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[turbobike] Re: coatings

Jeff Churchill (jcperformance@juno.com)
Tue, 9 Nov 1999 13:22:27 est

   You are absolutely correct,.....  I use the skirt coating as another
insurance policy,...the 
combustion chamber coatings I believe,  are very functional in many
respects,..not the least of which is heat rejection,...which helps the
piston survive,..and leaves more heat
in the gasses where it belongs and contributes to increased power.
   Remember I do a lot of work for the Harley air-cooled motors and
improper warm-up and break-in seems to part of the life style,...no
matter what you do,  someone can ruin good work quickly !
  The coatings are applied with a detail air-brush and heat cured.  I
think the non- OEM coatings are more sacrificial than permanent,....but
they are relatively inexpensive,...and I
honestly have not observed any component failures on any coated parts, 
mine or others !

Jeff Churchill

J.C. Performance    617-06  Bicycle Path   Port Jefferson Station   NY  
11776    USA
tech:  516-928-6679  or  516-928-9863
website:     http://www.jcperformance.com/

On Tue, 9 Nov 1999 09:46:42 -0500 <shammar@nsk-corp.com> writes:
> Are you using that Dow Corning Molykote on the skirts?  How is it 
> applied?  When
> I worked with them on a development project in a previous life as a 
> piston
> engineer, they were promoting a screen printing process.  We found 
> that getting
> the coating to stay there over the long haul was difficult, although 
> it has made
> its way into some production programs.  Gimmick or true benefit, I'm 
> not really
> sure.  Any opinion/data on this?
> In my opinion getting the ovality and profile of the skirt right are 
> more
> important.  Since the skirt/cylinder interface operates under 
> hydrodynamic
> lubrication once the engine is running, frictional loss is a 
> function of the oil
> viscosity (shearing forces) as long as there is no hard contact due 
> to a profile
> problem.  Therefore the only benefit of the skirt coating should be 
> on startup,
> or if the shape of the skirt is marginal to begin with.
> I don't mean to bash your process- those are just my thoughts, based 
> on what my
> Brazilian friends at Metal Leve taught me.
> Regards,
> Bob