Quiet Engine techniques?
 

Hi folks, I am building a Lazy Bee for flying in a residential park close to my house. I am planning on using an OS.15 but need it to be super quiet. Any tips or tricks to really quiet this little engine down? Loss of power does not really concern me as long as it still runs good. I plan to use the extended exhaust pipe and maybe a cowl? Or will an intake filter help? Maybe a different engine would be better?

Thanks,
Bill Cripe

Quiet Engine techniques?
 

Martin Hepperle has some downloadable software for designing a silencer:
http://www.mh-aerotools.de/airfoils/software.htm
I don't think it'll rob too much power from it. Check it out.

Quiet Engine techniques?
 

The europeans have been devling into making quiet engines for the last decade...

Basically, there are four rules to making an engine quiet..

1. Prop noise... try using a scimitar prop blade (i.e. apc) and swing a little more diameter than you would normally, this keeps engine revs down and stops the noise associated with supersonic tip speeds.

2. airframe vibration. Simple fix here, soft mount the engine, either buy building a soft beam mount system or buying one of the proprietary items from your hobby store..

3. Exhaust noise, you might want to try one of the proprietary after mufflers, or something like that, or failing that, facing an exhaust deflector straight up will kill a fair whack of in flight noise..

4. carb noise. This is one that is forgotten time and time again... The europeans actually started to make carb ducts which sucked air over the top of the head, not good for performance but greatly reduced the db's.. intake filters and the like will make some difference... but you really need to make sure that the carb is not out in the open or the induction noise will be the killer..

Enjoy :D

Quiet Engine techniques?
 

Are you stuck on Glow power? Maybe an electric would better suit your needs?

Mike

Exhaust Deflectors
 

Those silicone exhaust deflectors made by Dubro and Hobbico will Knock the noise down a db or two.

Happy Fly'n....

Quiet Engine techniques?
 

Are you planning to get the O.S. .15 LA? As far as I can tell from Towers, it uses the #871 muffler with a baffle. My O.S. .15 FP uses this same muffler, and is the quietest engine I have ever heard. It's definitely quieter than a brushless electric.

I've owned quite a few engines over the years, and the .15 FP is my favorite.

Robb

Quiet Engine techniques?
 

I dont really want to go electric because of the added complexity and most important weight. I am really working hard to get this little bugger under 2 pounds. More like 1.4 pounds is my target. I dont mind just taking a fuel bulb and a glow plugger and hand starting it. Maybe a piece of neoprene behind the mount will help. How do I engineer a carb silencer?

thanks,
BC

Quiet Engine techniques?
 

Oh yea, I just bought an OS .15FP NIB

Mousse Can After Mufflers
 

I've made a whack of mousse can after mufflers which really quieten things down. I see on E-Bay there's always these silicone tuned pipe looking after mufflers for sale. They appear to be available in 3 different sizes, the smallest appearing to be ideal for small .15 to .25 size engines... from their looks I'd say they'd do a surprisingly good job of quieting things down. If you try 'em out report back how they work. I know the mousse can idea works very well - I've even built mufflers using smaller aluminum shaving cans, obviously intended for travellers. Check out the (hopefully) attached image to see how I do it... An aluminum plug is inserted half way dow the tube which forces the exhaust gases to travel through the holes in the centre tube. The gases expand in the can of course and the tube acts as baffling. The tube is epoxied to the can using JB Weld. If you use aluminum tubing and cans, the end result can be quite light, very quiet and have minimal impact on performance. I've used them as after mufflers (attached to the stock muffler) and as the primary muffler on a header. You can find aluminum cans like this in a variety of sizes suitable for a wide range of engines. I dare say I think they work better than anything you can buy.

Quiet Engine techniques?
 

Of course with some funky engineering you can make your store bought muffler a Sh*tload quieter... depends on the design of the standard muffler...

For some quiet tips that are really too hard to explain over a BB, just email me dude.

I'll be happy to help.

Might even dig up some photos for the rest of you...:)

Quiet Engine techniques?
 

Any tips would be great. What would be a good way to soft mount this engine? I was thinking about getting the backplate mount from OS and maybe sandwiching a piece of neoprene behind it. Any disadvantage to the backplate mount? Might even save a little weight. Also, I wonder if one of those car airfilters would help make if quieter?

Thanks,
BC

Quiet Engine techniques?
 

I personally prefer earplugs to quiet and engine down. Insert one in each ear and offending noise is greatly reduced.


Sorry, I couldn't help myself. Personally I don't understand how people can complain about the noise of an RC glow engine. My neighbor's lawnmowers, weedwacker, and kids are just as loud.

