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Mike the Boilerman

Quietening a semi-diesel exhaust

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Long pipe about 5-6 inches diameter and make it too long to start with and then cut small pieces untill it it sounds good:).

I tried on my own old boat with a "normal" length but to loud,made an extension that i fiddled with in length untill i was satisfied.

Bigger diameter pipe will make the Hz lower,longer the same.

Try to have as low restrictions as possible on a two stroke.

also remember that all the oil that follow the exthaustgases will finaly burn so better to have oil on deck or clothes than in a silencer.

When you have your first exthaust fire its an experience...........

 

cheers.gif

/Chistian

 

Edit:on my little 15hp Seffle i had a 4"pipe 5 feet long and the Skandia 120 is a "bit" bigger in deplacement.

Edited by BM 1051

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Thanks! Just had a look at MIJ's ebay shop and they have what looks like just the job.

 

http://www.ebay.co.uk/itm/8-Silencer-Box-3-3-5-4-4-5-Inch-Inlet-Lorry-Van-Truck-Tractor-Scania-Iveco-/221150403144?pt=LH_DefaultDomain_3&var=&hash=item7919ab9b5b

 

Except that at 46" long it aint gonna fit... Time to seef they'll make a short one. Or get TW Marine to do it!

 

Drop them an email with the necessary dimensions and they will quote you I'm sure. They have done some good ones for us, not expensive either

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This is my concern too, and why I wasn't planning to take the advice I dished out and was quoted earlier for adjusting the exhaust note on a four stroke Gardner.

Same problem though in terms of silencing. You have two general choices, add volume to the exhaust or add baffles. The latter is likely to be not much use on a two stroke as you probably do not want the restriction, so you need volume (as you and others have been saying).

 

By the way, what did the OEM fit? Is this known?

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Don't forget thet what comes out the engine will have a fair amount of sticky solids amongst it.

Smuts black and tacky will soon make up any mesh inside the box.

Tim

 

15hp Bolinder

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Sounds like a weekend with various sizes of pipes and configuartions to get it right.

 

I did notice one thing on mine - the trial 4" flexible tube "deadened" my exhaust sound somewhat. Not sure if that was down to the material or additional volume or both.

 

The 3" expansion box was same sound as 2" but bassier. The 2" was harsher sound (more velocity different pitch?). This was however on a 4 stroke as you know.

 

You may end up by making a large offset expansion box with two exits branch off it and tee-ing up before exiting the roof.

Edited by mark99

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When I had the Seffle it had a straight through exhaust - probably about 4", I can't remember. It made, IMO, a satisfying deep pop-pop-pop sound. The only time I found it a bit much was when I was belting through tunnels. I then wore ear defenders!

 

I hope a lorry exhaust won't interfere with the production of impressive smoke rings.

The Seffle I had came with, what I would guess was an OEM extension silencer, It bolted directly on top of the water cooled expansion box & reached up to approx 4"from the engine room roof a 4" (i think) pipe with welded flange bolted to the top protruding through the roof collar about 2" It must have been an absorption type as when not fitted you could see straight through it with what appeared to be a 5" or so inch hole, it was approx 14"s OD. Ike Argent told me sometime after I'd sold the boat that the current owner had not worked the motor hard enough to catch the exhaust on fire, & the silencer had got so gunged up that it was spoiling performance so he had removed it, so I have no idea of the from then on exhaust system. With the silencer in place the smoke rings were unaffected As an aside there is a Utube video of Jem Bates boat at Braunston that has the actual Seffle I had, you can hear what the exhaust note is like although no idea of the exhaust set up + he doesn't seem to understand the niceties of the oil rod ( Injecter/sprayer) adjustment judging by the amount of smoke.

Edited by X Alan W

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Bizzard your agony aunt speaking. May I suggest adapting a 40 gallon oil drum into an expansion box. Should make a nice booming bloomin noise.

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I would avoid any restriction whatever below the nominal size, maybe see whether you can go bigger for the last section.

 

Tim

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Bizzard your agony aunt speaking. May I suggest adapting a 40 gallon oil drum into an expansion box. Should make a nice booming bloomin noise.

The Ruston Bucyrus excavators on a site I worked on, had 45 gallon oil drums with 4 6' dia holes cut in each end fitted over the exhaust This MOD was supposedly fitted to allow them to continue working through the night

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Bizzard your agony aunt speaking. May I suggest adapting a 40 gallon oil drum into an expansion box. Should make a nice booming bloomin noise.

 

 

But Unkle Bizz, you misunderstand. I'd LOVE the pesky thing to be quiet. I don't want a "nice booming blooming noise". This thread is about how to achieve quietness for when I come up your way so I don't wake you up.

 

The best idea I've some up with so far is I've ordered a five metre length of stainless steel flue liner to plug onto the exhaust outlet. I'll tie a 56lb mudweight to the other end and chuck it in the cut, so it stays underwater as I cruise along and the cut acts as a giant silencer.

 

Do you think this will work? I think it will, probubbly bubbly.

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But Unkle Bizz, you misunderstand. I'd LOVE the pesky thing to be quiet. I don't want a "nice booming blooming noise". This thread is about how to achieve quietness for when I come up your way so I don't wake you up.

 

The best idea I've some up with so far is I've ordered a five metre length of stainless steel flue liner to plug onto the exhaust outlet. I'll tie a 56lb mudweight to the other end and chuck it in the cut, so it stays underwater as I cruise along and the cut acts as a giant silencer.

