Greg McNair

My Feedback: (3)

Folks, I have a question. I am building a 1/3 scale project which is utilizing a 60cc gasoline 2 stroke chainsaw engine (made by Partner). I have seen/heard a completed and flying example of this machine, and it is far too loud for my satisfaction. My question is simple. How can I silence this beast? For what it's worth, I have an abundance of room in which to fit this silencer, but I have to keep the system light.

I considered utilizing a silencer system from a moped/large displacement scooter, but I don't know if that will be too restrictive. I will likely also build a large chamber for the air intake to help silence that somewhat. Any advice or suggestions you may have will be most appreciated. Surely there must be an effort among engine manufacturers to silence 2-stroke engines in this day and age of lawsuit-happy individuals who want their free speech to be heard over their neighbor's backpack blower?

akflyer

My Feedback: (7)

Put it on a K&S or PEFA canister and you will be amazed at how quiet it is. A moped exhaust would weight 10#.

sfaust

My Feedback: (11)

The difference between my 40% Extra with a DA-150, stock mufflers, and 2 blade prop, and my 40% Extra with DA-150, PEFA canisters, and a two or three blade prop is significant. People notice both airplanes. The first they mention how noisy it is, the second, they mention how quite it is! I've noticed that the engine/muffler noise was the most significant factor on the second airplane, and with the canisters it is significantly quieter. The three blade prop only made a marginal difference, but added to the quite as well.

My suggestion would be PEFA or K&S canisters if they make then in the correct size for your engine.

JohnVH

My Feedback: (38)

Stephen, I put a post in the gas engine forum on the can setup.

WHat are you running for sizes and any pics? Im thinking KS Cans on my 150

Thanks

Greg McNair

My Feedback: (3)

Ok, now I feel silly. All this time and I didn't realize there is a gas engine forum! Had I known this, I would have posted there. Moderator, would you mind moving this post over there? I'm sure there's others that can benefit from the discussion, that otherwise might not see the post in the giant scale section.

Now, about these cannisters, can you guys direct me to a retailer who sells these? Thanks for the info so far!

JohnVH

My Feedback: (38)

Well, not alot of help on this topic in the gas forum, lets try it here for a bit first I want to know too!

sfaust

My Feedback: (11)

Here is a link to a [link=http://www.giantscalerc.com/canisters/index.html]web page I created [/link] that has many examples of canister installations. These were done by a few different pilots, as well as some by myself. Hope they help. Also the photos posted below are from my 40% Lexus Extra 330s

sfaust

My Feedback: (11)

a few more

rmh

Greg- on a good 60 cc- the JMB 70 mmx300mm muffler will work very well- all up weight with a very short ( say 6") header and coupler will be about a lb.
These are the quietest of any of the present cans on the market - we have compared some KS / JMB/ and me Pefas.
These are not really tuned devices -just quiet mufflers that flow well.

Greg McNair

My Feedback: (3)

Thanks for the info so far. I've watched the video that MVVS posted, and have seen some others, and that is still a bit louder than I am wanting. I have nearly 2 cubic feet of space behind the CG, and 3 cubic feet ahead of it, so space/volume won't be an issue. Weight is the only issue. This model's target weight is ~45 lbs, but I can afford to go up as high as 50.

Anyone know how to get in touch with the manufacturers of these JMB and PEFA cannisters? I'd like to bend the ear of an engineer for a bit and see if we could come up with something a bit quieter.

rmh

OK- the JMB is from RCShowcase -- and the engineers who design em are in Czech Republic -but here is a bit of insight on muffling:
You need flow reversal/dispersion and expansion -- all or some of each.
Make your life easy.
Get two of these mufflers and simply duct one to the other -then to atmosphere.
OR---
The mufflers on two stroke Mopeds are closer to the dead silent type you are may be asking about.
The engine size is comparable.
The mufflers should work and are not all that heavy .
Take a look at Honda Mopeds - probably the best of the lot .
Are you working a secret, low noise loitering vehicle - for use in "spy" work?

will

You might give this link a try. You could experiment a bit.

http://www.rcmodelstuff.com/aba/neat.html

Greg McNair

My Feedback: (3)

Dick, i'm thinking what you're thinking. The honda moped muffler was my first thought at the very onset. In my youth, I had a Honda Express that was extremely quiet, and I recall taking the muffler off more than once (for what reason I can't recall), and although it was steel, it wasn't very heavy. However, it was much heavier than the options outlined in the cannisters mentioned above. That soup can homologation is quite interesting to be sure Will!

My next question was going to be if someone had a cutaway of some of these quieter cans (PEFA, JMB) to learn more about what makes them quiet. Dick, your suggestion of reversal/dispersion and expansion is spot-on. I don't understand mufflers much, but I do know that an engine must breathe, and the more it is restricted, the less power it puts out. If I could find a way to allow the gasses to expand into a series of baffled chambers, and yet maintain a good flow, then I might be able to achieve my goal? My project isn't anything for government or spy use. It's just a large aircraft that I don't want to sound like a flying chainsaw. I would divulge more, but I haven't publicly announced the details in any forum yet. I dropped an email to Gianelli, makers of fine Italian motorcycle exhaust systems, and I received a very helpful email on this topic. They included a link to "the birth of a muffler", shown here: http://www.giannelli.com/img_pdf/his...xhaust_eng.pdf

When I watch these acro plane videos and hear the engines, it's difficult for me to separate the engine and prop sounds.

rmh

Here is a pic of one I designed -which works very well and basically is a combo of the current "tuned can/ muffler setups on the market.
on this one -if the primary pipe(header ) is shortened IN the can so that there is no reflector-- the waves travel more freely.
The reflector, setup as shown makes for a tuning length within reason.
The funny baffle in the lower drawing, is a path thru holes and an annular path around th inlet pipe.
By controlling the size of the final outlet pipe (to atmosphere), the internal pressure in the can will greatly affect the tuning.
The internal pressures of the can are important but none of the so called tuning textbooks refer to em -
I really believe that most of the so called theory is bullscat and the results are simply observations from cut and try -
There are simply too many variables to quantify an exact system short of running the MF and seeing what really happens.

Homebrewer

My Feedback: (8)

I find that foam earplugs are the most cost effective way to reduce engine noise without ANY degradation of engine power.

rmh

NO -most cost effective is to simply stay home -