Mailing List flyrotary@lancaironline.net Message #14045
From: Ed Anderson <eanderson@carolina.rr.com>
Subject: Great to hear: was [FlyRotary] I'm better now
Date: Sat, 18 Dec 2004 08:20:39 -0500
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Message
Rusty, glad to hear you have reconsidered, especially given the amount of effort and how close (I think) to working out all the bugs.
 
Having experienced several similar   heart thumping, cushion gripping events myself, I understand what you are going though.  After all we are putting ourselves at some degree of risk.  However, I personally consider the most dangerous part of each flight the 10 mile drive to the airpatch on a narrow two lane road with everything from very senior citizens to huge dump trucks passing me at a closure rate of 90 mph two feet or so away.  Think about it!
 
Regarding the core.  I think there are some significant difference between the pressures and impulses encounter in the coolant system and the oil system.  For one the oil pump is a positive displacement pump meaning that it is going to put out 156 psi (dropping to 80 psi by oil controller activates) in rapid pulsation - regardless of what resistance it encounters.    The coolant pump on the other hand is a centrifugal type pump, it does not have the high peak pulsation of the lobed oil pump (smoother flow), plus if it encounters flow resistance, it simply slows down the flow (head pressure increases)  or it causes the pump to cavitate.  Also we have a difference in stress between a 80-100 psi pulsating operating pressure and a 5-15 psi operating pressure in the cores. I suspect the difference in viscosity is also a factor as the cross channels are something on the order of 1/8-3/16 sq inches each.  I would imagine that cold 40-50 weigh oil encounters considerable resistance to flow in these channels.  Got to cause more stress on the cores than water at least on startup before the oil has warmed up..
 
Now  I am not a pump expert (nor any other kind - even on TV) but I believe there are these significant differences between the stresses encounter in the two different core applications. Besides, the core has been used by numerous folks for coolant without problems and if mounted correctly and with consideration of stresses on fittings I believe you will do just fine in that application.
 
However, if your confidence about using cores is somewhat understandably shakened, then by all means have custom radiators built - worth it for you peace of mind and still a small cost compared to your total investment in the project. 
 
Whatever you do don't sell it, but if you do sell it - don't sell it to Ken Powers, he has more than enough unfinished projects {:>)
 
Ed Anderson
 
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