Fuel/Water, Bearing/Rust

[Earl Vincent]

Vicente, you are on the right track, 4 stroke crank case does not get any
burnt nitro residue and when the engine is cooling down it is not open to
the pipe to condense any gases still in the pipe, the
chemical engineers on this site would know better than I would what acid is
formed as a biproduct when nitro and methanol is burnt. Four stroke engines
burn more efficient than a 2 stroke leaving less unburnt gas etc in the head
to begin with. I have tried running the 2 stroke engines at the end of the
day with no nitro fuels, used afterrun oil, even put a nipple on the back of
the crankcase with a fuel dot so I could inject rust inhibitors inside, some
of this helped but was still putting a new bearing in in about 30- 40
flights,when I put a stainless bearing in I ran the rest of the season
without a problem, in my case I removed the shields, I have heard 200+ runs
either way.
The SS bearings are not all stainless mostly the cage is pure stainless,
that is what has the highest iron content in the regular steel bearings and
breaks down to the acids forming rust ginding compound that degrade the
balls and race.
The Webra 120 side exaust engine I had in an Ultimate bipe with a muffler
had no bearing problems, when I put it into the Quest with a tune pipe the
bearing went in about 20 flights, the pipe pulses
unburt and burnt gases back into the engine where I guess some stay in the
crankcase when shut down. Good news is that the Webra 120 and the OS 140
have the same size rear bearing so I installed a SS bearing in the Webra and
have about 30 to 40 flights on it and is still smooth, no after run just run
dry.
Marlin Groninger used to run FAI fuel at the end of the day on the OS pumped
61 then would remove the tuned pipe and cap the header and carb intake, I
remember him getting a whole season on one bearing back then, just seems
like a lot of work when a SS solves the problem. I think the Hanno
came with a SS bearing I had 2 of them and do not remember replacing
bearings and I was running 20-30% nitro.
Earl Vincent

----- Original Message ----- 
From: <Vicenterc at comcast.net>
To: <discussion at nsrca.org>
Cc: "Jeff Hughes" <jhughes at hsonline.net>; <discussion at nsrca.org>; "Bob
Pastorello" <rcaerobob at cox.net>; <discussion at nsrca.org>
Sent: Saturday, December 06, 2003 10:11 PM
Subject: Re: Fuel/Water, Bearing/Rust


> I think the reason is that there are very little chance to get burned fuel
in the bearings area in the 4C.  The 2C is more open for combustion gases to
blow back and stay there after runing.  If you run the engine with no nitro
fuel you will clean al residues of nitro and the chances to form acids would
be less.
>
> Vicente
> > so why don't the 4stroke guys have problems? they are running much
higher
> > nitro contents than the two stroke guys (typically)?
> >
> >
> > ----- Original Message -----
> > From: <vicenterc at comcast.net>
> > To: <discussion at nsrca.org>
> > Cc: Bob Pastorello <rcaerobob at cox.net>; <discussion at nsrca.org>
> > Sent: Saturday, December 06, 2003 4:18 PM
> > Subject: Re: Fuel/Water, Bearing/Rust
> >
> >
> > > I remember reading the Mintor instructions.  The instructions
recommends
> > to run the engine with NO nitro if you are not planing to fly again for
more
> > than a week.  Also, I remember many years ago when I flew in Venezuela
with
> > NO nitro and we didn't have bearings problems.  Looks like we need to
find
> > out if Nitro is causing the problems particularly in 2 C engines with
large
> > pipes.  I think the nitro residues condense and form strong acid that
> > attacks the metals.
> > >
> > > Vicente
> > >
> > > =====================================
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> > >
> > >
> >
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