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John H[_7_]

On Mon, 8 Sep 2008 11:56:46 -0700 (PDT), wrote:

On Sep 8, 2:35*pm, wrote:
On Sep 8, 2:29*pm, wrote:

On Sep 8, 1:33*pm, (Richard Casady) wrote:

On Mon, 8 Sep 2008 08:31:27 -0700 (PDT), wrote:
Normal IC aircraft engines aren't muffled, and the back pressure has
an affect on them if you try to.

Most, maybe all, of the planes I have experience with have had
mufflers. Includes radial engines from the thirties, and the usual
Piper, Beech, and Cessna planes in use from the forties on. Still
loud, every one of them.

Casady

Expansion chambers.

They aren't really mufflers, but are designed to make some
backpressure in normally aspirated engines. My uncle was an aviation
machinist. Been around small IC engined aircraft a lot!

AHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!
COULD THEY MAKE THEM QUIETER IF THEY WANTED TO?????????

Please answer me..... * I gotta' know... sniff * - Hide quoted text -

- Show quoted text -

There is not really any reason they could not have mufflers on the
engine. It would probably take a few mph off the top end. But much
of the noise is from the prop. Many simply bolt the prop to the
engine output so there is not a lot you can do with prop redesign.
More blades may allow you to run a smaller diameter but probably not a
lot smaller. So the prop tip speeds are still going to be pretty
high.

I just spoke with a young man in Orlando. He's at Don George
Aircraft Engines & Parts
Orlando, Florida 32805
407.422.0188

I remembered that the airboat I rode on had a Lycoming engine, which gave
me a starting place. According to the guy I spoke with, the law in Florida
requires mufflers on *all* airboat engines. The loudness comes from the
propellor. Problem solved.