Paul,

All the X & Y dimensions are from the flat firewall.
Note there are five mounting points. Designer call for up
   to
180hp with the four point, with up to 260hp with five
points.

I'm trying to get an idea of the room using either a 13B
   or
20B. Only one Bearhawk is flying (Elden Yates). Little
details, but Elden ended up putting his battery next to
   the
PSRU to get some weight out on the nose!

Plan is to use Tracy Cooks PSRU.  With 180hp,
   Bearhawk
cruise is 140mph, with 260hp it is at 160 mph (75% on
   both
numbers).

--Tom

There are five mounting points on the Bearhawk Firewall.
Firewall is
approximately 2" larger at all mounting points.

In Inches:
  XY
Lower Left3.500
   0.000referenceLower Right
 31.1880.000
  Upper Left
   0.00020.188
Upper Right
 34.68820.188
  Upper Middle
   17.34424.844

  THRUST LINE
   17.34415.844Firewall
set back at 6 degrees (top towards tail).

   Prop Flange (front edge) to
   VERTICAL MOUNT -
40.625"Note, from firewall (6
   degree lean back - top towards tail)
is sin 6 *
(Thrust Y position) or an additional
1.656"
-- end of email ---


Does this look right?

Now you want me to lay it back 6 degrees?

Paul Lamar


 Paul,

   The bottom measurement should be changed from 27.500 to
   27.688"

   Upper middle is 24.844" from the lowest two holes.

   Correct, rotate the firewall back 6 degrees. Point of
   rotation is from
   the lowest two points on the firewall.

   Thank You,

   Tom

   OK Tom Here it is.

   Paul Lamar


Looks good.

  Bob Barrows, the designer, doesn't have an email account! No
 computer,
  either! I suspect that is why he gets so much done.

  Thanks,

  Tom

  I'll see Bob at OSH and show him some of this stuff.

  Here are some preliminary 3Ds. Ask questions if you see something
  that looks strange. Upper motor mount is not in yet but we
  will use a rubber ball jointed strut mount to above the water pump.
  Are you using an RX8 engine? That area differs from the 13B.

  Paul Lamar

 Paul, am I interpreting the 6 degrees incorrectly...that the mount
 has 6
 degrees of upthrust?  Also, related question, on your mount design
 that
 Jerry has been welding, is the prop flange 90 degrees vertical?

 Steve Beckham

 No the BearHawk firewall is laid back six degrees. This mount has
 no down
 thrust or side thrust. The down thrust angle can be adjusted
 however by
 using left and right hand threads on the top strut.

 Jerry's jig can accommodate down thrust and side thrust.

 For the new guys we have been doing these motor mount designs for
 about
 the past seven years. A free service of the newsletter.

 Paul Lamar
 --
 The Rotary Engine NewsLetter. Powered by Linux.
 ACRE NL web site. http://www.rotaryeng.net
 Youtube key word UTUBPLEASE
 Copyright 1998-2009 All world wide rights reserved.

 <BearHawk-SF-Dims.jpg


 http://finance.groups.yahoo.com/group/BH-PATROL/



Paul, I am impressed with the drawings of the motor mounts and the
completeness of main shapes.  In what forms could I pull them into my
Solidworks?  And for example, if you extracted a single tube, such as
a brace tube that would have a profile on it, do you have that
profile already done?

I do the work for the Patrol frame and of course that has slightly
different hole placements but I believe the set back angle is the
same...

keep up the good work...I would think this is one of the major
hurdles for going to non-aviation motor. Always good to see the end
result before a dollar is spent.

Scott


Scott- Iron Design L.L.C.
Scott Weinberg
13631 Vail Ave
Clarksville, Iowa 50619
319-276-4400 home/office
319-404-4401  cell/shop/office
scottw@butler-bremer.com
http://www.irondesign-airparts.com/Tailwheels.htm


We have done this in the past using stp format. Here is a RV7 motor
mount in stp format zipped. It is better than iges or dxf. Just un zip
it and import it into Solid Works. It is not always perfect but it is
usually very easy to fix one or two flaws. The jpgs will show you
what it is supposed to look like after being rendered.

I only ask that you check with me first before you make any modifications
as these mounts are subtle and they have been developed and tested for the last
seven or eight years with the help of many people. That includes at least
one crash due to pilot error. I don't want any failures. If somebody changes
it and it fails they are on their own. In general I use .049 wall 4130
tubing tig welded. The beam is available from Jerry Hey. The rubber bushings
can be bought at McMaster Carr and unlike an aircraft rubber mount they
are less than $10. They are made from the same rubber by the same
company that makes aircraft mounts. Namely Barry Controls.

Also read http://www.rotaryeng.net/motor.html for the design rational.

I am always open for suggestion and improvements as this is the way
the mount evolved in the first place. One of the functions of this
newsletter.

Paul Lamar