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From: "George Lendich" <lendich@optusnet.com.au>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
References: <list-1453276@logan.com>
Subject: Re: [FlyRotary] Re: Exhaust Update
Date: Wed, 11 Oct 2006 06:46:30 +1000
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Ken/Buly,
The Mazda's high heat has proven to cause cracking at the joint of the 
exhaust flange to the exhaust pipe UNLESS there is room to expand and 
contract due to the heat cycling. Welding the inside and only having four 
tack welds of a reasonable length, have proven to be satisfactory and better 
than full welding inside and outside the flange.
There are other methods which separate the pipe from the flange - such as 
the motorbike style fitting, where you have a small round tapered flange 
which is captured by the larger flange( clamping action), as it is bolted 
up. This would be my preferred style of fitting, which would completely 
eliminate the pipe cracking  problem. The muffler would need to be supported 
independently, which is the preferred method anyway.
George ( down under)

> On Oct 9, 2006, at 11:15 PM, kenpowell@comcast.net wrote:
>
>> Hi Joe,
>>  Just a heads up - it looks like your new "header flange to  pipe" 
>> (picture 5) was welded on the outside.  I think that  'acceptable 
>> practices' state that there should only be a tack weld  on the outside 
>> and the actual structural weld should be on the  inside.  What does 
>> everyone else say?   In any event be sure to  keep an eye on the welds.
>>
>> Ken Powell
>> Bryant, Arkansas
>> 501-847-4721
>> C150 / RV-4 under construction
>
> Ken, I had the chance to inspect hundreds of aircraft exhaust systems 
> from C-150 to the big twins. On 99% of them the flange is welded on  the 
> outside. I have seen only one model aircraft that requires  welding on the 
> inside only?
> Buly
>
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