Bad Mufflers
01-27-2013, 05:17 AM
#1
Thread Starter
Bad Mufflers
Talking about bad engines in another thread got me thinking, how about bad mufflers?
Here is one. I installed a Tatone 09-19 Calumet muffler on an Enya .19-VI TV. The engine ran unreasonably hot. I removed all the internal baffles, it still was hot. Then I added a copper cap to the muffler's exhaust outlet and converted it to a tongue muffler.
Feedback I got on the Ringmaster Brotherhood forum was the muffler was too restrictive. It might work for an .09 or .10, but not a .19. My running it proved them correct.
So I turned a sow's ear into a silk purse. Now it's a tongue muffler. So, what are your bad experiences? Any engines got ruined as a result?
Here is one. I installed a Tatone 09-19 Calumet muffler on an Enya .19-VI TV. The engine ran unreasonably hot. I removed all the internal baffles, it still was hot. Then I added a copper cap to the muffler's exhaust outlet and converted it to a tongue muffler.
Feedback I got on the Ringmaster Brotherhood forum was the muffler was too restrictive. It might work for an .09 or .10, but not a .19. My running it proved them correct.
So I turned a sow's ear into a silk purse. Now it's a tongue muffler. So, what are your bad experiences? Any engines got ruined as a result?
01-27-2013, 05:47 AM
#3
RE: Bad Mufflers
Well one problem for manufacturers came when they had to include a muffler with the engine in the same box. The the rule was that the muffler had to fit in the box. Maybe a little styling thrown in after they got it to fit in the box too. Plus it had to be cheap or low cost as well. There was little to no regard as to whether the muffler reduced power or not. I have seen stock OEM mufflers restrict a engine by as much as 4,000 RPMs before. Plus the mufflers didn't reduce noise all that much either. So basically most all of the stock OEM mufflers that come with a engine reduce its power output. Some engine manufacturers sold or sell the engines without a muffler of course, and in that case you had to buy one separate. Thus you could get a better muffler or exhaust system for it then.
A "good" muffler is more expensive and few modellers would want to buy them. But to be a "good" muffler it had to not reduce or restrict the engines' power output or RPMs and even improve its power or RPMs as well. That is where you see the "tuned" mufflers and "tuned" pipes of course, being sold as options or aftermarket items. of course they cost more too. Unfortunately the "good" mufflers do not fit in the box with the engine of course, and the manufacturers are loath to make a huge box to sell the engines in.
I think the worst mufflers were the little cast Tatone mufflers. Unfortunately, sometimes that was all you could find at the time that would fit the engine you had. That was the era where no one included a muffler with the engine. Plus hobby shops seldom stocked the OEM mufflers as they were too expensive. The hobby shops tended to stock the cheaper mufflers as modellers tended to not want to pay the high prices for the stock mufflers.
Of course the tongue mufflers were a close second to those little cast mufflers. I remember using them off and on too. The control line people still seem to love using them. But control line uses the engines differently, except for racing and combat, they don't need lots of RPMs when flying control line. Usually it was easy to find a tongue muffler to fit your engine and they cost a quarter of what the OEM muffler cost and weighed less.
I sort of liked the old Dubro exhaust stacks with either the adjustable spring inside or the layers of baffles you could add or remove on the units. The spring was compressed to increase back pressure and reduce noise on the one type of muffler. The other muffler used a bunch of metal baffle plates that you either add more baffles or reduce the number of baffles to control the noise or back pressure. Both muffler types were quite loud but they didn't work all that bad and didn't add much more weight to the engine either. They did reduce power output though, but being more of a exhaust stack they tended to get the exhaust residue out of the engine compartment. But alas we can't use them much anymore as they are too loud for most of our flying fields today.
Some of the tongue muffler examples shown here:
A "good" muffler is more expensive and few modellers would want to buy them. But to be a "good" muffler it had to not reduce or restrict the engines' power output or RPMs and even improve its power or RPMs as well. That is where you see the "tuned" mufflers and "tuned" pipes of course, being sold as options or aftermarket items. of course they cost more too. Unfortunately the "good" mufflers do not fit in the box with the engine of course, and the manufacturers are loath to make a huge box to sell the engines in.
