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Bernie,
You are precisely correct. Most of the cog belt systems are put together with no dampening device whatsoever. These systems were usually never checked for torsional vibration at all. Most of the time the builders were just lucky enough that the vibration period was outside the normal operational range. Having read the article you can see that even experts have often overlooked these checks. Now dual-mass flywheels are also available to help get the vibration out of the normal operational range.
Bill Jepson
-----Original Message-----
From: Berniehb7448@wmconnect.com
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Tue, Jul 7, 2009 7:31 pm
Subject: [FlyRotary] Re: INJECTION OIL IN FUEL
This is excellent reading, Bill! Maybe this should have its own heading, like "Cog Belt PSRUs".
I've been collecting pictures and descriptions of cog belt PSRUs just for my own information, looking at different examples. Plus looking at other types of PSRUs, this is the way I started to understand that COG BELTS CANNOT BE USED TO ISOLATE TORTIONAL VIBRATION. One thing that bothered me - unless most of the anti-vibration couplers were very cleverly hidden, I did not see any at all, because the input cog pulleys all looked like they were mounted directly onto the flywheel. How come? Unless I'm really, REALLY missing something. What say you?
Bernie.
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