Got a 32 , not quite burned down , but gummed, will do a clean up and a bearing and a C/L convert , that makes what 5 engines for my plane , Im ecstatic

Stop winjin and buy a fourstroke

Do you recommend a 4 stroke for a C/L plane ?

You will have to be a whole lot more specific to find the answer that suits you, and the question as it is now is a bit like asking ' will unleaded fuel suit my car?'

There are a million variables to be answered before any meaningful conclusion can be reached.

4 strokes in control line work very well but at the moment are competition winners (or can be close to it) in stunt and scale.

Why? Because they are generally heavy, trickier to start and have a milder power output than equivalent control line engines.

The strong point is the milder power output that suits stunt and scale very well and the most popular 4 stroke in Australian CL is Saito due to its relative simplicity.

So what specific application do you have in mind mate?

It was a joke. Just think of it as a strine similie, not unlike "dry as a dead dingoes donger" or 'Ugly as a half sucked mango seed". I have a sneaking suspicion that emoticons (smilies) belittle the intelligence of the reader, and whats more, they're like a laxative ( they irritate the $h1T out of me!) so I rarely, if ever use them. Just take everything I say with a grain of salt and we'll be right.


Now, as for the Prestone's, no I didnt use that, I used Tectalloy thinking that if it was safe for alloy engine components it'd be fine for the engine. May not have been my greatest shining moment of intelligence in hindsight.
Might have to get some Prestone's. Who sells it in Aus?

Ah Renegade, I now see that your an Aussie like me - so of course its taken as a joke!

Prestones is sold by Super Cheap mate and if in doubt as to the suitabilty with use on a particular alloy, then simply try it on a corner of the muffler.
But be warned, this stuff WILLstrip all paint and anodising, its that effective when used on a boil.
15 minutes worth of boiling got an engine that was so coked up you could not see the piston through the exhaust port perfectly clean.

The other point worth noting is the fumes - it must be done outside and keep your head away from the top of the container.

Cheers (mother wears army boots, mumble, mumble.........)

Scott Bair did the actual test by putting a pressure sensor in a Super Tigre 46 and logging pressure against crank angles (I think this was part of an engineering thesis). Brett Buck took the raw data and converted it into a graph which showed the torque this pressure produced on the crankshaft. This was theoretical torque and actual torque would have been different because of friction losses in the engine but the output curves would have looked the same except lower. The second graph he made was a calculation of the affect this varying torque would have on prop speed at different crank angles and shows how the prop (a wood 12x5) varies in speed by a surprising amount. What I found interesting was the surprising amount of peak torque on an actual firing stroke which of course tends to tighten the prop nut.

OK, after all that blather, I've got the graphs [link=http://www.holdfastmac.com.au/424stroking.html]here[/link] on the web page I do for my local club. Just for interest's sake, I had permission from Brett to put his work on the web page.

Thanks for the link Brian, and just as a point of interest, gasoline powered two stroke engines can 'four stroke' as well!

This fits in similarly with what I've read about there being little discernible change in RPM from 4-2 in certain stunt engines. Can't remember where I read it exactly.

Interesting info though!

Sorry this is off post but you do mention fourstroking and i like to add smilies because aussies tend to say things a bit more bluntly than our american cousins!

Does anyone here have a link to fourstroke exhaust design in relation to fuel pressure nipples and whether they are necessary?..i want to run my saito220 with a short shotgun pipe in a percival mew gull,but am wary of a lean run and throwing a large prop.Any pointers appreciated,cheers

Even a straight pipe (on motorcycles they are called drag pipes) has some pressure in the tube.

I am running a straight pipe on my Enya R1.20 in a biplane. But I pinched the end a little and drilled a number of holes in the end as well. The pressure fitting is about 1.5 inches from the exhaust pipe beginning at the engine.