I think the worst mufflers were the little cast Tatone mufflers. Unfortunately, sometimes that was all you could find at the time that would fit the engine you had. That was the era where no one included a muffler with the engine. Plus hobby shops seldom stocked the OEM mufflers as they were too expensive. The hobby shops tended to stock the cheaper mufflers as modellers tended to not want to pay the high prices for the stock mufflers.
Of course the tongue mufflers were a close second to those little cast mufflers. I remember using them off and on too. The control line people still seem to love using them. But control line uses the engines differently, except for racing and combat, they don't need lots of RPMs when flying control line. Usually it was easy to find a tongue muffler to fit your engine and they cost a quarter of what the OEM muffler cost and weighed less.
I sort of liked the old Dubro exhaust stacks with either the adjustable spring inside or the layers of baffles you could add or remove on the units. The spring was compressed to increase back pressure and reduce noise on the one type of muffler. The other muffler used a bunch of metal baffle plates that you either add more baffles or reduce the number of baffles to control the noise or back pressure. Both muffler types were quite loud but they didn't work all that bad and didn't add much more weight to the engine either. They did reduce power output though, but being more of a exhaust stack they tended to get the exhaust residue out of the engine compartment. But alas we can't use them much anymore as they are too loud for most of our flying fields today.
Some of the tongue muffler examples shown here:
01-27-2013, 07:19 AM
#4
RE: Bad Mufflers
OH yeah, here is pics of a couple of the Dubro Muffle'Aire tongue mufflers too. You basically added or removed baffle plates as needed. it used thin washers in between each plate. A end plate that didn't have holes in it was used to cap off the stack. The mufflers weren't all that bad, but some people hated them though. So it depends on the user. But you defintely had a perfoermance drop using them. The mufflers were used with clamps around the engine cylinder in this time period as the engines were normally not designed for bolt on mufflers yet. A couple of alignment tabs were filed to fit the exhaust outlet on the engine you mounted them on.
01-27-2013, 01:09 PM
#5
Thread Starter
RE: Bad Mufflers
ORIGINAL: earlwb Well one problem for manufacturers came when they had to include a muffler with the engine in the same box. The the rule was that the muffler had to fit in the box. Maybe a little styling thrown in after they got it to fit in the box too. Plus it had to be cheap or low cost as well. There was little to no regard as to whether the muffler reduced power or not. I have seen stock OEM mufflers restrict a engine by as much as 4,000 RPMs before. Plus the mufflers didn't reduce noise all that much either. So basically most all of the stock OEM mufflers that come with a engine reduce its power output. Some engine manufacturers sold or sell the engines without a muffler of course, and in that case you had to buy one separate. Thus you could get a better muffler or exhaust system for it then.
A ''good'' muffler is more expensive and few modellers would want to buy them. But to be a ''good'' muffler it had to not reduce or restrict the engines' power output or RPMs and even improve its power or RPMs as well. That is where you see the ''tuned'' mufflers and ''tuned'' pipes of course, being sold as options or aftermarket items. of course they cost more too. Unfortunately the ''good'' mufflers do not fit in the box with the engine of course, and the manufacturers are loath to make a huge box to sell the engines in.
I think the worst mufflers were the little cast Tatone mufflers. Unfortunately, sometimes that was all you could find at the time that would fit the engine you had. That was the era where no one included a muffler with the engine. Plus hobby shops seldom stocked the OEM mufflers as they were too expensive. The hobby shops tended to stock the cheaper mufflers as modellers tended to not want to pay the high prices for the stock mufflers.
Of course the tongue mufflers were a close second to those little cast mufflers. I remember using them off and on too. The control line people still seem to love using them. But control line uses the engines differently, except for racing and combat, they don't need lots of RPMs when flying control line. Usually it was easy to find a tongue muffler to fit your engine and they cost a quarter of what the OEM muffler cost and weighed less.
I sort of liked the old Dubro exhaust stacks with either the adjustable spring inside or the layers of baffles you could add or remove on the units. The spring was compressed to increase back pressure and reduce noise on the one type of muffler. The other muffler used a bunch of metal baffle plates that you either add more baffles or reduce the number of baffles to control the noise or back pressure. Both muffler types were quite loud but they didn't work all that bad and didn't add much more weight to the engine either. They did reduce power output though, but being more of a exhaust stack they tended to get the exhaust residue out of the engine compartment. But alas we can't use them much anymore as they are too loud for most of our flying fields today. Some of the tongue muffler examples shown here:
At least now I know there is still a following with the Dubro's as long as one does proper preventative maintenance by periodically cleaning the springs and plates, and provided that noise is not a banning criteria.
