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Dec 01, 2019, 03:19 AM
Living in the south of France
paulinfrance's Avatar
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Discussion

Noisy petrol engine exhausts DLE 20cc


Hi, I was contemplating getting a 2 metre Spitfire and a 35cc DLE for it , however after flying my DLE 20cc after my OS .80 four stroke Hurricane, I decided that it would be too noisy and didn't go ahead with it.
'But' now I have come up with the idea :co of fixing 'back to back' another 20cc RA exhaust on my ME 109 and see what it sounds like, Has anyone tried this ?.
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Dec 01, 2019, 06:39 AM
Fly low and fast
Quote:
Originally Posted by paulinfrance
Hi, I was contemplating getting a 2 metre Spitfire and a 35cc DLE for it , however after flying my DLE 20cc after my OS .80 four stroke Hurricane, I decided that it would be too noisy and didn't go ahead with it.
'But' now I have come up with the idea :co of fixing 'back to back' another 20cc RA exhaust on my ME 109 and see what it sounds like, Has anyone tried this ?.
If you are having noise issues on your field I wouldn’t experiment with DYI silencers. For me it is just too time consuming.
KS manufactures silencers for all kind of applications. I used several over the last few years. My DLE 35 RA runs at 78 dB A with their canister. Your prop has also a huge influence of the noise.

https://www.krumscheid-metallwaren.de/

Cheers
Dec 01, 2019, 07:58 AM
Living in the south of France
paulinfrance's Avatar
Thread OP
Quote:
Originally Posted by Aviator1165
If you are having noise issues on your field I wouldn’t experiment with DYI silencers. For me it is just too time consuming.
KS manufactures silencers for all kind of applications. I used several over the last few years. My DLE 35 RA runs at 78 dB A with their canister. Your prop has also a huge influence of the noise.

https://www.krumscheid-metallwaren.de/

Cheers
Yes thanks, we have a couple of them on the model field on the 'tow' planes, Wilga etc, but a canister on a Spitfire or even my 109,,,

The KS looks nice but at 198€,,,,
Dec 01, 2019, 10:17 AM
Registered User
These after muffler things were available for a while. Not too hard to make. https://hobbyking.com/en_us/dle-30-m...-silencer.html They would rob a bit of power but might be a bit quieter. The smaller glow motors on boats have a smaller sort of muffler that is attached to the tuned pipes with silicone tubing. It does not seem to rob any power. They sort of look like two small funnels attached together at the top rim.
Dec 01, 2019, 11:30 AM
Living in the south of France
paulinfrance's Avatar
Thread OP
Quote:
Originally Posted by aspeed
These after muffler things were available for a while. Not too hard to make. https://hobbyking.com/en_us/dle-30-m...-silencer.html They would rob a bit of power but might be a bit quieter. The smaller glow motors on boats have a smaller sort of muffler that is attached to the tuned pipes with silicone tubing. It does not seem to rob any power. They sort of look like two small funnels attached together at the top rim.
Thanks I have seen them but I have talked to a couple of people who used them and weren't satisfied with the little reduced noise and power.

I have ordered 2 boat silencers and some stainless tubing, I will probably solder / weld a couple of bits of piping to the side of them and block the inlet end up, then plug them into the outlet on the original Dle silencer,,
Dec 01, 2019, 11:31 AM
Living in the south of France
paulinfrance's Avatar
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I can't post my picture of my eboot order I keep getting 'Bad Gateway',,

opps it has posted, but now I can't cancel this post,,
Dec 01, 2019, 01:09 PM
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EloyM's Avatar
Think of it not as noise, but as music. And they are realistic - prop driven full size aircraft do make a type of noise which model aircraft duplicate somewhat.
Electric airplanes sound like hair dryers - bah humbug!
Last edited by EloyM; Dec 01, 2019 at 01:09 PM. Reason: spelling
Dec 01, 2019, 02:55 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by paulinfrance
Hi, I was contemplating getting a 2 metre Spitfire and a 35cc DLE for it , however after flying my DLE 20cc after my OS .80 four stroke Hurricane, I decided that it would be too noisy and didn't go ahead with it.
'But' now I have come up with the idea :co of fixing 'back to back' another 20cc RA exhaust on my ME 109 and see what it sounds like, Has anyone tried this ?.
There is something called Snuffler Muffler.
http://www.jtecrc.com/snufflermufflers.htm

Made by J'Tec. More specifically J'Tec took some chain saw engine mufflers and mated it to their muffler for our hobby engine use. Yes they are quieter than a lot of canister type muffler but they are definitely heavy and rob performance.

