DLE 30 noise reduction

[Mike Bell]

I have a DLE 30 which I ran for the first time at the weekend. Very impressed with the easy starting and the power available, but less than impressed by the naff muffler that comes with it. The volume is ridiculously small so it was no surprise that it was not effective at all.

 

Does anyone out ther have any experience of alternative silencers for this engine? I have my eye on the Weston UK canister type muffler so I would be particularly interested if anyone has any experience with these.

 

Thanks

Mike

[Snorbitz]

Hi Mike

In last months magazine there was a nice little article on just this problem. I have a CRRC26Rcc engine which is pretty noisy to say the least so i tried wrapping the can in fiberglass and high temp orange sealant as it shows in the mag and i have to say it really does sound a lot better. I should have done a Db check before and after but its too late for that now. I might add some silicone tube to the exit hole when i next go out to see if that helps/hinders. Going up a prop size from 16x10 to 18x8 to 18x10 also really helped too.

I like the look of the alternative silencers from Just Engines but i'll have to save my pennies for one of those.

Good luck.

[Bob Webster]

I have a MVVS 26 cc petrol and I am just waiting to see what it's noise is like in the air.

It didn't seem too bad on the ground with the stock dustbin silencer but it's a different silencer (Just Engines) for flying. JE silencer doesn't fit the ground rig and the dustbin doen't fit the Spacewalker!

Watch this space!

Bob

 

[Snorbitz]

After running in on a bench which is obviously very noisy i first run my engine up over the lawn...Sounds very quiet i thought but when i first took it to the patch and took off i though holy shish.....it does sound great but boy was it noisy. My work friends tell me they can hear it pretty clearly it over a mile away!! Remember your nieghbours thats all i'd say.

[Mike Bell]

I did see the WOO article and I daresay it would have some effect, but I'm convinced that lack of volume is the biggest issue, hence my leaning towards a canister type. It's an expensive solution mind you, hence my hope that someone else had tried it first before I pawn the wife.

[Merlin spit]

i have a dle 30 with a chinese cannister ,its not the best one out there but it gets the noise down to 87db with a 18x10 or 19x8 prop measured from the front 7 meters on the ground this is our clubs standardized test

the standard dustbin is 95db so a good reduction ,

i still feel at 87db my plane sounds plenty loud enough at full throttle but i hardly need to fly at full throttle for long

[BB]

I have a Zenoah 23cc with a can from a CRRC 26cc v2 (same mount). I wrapped it in silicone tape (Rescue Tape). The noise reduction on the bench was 6db down from 92db.

 

Tape wouldn't stay on though. Despite being 290c rated.

 

I'm trying to source some silicone so I can wrap it as per the article, with fibre glass cloth. Any one know of a stockist ?

 

BB

 

Edited By Basildon Biggles on 12/04/2011 17:58:23

[Mike Bell]

Thanks Austen, nice to have some figures. Sounds encouraging. With the increasing popularity of petrol engines I think it's about time the manufacturers were taken to task over supplying better solutions as stock.

 

Interesting to hear your experience with the tape BB. I had my suspicions about adhesion, petrol silencers get mad hot.

[Bucksboy]

Ive got one of the CRRC 26 cc engines and used the red silicone and tape too. Its come straight off despite de greasing the exhaust first. It is still wrapped around hte exhaust but no longer attached. The engine was too noisy and its been retired until i can find a quieter exhaust that will fit. The silicone was suitable for glueing gas exhausts together, i think its the right stuff.
BB

[Merlin spit]

I have to agree ,the manufactures should either other no exhaust at a cheaper price or a useable Pitts type.

The evolution 26cc pitts exhaust is a good option for a dle 30 it needs the mounting holes enlarging slightly but does fit tight and is a steady 88db with a better overall tone than standard .

i wonder if high temperature silicone sealant gun could be used instead/with the tape??

[Paul Adams]

Having tried to silence my CRRC 26cc engine, I have at last found a silencer which does the job. Its a canister silencer, see picture.

