<br><font size=2 face="sans-serif">Gear mount plate failure is independent
of the gear itself, although it is safe to say that a too stiff gear will
put more stress on the plate. So needs to flex so reduce stress, but not
a spring.</font>
<br>
<br><font size=2 face="sans-serif">Your failure across the fibers is strange,
but not unheard of. Composites weak link is compression, because it is
the duty of the resin to transfer compression load from one fiber to the
next, and resin is orders of magnitude weaker than fibers. A genereal rule
of thumb is for every 2% void volume in the laminate equals about a 20%
drop in compression strength. It sounds as if your failure was a compression
initated failure, as what you describe sounds like a compression failure.
</font>
<br><font size=2 face="sans-serif">Every RC gear I have looked at, I can
visually see voids. Normally a void volume greater than 15% is required
to be able to be seen without a microscope. When I first posted that AeroSlave
gear would be Autoclave processed, that is to keep the void volume below
2%, and industry standard. Your failure was most ikely as you described..a
hidden flaw in the laminate. In the real world we ultrasonically scan composites
for voids-not feasible($$$) for RC models.<br>
</font>
<br><font size=2 face="sans-serif"><br>
<br>
<br>
Gray Fowler<br>
Senior Principal Chemical Engineer<br>
Radomes and Specialty Apertures<br>
Technical Staff Composites Engineering<br>
Raytheon</font>
<br>
<br>
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<td width=40%><font size=1 face="sans-serif"><b><glmiller3@suddenlink.net></b>
</font>
<br><font size=1 face="sans-serif">Sent by: nsrca-discussion-bounces@lists.nsrca.org</font>
<p><font size=1 face="sans-serif">01/19/2009 09:34 AM</font>
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<div align=center><font size=1 face="sans-serif">Please respond to<br>
General pattern discussion <nsrca-discussion@lists.nsrca.org></font></div></table>
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<div align=right><font size=1 face="sans-serif">To</font></div>
<td><font size=1 face="sans-serif">General pattern discussion <nsrca-discussion@lists.nsrca.org></font>
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<div align=right><font size=1 face="sans-serif">cc</font></div>
<td><font size=1 face="sans-serif">aeroslave@tx.rr.com</font>
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<div align=right><font size=1 face="sans-serif">Subject</font></div>
<td><font size=1 face="sans-serif">Re: [NSRCA-discussion] Mo'CF gear talk
from AeroSlave</font></table>
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<br><tt><font size=2>I had an ES gear failure in Crowley two years ago-
grass field and the landing was a 9 before the broken gear leg zeroed it.
The gear strut broke straight across perpendicular to the long
axis about half way between the fuse and wheel. In a human bone,
I would call this a "pathologic fracture" ie, implying an underlying
pathologic defect. I actually patched this gear by splinting it with
a piece of carbon plate, wrapping it with carbon cloth, soaking the whole
thing with epoxy and wrapping it up tight with celophane and tape. It
isn't pretty, but it is quite funtional. Since it was one of my last
long ES gears I'm still using it. <br>
<br>
No manufacturing process is perfect, and I think somehow there was a structural
weakness that failed here. However, not all the preceding landings
were 10's, so I might have cracked it on an earlier landing and it failed
later.<br>
<br>
Interestingly enough I had a gear plate failure on that same airplane (E
Pinnacle- Oxai). the gear plate was made with carbon reinforcing
the bottom of a light ply plate. I had drilled it and put screws
with large washers through from above and locknuts below. As I flew,
the gear would loosen as the washers were pulled into the light ply. After
several rounds of tightening, I noticed fatigue around the washers and
upsized them, but eventually, (again in Crowley on a grass field) the screw
and washers pulled through the plate...leaving nice holes in the plate
which stayed attached to the fuse sides. The carbon cloth pulled
off the bottom and added no significant strength. I repaired
it with a hardply top surface and it never was a problem again. <br>
<br>
George<br>
---- aeroslave@tx.rr.com wrote: <br>
<br>
=============<br>
Dave<br>
<br>
Concerning your earlier email<br>
<br>
"I am not a fan of the typical 2 piece gear – where each half stops
short of the middle, and a nasty bending load is created in the center
of the gear plate (unless a spreader plate/joiner is attached between the
two legs). "<br>
--<br>
<br>
Here's how I see the stress...<br>
<br>
On a landing, hard or soft when the gear impact, the load will be tension
on the bolt closest to the edge of the "Half gear". Bolts work
really good in tension. The other load is the bending back of the bolts-a
load at which bolts suck. So a rough landing using a two piece gear wants
to either pull the bolt through its mounting in the plane (cuz 11lbs
ain't gonna tension fail the bolt) or its gonna bend the bolt heads ...resulting
in a semi tension on the plane bolt mount, wanting to once again pull it
through. What happens in reality is the bolts do not break, but the entire
mounting plate is stress tension up front, compression in the rear until
it find sthat weak "terminated area" and rips out at that point.
My whole thinking here is that regardless of a 1 piece or two piece design,
the weak link to failure lay elsewhere-so 1 or 2 piece does not matter.
Speaking of failures.......<br>
<br>
Anyone who has had a gear failure...please let me hear it. Describe the
landing (wasn't a 10 now was it???? be honest) describe the failure...bolts,
plane mount, fuse sides, gear break..whatever.<br>
<br>
My landing are always scored about 9.24-9.56, which is why Lance is testing
the prototype gear.<br>
<br>
Gray <br>
<br>
AeroSlave Dude #2 (Lance is #1-I default to him) <br>
<br>
AeroSlave<br>
4408 Elmhurst Dr<br>
Plano, TX 75093<br>
www.aeroslave.com<br>
PayPal: aeroslave@tx.rr.com<br>
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