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Date: Mon, 23 Jan 2012 14:22:30 -0500
From: Ernest Christley <echristley@nc.rr.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Top 7 reasons for using an auto conversion
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Patrick wrote:
> If it's more reliable and cheaper, double bonus. If it's just cheaper,
> I start getting scared.
>
> Imagine the conversation with your spouse if the airplane suddenly
> becomes a glider: "But Honey, I saved a bunch of money by switching to
> cheap parts...."
> Can't see that ending well.
Try that same conversation after you just robbed the 401K to spend $18K
on a certified engine without any of the accessories.  I don't see it
ending any better by using the defense that you paid to much for crap
parts.  8*)
>
> John Slade's descriptive narration of the failures of several turbos
> that he used _because_ they were cheap is an excellent example. In the
> end, the correct part was more reliable and ultimately cheaper than
> the cost of buying three "cheap" turbos and the resulting engine
> overhaul.
That's what we call "getting an education".  John paid dearly so that we
can all be smarter.  He did the hard work.  Now that the education is
complete, we know the lower limit of acceptibility for a rotary aircraft
turbo.  There was all sorts of turbo maps flying around that resulted in
the requirements parameters getting nailed down pretty well.  John could
have started with the cheap parts, and kept spending more until he got
to a reliable solution.  Or he could have spent the $20K that some
companies want for a certified turbo, and possibly still kept spending
more until he got to a reliable solution.  I believe the final solution
is STILL a fraction of the cost of a certified turbo.

Looking for a cheaper solution doesn't necessarily mean being stupid. 
I've looked for the least expensive/lightest weight solution whenever I
could, but I never gave serious thought to using that really cheap epoxy
resin that the hardware store has on the shelf.  It is not up to the
task requirements, and no amount of hand waving will make it so.  But I
did come down from MGS's expensive 285 system, and used cheap ol' West
systems for the micro fill-and-sand.