[stegl]

We are instituting sound control at our new trial field and would like some suggestions on how to control the sound on all nitro and gas motors. Ie muffler types , props used and anything that might be of interest; other than going electric. This for the benifit of the guy's that are using fuel. If any clubs out there are using sound control; I would greatly appreciate your input. I thank all those, in advance ;that take the time with positive input. PM's are fine also.
Thanks
Len

PS::: I might add that what we are trying to get at is the mechanics of what people have tried to quieten nitro and gas motors ; type of mufflers , muffler add-on , what are quiet props and things like this .
Many thanks again for the input.

[guyl]

First get a sound meter. On Ebay you may find an old Radio Shack model.

Have model 1 meter above ground running at full throttle when doing measurements.
Downwind from the model do your sound tests. Three tests at 45degrees,90d.and
135degrees at a distance of 25 meters.
Gas/Nitro should be below 82db
Turbine should be below 90db
At a closer range most all engines are noisy. Large displacement engines
may surpass the decibel levels if appropriate measures are not taken.

3 blade props and canister mufflers do help a lot in reducing noise.
Limit your air time to a reasonable amount. Ex 10 minutes
Those who practice patterns/manoeuvre have the tendency to
be annoying by repeating the same exercise all the time. They
should alternate.
On weekends give your neighbours a rest by having flying hours after 9:00AM
MAAC has nothing on the model. These are from article in Modell Flieger.
Hope it may steer you in the right direction....

[VA6WGO]

Every club has their regulations. 25 mts away (about 75 feet) away is a lot!

As for your reference. Our club mesures noise levels that shouldn't exceed 99dba @ 9 feet away at 1 foot above the ground from all 4 angles.

Electrics are still included. Most of the noise comes from the actual prop regardles the what power plant the airplane is using.

Will

[aspeed]

The big giant Imac motors, the low freq. sound carries further. (like elephants) I lived about a mile from the field and could always hear the big ones when they climbed real high, but the .40 to .60 size ones I could seldom hear. I believe the exhaust pointing up keeps a lot of the noise away from the neighbours unless you fly inverted all the time. (I don't do this because my smaller motors flood and it is a hassle to drain.) Exhaust extensions help a bit too.

[Max]

Originally Posted by stegl

We are instituting sound control at our new trial field and would like some suggestions on how to control the sound on all nitro and gas motors. Ie muffler types , props used and anything that might be of interest; other than going electric. This for the benifit of the guy's that are using fuel. If any clubs out there are using sound control; I would greatly appreciate your input. I thank all those, in advance ;that take the time with positive input. PM's are fine also.
Thanks
Len

PS::: I might add that what we are trying to get at is the mechanics of what people have tried to quieten nitro and gas motors ; type of mufflers , muffler add-on , what are quiet props and things like this .
Many thanks again for the input.

One if the most effective methods we used (before electrics came about and brought on a quiet revolution) was a secondary muffler made from a pop can. Not the larger 12 oz can, but the 1/2 size cans. They are a little stiffer and dont resonate like the large pop cans often did.



We used a piece of silicon pipe to connect the exhaust of the engine's muffler to the can. The lenght of this piece of pipe varied depending on where the owner wanted to locate the secondary muffler. Some were short, others up to 8-12" from the engine. Then a short piece of pipe out the back of the can. Those with welding skills welded a piece of aluminum tube to either end of the can and clamped the silicon tune to that. The diameter of the tube had to be the same diameter as the exhaust from the original muffler or slightly larger to allow the engine to breathe properly. Those of us that didn't have the welding skills slit the hole into the pop can so it was just a tad smaller than the silicon tube (of which we used a larger diameter), when it was press fit into the hole on either end.

The whole assembly was clamped to the fuselage side, or where possible, kept inside the cowl of the larger engines.

My friend even modded one of his planes so that it was inside the fuselage, with only a short piece of tubing protruding from the bottom of the fuselage, Neat and clean!!!

It was remarkably quiet, and it had the added benefit of keeping your plane clean

The

[aceplant00]

I had thought there were a set of sound recommendations from MAAC. From above there is not a consistant rule.

[Max]

Originally Posted by aceplant00

I had thought there were a set of sound recommendations from MAAC. From above there is not a consistant rule.

There is:

Originally Posted by MAAC Canada

MAAC noise limits apply measured at 3 meters (10 feet) with full throttle. As of April 1999,
MAAC noise guide lines are:
 98 dba @ 3 meters on hard surface
 96 dba @ 3 meters on soft surface

http://www.maac.ca/docs/2006/doc_fli...g_course_e.pdf

There are other limiting factors. For example, at our club, we have to abide by town noise regulations for small engines, which is 90dB

[stegl]

I guess MAX is the only one that got my message. Will try it again. We want to know what the guys are doing, to cut down the noise on most IC motors ( nitro or Gas) as we have a few gas ones that are quit noisey as well as a couple of 2 cycles. The 4 strokers are usually ok . Any preference on prop makes; that cut the noise. Many thanks again .

It would be very simple to convert to electrics but I don't think the fuelers want to do that !

[Hughes500E]

Geno has put a lot of effort and funds into his aircraft in an effort to make them perform, quietly. I'm not sure that one could do any more than what Geno has done. Benchmarks can be obtained from his setups. If you are looking for quieter large scale gas engines, I don't think it's possible. Next to that, Ross has a great setup with the MTW75K canister for the 50-60cc market and I see Chuck has a can hanging from one or two of his fuses now.

It may be easier to implement a few "guidelines". No stock mufflers, no pitts style mufflers (inverted or wrap around) and gas engines must be propped for a maximum static rpm of 6500-6700.

The most abnoxious noise, 2 strokes running low pitch props. That said, ALL glow powered I/C engines must be setup for a maximum RPM of 9000.

Exhaust and prop selection are paramount. As there are so many variables, the above may prove the most satisfying.

[stegl]

Thanks , Steve;
This is what I am looking for . Specifics on HOW flyers are lowering the Db sound of their motors. I am getting a lot of how to measure but not enough of what flyers are using for muffleing systems in order to lower the noise ; like engine rpm , prop makes and sizes , like tuned pipes and so on . I am hoping the discussion turns that way.
Len