 

Do you think this will work? I think it will, probubbly bubbly.

Steam railway locomotives of the Bullied pacific types amongst others used multiple exhaust blast pipes of the Lemaitre type which were very quiet. Google Lemaitre steam blast pipes.

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Jon Deere for the BD3

 

No, Ford for a BD3.

 

John Deere for a JD3.

 

Sorry for being off topic MTB

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No, Ford for a BD3.

 

John Deere for a JD3.

 

Sorry for being off topic MTB

 

 

No problem. BD3 and JD3 engines are completely different, obviously! I simply can't understand how people can mix them up...

The Seffle I had came with, what I would guess was an OEM extension silencer, It bolted directly on top of the water cooled expansion box & reached up to approx 4"from the engine room roof a 4" (i think) pipe with welded flange bolted to the top protruding through the roof collar about 2" It must have been an absorption type as when not fitted you could see straight through it with what appeared to be a 5" or so inch hole, it was approx 14"s OD. Ike Argent told me sometime after I'd sold the boat that the current owner had not worked the motor hard enough to catch the exhaust on fire, & the silencer had got so gunged up that it was spoiling performance so he had removed it, so I have no idea of the from then on exhaust system. With the silencer in place the smoke rings were unaffected As an aside there is a Utube video of Jem Bates boat at Braunston that has the actual Seffle I had, you can hear what the exhaust note is like although no idea of the exhaust set up + he doesn't seem to understand the niceties of the oil rod ( Injecter/sprayer) adjustment judging by the amount of smoke.

 

 

Thanks Alan. I'm veering towards getting a massive absorbtion silencer too. Two in fact, so one can be unbolted and replace with the other if/when it gunks up. Then the gunked up one can be cleaned and prepared ready for next time around. OR is that just mad an unnecessary?

 

I'll have a look for the Jem Bates vid, thanks!

 

 

(Spilling edtit.)

Edited by Mike the Boilerman

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Oh no, oh no....

 

The OH's chief reason for me to not fit a semi diesel in Willow like it originally had is "I don't want so etching so stupidly loud".

 

If you can make them quieter..... I may get into trouble.

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I've now found a couple of pictures showing the exhaust arrangement when I had the Seffle. The exhaust pipe was just a straight through 4" pipe from the expansion chamber to the roof with a 4" chimney. Any muck was shot out of the exhaust onto the roof (or me). I did have a couple of dramatic exhaust fires mentioned by Alan.

 

I was able to remove the cutter so as not to ruin the smoke rings. I'd then replace it when I went through tunnels.

 

post-5123-0-91080400-1438787359_thumb.jpg

post-5123-0-43012300-1438787378_thumb.jpg

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Thanks! Just had a look at MIJ's ebay shop and they have what looks like just the job.

 

http://www.ebay.co.uk/itm/8-Silencer-Box-3-3-5-4-4-5-Inch-Inlet-Lorry-Van-Truck-Tractor-Scania-Iveco-/221150403144?pt=LH_DefaultDomain_3&var=&hash=item7919ab9b5b

 

Except that at 46" long it aint gonna fit... Time to seef they'll make a short one. Or get TW Marine to do it!

Choose what size you want?

http://www.ebay.co.uk/itm/231404659787?_trksid=p2055119.m1438.l2649&var=530664158223&ssPageName=STRK%3AMEBIDX%3AIT

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On the Kromhout I used 4" straight through from the expansion/scavenging box. Two things I did reduced the noise. A rubber section in the 4" pipe near to the expansion box and a longer external end pipe. I used a stove chimney.

Edited by Jacq

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It didn't sound that bad too me! - I feel sure William is a fair bit louder!

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It didn't sound that bad too me! - I feel sure William is a fair bit louder!

 

 

It's still so loud that I need ear protection. This was totally unexpected and is a big disincentive to use the boat.

 

I'll need to change the engine again if I can't make it substantially quieter.

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On the Kromhout I used 4" straight through from the expansion/scavenging box. Two things I did reduced the noise. A rubber section in the 4" pipe near to the expansion box and a longer external end pipe. I used a stove chimney.

 

 

Thanks, this seems a Good Idea.

 

Replacing the metal tall pipe on Reg with a length of plastic dain pipe causes a norticeable reduction in noise, surprisingly. I think this is due to the slight 'give' in the nature of the material. A length of rubber will probably be even more effective. Where did you find rubber tube that big?!

 

Another idea, as a couple of people have suggested to me that increasing the length of the exhaust tube is the answer, is to insert a couple of metres of stainless steel flexible flue liner in a coil into the exhaust outlet from the expansion box.

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It's still so loud that I need ear protection. This was totally unexpected and is a big disincentive to use the boat.

 

I'll need to change the engine again if I can't make it substantially quieter.

If the pipe keeps getting goo'd up being a two stroke an after burner would be required to burn the goo off. This could be achieved by ramming a wad of Cordite down the pipe and letting the engine set it off. An armour piercing shell could be plonked on top of it from outside which would be ejected from the stack to let you know when the Cordite has done its job.

I recommend a rifled bore exhaust pipe for this to function properly. closedeyes.gif

Edited by bizzard

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At one time it was no un-common to de-smut a Bolinder by adding mothballs to the oil in the daytank!

Said to make it run hot!

Tim

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At one time it was no un-common to de-smut a Bolinder by adding mothballs to the oil in the daytank!

Said to make it run hot!

Tim

Naptha.

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