01-27-2013, 04:49 PM
#6
RE: Bad Mufflers
Yeah the tongue mufflers are still quite popular for control line flying due to the 4-2-4 cycle break the CL people run the engines at, plus they run the engines at lower RPMs too.
There were "good" mufflers one could get, but they cost more though. That tended to prevent people from using them. But usually once a person saw how good the good mufflers worked, then they were sold on them, and they would buy them then. But the companies quit making and selling the good mufflers as people just weren't buying enough of them to keep on selling them.
Performance Specialties used to sell the Ultra Thrust tuned mufflers, which were tuned more for a sport range of RPMs. Nelson made the mufflers at the time. They used to make them for a wide range of engines too.
Fox Manufactuing made the Fox Quiet Mufflers, which were also tuned for sport RPMs and the mufflers were much more quiet as well. The mufflers worked really well and the engine performed well with the mufflers. Fox also made a series of sport tuned mufflers that looked like shorty, art deco, BuckRodgers, kind of thing.Those tuned mufflers really offered good performance too. Fox also used to make a special Fox Quickie 500 racing tuned muffler for their Fox .40Quickie engine too.
K&B made a tuned high performance muffler for their K&B .60 engines. It was last seen mated with the K&B .61 Twister engines.
Jett Engineering still makes a sport and racing tuned mufflers that fits some engines too. Evolution sells a version for the .45 through .60 engines they sell.
Davis DieselDevelopment used to sell the SoundMaster mufflers. These mufflers work really well and have little to no performance loss with a engine and they quiet the engine down quite a bit too. DDD stated that the mufflers would limit the engine noise to 88 DB too.
Tower Hobbies used to sell their Tower engines with a really nice semi-tuned muffler that didn't restrict the engine much, if any too.
MVVS still sells some mufflers that offer good performance.These mufflers tend to look more like Mousse Can mufflers. But they work good though.
A company inAustralia used to make a unusual long tube muffler that had a threaded rod in the center of it with a baffle that you moved back and forth to tune the muffler. it actually worked pretty good, but like other "good" mufflers it wasn't popular.
Note all of the good mufflers have a common theme in being long with a large inside cavity. The size tended to be a detractor as well as the cost of course.
In the pics below, there are some examples of the "Good" mufflers:
1 - Fox Quiet Muffler and a Performance Specialties Ultra Thrust Muffler
2 - Fox Tuned Pipe style muffler
3 - Fox .40 Q500 tuned muffler
4 - The Evolution/Jett tuned muffler
5 - K&B Twister .61 tuned muffler
6 - Davis Diesel Development SoundMaster muffler
7 - Tower Hobbies muffler
There were "good" mufflers one could get, but they cost more though. That tended to prevent people from using them. But usually once a person saw how good the good mufflers worked, then they were sold on them, and they would buy them then. But the companies quit making and selling the good mufflers as people just weren't buying enough of them to keep on selling them.
Performance Specialties used to sell the Ultra Thrust tuned mufflers, which were tuned more for a sport range of RPMs. Nelson made the mufflers at the time. They used to make them for a wide range of engines too.
Fox Manufactuing made the Fox Quiet Mufflers, which were also tuned for sport RPMs and the mufflers were much more quiet as well. The mufflers worked really well and the engine performed well with the mufflers. Fox also made a series of sport tuned mufflers that looked like shorty, art deco, BuckRodgers, kind of thing.Those tuned mufflers really offered good performance too. Fox also used to make a special Fox Quickie 500 racing tuned muffler for their Fox .40Quickie engine too.
K&B made a tuned high performance muffler for their K&B .60 engines. It was last seen mated with the K&B .61 Twister engines.
Jett Engineering still makes a sport and racing tuned mufflers that fits some engines too. Evolution sells a version for the .45 through .60 engines they sell.
Davis DieselDevelopment used to sell the SoundMaster mufflers. These mufflers work really well and have little to no performance loss with a engine and they quiet the engine down quite a bit too. DDD stated that the mufflers would limit the engine noise to 88 DB too.
Tower Hobbies used to sell their Tower engines with a really nice semi-tuned muffler that didn't restrict the engine much, if any too.
