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From: "Ed Anderson" <eanderson@carolina.rr.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1581835@logan.com>
Subject: Re: [FlyRotary] Re: Spark Plugs
Date: Sun, 19 Nov 2006 09:37:22 -0500
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----- Original Message ----- 
From: "Charlie England" <ceengland@bellsouth.net>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, November 19, 2006 9:23 AM
Subject: [FlyRotary] Re: Spark Plugs


> Ed Anderson wrote:
>
>> I agree that the "idea" auto spark plug for the flying rotary is still 
>> waiting in the wings.  I am currently using a special lead scavenging 
>> formula to see if it can extend the useful life of lead fouled spark 
>> plugs (don't ask I don't know what's in it {:>)). Well, see whether it 
>> does anything for the problem.
>>
>> I normally get approx 25 hours on a set before SAG sets in using 100LL. 
>> I speculate that one reason that such things as TCP do not appear to do 
>> much for the rotary engine is that the chemical reaction apparently 
>> (according to reports) requires the high cylinder head temperatures of 
>> air cooled cylinders (like 375F +).  I believe that with our plugs buried 
>> within the housing (as opposed to protruding into the combustion chamber 
>> (and they had better not or you will clip your apex seals), that the 
>> plugs do not reach a sufficiently high temperature to deter fouling or to 
>> activate the TCP chemical reaction.  So perhaps a "hotter" plug might 
>> help - on the other hand, since we are running WOT for longer periods 
>> that many rotary racers - I'm not certain I want a hotter plug.
>>
>> I have tried fine wire and the stock plugs - but both seemed to have the 
>> same problem of lead fouling the ceramic cone and "bleeding" off spark 
>> causing misfiring.
>>
>> My $0.02
>>
>> Ed
>
>
> Back in the bad old days when cars ran leaded gas & transistors were only 
> found in spacecraft, there was an after market plug with construction 
> known as 'surface gap'. The porcelain filled the area between the 
> electrode & thread body. The 'gap' was the distance from the electrode to 
> the thread body.
>
> Anyone know whether these plugs are still available? It would seem that if 
> nothing else, it might make cleaning the lead a bit easier.
>
> Charlie
>
>
Actually,Charlie,  they still make them and they are available.  Jason had 
them in his engine at Pecan Plantation.  I looked into using them but when I 
read that one of the possible short-comings of this type of "surface gap" 
plug was fouling, I decided not to even buy a set, but wait until Jason 
reported back on how his were working out.  I agree they would appear easier 
to clean once they fouled, but if they fouled twice as readily, not much 
gained {:>)

Ed