Flying Information
How to remove the "Gunk" from your muffler.
By Mike Fortune
There is nothing that makes a model look
more neglected than the "Gunk" that accumulates
on the muffler. The problem is
now that it's on thereÉhow do you go
about getting it off? Well, before we try to
remove itÉwe need to know what it is.
Our model engines run on what we call
"Fuel":). Fuel is actually a blend of several
basic components: alcohol, nitromethane
and oil. The alcohol and nitro are there to
promote combustion, make the engine run
and produce power. However, with just
these two components the engine would
run for just a few seconds and the engine
would be a total loss. At this rate, none of
us could have ever learned to hover! Someone
figured out years ago that adding oil to
the blend made the engine run better and
longer! However this came at the expense
of loss of horsepower. Now, when all things
were considered, this loss was actually a
long-term gain as our engines last longer
and are more reliable.
Well, with this new blend (Alcohol, nitro
and oil) now in hand and long engine runs
now possible, a new problem occurred (Isn't
that just like this hobby? You over come
one problem only to discover another!).
During these extended engine runs, the
muffler was now getting hot and the exhaust
from the engine seemed to hang in
the air. Soon after this we noticed the once
shiny muffler had started to develop a really
bad case of what looked like freckles
(known by arteests as a "wonderful patina"
-ED).
These brown stains seem to be everywhere
on the muffler and some even on the
engine. Soon it was discovered that these
spots were only occurring after we added
the oil to our fuel blend. While the alcohol
and nitro actually burn inside the combustion
chamber, oil, for the most part,
does not. The oil is the primary component
that is passed out the exhaust having previously
lubricated the all the moving parts
and providing cooling for the engine.
OK, now that we know what it isÉwhere
does it come from? Why are certain areas
of the muffler darker than others? Most of
the time the darkest areas are around the
portion of the muffler that bolts to the engine.
Why? This is the area that is hottest
and also where the muffler and engine join
together. It is at this joint where leakage can
occur. Any leaks in this area are quickly deposited
on to the hot muffler. At this point
the leaked oil is actually baked on to the muffler.
So, now that we know where it comes
from, how do we prevent it? The joint between
the muffler and the engine must be
sealed. I have read many suggestions concerning
how to seal this joint. I've heard of
guys suggesting the use of epoxy, gaskets,
silicon sealant, JB weld, and card stock.
My personal favorite was that of silicone
sealant. I just put a gob between the engine
and muffler and hoped for the best. This
was always met with mixed results. Sometimes
it worked and sometimes it didn't. I
have tried all these other methods, with the
exception of the epoxy, but I continued to
have leaks at this joint. It was after a conversation
I had with Wayne Mann on this
subject that I adopted this secret of sealing
the joint between the muffler and the
engine. Here's the equipment: a piece of
glass, sandpaper and oil. Here's what to do:
Lay the sandpaper (400 grit, good quality
wet/dry type) on top of the glass and add
a few drops of light oil on the sandpaper.
Next, moving only in a figure eight pattern,
sand the muffler flange until it is perfectly
flat. You should see a nice even flat surface
on the face of the muffler flange. After
carefully plugging the exhaust port (Or
preferably, with the engine completely disassembled),
repeat the same on the engine
exhaust port. Again, you should see a nice
even and flat surface on the engine exhaust
port. Next, clean this area with a
good degreasing agent. I use paint thinner.
Now, apply a very thin coat of blue silicone
sealant to the muffler flange. This
should be thin enough that you can barely
see it on the muffler flange. Now, join the
two as normal.
Sanding the two on the glass gives a
smooth, flat flange surface that has very
fine texture: "swirl" grooves from the
sandpaper, that is otherwise hard to duplicate.
The joint is so tight now, hardly any
sealant will be left in the joint itself. The
swirl texture actually helps hold the silicone sealant
in place and resists any blow out occurences. For
those running muffler pressure, you should see a
more reliable and constant fuel mixture as the muffler
is no longer losing pressure during the flight.
So now that we have the leak sealed, how do we return
the muffler back to its once beautiful shine? There
is a product for this that is called Simichrome. It comes
in a small tube and it cost about $5.00. I bought this
tube at a local motorcycle shop. ItÕs truly amazing how
effectively this product not only removes the "gunk," but also polishes the muffler at the same time. Not only
is it effective, but also it's also quick! It takes just a few
minutes to polish an entire muffler. It comes in paste
form and basically is rubbed on and rubbed off. (See
box label for a more precise description.)
For those of you wanting to remove the "Gunk"
from your muffler, give these methods a try.
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