MVVS still sells some mufflers that offer good performance.These mufflers tend to look more like Mousse Can mufflers. But they work good though.
A company inAustralia used to make a unusual long tube muffler that had a threaded rod in the center of it with a baffle that you moved back and forth to tune the muffler. it actually worked pretty good, but like other "good" mufflers it wasn't popular.
Note all of the good mufflers have a common theme in being long with a large inside cavity. The size tended to be a detractor as well as the cost of course.
In the pics below, there are some examples of the "Good" mufflers:
1 - Fox Quiet Muffler and a Performance Specialties Ultra Thrust Muffler
2 - Fox Tuned Pipe style muffler
3 - Fox .40 Q500 tuned muffler
4 - The Evolution/Jett tuned muffler
5 - K&B Twister .61 tuned muffler
6 - Davis Diesel Development SoundMaster muffler
7 - Tower Hobbies muffler
01-28-2013, 08:43 PM
#7
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Join Date: Mar 2002
Location: sydney, AUSTRALIA
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RE: Bad Mufflers
The adjustable pipe was sold here in Australia as a Wally-pipe and featured a sliding internal baffle/venturi.
It did muffle and also gave some performance increase when set up correctly, in effect a tuneable time pipe. I have a couple of them tucked away.
While on the subject of venturis, some early OEM mufflers had a front air intake supposedly to pull air through the muffler itself. My example as supplied with a ST G60 robs power and doesn't muffle either.
Similar useless units also supplied by Webra and HB.
It did muffle and also gave some performance increase when set up correctly, in effect a tuneable time pipe. I have a couple of them tucked away.
While on the subject of venturis, some early OEM mufflers had a front air intake supposedly to pull air through the muffler itself. My example as supplied with a ST G60 robs power and doesn't muffle either.
Similar useless units also supplied by Webra and HB.
01-29-2013, 04:20 AM
#8
RE: Bad Mufflers
Thanks for the information.
I found a magazine article that Clarence Lee did about the Wally Pipes here http://www.rcmplans.com/issues/reque...-011984-1.html
They did import and sell some as a Magic Muffler here in the USA too. He found that the pipe could yield a 1,000 RPMs gain over running no muffler on some engines. I can see this pipe being great to use on rear exhaust engines as it used up less room inside of a fuselage.
I still have some of those open front mufflers too. At the time many clubs required a muffler on a engine. It didn't have to quiet much, the rule was you had to have a muffler. So actually the open front mufflers didn't restrict the exhaust as much as a closed front muffler, so many guys went with them as they didn't lose as much power as a closed front muffler did. But yeah those things were pretty loud. At the time most engines were still being sold without mufflers as it was optional. Plus most engines had to use clamps as there were no muffler tabs or attach points either. But the mufflers one could get were very restrictive so the fad towards using the open front mufflers was in full swing. At the time the idea going around was the air flowing through the muffler would help scavenge or draw the exhaust out of the engine thus increasing power. But in fact it was simply a less restrictive muffler, air flowing through did not really flow through it, it was the exhaust gasses having a easier way out of the engine instead.
They have an example of the SEMCO flow though muffler on that auction site at this time too. In case someone wants to see what it looks like. MAC"s used to make some too.
http://www.ebay.com/itm/Vintage-Semc...item2327684816
I found a magazine article that Clarence Lee did about the Wally Pipes here http://www.rcmplans.com/issues/reque...-011984-1.html
They did import and sell some as a Magic Muffler here in the USA too. He found that the pipe could yield a 1,000 RPMs gain over running no muffler on some engines. I can see this pipe being great to use on rear exhaust engines as it used up less room inside of a fuselage.
I still have some of those open front mufflers too. At the time many clubs required a muffler on a engine. It didn't have to quiet much, the rule was you had to have a muffler. So actually the open front mufflers didn't restrict the exhaust as much as a closed front muffler, so many guys went with them as they didn't lose as much power as a closed front muffler did. But yeah those things were pretty loud. At the time most engines were still being sold without mufflers as it was optional. Plus most engines had to use clamps as there were no muffler tabs or attach points either. But the mufflers one could get were very restrictive so the fad towards using the open front mufflers was in full swing. At the time the idea going around was the air flowing through the muffler would help scavenge or draw the exhaust out of the engine thus increasing power. But in fact it was simply a less restrictive muffler, air flowing through did not really flow through it, it was the exhaust gasses having a easier way out of the engine instead.
