No noise mufflers
02-05-2006, 11:02 PM
#1
Thread Starter
No noise mufflers
Is there any reason why the engine exhaust can not be directed to a chamber lined with soft closed foam rubber and a series of up and down baffle strips of the same foam to smother noise and let the wet exhaust drip out the bottom hole / pipe.
It could be any shape to use space on both sides of the firewall.
I think we could do away with the big metal completly. Especially if AMA got the engine MFGRS. to go to rear exhaust round tube types.
Yes, it is asking a lot of the Dolittles.
I have built a box and am ordering some foams to see if it really makes a difference.
I will be buying only rear exhaust engines in the future for many reasons. This is just one of them.
It could be any shape to use space on both sides of the firewall.
I think we could do away with the big metal completly. Especially if AMA got the engine MFGRS. to go to rear exhaust round tube types.
Yes, it is asking a lot of the Dolittles.
I have built a box and am ordering some foams to see if it really makes a difference.
I will be buying only rear exhaust engines in the future for many reasons. This is just one of them.
02-06-2006, 12:27 AM
#3
Thread Starter
RE: No noise mufflers
At first I thought you were joking. Either way, sound reduction is sometimes very similar in the ways it can be done.
I will check the idea out with a couple of local pistol clubs and mfgrs.
Hindsite is telling me I forgot about the continous hot exhaust temperatures.
Some of the foams are Silicone based. We will see.
I will check the idea out with a couple of local pistol clubs and mfgrs.
Hindsite is telling me I forgot about the continous hot exhaust temperatures.
Some of the foams are Silicone based. We will see.
02-06-2006, 08:24 AM
#4
RE: No noise mufflers
Some of the closed cell foam is rather heavy, especially the type sold for protecting rc receivers. The mass could add up fast.
The oil residue might effect the foam too possibly soaking in.
You may find the Fly Quiet pipes easier to install internally, since their shape could be run along the inside of the fuse, finally exiting just the last bit somewhere aft of the wing on the underside of the plane.
The oil residue might effect the foam too possibly soaking in.
You may find the Fly Quiet pipes easier to install internally, since their shape could be run along the inside of the fuse, finally exiting just the last bit somewhere aft of the wing on the underside of the plane.
02-06-2006, 10:12 AM
#5
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RE: No noise mufflers
Hi:
Your thinking in the right direction. Except the foam idea is not good. You can use stainless steel scrub pads that will not rust and they will highly reduce the sound. In fact if you want to do testing of even large engines outside your workshop in the back yard. You can take a 5 gallon bucket and run a (large) hose from the engines exhaust to the bucket. Fill the bottom of the bucket with steel wool or sand and direct the exhaust into this. Make the outlet at the top of the bucket about 1 inch ID. It will make it possible to test your engines at home. This will not work if you are testing a OPS .60 with a small prop because the prop noise completely over powers the exhaust noise. As far as the pistol silencer they work very good. The very first muffler that I made years ago was a reverse baffle system that took up the whole rear of the fuselage of a Piece of Cake. You couldn't hear the plane 150 feet away. The only problem was that it was a lead sled. The whole inside was coated with epoxy and six reverse baffles. Still the plane flew great. Having said you can use the fuselage as a muffler. It's fine for a .049. Don't try this on a .40 size. It was done 20 years ago and the planes catching on fire in flight was spectacular. They made the section behind the firewall into a large expansion chamber. Wood makes a good tinder box.
Ron
Your thinking in the right direction. Except the foam idea is not good. You can use stainless steel scrub pads that will not rust and they will highly reduce the sound. In fact if you want to do testing of even large engines outside your workshop in the back yard. You can take a 5 gallon bucket and run a (large) hose from the engines exhaust to the bucket. Fill the bottom of the bucket with steel wool or sand and direct the exhaust into this. Make the outlet at the top of the bucket about 1 inch ID. It will make it possible to test your engines at home. This will not work if you are testing a OPS .60 with a small prop because the prop noise completely over powers the exhaust noise. As far as the pistol silencer they work very good. The very first muffler that I made years ago was a reverse baffle system that took up the whole rear of the fuselage of a Piece of Cake. You couldn't hear the plane 150 feet away. The only problem was that it was a lead sled. The whole inside was coated with epoxy and six reverse baffles. Still the plane flew great. Having said you can use the fuselage as a muffler. It's fine for a .049. Don't try this on a .40 size. It was done 20 years ago and the planes catching on fire in flight was spectacular. They made the section behind the firewall into a large expansion chamber. Wood makes a good tinder box.
