aspeed

The FAI combat motors had silicon rubber mufflers for a while too.  I think they would be ideal.  Tear off in a crash and not wreck the motor casting at the same time.  An o ring is needed anyway to get a seal.

GallopingGhostler

I have one of those on a .049 R/C Bee, predecessor of the .049 Dragonfly. It did a decent job of muffling without degrading the top end too much. After 100+ flights, the silicon exhaust ring cover is still intact and usable, although there are slightly charred spots where the exhaust ports faced the silicon.

Sounds like a neat concept. I've been wondering if anyone tried making fiberglass mufflers. I see them on dual sport, dirt and sport bikes. The glow exhaust isn't has hot as petrol exhaust. Thus it sounds like one could reasonably easily manufacture one.

aspeed

There is a carbon fibre one available from someone, so it is available. I forget the company name of course. I thought I might try to make one over a wax form.  I made a mold for the wax part on a 1/2A and a .15 size pipe, but am on a holiday (from hobbies?) and won't get back to it for a while.  I am not sure what resin to use either.

GallopingGhostler

Okay, gotcha aspeed. Yes, I can see why you are on hobby holiday. Down here in New Mexico we've been bouncing between 10 Deg C and -10 Deg C, depending on what day it is.

aspeed

Kissimmee Fla. real nice weather here, then going to Perry Georgia for the swap.  I want to maybe just use polyester resin for the bulge part of the pipe, and alum. tubing for the inlet and outlet tubes with maybe a knurl on to hold better.  I know the header part of the pipe gets super hot because the silicone joiners sometimes blow.

GallopingGhostler

Oh, okay, escaping the cold weather then, eh? You have valid points there, aspeed. I've been looking at 1/2" (13 mm) square aluminum tube available at the home improvement centers. I think I can take a 5" section and make a muffler for 2 of my OS Max10R/C cross scavenged baffle piston engines. Those engines can't accept a universal muffler because the carburetor butts up against the cylinder with nary a gap.

1QwkSport2.5r

I have another bad muffler to post about. From what I've read on here and elsewhere, there was a time when the muffler had to fit in the box and that didnt necessarily mean it was good for performance. This came with my Super Tigre S29 engine. It looks like it would work 'O.K' on a .12 or .15, but not a .29 sized engine. I never used this muffler on the engine as it came with a Macs tuned pipe.

It serves as a conversation piece, but nothing more in my opinion. I assume its performance losses would be worse than the Enya SS30 muffler I posted about earlier.

GallopingGhostler

Perhaps one of these days you'll have a use of that muffler for an engine that uses the same bolt pattern, 1QwkSport2.5r.

I finally bought an eary Enya .09 TV with Tatone 09-19 Peace Pipe muffler. I would definitely not use this muffler on a .19, it has a small chamber and a small exit outlet. It's got roughly a 3/16th in (4.7 mm) exit hole with an inner ridge ring of 1/8th in (3.2 mm) that I am going to drill out.

Now I understand why the Tatone 29-40 Peace Pipe is a better muffler for the .19 engines. It is larger chambered and both the Enya .19-VI and Testors McCoy .19 Red Head ran without overheating.

GallopingGhostler

Here's one of the reasons why the Tatone Peace Pipe was a poor muffler particularly toward the upper end of its rated range. I have the larger Peace Pipe for .29 to .40 motors installed on my Enya .19-VI TV engine. It has a 1/4 inch (6.4 mm) hole and an ample expansion chamber. The Enya does not overheat when using this muffler.

Next to it I have the Peace Pipe for .09 to .19 motors. It had a constriction ring just inside the muffler of about 1/8 inch (3.2 mm) diameter. I noticed that one of the previous owners drilled out the carburetor's outer idle air bleed orifice in the early model left exhaust Enya .09 TV engine that used it. No wonder, with the additional back pressure, he probably couldn't get it to idle properly being too rich. That exhaust exit opening is what my Thunder Tiger GP-07 engine has.

A 1/4 inch hole has 0.049 square inches area; a 3/16 is 0.028 s.i.; a 1/8 is 0.012 s.i. Thus you see that each smaller one is about one half the area of of the larger one. This is what exhaust is squeezing through.

I took a 3/16 inch (4.8 mm) drill bit, and drilled out this constriction ring that was about a 1/4 inch inside the muffler's tail pipe end. I'm planning to use this engine on a 29 inch (737 mm) wingspan Pilot Cessna 177 CL sport model. Sometime next week if all goes well, I will test it on my .09 Enya with unmodified carburetor, to see how it performs.

