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Old 06-10-2008, 09:19 AM
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rmh
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Default RE: Need to quiet down my DL 50

ORIGINAL: Rfabbre


ORIGINAL: Cambo

ORIGINAL: dick Hanson


ORIGINAL: pe reivers

No,
In my .15 diesels, 8x6 graupner 3-blades, in my gassers I use Mejzlik.

Today I test flew my "new" 1/4 scale piper cub (@25lbs) with 58ccMVVS, side muffler and much reduced stinger outlet. Test prop was a 3W 22x12, and the engine was quite silent. Still enough power vor nearly vertical climb.
I had planned to put on a 22x10x3 Mejzlik, but the plane is a floater and needs a prop that puts the brakes on so I can land on the strip instead of the ditch at the strips end. So I will choose a 24x8x2 for the next tests. This goes to show, that there is not always freedom of choice. The plane has a voice in this as well.
No one will like this -as you actually have to construct it - but it is incowl
the problem is getting enough volume and no exhaust port restriction and NONE of th commercial Pitts do this as well as needed - the large Supersonic works well but noise is still high.
You can't have your Kate and Edith too-
I was thinking of doing such a thing myself. I asked before but seemed to get no reply. Why can't one just make a "canister like" large chamber can and run it back behind the engine. What if you placed a canister sideways parallel to the engine. Oh, and were do you get headers that make a full u turn.

Cameron

Cameron,

That's exactly what I did,

Here are a couple of pics. One shows the size of the can compared to the stock muffler. I don't have any way to measure sound level but it is quieter than the stock muffler.



Rich

PS-PM me if you are interested in specifics.
nice - If you want even more muffling use even larger can and make a double chamber inside .
The BEST two stroke muffling today is used on two stroke scooters and non performance small motorcycles - look at those designs
On a more POSSIBLE practical approach if possible select the largest can available - a little larger - can make a huge difference as th volume increases a LOT with only a bit larger outside dimension.
This then allows you to use a smaller moffler outlet -
The theory goes like this : each exhaust pulse can expand more easily (quickly) which brings in MORE fuel charge for next power stroke
the larger can also cools the charge more- as the pressure in the can reduces ( reduce pressure and you reduce temperature)
a smaller outlet is then permissible-each pulse then extends time wise and if the can were large enough and multiple changes in direction of flow happened -the outlet sound would become a "whoose" rather than a "pop" .
The theory is a 100 years old -at least . well proven.
The weight and power are the most inportant parts of selecting a gasser for a model and the cheaper products on the market simply do not address noise -why ?
the majority of buyers simply never have cared about it .
many want the noise -the louder the better "look at me!"