They have an example of the SEMCO flow though muffler on that auction site at this time too. In case someone wants to see what it looks like. MAC"s used to make some too.
http://www.ebay.com/itm/Vintage-Semc...item2327684816
01-30-2013, 08:56 AM
#9
Thread Starter
RE: Bad Mufflers
Speaking of bad mufflers, I decided to this (see attached). It is a YS muffler mounted to a Testors Series 21 McCoy .40 Black Head. I cut a narrow hose clamp, drilled holes in the cut end, drilled and tapped the muffler, mounted it with 4-40 screws.
Soon I'll test it. I figure the larger chamber should allow it to be reasonably quiet without power loss. This is one bad muffler.
Soon I'll test it. I figure the larger chamber should allow it to be reasonably quiet without power loss. This is one bad muffler.
01-30-2013, 09:28 AM
#10
RE: Bad Mufflers
A Testors Series 21 .40 engine? Heck it is not worth even putting a decent glow plug in one of those engines. The one I had did run, but the stupid drive washer was made from soft aluminum, and when I try to tighten up the prop, it would expand out and back and jam up aganst the crankcase front.
But the YS muffler does fit the engine pretty good though. Do let us know how it goes. You can make measurements with and without the muffler to see what it does to performance.
But the YS muffler does fit the engine pretty good though. Do let us know how it goes. You can make measurements with and without the muffler to see what it does to performance.
01-30-2013, 09:44 AM
#11
Thread Starter
RE: Bad Mufflers
You must have had a defective part, earlwb, because mine holds the props without any problem. This includes the 10x5 I used for break-in, I'll be testing it with the 11x3 but don't anticipate any problems. I don't have a tachometer, so testing is subjective. The real test will be in flight.
01-30-2013, 10:19 AM
#12
RE: Bad Mufflers
Someone gave me one of those McCoy motors, and I can't even guess where the compression is to flip it there is so little compression. I am glad I didn't buy one back in the day. I thought they looked pretty nice and was thinking of getting one then. Sometimes I will block off the flange where the exh mates to the motor and blow into the end to get the pitch and look up the rpm that it matches to see if it is in the range I wish to run the motor at. It works well on tuned pipes to get in the ballpark. The exit hole size makes a bit of difference for power and engine temperature too. If you go too big you may sacrifice idle on a throttled motor, and get too loud for your field. I was thinking of making one of those Aussie mufflers, but it is kind of hard to locate the thin aluminum tubing. Stainless tubing was used then when they were made. I never saw one over here, so I guess they just gave up on selling them.
01-30-2013, 11:42 AM
#14
Thread Starter
RE: Bad Mufflers
ORIGINAL: aspeed Someone gave me one of those McCoy motors, and I can't even guess where the compression is to flip it there is so little compression. I am glad I didn't buy one back in the day. I thought they looked pretty nice and was thinking of getting one then.
Sometimes I will block off the flange where the exh mates to the motor and blow into the end to get the pitch and look up the rpm that it matches to see if it is in the range I wish to run the motor at. It works well on tuned pipes to get in the ballpark. The exit hole size makes a bit of difference for power and engine temperature too. If you go too big you may sacrifice idle on a throttled motor, and get too loud for your field. I was thinking of making one of those Aussie mufflers, but it is kind of hard to locate the thin aluminum tubing. Stainless tubing was used then when they were made. I never saw one over here, so I guess they just gave up on selling them.
02-08-2013, 04:16 AM
#15
Thread Starter
RE: Bad Mufflers
Here, I'm taking a bad muffler and making it into good. The chamber and internal baffles were way to small for the Enya .19-VI TV, so I made the Tatone EM-4 Calumet muffler into a tongue muffler for my Testors McCoy .19 Red Head. My second NOS EM-4, I am adapting to an Enya .09-III TV. It seems more suited to this size.
02-10-2013, 07:22 PM
#16
Thread Starter
RE: Bad Mufflers
I ran the Enya .09-III TV with the stock Calumet muffler today. To say nonetheless, it started overheating, so I removed the muffler and ran off the rest of the tank. A muffler baffledectomy is in order.
