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Lynn,
Had the same concerns myself at first glance, but when advised
that it was standard on light weight engine mounts, I felt a little better about
it.
My approach would have been a piece of triangled 4130 - of
course this causes bolt/nut access problems, but could be overcome, in a
number of ways.
What it does give is a nice flat area on which to weld the
tubes as well as a wider area to spread the load and two bolts through the
firewall hard points, compared to one.
One idea might be a triangle with two small tubes to carry the
firewall bolts.
Just some of my thoughts on the subject, always looking for
better ways!!
George ( down under)
----- Original Message -----
Sent: Sunday, May 06, 2007 10:44 PM
Subject: [FlyRotary] Re: Engine mount
mockup
Kelly:
The angle bracket on the firewall is actually per the
design of the Falconar
F-12. A lot of Jodel engine mounts are this as
well. The plans are unclear
as to material it only indicates 1&½"
x1/8 thick angle. I tried finding this
in 4130 but was unable to so I
settled for mild steel. The triangular end
caps are a great idea and I
think I will use it. The design does call, for a
strap to be welded so
that it bridges the tube to angle iron on the back
side as well. Here is
an example as seen on Hans Teijgeler's Jodel DR1050
with a Subaru in
Holland.
The design is not what is commonly seen for that kind of junction. It
leaves the angles in bending along the fold lines. However, if the loads are
not enough to cycle the joint in bending, then it's good enough. The mild
steel to 4130 connection is OK for light loads.
The angle inserts in 4130 would help a bit. Double the part of the angle
against the firewall with a piece of 1/8 4130 as a big washer but don't load
the bend (or weld area).
Paint the bend and the tube to angle joints with just a bit of white
lacquer. Grit blast the joints with rice hulls and paint without any primer.
Just enough to prevent rusting.
Should a problem develop, the paint will crack along the failure and be
obvious. Enamels and powder coats will stretch and conceal the
crack.
Lynn E. Hanover
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