Message-ID: <4010293B.E7335181@frontiernet.net>
Date: Thu, 22 Jan 2004 13:49:16 -0600
From: Jim Sower <canarder@frontiernet.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Torsionals
References: <list-2943881@logan.com>
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<...  The resonant frequency for his drive is down low in RPM.  So the rubber
bushing actually help push it lower ...>
OK.  I thought Tracy's was high.  So Tracy's can rattle some at low idle so
raise idle rpm out of that range, rubber bushings would (presumably) drive
Tracy's all the way below idle range, or at least "soften the blow" when it did
rattle.
Am I getting any warmer? ... Jim S.

Ed Anderson wrote:

> Actually, Jim
>     After looking at the pros and cons of both approaches, Tracy went with
> the looser tolerance route and that is why you get a 42 lb gear box rather
> than a 60 lb gearbox.  The resonant frequency for his drive is down low in
> RPM.  So the rubber bushing actually help push it lower.  An example of the
> other approach is PowerSports Spur drive gear box.  They went to tighter
> tolerances (more precision machining required) and stiffer components which
> raised the resonant freq above our normal operating range. Both approaches
> work.  PowerSport had their own CNC machining company so its not surprising
> they took that route.  Tracy had considerably less machining capability -
> but more smarts {:>) IMHO
>
> Ed Anderson
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html