Quiet speed (again)  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> Jett Engineering Support >> Quiet speed (again)
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Quiet speed (again) - 6/16/2006 12:31:19 AM   
Rebellion



Posts: 977
Joined: 2/22/2004
From: Central, GA, USA
Status: offline 		Hi Bob,
I'm thinking about a new engine for my Shrike but will need to keep the sound down to 98db at nine feet. I was thinking maybe a SJ 60L FIRE with a F/L quiet pipe propped to turn in the 15k rpm range.

I know that estimating noise levels is a good guess at best but I'd appreciate your input on this.

Thanks,

Dave
       Post #: 1

RE: Quiet speed (again) - 6/16/2006 3:20:05 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Hi Dave.....

Id suggest the 60L set up with the the pipe very long, tune it for more around 14,000 to start with. Get the sound measurement. Then if you have margin, shorten the pipe a bit and let the rpm climb.

I currently get 96 db with my Mustang - SJ-46, turbo-jett, 12x4, peaks at 14,100, ground is 13,700. This at 3 meters, on grass.

Hitting 98db at 3 meters (9 feet) is not that hard with the right prop and a real good pipe. The trick is the tip speed and prop noise. Also, consider using a Hyde mount, or other soft engine mount. Those are good for nearly 2db all by themselves on most planes.

Getting the right prop might be the big challenge. A 9x9 would be the smallest I think might work (but we know the 9x9 can turn 16,000 easily on a SJ60L anyway). Might take using a 10x10 and clipping it down a bit, or just running a 10x7 or 10x8.


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Rebellion)
       Post #: 2

RE: Quiet speed (again) - 6/17/2006 5:26:19 PM   
Rebellion



Posts: 977
Joined: 2/22/2004
From: Central, GA, USA
Status: offline 		Thanks Bob. I think I'll have to try this one out. Hey, if I can't get the speed I'm looking for and keep it quiet I can always put the engine on my Ultra Stick 40, hehe. In all seriousness, the 60L would seem to be a very versatile engine.

Thanks again,

Dave

(in reply to bob27s)
       Post #: 3

RE: Quiet speed (again) - 6/19/2006 1:52:06 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		No problem Dave...

Yes, the 60L is a very versitile engine. Loves everything from big full pipes down to the lite-jett muffler (untuned). Really runs well with a turbo-jett for scale use. And of course makes an awesome sport flying engine too!


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to Rebellion)
       Post #: 4

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