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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-936300@logan.com>
Subject: Re: [FlyRotary] Detonation? (was: Seal Hrdness)
Date: Sun, 8 May 2005 07:33:39 -0400
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Bill, The only time I have ever encountered "detonation" in a NA rotary 
engine was early on with the   86 NA engine I was flying with.  I screwed up 
and by mistake set the ignition advance to something like 40-45 degrees 
BTDC.  Take off and climbout were OK but when I tried to open it up and the 
rpm's increased I encountered a "shuddering" vibration and backed off.  When 
I landed I took out the spark plugs and found them severely damaged.  The 
two leading plugs   had 1/2 of the ceramic center cone gone (split and broke 
off), the ground electrode (this was a type that had only one ground 
electrode) was badly eaten and gone in one case.  The distance between 
ground and center electrode had grown to approx 1/8 -3/16".   The trailing 
edge plugs had cracked ceramic also and the electrodes showed erosion 
similar to the lead plugs - just not as bad. I still have the plugs as a 
reminder not to over advance the ignition

 However, at least on that occasion the three piece 2mm apex seals survived.


Ed
----- Original Message ----- 
From: "BillDube@killacycle.com" <billdube@killacycle.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, May 08, 2005 12:56 AM
Subject: [FlyRotary] Detonation? (was: Seal Hrdness)


> It occurred to me after I sent the last note that perhaps detonation cased 
> the apex seal grove to wallow out and the apex seal to fail. This is just 
> a guess on my part.
>
> On a piston engine, I have seen severe detonation shear the ring lands 
> right off the pistons. This happened on a supercharged small block with 
> stock pistons. The detonation was very severe, but brief (drag race.) The 
> tops of the pistons did not have time to burn and melt like they would 
> with more marginal, but long-term, detonation conditions. The force of the 
> detonation did the damage directly rather than the high combustion 
> temperatures.
>
> Just a though.
>
> Bill Dube <LED@Killacycle.com>
> http://www.killacycle.com/Lights.htm
>
>
>
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