If you are comparing the noise from a 4 stroke engine to a gasoline 2 stroke engine you will never be able to quiet down a 2 stroke gasoline engine to that level. 1) The 4 stroke engine only fires every other stroke. So if you run it at 10,000 rpm you get an exhaust note only 5,000 times per minute. A 2 stroke engine is once every stroke so a 10,000 rpm engine has 10,000 explosion every minute. 2) The 4 stroke exhaust has a full stroke for the gas to cool down before exiting the exhaust valve. That really calm down the explosive noise before the gas is exiting. In a 2 stroke engine the exhaust gas is exiting the engine not too long after the explosion occurred when the piston is coming down from TDC.

There were also muffler on the market called the after muffler. Pretty much what you described as "back to back" exhaust. You can take one of those snuffler muffler and add that to the existing exhaust as an after muffler. The cost of reducing noise is weight and performance.

Then the next thing to do is to reduce the RPM of the engine. Back in 1986 that's exactly what the trend was in F3A pattern contest. The F3A pattern plane competitions were limited to a 10cc 2 stroke engine at the time. Lots of airfields were lost because of noise issues. So the regulating body decided to add a noise bonus/penalty. O.S. started making a .60 engine in a "long stroke" configuration to reduce RPM. APC started making propellers that were suppose to cut back on the prop noise. Then the four stroke engines starter to become popular by 1987 and the long stroke engines started to lose their place in competition but they were still popular as sport engines.
Dec 02, 2019, 10:26 AM
Living in the south of France
paulinfrance's Avatar
Thread OP
Electric ! are you aware that some modellers like me are deeply offended by these inventions of the devil !.

Thanks for the snuffers, sorry but at $28 'each' and 2 for every engine,, but you have given me a great idea,
I will chop up some tubing and make a couple, as it's winter and nothing to build it will keep me busy.
Dec 02, 2019, 12:25 PM
AMA 46133
SeismicCWave's Avatar
Quote:
Originally Posted by paulinfrance
Electric ! are you aware that some modellers like me are deeply offended by these inventions of the devil !.

Thanks for the snuffers, sorry but at $28 'each' and 2 for every engine,, but you have given me a great idea,
I will chop up some tubing and make a couple, as it's winter and nothing to build it will keep me busy.
I don't know where you live and what kind of gardening supply store you have locally. However I believe the Snuffler is an inexpensive muffler for the chainsaw, weed wacker engines. You can probably find them in the garden supply store for less.
Dec 03, 2019, 02:48 AM
Living in the south of France
paulinfrance's Avatar
Thread OP
I live in the South of France,
There are a lot of gardening stores, but like most French shops they only sell spares 'if' you have a part N°
service is crap in 90% of shops here so a complete waste of time,,
Dec 03, 2019, 08:24 AM
Registered User
Paul, there are a few exceptions here and there, but otherwise the knowledge on the other side of the counter is most often limited to reading the box for you. Point being, service not much better stateside. That's what makes places like this one important.

The trick will be finding volume in the cannister section of the muffler. Or, you can dampen the output, but that will often cost you rpm. -Al
Dec 03, 2019, 10:09 AM
Living in the south of France
paulinfrance's Avatar
Thread OP
Yes it's going to take a lot of thinking and fiddling about,
I have a watchmakers lathe and oxy*/acetylene gear,
I know how to use a file and 20 years of experience as a mechanic and another 20 years as a model shop owner,,
I will post my ideas, and tests on this post,,

And nothing better to do this winter,,,
Dec 03, 2019, 10:53 AM
Registered User
Something like a Mousse can muffler maybe. Use an aluminum beer bottle in the 1 litre? size. Normally the parts are siliconed on but the gas might be too hot. Something to think about at least.
Dec 16, 2019, 11:26 AM
Living in the south of France
paulinfrance's Avatar
Thread OP
Still Waiting for my Tiger Moth to be delivered by GLS ( idiots ), so I made my exhaust up today, It weighs in at 200 grams, a friend on the field came with his Dle 20cc powered P 47 and it clocked in at 99Db on the grass, yesterday, tomorrow I will see what my Dle 20 Ra gives me in my P 47 and then a trial run of the engine with my new exhaust, and see what the RPM losses are,,


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