Received-SPF: none
 receiver=logan.com; client-ip=204.127.203.211; envelope-from=btilley@mchsi.com
Mime-Version: 1.0 (Apple Message framework v752.3)
In-Reply-To: <list-2495858@logan.com>
References: <list-2495858@logan.com>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
Message-Id: <506F522D-2C46-4851-9AFA-A7E7494306B7@mchsi.com>
Content-Transfer-Encoding: 7bit
From: Bob Tilley <btilley@mchsi.com>
Subject: Re: [FlyRotary] Re: 16X Rotary Engine.
Date: Mon, 19 Nov 2007 19:34:36 -0500
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>

Tracy,

Yes, I was joking, to a point.  BUT, since you brought it up. I'd bet  
that with the longer stroke the best BSFC on the new engine will be  
at a higher rpm.  Mazda probably went to the longer stroke to  
lengthened the time for the fuel to burn more completely. I'm betting  
there is a lower exhaust temp there as well.  Can't wait to get my  
hands on one;-).

Bob


On Nov 19, 2007, at 10:32 AM, Tracy Crook wrote:

> I know you're kidding, (you know how much time it takes to come up  
> with a new design & put it into production) but here's the other  
> reasons for not doing a 3.5 : 1 gear drive.
>
>  I would agree with the estimate but I don't think it makes sense  
> in aircraft use.  Not that I'm against the HP, it's the BSFC that  
> bothers me.  The rotary gets the best BSFC around 5000 - 5500  
> rpm.   Go higher and it gets worse which is OK for short periods  
> (climb, racing, etc) but if you are going to really spend serious  
> hours in the air, you want the engine running near the sweet spot  
> of BSFC.  With a fixed pitch prop, this limits us to around 7250  
> for top end and still cruise around 5400 - 5600 rpm.  A CS prop  
> really helps here but that sort of thing is out of economic reach  
> for most of us.  Even if you had the 3.5 : 1 gear drive, the design  
> of the prop gets really funky. If you ask MT or anyone else for a  
> prop that works best at 1500 rpm (cruise setting with engine near  
> 5000) they won't have it.
>
> The 16B plays right into our hands.  If we are limited on rpm (7250  
> is not TOO limiting : ), there is no substitute for cubic inches  
> and lower weight. Even with the 7250 limit, that comes out to ~ 280  
> HP.  Not bad for a 150lb (bare block) engine!
>
> Tracy