[NSRCA-discussion] The good, the bad, and the ugly

[Michael Cohen]

For those of you on the edge of your seat waiting to hear what was the likely cause ..... well....... a neighbor with a gear puller helped me pop of the thrust washer and after removing the crank shaft, I found the main bearing had eaten itself.  The race had come apart and the balls we free to slap around.  The bearing probably went first allowing the crank to wobble taking on the connecting rod.  Bob Kane has come to my rescue with pieces of Mark Atwood's old and damaged 160DZ.  I will attempt to make one running engine out of two.

 

I have not heard of bearing failures with YS engines.  I is there some preventative maintenance I could have done to keep this from happening?  Did I make some mistake that leads to this kind of failure?  Is it just one of those things that is bound to happen one of these days?
 


From: precisionaero at hotmail.com
To: nsrca-discussion at lists.nsrca.org
Date: Thu, 21 May 2009 04:58:52 -0600
Subject: Re: [NSRCA-discussion] The good, the bad, and the ugly



Low viscosity PowerMaster DZ blend, 30% nitro, 20% synthetic is the fuel.  I had replaced the ring a few months ago, so I had taken apart most of the engine and re-assembled it using Klotz so it would not be dry the first time fuel ran through it.  By the way, I was 1.75 turn out on the main needle.  That seemed to be the RPM sweet spot +1/8 turn rich for good luck.  The pump was just right, the engine would chug along at 1900 RPM with a 4 blade nicely.  I had a nice smoke trail too, almost until the abrupt stop.
 


Date: Wed, 20 May 2009 19:08:40 -0700
From: getterflash at yahoo.com
To: nsrca-discussion at lists.nsrca.org
Subject: Re: [NSRCA-discussion] The good, the bad, and the ugly




Sorry to hear about your streak of bad luck.  What kind of fuel?  Was the engine stored with after run oil? 

 Bob Kane
getterflash at yahoo.com 






From: Michael Cohen <precisionaero at hotmail.com>
To: nsrca-discussion at lists.nsrca.org
Sent: Wednesday, May 20, 2009 8:24:18 PM
Subject: [NSRCA-discussion] The good, the bad, and the ugly



The Good:  I finally got out to fly today and put up flights 6 and 7 for the season.
 
The Bad:  To say I practiced flying the Masters Pattern might not hold up in court.  It had looping segments (of various radii), straight lines (some of very, very short length), roles (lets talk about mortgage rates instead); in other words, it had all the basic elements.  It also could be argued that I was flying the Wonkavator, up ways and down ways, sideways and back ways and slantways......
 
The Ugly:  5 minutes into flight #2, the engine stopped.  After a fun crosswind glide, I took the engine apart at the field to find the crankshaft-piston area very dry with shaving's everywhere, a mashed and bent (sort of) connecting rod, and a damage to the rotary valve.  I need to take pictures and post them because I have never seen damage like this.  It looks like lubricating oil was unable to get into the region and the engine just ate itself.
 
This was my 160DZ and is on the heals of breaking the shaft that supports the rocker arms on a 140DZ suddenly a month or so ago.  Is there something wrong with the lubrication system on these motors due to some kind of blockage?  Any suggestions on what to check would be appreciated.  The engines all looked clean and free of and kind of FOD when I took them apart and re-assembled them this late winter/early fall.  Before I go killing my last 170DZ, I am open to what people think I should look for (beside an OS, going electric, or gas).
 
Mike Cohen
D4
 



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