Quiet Engine techniques?
 

If you get that little bugger under 2lbs its going to be way overpowered with the .15.

I've got a Ripmax Zephyr at 2lb 5oz and that will climb out of earshot within 10 seconds on a OS 15LA.

You might have problems getting it back down too. Mine won't land with the engine running! :D

Last time I flew It took me about 5 mins to realise it was dead stick!

Quiet Engine techniques?
 

I dont understand it either but you know people will complain. I had one with a .15 and it was pretty good. I can give up some power for sure. A .15 is slightly lighter than a .10. Basically same engine just bored out to .15. OS FP.

Quiet Engine techniques?
 

"My neighbor's lawnmowers, weedwacker, and kids are just as loud."

i realy have to 2nd that, i live in a town where no one hardly does there own lawn, once every other week for about 5 hours, these guys go house to house giving a ugly cut, i hear 2 5HP engines for 5 hours, and at times 25 feet from me, ill admit it is loud and anoying, but a plane in the air 100 feet overhead wouldnt cause nearly that much noise.
allthough i would like a more quieter plane, i love the noise of nitro.

Quiet Engine techniques?
 

Have you considered going the diesel route? Quieter and if you route the exhaust to rear of the plane with plastic or aluminum tubing, it is quieter still and your plane will be much cleaner. Your .15 won't be much louder than an electric.

You won't lose any power - in fact you will gain with the ability to swing much larger props (even a 10in. prop is not unreasonable on .15 size diesel).

Quiet Engine techniques?
 

I dont know very much about diesels except that I have heard that there is alot more fiddling and finicky than a glow. I am just looking for a simple, flip it to get started setup. Is that possible with a diesel?

TIA
BC

Quiet Engine techniques?
 

Is it possible with a diesel? Well you know how everyone loves to hold their brand new engine in their hand, put a little fuel in it and flick it over just to admire it? Try that with a diesel and you're likely to have a handfull of screaming monster :)

However, Murphy's Law states that when you put it on a test stand you won't be able to start it.........

Quiet Engine techniques?
 

brarp brarp brarp brarp braarp braaap braaaaap burp burp
BRAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.....


Ahhh taipans:)

Quiet Engine techniques?
 

I'm in the process of breaking in a PAW .19BR diesel for my Lazybee. I've never owed a nitro or diesel before.

Coming from electric the noise issue was very important for me. After a rough first attempt, getting it started has been fairly easy and the adjustments are far from complex.

I just hope that the .19 isn't way too much power for it!

Here's some great info on diesels http://www.carlsonengineimports.com/...eselinfo.shtml

Quiet Engine techniques?
 

I'm with you there. The best diesel I ever owned was a Taipan 2.5 with twin ball races and a rear drum induction. You only had to look hard at it and it'd start :)

Quiet Engine techniques?
 

In the mid 60's I had an ED 2.5 Redhead diesel that was a nice running engine but was not as good as the Oliver Tigres of that era. Is the ED brand still available.

Quiet Engine techniques?
 

The ED's have gone now but I've still got a crankcase for one of them somewhere. There are replicas available though. The Ollie Tiger was magnificent and so was the MVVS 2.5 although the only one I have in their class is an ETA Elite...still haven't run it though (it's second hand).

Quiet Engine techniques?
 

Downunder,
Where are the replicas available from, and do they make any for the O/Tigres .

Re: Mousse Can After Mufflers
 

Before reading any of this....

I built (if you can call it that :) ) a mouse can after muffler using, coincidentally, the exact same Mouse can pictured in post 9.
The can cost a wooping $1.33 (CDN no less). I used some cheap, hardware store, copper tubing. Total cost - less than $2.

I used Martin Hepplers software as well. My mousse can is setup as a simple exansion chamber, but I built a couple of others (other types of can's - but the mousse is nicest) setup as high frequency band stop filters to test as well.
The expansion chamber has very low attenuation at multiples of it's own resonant frequence. I tried to set it up so that these did not align with multiples of the engine's firing rate at max throttle.

I have a OS46FX with a Jett Stream muffler that generated about 100 dB at 9 feet, 90 dB at 20 ft. Not crazy, but a bit too loud for mixed company.

I'll get the mousse muffled dB measurements and let you know how it worked.

My long term solution is a Mac's quiet pipe. As a quick work around the mouse can is great. It may find a permanent home on another plane.

(It was quieter, when I tried it it, but it certainly didn't seem as quiet as I expected based on the reduction predicted by the software. Took away about 500 rpm.)