1QwkSport2.5r

Unless I find someone that wants to buy the SuperTigre S29 muffler from me, it's staying in the box. It is too small for anything I'm going to be running, not to mention the exhaust outlet is about 3/32" in diameter if that even. I've taken a liking to Jett's Jettstream mufflers and will likely replace most of my stock mufflers with Jett mufflers. I tried my .46 Jett muffler on my ST G51 and it seemed a little choked down on it versus using a stock ST 'quiet muffler'. Otherwise the other engines I have seem to like them, even my Enya SS30 as I mentioned previously.

I tried a mousse can on the S29 last summer but the can wasn't large enough. I have a .30 size Jettstream now (came with a BSE .35) that I may try on the S29. I like experimenting, not specifically for performance or squeezing every last rpm from an engine but more just to run some engines. Some mufflers can make an engine run poorly or give surprising gains of power.

The only downside to the Jett mufflers is the fact they are quite loud.

GallopingGhostler

Will one of those aftermarket (Dubro, Great Planes, etc.) silicone exhaust redirector tail pipes help to quiet them down?

1QwkSport2.5r

One can be used, but it doesn't do much in the way of quieting it down, plus they don't have much of an exhaust stinger so keeping the deflector on the muffler can be a pain. Besides that, I noticed a 300-400rpm hit when using one on my TT .46 pro. It's a performance pipe and a side effect is more noise because of its tuned rpm band. The red pipes are tuned for 15-18k or so, any less and the engine isn't getting fully 'on the pipe' so you get pipe noise and a lot of prop noise too.

The noise doesn't bother me at all, but it might bug my neighbors although they haven't said anything anytime I've ran an engine in the yard. I have a spot a couple miles away from my house that I use to break engines in. This way I can let 'er buck and not worry about bothering anyone no matter what pipe I'm using (or no muffler at all).

earlwb

Well the Dubro exhaust deflectors will tend to reduce the exhaust noise slightly. The silicon tip sort of expands and contracts rapidly with the power pulses traveling down the muffler. But it isn't much though. But if you ran the engine with and without the deflector on it, you would notice a slight difference in the tone of the noise.

aspeed

There is an APP for a decibal meter if you have the cellphone.  Naturally I don't have one.  It  could be useful for checking stuff like the rubber extension.

earlwb

I have a couple of those DB meter apps on my iPhone and they seem to work pretty good. I compared the readings from a regular DB meter to the apps and they were displaying results that looked pretty much the same. But if the engine is really loud, I am not so sure as the iPhone may limit the noise level after it exceeds a certain level. But that is like exceeding something around 100DB or so.

GallopingGhostler

Brother earlwb, isn't the AMA criteria to check noise at least 10 feet away from the engine? And it is what, 89 DB? I think that is what the US DOT standard is for motorcycles.

1QwkSport2.5r

I'll have to get some of those apps. Earl: are the ones you have of the freebie variety?

earlwb

Yeah they are freebies. They don't work too bad either. The AMA suggests that 96db and 98 db are the max noise levels. With 96 dB measured from a 20-foot distance over soft field (sod) and 98 dB is measured from a 20-foot distance over hard surface (pavement/concrete). Reference <cite>www.modelaircraft.org/files/927.pdf</cite>

I made a baffle insert for my SV-17cc engine and it it reduced the noise by about two to three DB. The can muffler was essentially a hollow can with a large diameter outlet tube. The baffle dropped the RPMs by about 200 rpms or so.

Here is are some pics of one of the DB meter apps measuring the noise level of my SV-17cc engine at about three feet away from it for example. Without the baffle and with the baffle inserted.

1QwkSport2.5r

I think I downloaded the same app, Earl. I'll test it out on an engine when it's warm enough to do so. We are hitting another cold snap.... -25*F windchill and +7*F air temp tomorrow.

earlwb

Yeah I am sorta bummed, I wanted to go flying today, the weather is great, except for the winds. 16 to 31 mph.
Maybe I'll test run something to get it out of my system.

GallopingGhostler

Yeah, understand the feeling, earlwb. Here is Clovis the winds have whipped up for now and its chilly outside. As the day warms up I may break in my TT GP-07 in the back yard.

earlwb

Yeah it even got more windy now.
Another DB Meter that works pretty good is db Meter Pro. As well as ProDBSPL too.

Another really cool app is RCSpeedo, it uses Doppler shift technology to measure airspeed as a plane does a flyby.
SpeedGun is another Doppler Shift speed indicator too.
 

aspeed

I may have to get a cellphone sometime.The weather is fine here in Florida, maybe a little windy.  I have no planes.  Just a Supertiger .75 monster  motor I picked up at a swap meet in Kalamazoo on the way down here.