From: Lehanover@aol.com
Message-ID: <11c.29e3b5f8.2d226e90@aol.com>
Date: Tue, 30 Dec 2003 01:00:48 EST
Subject: Re: [FlyRotary] Re: aluminum hose bungs/fittings
To: flyrotary@lancaironline.net
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 Wrap the end of the core with a few layers of soaking wet towel while
 welding
 on the fittings.
 
  
 Thanks for all the construction tips Lynn, particularly this bit about the
 wet towels.  As I've thought of welding these things, I couldn't help but
 wonder how much of the factory core I would be un-welding in the process.
 How exactly are these constructed?  I assume they're brazed, and something
 of a lower temp than welding??  
 
 The cores are furnace brazed and if over heated, become cooler kits.
 
  This is a job for a TIG machine only.  Weld three tacks 120 degrees apart 
and quench the welds with a wet rag. Let everything cool down to room temp. 
Weld between two of the tacks and quench again. And so on until finished.

 The cores will have oil in them that circulates in the system to lubricate
 the compressor. Let them drain for a few days and the rinse them out with
 ketone or similar and then soap and water. Blow it out to get it as dry as 
possible
 before welding. If you short cut this step, be aware that the jet of orange
 oil vapor flame that shoots out of the proposed fitting holes is about a
 foot long and will blow your welding helmet clean off of your head.
  
 Another wise piece of advice.  I haven't looked for junk cores, but the
 problem I've found with the new ones is that none of them are made the same.
 I had planned to do plenty of practice on similar thicknesses of aluminum,
 and then try the new core.  If I screw up enough of them, I'll surely be
 looking for some of those junk cores for more practice.  
 
 
 These things work well for water or oil cooling. They are tough as nails.
 (the GM stuff). If you have room, you can cut one side off of a bulkhead
 fitting
 and use the hex as a welding flange. Better for oil cooling where the
 fittings
 hose ends are going to be heavy anyway. For water service, the AN fittings
 and hose ends will be too big (dash 16 or 20) and too heavy.
  
 I thought about the cut off fitting, but aluminum AN bungs are pretty
 reasonably priced, so I'll probably just use those.  With everything in
 place this afternoon, it looks like I have room to use an AN-12 bung
 (remember, parallel cores) and 90 degree hose fitting, so I'm leaning
 strongly toward going that route.  As much as it pains me to buy all that AN
 hose, it's really the "right" thing to do.  I'm sure the silicone hose is
 perfectly fine, but the more I can conform to "aircraft quality", the less
 grief I'll get from all the people who look at it.  I think Tracy actually
 mentioned this as a significant downside to using auto hose.   
 
 Mount the core in foam lined brackets. Don't let anything rub against them
 (but a foam seal strip).
 
 I have the cores attached to the redrive plate with aluminum angle on top,
 and bottom.  The idea was to weld the angle to the cores, then bolt it to
 the redrive plate.  I hadn't planned to put any sort of rubber dampening,
 since the cores are very solidly mounted (can't twist, or bend).  Should I
 put a 1/8" or so piece of rubber between the angle and mounts?  That just
 doesn't strike me as a good idea, but I'm open to suggestion.  
  
 Also, when mounting the cores to the angle.  I planned to weld the angle to
 the cores on top and bottom, but for test fitting, I drilled and clecoed the
 angle to the end plates on the core.  With only 6 clecoes, this thing is
 VERY solid.  I'm now wondering if I couldn't just put about a dozen 1/8" pop
 rivets, rather than welding the angle.  I have to admit, that I'm thinking
 about easy of replacement if one ever gets damaged away from home.  Assuming
 I keep a spare core with two AN12 fittings welded to it, all I'd have to do
 to replace a core is drill out the rivets, then drill and pop rivet the new
 core.  This may sound paranoid, but I know that Ed and Finn have both
 replaced leaking cores.  I'm also thinking about lessoning the chance of
 damaging a core by overheating it with the torch.  
  
 Thanks,
 Rusty (sure would be easier if it was at home)    
 
 
  The pop rivets are fine. Stainless in a staggered pattern. But think about 
this. You are about to rigidly attach a heavy aluminum cooler to (in effect) 
an engine that can ring it's own case bolts hard enough to fatigue them to 
death. The brackets are 
what? 6061-0? fatigue life at high cyclic rates of one hour. Maybe 2024-T3 
would be better but it just gives you a false sense of security. Instead of 
cracking during taxi testing, it will crack during flight. The cooler is also very 
soft stuff and has a similar problem. The small lighter, coolers on big flat 
engines last a long time and work fine. 

But these coolers are heavy and don't like to move at anything like the speed 
of a rotary. They have to be protected from that movement. Even though it is 
slight in amplitude and at a much higher frequency (engine speed). I would not 
even clamp the hoses down tight close, to the cooler. Its just bad practice. 

My three oil coolers are strapped down on a strip of foam weather strip all 
the way around. with two tie wraps (Zip Ties) at each corner.  The car has been 
hit hard several times. No damage to the coolers or the radiator. Also 
mounted in foam lined brackets.  

Lynn E. Hanover