Its a bit big, but works well. I was also considering adding some form of silicon tape to the outside to see if it reduces the noise even further.

 

I have tried a Pitts silencer in the past, but still over the noise limit, although blocking off one of the outlets did help.

 

Another thing I found affected the noise was the propeller. A prop with squarish ends increased the noise significantly, so try a prop which tapers to a point.

[Snorbitz]

I 'll check the tech specs on the orange/red high temp silicone i've used on my wrapping experiment and post it here tommorow if thats a help to anyone.

 

[BB]

My next idea is to use the Rescue Tape again. Then coat/cover that with resin and fibreglass sheet.

 

I have also been looking at fire proof silicone Here

 

 

BB

 

 

[Mike Bell]

One thing I don't get with this silicone solution is that I've seen it written that cooling of the muffler is quite important, yet silicone is a very good insulator so will encourage heat build up. I'm not sure if this heat retention has any actual harmful effects except maybe it hinders cooling of the engine itself but it just seems wrong when cooling of the engine bay is considered so important, especially for petrol.

Anyway, Pauls comments about canister versus pitts style mufflers has convinced me fo go the canister way, just need some pennies now.

[BB]

Posted by Mike Bell on 13/04/2011 19:08:27:

One thing I don't get with this silicone solution is that I've seen it written that cooling of the muffler is quite important, yet silicone is a very good insulator so will encourage heat build up. I'm not sure if this heat retention has any actual harmful effects except maybe it hinders cooling of the engine itself but it just seems wrong when cooling of the engine bay is considered so important, especially for petrol.

Anyway, Pauls comments about canister versus pitts style mufflers has convinced me fo go the canister way, just need some pennies now.

 

Agree with you there Mike. But as my engine is not cowled I don't have major concerns regarding overheating. I'll be testing it tomorrow weather permitting.

 

BB

[BB]

Tested & kak . louder than ever. It was quieter with just the silicone tape. Adding Fb/glass didn't work at all.

 

But I did find out a guy at my field can make me a new manifold & pipe.

 

BB

[Bucksboy]

My silicone was for sealing gas exhausts on domestic boilers, I thought it would withstand ghe heat ok. It seems to have expanded and broken the seal between the goo and the exhaust so that now the two are seperate. Because it was moulded all the way around the exhaust it still surrounds the exhaust. Ive done this twice with the same results so I think the sealant cannot stand the heat. What have others used successfully?

Bucks

[Engine Doctor]

I modified a silencer for my sons dl 50 as the stock item sounded like a machine canon !

The mod consisted of a ali tube with O/D approx 5/8 the I/D of the exhuast outlet. This tube has a reasonably thick wall thickness,approx2.5mm.The tube was insteted in the exhaust pipe and pushed up to touch the canister wall then marked and cut to lenght. About 1 1/2 inch from the end this tube was squashed almost flat and the other end was pinched to a point . The outlet on the muffler was drilled so as to line up with the squashed part of the tube and the canister was drilled to accept the pointed end of the tube . This tube was welded to the exhaust canister through the hole drilled in the canister wall and through the holes drilled in the outlet pipe. I used Techno weld for the welding . The good news is that it worked very well with a much quiter exhaust note ad no noticable power loss . The downside is that the chinese silencers are made of vevy thin alloy and they crack after about two hours use .Still worth a try, your silencer may have been made from better quality coke cans I have just this week done a similar mod to a pits silencer fitted to an OS90 for a club mate . It was flown on Sat and Worked really well .

As for wrapping your mufflers with silicone etc ,it will only stop any noise caused by the walls resonating and not tackle the cause .

Regards

[Mike Bell]

Thanks Doc. I've actually taken the plunge and just taken delivery of a mini pipe type canister from Weston UK. Once I have mounted it I'll measure up and have them make me a header. I expect the extra volume and the longer exit path should make a significant difference. I'll report back in a couple of weeks when I get it sorted.