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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1981304@logan.com>
Subject: Re: [FlyRotary] Re: Mount offset
Date: Thu, 12 Apr 2007 09:44:43 -0400
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Hi Bobby,

When I designed my original motor mount for a 2.17 gear ratio I offset it 
5/8" to the left.  Now that I have a 2.85 (opposite prop rotation), I still 
fly with it offset the same.  The only place where I notice this "incorrect" 
offset really gets my attention is on take off.  I could really use the prop 
pointing slightly to the right instead of the left.  In cruise at 170 MPH 
TAS it is within 1/2 ball.  My vertical fin has not offset.  Personally, if 
I were to do the motor mount again, I think I would shoot for 0 deg offset. 
Just my 0.02 worth

Ed
----- Original Message ----- 
From: "Bobby J. Hughes" <bhughes@qnsi.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Thursday, April 12, 2007 9:27 AM
Subject: [FlyRotary] Re: Mount offset


I did say simple and no I am done with geometry :)

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Ernest Christley
Sent: Wednesday, April 11, 2007 8:03 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Mount offset

Lehanover@aol.com wrote:

>
> With no experience at all in this area, I had imagined that the engine

> would be turned about a vertical line through the prop flange. This,
> to induce the required side thrust while keeping the spinner back
> plate centered over the hole in the cowling.
>
> Lynn E. Hanover
>
This will have very little to do with RVs, but John Dyke specifies 2/3rd
of one degree right thrust on the Dyke Delta.  That is hinged at the
prop flange.  He also specifies 1.5 degree upthrust, but that is hinged
at the firewall.

Bobby, a better way to measure the offset is to break out the old
geometry book and calculate the offset.  The sin(1.25)x47" is 1.02".
The end of the engine will move off center by a long inch.  You won't be
able to read 1/4 degree on most protractors, but an inch is easy to make
out.

-- 
         ,|"|"|,              Ernest Christley       |
----===<{{(oQo)}}>===----    Dyke Delta Builder      |
        o|  d  |o        http://ernest.isa-geek.org  |

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