I have been thinking about this post and would like to contribute an

idea.  What may be happening here could have nothing to do with hardware and everything to do with rheology.  Many common fluids are Newtonian; that is to

say their viscosity is constant with regard to shear rate.  However, others, such as polymers, are non-Newtonian and exhibit a reduction in viscosity with
regard to shear.  Single grade oils and multi-grade synthetic oils are pure substances and therefore Newtonian.  But multi-grade mineral based oils achieve a
viscosity range by adding a polymer to the oil base.  This may transform the oil to a non-Newtonian fluid and could exhibit shear thinning.  When the wall
shear stress builds sufficiently, this has a tendency to cause a flow disruption.  In extrusion of polymers it is called melt fracture and is accompanied by
wild fluctuations in pressure and flow; essentially a chaotic system.  This phenomena is often accompanied by rather distinct changes in the sounds

 produced by the process.  This sounds a lot like the description of the oil pump issue.  If true, it would require standard mineral based multi-grade to make
this happen and not with single grade or synthetic grades.

Just an idea.

Charlie Smith

KIS Cruiser 4021

Now, Charlie, that's an idea!  It might even be the RIGHT idea!  Brilliant! Nice to have a rheology expert!

I just checked our lab journal and confirmed that we made the tests with AeroShell 15W50 because we had plenty left over.  If I am not mistaken 15W50 is
precisely a multi-grade mineral-based oil!

I can't wait for tomorrow to repeat the test with a single-grade oil.

Having said this, we still had only 9.5 gal/mn on the Arrow (versus 16 gal/mn and more on the rig) despite using Mobil 1.  Maybe the pump in the Arrow is
damaged for having run over 50 hours with the wrong oil!

You can be sure I'll keep you posted.

Now, it's 2:40am here, time for me to hit the sack.  Talk to you tomorrow!

Francois Badoux

 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2003 All world wide rights reserved.