Ultimate

I am about to install a zg62 into a Glens cap232.

My flying field is noise sensitive, so I need to get the noise level down to 82db or something that sounds like 82db. I asked Glen of Glens models, who suggested the new standard type of silencer for the zg62 with the two pipes that stick out the bottom of the cowl.

Is anyone using this silencer, and how effective is it ? What alternatives are there ? I know JE could build me a custom job that would fit in the cowl but its over £100, there must ba a cheaper alternative.

Anyone built their own silencer ? The instructions show details of a silencer made from 2 camping gaz canisters.....


Chris

mr_apollo

Hi Chris i was ripping my prop on a glens cap simalar setup the thing to do if you have nois problem is get a three bladed prop, i would suggest something like a 20 x 10 mejzlik carbon you will be supprised at how quiet it will be [8D]

Antique

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Check out the Toni Clark website...

BigBirdFlyer

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Bisson sells a pitts muffler for it. I just use a B & B specialties muffler. I am not sure what the DB is but it seems quite.

http://www.bennettbuilt.com/

http://www.bissonmufflers.com/en/index.html

Daryl Martel

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How's this? Very effective - 96 Db from the sides and rear, 98 Db from the front (@ standard distance). Davis Diesel muffler and flex pipe - APC 3 blade component prop, 20 X 10 I think if I remember correctly. Those Pefa Can Mufflers look pretty effective too. I think a header wouldn't rob as much power as a flex pipe - a point discussed here occasionally.

tkg

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82db at what distance?? You will most likely need a muffler and an after muffler to get under 90db @ 3m.
Check out the Just Engines site.

Daryl Martel

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Ultimate - I don't mean to rain on your parade, but I think if you really look into this, your goal of 82 Db will be very difficult to achieve. Frankly, in the time I've been cruising the web, I can't recall anyone getting a big gas engine that quiet, heck, 96 Db is quite an achievement and 93 very noteworthy - 82 Db would be a remarkable achievement! There is (if I recall correctly) a doubling/halving of the noise level for every 3 Db increase/decrease. Bigger engines make more noise - more cylinder volume (bigger bang) swinging a bigger prop makes it that much more difficult to quieten things down. Airframe noise is something that can't be lightly dismissed either, especially for a large single cylinder - the "buzz" really creates a mean resonance on some planes that really radiates sound. I just got transferred to a new city and left a club where noise was a big concern. I had lots of experience playing with muffler and props (as well as soft mounting engines/airframe components) in an effort to quieten things down. Where I'm at now, it's not much of a concern and I can reduce my efforts towards keeping things quiet. I can tell you however it's not easy getting things quiet! You will usually pay a performance penalty - the trick is obviously in effective muffling, but also in keeping prop tip speeds down, the lower the better - the closer you run the prop tip speed to Mach/supersonic, the louder things get! To reduce prop tip speeds, normally you run less diameter and more pitch to load the engine down and reduce RPM. A 3 blade prop can help here too. I run APCs, but there are a few other manufacturers with pretty efficient propellor designs. Unfortunately the negatives involved understandably turn off a lot of people - running a lot of pitch makes a plane more difficult to land. When you're running a 12 or 16" pitch prop it tends to really keep pulling pretty good, even at idle! The weight of a larger exhaust system some people find too much of a performance penalty. Some people can't stand hanging big cans outside the airframe - if you're a real scale buff I can understand that too. With all of that said, the fact that a lot of the bigger TOC style planes have pretty effective fully enclosed exhaust systems proves in my mind you can have it all - it just has to be very intelligently designed and manufactured. Sorry for the length of this post - maybe some other people can come up with some factual numbers regarding actual measured Db readings recorded for big gas engines?

Ultimate

thanks for the replies

the 82db is a general rule, but as long as I can get the moise down so it sounds sensible then it will be OK. I take your point Daryl about the db measurements. With the bigger engines it should be the percieved noise thats taken into consideration, rather than a db measurement.

I can buy an off the shelf solution but its expensive. I have access to as much aluminium as I want and I have been shown an "easy" way of welding it (Technoweld), so I think I have an experiment with making my own silencer first. I'll buy a ready made manifold and flexible pipe and build the expansion box myself.


Any one know the basics of silencer design, baffling etc etc to optimise power and reduce noise ?

Chris