02-11-2013, 10:27 AM
#18
RE: Bad Mufflers
ORIGINAL: earlwb
A Testors Series 21 .40 engine? Heck it is not worth even putting a decent glow plug in one of those engines. The one I had did run, but the stupid drive washer was made from soft aluminum, and when I try to tighten up the prop, it would expand out and back and jam up aganst the crankcase front.
But the YS muffler does fit the engine pretty good though. Do let us know how it goes. You can make measurements with and without the muffler to see what it does to performance.
A Testors Series 21 .40 engine? Heck it is not worth even putting a decent glow plug in one of those engines. The one I had did run, but the stupid drive washer was made from soft aluminum, and when I try to tighten up the prop, it would expand out and back and jam up aganst the crankcase front.
But the YS muffler does fit the engine pretty good though. Do let us know how it goes. You can make measurements with and without the muffler to see what it does to performance.
The thrust plate had a steep taper. A crash would crack the thrust plate and they would do as you describe. I had one on a control line and bought several thrust plates. Still have the engine, sans thurst plates. Other than cracking the thrust plate it was a powerful and reliable engine. Though the dykes ring made hot restarts impossible by hand. I just switched planes while it cooled off.
02-11-2013, 10:30 AM
#19
RE: Bad Mufflers
ORIGINAL: fizzwater2
I had a Testors/McCoy series 21 in a .40 size, RC.
Be glad you didn't buy one. It ran, but let's just say it wasn't strong running, and it didn't last long.
I had a Testors/McCoy series 21 in a .40 size, RC.
Be glad you didn't buy one. It ran, but let's just say it wasn't strong running, and it didn't last long.
02-11-2013, 04:11 PM
#20
Thread Starter
RE: Bad Mufflers
ORIGINAL: 1QwkSport2.5r My vote for a bad muffler is this one that came with my Enya SS30bb. Robs 3000rpm+ on a 9x5 APC.
OTOH, this YS muffler resulted in no performance loss on my Testors .40 Series 21 Black Head.
02-11-2013, 04:54 PM
#21
RE: Bad Mufflers
I don't know that it would do all that well on a tuned pipe. The port timing is somewhat conservative. Using 5/25 fuel, it turns an APC 9x5 at 13,500 on the stock muffler. On a TT .46 pro muffler it turns the same prop at 15,200rpm. A .46 size red Jettstream muffler it turns 15,900rpm. Open faced exhaust is 15,700rpm. I think the exhaust timing is around 150* or so. This muffler would probably rock on an .09.
02-12-2013, 03:45 PM
#23
RE: Bad Mufflers
In the 70's there was a muffler I used to call "The Raspberry"...can't recall the manufacturer right off hand though...
The muffler body was cast Aluminum...sort of rectangular in cross section...looked a little like the DuBro muffle-aire shown above, except it had a silicone sleeve wrapped snuggly around it...
When idling, the engine would have a distinctive "pooting"
sound...or like blowing a constant raspberry...
Anyone know who made it? Earl...you got one?
The muffler body was cast Aluminum...sort of rectangular in cross section...looked a little like the DuBro muffle-aire shown above, except it had a silicone sleeve wrapped snuggly around it...
When idling, the engine would have a distinctive "pooting"
sound...or like blowing a constant raspberry...Anyone know who made it? Earl...you got one?
02-12-2013, 04:21 PM
#24
RE: Bad Mufflers
Someone made a silicon balloon type after muffler that clamped on to the back of a regular muffler to quiet it down a bit more too. It had little slits cut into it so I think it may have been messy. They were a bit expensive so I guess they didn't sell too well especially if they didn't direct the exh. well too. For the Tatone muffler to perform better, a bigger hole may help, I wouldn't go any bigger than a similar muffler that is matched for the size of motor used in case the idle would suffer.
02-12-2013, 06:27 PM
#25
RE: Bad Mufflers
I vaguely remember that "Rasberry" muffler. But I never had one though. I did like the Cox .049 silicon mufflers though. They tended to bulge out when the engine was running and let the exhaust gasses out around the edges.
Now I still have a couple of silicon tuned pipe mufflers though. They look like a tuned pipe but they are made out of silicon instead of metal. Pretty neat too. They are very quiet too. If I can find my pics of them I'll post it.
Now I still have a couple of silicon tuned pipe mufflers though. They look like a tuned pipe but they are made out of silicon instead of metal. Pretty neat too. They are very quiet too. If I can find my pics of them I'll post it.