Ron
02-06-2006, 06:30 PM
#6
Thread Starter
RE: No noise mufflers
Flyquiet. Could we get together and save my house ?
I have a metal fabracating shop I can use. Could you sketch up the baffle angles, #, etc. to get me started in the right direction ?
Metal all the way. No heat or soggy problems. I have SS and Brass shim stock for fabricating.
My medication screws up the brain to typed information lots of times. When I read statements they are not what I had intended.
Thaks for any help< Rich.
I have a metal fabracating shop I can use. Could you sketch up the baffle angles, #, etc. to get me started in the right direction ?
Metal all the way. No heat or soggy problems. I have SS and Brass shim stock for fabricating.
My medication screws up the brain to typed information lots of times. When I read statements they are not what I had intended.
Thaks for any help< Rich.
02-07-2006, 10:22 AM
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RE: No noise mufflers
Hi Rich:
Thanks for the invitation. About your metal pipe. They weight too much. To explain. I started out with 800 degree silicon injected into molds for the sound cancellation muffler. They were too heavy so I came up with a spot welded .004 stainless steel muffler for the Cox .049, the Norvel engine wasn't even on the market then. The muffler was 2 1/4 inches long, 1 3/8 inch wide, 1/2 inch thick and weight 1/2 ounce. Since you work with metal can you spot weld .004 stainless? Now the practical point of this. The muffler was so complicated it is totally unmarketable. It was just for fun. To make spun aluminum tuned pipes, it already is done. I have a lath and can spin aluminum but there is no reason. The silicon pipes we make are much, much cheaper than metal pipes. But they are all hand made and require time. It gives a old man something to do.
Ron
Thanks for the invitation. About your metal pipe. They weight too much. To explain. I started out with 800 degree silicon injected into molds for the sound cancellation muffler. They were too heavy so I came up with a spot welded .004 stainless steel muffler for the Cox .049, the Norvel engine wasn't even on the market then. The muffler was 2 1/4 inches long, 1 3/8 inch wide, 1/2 inch thick and weight 1/2 ounce. Since you work with metal can you spot weld .004 stainless? Now the practical point of this. The muffler was so complicated it is totally unmarketable. It was just for fun. To make spun aluminum tuned pipes, it already is done. I have a lath and can spin aluminum but there is no reason. The silicon pipes we make are much, much cheaper than metal pipes. But they are all hand made and require time. It gives a old man something to do.
Ron
02-07-2006, 02:31 PM
#8
Thread Starter
RE: No noise mufflers
Am I right that there are 2 ways to silence noise.
1 Cool the hot air of the explosions with metal surfaces. -----2 Absorb and convert the noise energy to heat as it is absorbed.
1 Cool the hot air of the explosions with metal surfaces. -----2 Absorb and convert the noise energy to heat as it is absorbed.
02-07-2006, 09:35 PM
#9
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RE: No noise mufflers
Hi:
Your right. There are several ways to reduce sound. One is what a factory muffler accomplishs, it compresses the exhaust and releases it producing the same thing as refrigeration. On a .40 size plain bearing engine the temperature can be 585 degrees one inch from the piston and by compressing the exhaust and releasing it in just 4 inches the temperature can drop 150 to 180 degrees. One reason that the sound is reduced is that the closer you can come to ambient temperature the less of a thermal shock. In the old days some guys put 4 to 5 inch metal cans they called stingers behind the muffler. One put 4 stingers under the plane, it sure was quiet. There are limits to what you can do with backpressure.
Ron
Your right. There are several ways to reduce sound. One is what a factory muffler accomplishs, it compresses the exhaust and releases it producing the same thing as refrigeration. On a .40 size plain bearing engine the temperature can be 585 degrees one inch from the piston and by compressing the exhaust and releasing it in just 4 inches the temperature can drop 150 to 180 degrees. One reason that the sound is reduced is that the closer you can come to ambient temperature the less of a thermal shock. In the old days some guys put 4 to 5 inch metal cans they called stingers behind the muffler. One put 4 stingers under the plane, it sure was quiet. There are limits to what you can do with backpressure.
Ron
02-08-2006, 08:27 AM
#10
Thread Starter
RE: No noise mufflers
Bless you Flyquiet. You have given me a usefull project to do. If I break any good new ground you can use the information First as you see fit. [sm=thumbup.gif][sm=thumbup.gif]
