Mailing List flyrotary@lancaironline.net Message #24547
From: Jack Ford <jackoford@theofficenet.com>
Subject: Re: Message with possible fraud attempt: [FlyRotary] Re: Coolant Leak
Date: Sun, 26 Jun 2005 17:51:46 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
 
----- Original Message -----
Sent: Sunday, June 26, 2005 11:39 AM
Subject: Message with possible fraud attempt: [FlyRotary] Re: Coolant Leak






On 6/26/05, Al Gietzen <ALVentures@cox.net> wrote:

 Al, all I can tell you is that the pressure would go immediately (within   2 seconds) to 21-24 psi.  Then as the engine warmed up the pressure would drop to a nominal 8 psi or so

 

It makes sense to me Ed.  Heat the coolant just a little, and it needs to expand just a little.  In order for any of the coolant to flow out past the cap (even just a little coolant), it must reach the pressure rating of the cap.

 

How much can the coolant heat up in 2 seconds after start?  Just about zero.  The only thing that is heated a little in that time is the rotor housing walls. Maybe that reduces coolant volume.  In any case, if you have any radiator hose in the system, it will expand enough to keep the pressure from increasing that much.  There is some weird science in here somewhere.

 

Al

Do you mean "just about zero", or absolutely zero?
 
Just about zero would imply something slightly larger than zero.  Which means that the coolant expands something just a little more than zero.  If you truly have no air in the system, an expansion of just about zero still has to open the pressure cap, which requires opening pressure.  If you sealed water in a steel box with no air, heating the water a fraction of a degree would raise the pressure hundreds of psi.  Just a few degrees will deform the steel box.  Its not weird science, its just weird freaks of nature. Not even a weird freak of nature, everything in the engine is related, in terms of stress and pressure transfer, under Hooke's and Pascal's Laws. The eensiest bit of expansion of the coolant must displace it's container walls in proportion to the pressure.
 
If you mean absolutely zero heating of the coolant a few seconds after starting I will take exception.  That flame is well over 2000 deg F and the rotor housing water jacket is not very thick. Easy to calculate if we know the BTU quantity per time and the heat tranfer coefficients (heat conductivity), thicknesses and areas of the materials present. Some (although small) heating of the coolant easily occurs within one second after starting the engine. Has to, or it wouldn't occur later, either.
 
Someone mentioned radiator hose expansion.  I don't know about your system, but my steel braided hose is going to take a lot more than 25 psi before it allows any expansion. Reread Hooke's Law. Will probably add to the "springiness" of the whole system). 25 PSI is nothing.  Not going to harm any part of anyone's cooling system except maybe with multiple cycles. Not likely even with multiple cycles, because the pressure is an insignificant fraction of the yield strength of any of the materials we are dealing with.  That said, I also believe in having an air spring/absorber.  The main part of my cooling system I keep full, but have a 1 qt pressurized overflow can that is empty at engine start. I like that so much I'm going to incorporate it (Shameless copy of an excellent idea). 
 
Jack Ford
(The friendly nit-picker).



Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster