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Date: Sat, 23 Apr 2005 09:01:24 -0500
From: Jim Sower <canarder@frontiernet.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: All Parts have arrived, Whew!
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It appears I've missed something along the way here.  We've got all 
these rotors being pitched because the apex seal slots are wallowed out 
a little.  The replacement price seems pretty high (and likely to 
inflate quickly when more folks start inspecting the slots of 
replacement rotors) and one has to wonder how long the "used rotor" 
supply will last.  What I seem to have missed is the compelling reason 
why we can't simply mill the slots out to 3 mm, install new seals and 
continue the march.  I know Tracy's "new formulation" seals only come in 
2 mm, but I speculate that would be pretty easy to change given the 
current rash of wallowed out 2 mm slots and the potential market for 3mm 
versions.  I've got this idea that 3 mm seals has been sort of "elective 
surgery" and perhaps priced accordingly.  Given the potential demand, it 
seems this could change significantly.

 From an engineering standpoint, what's the problem? ... Jim S.


George Lendich wrote:

> Ed,
> It could be their rotors don't exceed the tolerances - by design or 
> just luck!
> Also we are running continuous high power, unlike cars, so advice on 
> what's acceptable in cars, do not necessarily relate to Aviation.
>  
> I picked-up a number of damaged rotors from the local Rotary shop and 
> all the damaged rotors which quite obviously suffered broken apex 
> seals, which destroyed the rotors and quite obviously the rotor 
> housings - had out of spec slots.  There were some that seemed good 
> 9.7:1 rotors until the apex seals broke - they do a nasty job on the 
> inside of the motor!!
>  
> If your anything like me Ed - when there's a lemon I'm gunna get it!!
> I just live with that knowledge, and check everything now.
> It's any easy thing to check!
>  
> George (down under)
>
>     Well, George, I would not  take the conclusion that far.  We have
>     folks flying with several hundred more hours than I have with no
>     apex seal failures.  In fact to the best of my knowledge, I am the
>     only one I am aware of other than Chuck Dunlap who's rotary engine
>     swallowed a 1/4" dia steel bolt (it was retained - so we know) to
>     have an apex seal failure in an aircraft.  However, I do believe
>     that folks need to be more aware of the true condition of their
>     used engine components - I know all probably did was look at it
>     and not seeing any obviously defects or dings said - "good to go!"
>      
>     As you know, Leon is convinced my apex seal failure was also due
>     to foreign object ingestion - I certainly can not prove it was
>     something else (like the apex seal slop)  although I don't
>     believe a foreign object  to be the case - belief is not a fact {:>). 
>      
>      
>     Ed
>
>