more muffler fun
12-27-2011 | 08:37 PM
#1
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From: Salinas,
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more muffler fun
ON that same D-7 I made a huge muffler. It is like the one that are sold for Ryobi conversions but much longer.
The body is aluminum gas cylinder stock. I turned the outside to about 1/2 the original thickness. It is light but, on this airplane weight is not a problem. The end plates are aluminum flat stock disks that have a shoulder so they press fit in the cylinder. The front plate bolts to the engine. The aluminum spacer was needed to clear the cooling fins. A piece of all thread is used to keep the ends secure. The pipe is an old piece of camping chair or tent pole. The is nothing fancy inside. Just huge volume, which seems to be key. This airplane is unusual in that is has a perfect place to put such a huge can.
I may make some dummy engine parts to secure with hose clamps. If there are any signs of the bolts securing it to the manifold being stressed I'll secure the tail end. I think some thing simmilar could be made of a hair spray can or simmilar.
The body is aluminum gas cylinder stock. I turned the outside to about 1/2 the original thickness. It is light but, on this airplane weight is not a problem. The end plates are aluminum flat stock disks that have a shoulder so they press fit in the cylinder. The front plate bolts to the engine. The aluminum spacer was needed to clear the cooling fins. A piece of all thread is used to keep the ends secure. The pipe is an old piece of camping chair or tent pole. The is nothing fancy inside. Just huge volume, which seems to be key. This airplane is unusual in that is has a perfect place to put such a huge can.
I may make some dummy engine parts to secure with hose clamps. If there are any signs of the bolts securing it to the manifold being stressed I'll secure the tail end. I think some thing simmilar could be made of a hair spray can or simmilar.
12-28-2011 | 10:59 AM
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From: Salinas,
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RE: more muffler fun
The RPM's are about the same as without a muffler at all.
The exhaust pipe is about 5" long and has and ID of 0.7". That is large and free flowing. The big chamber seems to be acting like a shock obsorber, or "gasious capaciter" if there is such a thing. The gas in the chamber compresses when the pressure spikes. It is then released at a more constant pressure. There might be some resonant effect going on too. The chamber is 15X the volume of the engine's displacement. It has a quiet and pleasing low frequency sound.
At this point prop and intake noise are much more significant then the exhaust noise.
BTW, I am not an anti-noise, annoying type. My fellow club members aren't either. I have run straight pipes without complaint. My club is way out in the "boonies". It was more of a fun 2-hour project to see what happened.
The exhaust pipe is about 5" long and has and ID of 0.7". That is large and free flowing. The big chamber seems to be acting like a shock obsorber, or "gasious capaciter" if there is such a thing. The gas in the chamber compresses when the pressure spikes. It is then released at a more constant pressure. There might be some resonant effect going on too. The chamber is 15X the volume of the engine's displacement. It has a quiet and pleasing low frequency sound.
At this point prop and intake noise are much more significant then the exhaust noise.
BTW, I am not an anti-noise, annoying type. My fellow club members aren't either. I have run straight pipes without complaint. My club is way out in the "boonies". It was more of a fun 2-hour project to see what happened.
