be able to run the engine 24/7 but to do this I need it very quite.
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Justme
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« Reply #1 on: May 19, 2010, 10:27:06 PM »

Make sure you allow for cleaning it.
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knighty
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« Reply #2 on: May 19, 2010, 10:31:04 PM »

what about both ?

your square spiral, but with limited gap joining the 2, (6inch or whatever is recommended)

so the gasses still have to spiral around, but they also double up as expansion chambers ?



tho i think 6' might be a bit big for the joiners.... i'd use something the same size as the exhaust the engine has...
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Alan
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« Reply #3 on: May 19, 2010, 10:54:24 PM »

If you base a typical fuel with 1% sulphur content and you allow any part of the flue system to run at less than 116 Deg C then sulphuric acid will condense in the flue.
The surrounding area will be affected by acid concentrations if the temperature at the exit is close to the dew point.
It will also condense every time you start the engine until the flue system at the flue exit point is hotter than 116 Deg C.

Regards

Alan
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welshboy
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« Reply #4 on: May 19, 2010, 11:06:50 PM »

This is a link to how a gun silencer works- maybe of interest

http://www.google.co.uk/imgres?imgurl=http://www.freeinfosociety.com/science/pictures/Silencer3.gif&imgrefurl=http://www.freeinfosociety.com/science/silencer.html&usg=__oP5Ej2VGSTHobKiDiBulGrqQaro=&h=287&w=697&sz=11&hl=en&start=9&sig2=jMEzlh_8zKgvhu3TTmGjaQ&um=1&itbs=1&tbnid=Jh0bsFH46DeFYM:&tbnh=57&tbnw=139&prev=/images%3Fq%3Dgun%2Bsilencer%2Bdesign%26um%3D1%26hl%3Den%26sa%3DN%26tbs%3Disch:1&ei=FGD0S_SiJZOf_Aa2l5GADg
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bottleveg
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« Reply #5 on: May 20, 2010, 01:55:15 AM »

Guys, thanks for your input, and hello again Knighty.
Its getting late and my mind is shutting down. Ill read again tomorrow and ponder your ideas. Any more comments very welcome.
                   Mark.
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stephendv
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« Reply #6 on: May 20, 2010, 07:46:18 AM »

Some underground versions here: http://www.navitron.org.uk/forum/index.php/topic,9775.0.html

I think you'd need to get more mass in the chimney walls to help with dampening, e.g. fill the breeze blocks with concrete.
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bottleveg
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« Reply #7 on: May 20, 2010, 01:47:28 PM »

Thanks for the ideas. I was thinking of using solid 4 breezeblocks but I could do a double thickness on the first two layers or build the first two layers with concrete blocks. My thinking on breeze is that it will absorb the sound where as it would probably bounce off concrete.
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stephendv
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« Reply #8 on: May 20, 2010, 02:25:58 PM »

My gut feeling is that if the blocks are too light, they won't dampen the heavy bass thud of the lister, so I'd be inclined to use something with more mass, perhaps fill them with builders sand - so you get mass + absorption.  Or if you're going for a double wall, then you could leave a cavity between them and fill that with sand.
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noelsquibb
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« Reply #9 on: May 20, 2010, 10:29:56 PM »

Oddly, one of the most effective silencers Ive come across was on an old WW2 Lister driven sawbench.
It was a just a length of scaffold tube, with nowt on the end.

Ok it wasn't silent but the mechanical noise far outdid it, in the noise stakes.

Conversations with friends regarding ways to quell the pop that big 4 stroke motorcycles make, had us thinking that while mass absorption is clearly a very effective approach, we considered how we might progressively slow the sound pulse by sending it through a set of parallel pipes of different lengths, so some of the sound pulse is slowed by skin drag on the pipe walls. Different lengths to cause differing amounts of drag with the total sound emitting at a more constant rate as a 'fooof' rather than a 'pop'

We have had some success but really need longer pipe options. Use of the bike frame has been considered.

We reckoned the 6m long scaffold tube might be ideal for skin friction and mass but a bit impractical for a bike.

Further confirmation of the effect the pipe has, is the difference in noise from my 1.9 Citroen diesel when the exhaust pipe separates from the silencer, compared to when the pipe separates from the front down pipe.

One is a nuisance and a bit fumy but drivable the other is ear shatteringly noisy.
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Amy
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« Reply #10 on: May 20, 2010, 10:40:05 PM »

Hospital silencers as used on boats are pretty damn amazing. So named because they were first used for hospital generators so the noise didnt drive every one crazy
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« Reply #11 on: May 21, 2010, 12:40:59 AM »

Any pipe/chimney in the air is going to vibrate and make noise unless its made of tons of concrete the simplest is a shallow trench in the ground and a long pipe with lots of holes along it. The ground is to heavy to vibrate therefore no noise the exhaust gases will escape through the earth but silently just making little bubbles when it rains. The pipe from the engine can be soundproofed but it should run directly down into the ground. Engine mechanical noises can be eliminated by using silent type generator enclosures and then even building a second house around the generator.
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bottleveg
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« Reply #12 on: May 21, 2010, 10:02:18 AM »

Hello Roger, thanks for your input. I was trying to avoid the underground situation, it would involve going across my better halfs garden, but I can see your point.
How deep in the ground would you suggest the pipe needs to be run and what size holes drilled in it? Holes just in the bottom and sides to avoid too much soil ingress? How would it terminate? If I head towards the house then I could go up the wall in the standard soil pipe arrangement and terminate just above the gutter line.
I would have about 10m underground, would this be enough? I could build a chamber half way if needed.
I was hoping to do this part of the operation only once. I wont be too popular if I dig up my partners garden and still get noise at the end of it!
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KenB
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« Reply #13 on: May 21, 2010, 11:18:57 AM »

Bottleveg,

You will need a decent expansion chamber.  An old propane bottle, or 2 gallon fire extinguisher fitted with 2" pipe inlet and outlet is a good start.

Causing the exhaust gas to change direction through 180 degrees is a good way of losing some of the energy. This can be done by taking the inlet pipe down to the bottom of the propane bottle and having the outlet drawn from the top - cleverly done you will get 2 complete reversals of direction.

At the end of the day, the Lister 6/1 is only an engine. Get yourself down to Qwikfit and salvage some second hand car exhaust sections.

Next is the exhaust pit.  Dig an irregular shaped pit in the garden (no parallel sides), put some gravel in the bottom and line with high density concrete blocks. Arrange more blocks as baffles and a 2" thick paving slab over the top.  Use a 4" drain pipe to vent the exhaust skyward.  There was a thread a couple of years ago showing how Frotter constructed his "pit of doom".

Make sure that all sections of the exhaust system slope away from the engine to avoid condensation traps - gurgle gurgle is bad news.



Ken

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bottleveg
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« Reply #14 on: May 21, 2010, 12:15:18 PM »

 Hello Ken,
      Thanks for your input. I believe you have a lot of experience with these matters.
 I already have a cast iron Lister damper on the engine and that works quite well. My ultimate goal is to be able to run my 8/1 through the night, so thats why Im looking for extra silencing measures.
My thinking now is to run a buried soil pipe, with holes drilled in, build an exhaust pit, as you describe, and then another pipe from that to connect on to a conventional soil stack. Total underground pipe would be 10m.
How deep do you think my pipe should be and what size for the pit?
Ill do a search and see if I can find this pit of doom
                             Thanks for your help, Mark
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