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Chad:<br>
I have seen 1/4" aircraft ply to cf flex plate to soft mounts used
for nose ring setups. All have had failures. We had some suspicion
after my first failure (soft mounted) that a solid mount would solve
the problem. It didn't. The soft mount should work just as well as the
rigid setup as long as you have a back support. But as of now, I am not
aware of anyone who has done this with an outrunner.<br>
<br>
<br>
Chris<br>
<br>
<br>
<br>
Chad Northeast wrote:
<blockquote cite="mid44DEA094.1090900@f3acanada.org" type="cite">
<pre wrap="">Very interesting...and here I was going to get Pletty to make me a front
mounted 30-10 Evo....I guess there goes that idea :)
What is being used for the front mount?
I have always rear mounted (without a front support), and you can always
hear some vibration when you get large AOA changes...like in snaps, or
hard corners with slight rudder application. Always figured it was the
prop deflecting and vibrating the motor since is cantilivered so far
away from the rotational axis. I had figured a front mount would solve
this.
I did grab a couple of front mount setups while at the Nats and they all
felt like they had more movement than my rear mount setup has, which
surprised me somewhat.
Chad
Chris Moon wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Several of us have been collecting info on the many (upwards of a dozen)
fuse structural failures with people running the larger outrunners. The
common theme is that they are all front mounted to the nose ring without
any support at the rear of the motor. There have been some who have
mounted their motors this way that have not had failures, but all that
have failed were nose ring mounted without support for the back. Except
for one, and that looks like it was a problem with the fuse
manufacturer. In that case (today) the seam split due to a poorly glued
seam without good adhesion by the fiberglass seam tape. The problem
seems to be explained by a phenomenon called "whirl flutter" and
basically is caused by an outside force causing the prop and motor to
oscillate to the point where the structure will fail. Here is a video
of the phenomenon:
<a class="moz-txt-link-freetext" href="http://www.airspacemag.com/ASM/Web/Site/QT/PWFlutter.html">http://www.airspacemag.com/ASM/Web/Site/QT/PWFlutter.html</a>
(Thanks to Jerry Budd for the research and video link)
So, if you are planning to use the big outrunners like the Axi or Hacker
A60, the evidence is showing that a rear support of some kind is
necessary to prevent failure. I had 2 failures with my A60 set up until
I added a rear support. My first failure was on the 2nd flight and the
2nd failure was on the 15th flight (at the NATS).I now have almost 20
flight with the rear support and everything seems fine now. Of course
you can also mount the Axi to a firewall and we have not heard of any
failures with that set up. I spoke with Jerry Budd and he is planning
to be making a rear support available for the outrunners similar to the
one he now makes for the Hacker C50. Please if you are planning on using
a front mount outrunner consider the rear support before you get too far
along. I was going to write a KFactor article on this, but it seems
like a better idea to get this out more quickly via the mail list.
Chris Moon
D5 VP
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