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Message-ID: <042d01c5578e$c59906c0$e21decdc@george>
From: "George Lendich" <lendich@optusnet.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-919148@logan.com>
Subject: Re: [FlyRotary] Aluminum side housings
Date: Fri, 13 May 2005 17:37:49 +1000
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> We were discussing aluminum side and intermediate housings a couple of
> weeks ago.  A figure of somewhere around 15lbs per housing in weight
> savings was thrown out.  The exact figure isn't as important the fact
> that several Delta builders have had to stack approximately that much
> weight in the tail to get the proper W&B.  At $1400, one aluminum
> housing could possibly save me 30lbs, which is just under $50/lb.
> $50/lb is the figure that I like to use when deciding if more money is
> worth the weight savings.
>
> So, from the aluminum housings look like a winner, except that I read
> one of Mazda's brochures for the RX-8.  In the engine section they go on
> about how the engineers have worked so hard to reduce the engine weight,
> and how engineers of performance autos will give up major limbs to drop
> a few pounds.
>
> So why did they continue with the cast iron housings?  They had to
> redesign the castings for different exhaust anyway, and I assume the
> engineers have internet access and can look at what the racing shops are
> selling.  It seems that having to deal with only one type of casting
> material would simplify things.  Would the wear surface treatments still
> be prohibitively expensive even in production runs, or is there some
> hidden reliability gotcha that isn't advertised well?

Ernest,
Surface treatments are problematic- no real cost effective treatment as yet.
Composite( aluminium and steel) housings don't save that much weight, I
forget the exact figures but will save about 30 lbs, at best. A hell of a
lot of work ( and cost) to get that 30 lbs.

The side exhaust have thrown in another complexity, due to extra heat in the
side port.
I consider the technology used for the rotor housings the only real way to
go for strength and weight savings.
George ( down under)