----- Original Message -----

From: Michael McGee

Sent: Saturday, May 22, 2004 12:57 AM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: engine mount geometry

 

I've got some old RV-4 plans that have the motor mount off set
dimensions.  The prop flange stays on the centerline of the fuse/cowl and
the back of the engine is off set as required for the thrust angle.

Mike

At 19:10 2004-05-21, you wrote:
>I am fabricating the bed mount plate for my 20B in an rv-8.  my
>understanding, from Tracy's advice, is to offset the engine about 1 1/2
>degrees to the right if I use his 2.85 drive.  as I see it there is a
>centerline of the fuselage and a centerline of the engine/redrive.  if I
>mount them such that they are 1 1/2 degrees out of parallel, then those
>centerlines will intersect.  my question is where?  do I offset the prop
>flange 5/8" to 1", then draw an offset centerline back from there?  do I
>draw an offset line forward from the firewall, or from the center of gravity
>of the engine?  do I attempt to keep the engine "balanced" left and right
>along the centerline of the fuselage?  I don't think I have ever seen this
>topic discussed more than "offset the engine".  my prop flange will be about
>40" forward of the firewall.
>in attempting to see what had been done with the current left offset mount,
>it appears that the intersection of centerlines is close to the forward end
>of the engine.
>I originally bought the mount thinking a 2.15, left turning, redrive would
>be used.  Fred Breese is being, well, a dick about it, and tells me it is
>way too complicated for me to understand and I need to simply buy a new
>mount.  no surprise, this isn't the first time he has treated me poorly.  no
>wonder I'm building my own plate rather than buy his $500 one.  I'd like to
>hear why I need a new mount.  true the ears will be of different lengths,
>but it is hard to believe the 5/8ths plate I am using will ever break.  has
>anyone ideas?
>Kevin Lane  Portland, OR
>e-mail-> n3773@comcast.net
>web-> http://home.comcast.net/~n3773
>(browse w/ internet explorer)
>
>
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