Marvin Kaye wrote:

V. E. Welch wrote:

For you gentlemen that are currently running rotaries that have been
substituted for lycomings; how did you determine the location of the thrust
line in order to correctly fabricate your motor mounts?

Vince
RV-8A
under construction

One way of doing it is put the cowl on there and use
a string and  a level to mark a place on the firewall based
on the prop hole in the cowl.

You can also set the tail up with the firewall vertical
and use a clear plastic tube with water to locate the center
of the hole in the cowl and a corresponding point on the
firewall.

Some designs use about a degree and a half of downthrust on
a tractor. Some use a little side thrust.

I got a set of installation drawing for a Lycoming and verified the
dimensions of my factory supplied engine mount to determine the actual
thrust line, then I engineered my new mount to match, including the 1.5
degrees of left thrust that the reverse rotation of the rotary is going to
have.  It took some time, but it wasn't all that hard.

   <Marv>

 
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