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Since I'm involved in the design of a gearbox at present,
I just thought I'd add that this is non-trivial to do properly. The lawyers at
the gear manufacturer have made it impossible to use their design data, unless
you are designing stationary equipment (HEAVY!!). This means testing is required
to get accurate life data for each particular application. The problem is, to
have statistically meaningful data you will have to test at least 10 articles.
This is very expensive. Not something that a guy in his garage can afford to do
properly. If you have statistical design data...you don't give it out. So....the
best bet is to use something the airboat guys use successfully, or something
people are currently flying successfully.
The flexplate failure looks like typical high cycle
fatigue. Since these are used parts, we don't know the
part history. It could have been installed improperly in the car or had a
manufacturing defect. The fact that two people have experienced failures may be
a trend, maybe not.
1.) Inspect all flex plates very carefully before
installation. Magnaflux/Dye penetrant, etc.
2.) Replace the rubber dampers at annual
3.) Do regular Flexplate inspections.
4.) Use a new flex plate if possible.
If people continue to have failures, then it's time
for redesign, but I wouldn't say that just yet. The two failures were relatively
high power installations.
Monty
----- Original Message -----
Sent: Thursday, July 28, 2011 9:21
AM
Subject: [FlyRotary] Re: Kitplanes
Article - Safety is no Accident
Great article for sure..... The introduction picture
is kool too. <GG> Ben Haaswww.haaspowerair.com
To: flyrotary@lancaironline.netDate:
Wed, 27 Jul 2011 16:27:51 -0500 From: msteitle@gmail.comSubject:
[FlyRotary] Kitplanes Article - Safety is no Accident
There was an article in the February 2011 issue of Kitplanes titled,
"Safety is no Accident", by Ron Wanttaja. In light of the
recent flexplate failures, I found it interesting that it highlights
two areas where automotive engines tend to fail, the cooling system and
the gear reduction unit. To quote, "Note that auto conversions have
a higher accident rate right where you would expect it--in engine cooling and
in the systems that convert engine power to a slower speed for a propeller or
helicopter rotor." Seems that we've hit on one of the
primary failure modes here. According to Ron's calculations, the
accident rate for auto engine homebuilts was 23% higher than
for homebuilts with traditional engines. The rotary had the fewest total
accidents, but the rotary also has the fewest number of a/c flying. This
is a well written article that should be on everyone's reading
list.
Note: Mr. Wanttaja is a systems engineer, engaged in satellite
orbit/constellation design and analysis, launch vehicle and onboard propulsion
system trades, and operations concepts for space systems. He worked on
the early design studies for the International Space Station.
Mark
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