Usually the 4 stroke engines prefer a little back pressure in the exhaust. I remember simply running a 1/4 inch bolt near the end of my drag pipes to get the requisite back pressure, for the engine to work good. Plus it kept a police officer from running his nightstick down the pipe and then giving me a ticket for running straight pipes.

You can see the straight pipe he on my plane. At the time I wasn't really interested in taking pics of the exhaust system.

Actually it was let your 14 year old fly it

which means a 4 stroke might be more vulnerable to ploughing in the ground ,


your right It depends on application ,



for some its a religion , others just like to wreck gear all over the place , Im about middle , nudginging towards wrecking gear

You have to let the younger generation in<br type="_moz" />

Just as an aside here, here is the best explanation of why engines 'runaway' that I have ever read (kudos to 'VIC STUNT' site for this) -

TARMAC Notes for January and
February

They say that variety is the spice of life, so to hopefully
add some spice into the lives of any readers of these
simple missives (especially those with an interest in
engines), I have changed the format entirely for this
month. As mentioned last month, I have been fortunate
enough to get a very interesting and useful article from
Hans Bertina on the subject of engine management.

Hans is a clever and methodical worker who has had an
active interest in high performance engines that started
over forty years ago when he began working with team
racing engines. He then built his own Schneurle ported
speed engines shortly after the time that Bill Wisniewski
introduced them to the aeromodelling world by smashing
the world FAI speed record. Hans pioneered the use of
tuned pipes here in WA, firstly on model engines and then
on 100cc engines for Go Kart racing. He has also
demonstrated that he can set up the slower running stunt
engines. In essence, my message is that when it comes
to engines, Hans is a man that knows what he is talking
about. Due to the space constraints, he has supplied
much material of a general nature and the article is
intended to get you thinking, if you have an interest in any
particular area mentioned, please just ask and he will be
happy to give more details. Now, over to Hans.

HUMAN ENGINE MANAGEMENT

If you use an air-cooled engine to power your model
aircraft then this article may increase your know-how at
getting the best performance to suit your requirements. It
would be easy to write an entire book on this subject but I
don’t have the time yet (retirement takes up most of my
time). So here then, with the best intentions are my
experiences and opinions. These opinions could vary
from yours and in that case I am happy to debate them via
Email at [email protected].

Probably the most misunderstood component in our hobby
is the engine compartment. How often, for example, have
you seen Team racers that are very fast in practice only to
see them die in a race, or stunters with inconsistent engine
runs? In many cases possible winners have not achieved
their potential through lack of quality engine management.

To begin with, the most important concept to get in to your
brain is the idea of a “thermal cycle.” The running engine
produces heat, and up to a certain operating temperature
the unit behaves as expected. Beyond that, anything can
happen.

The beyond that is mostly seen as “lean runs,” burn
downs,” fall over,” and other aero modelling expressions.

At the point where the cooling process and heat generation
reach equilibrium we have a “STABLE THERMAL CYCLE”
and the motor will continue to run constantly and stable for
as long as you like. A stable cycle achieved at the
optimum for the particular motor will give optimum
performance a stable cycle at other than optimum is a
compromise and inherently can quickly become unstable.
Unfortunately many things affect the thermal cycle but
once you believe that a stable thermal cycle is required
then all you need to understand are the elements that
affect your particular environment.

Firstly the ONLY good heat is the heat from combustion, it
is the only thing that is controllable with the adjustments
available to you. It is also the only thing producing power.
Any other form of heating is bad news as it is unstable and
generally increases with stress. For example if your
bearings are not perfect they will generate heat and as
they get hotter cause more friction and even more heat.
Too tight a piston fit at running temperature will cause an
increase in heat generation because of the extra friction
and can lead to very rapid burn down or seizures. In fact,
any kind of misalignment will lead to “bad heat.” It is a fact
of life that both glow and diesel motors fire by compressing
the mixture to a self ignition point. Therefore increasing the
temperature at a given point advances the timing. This
can be very bad.

Why does all this matter? Well, simply because most
motors when used at their maximum power generate more
heat than air-cooling can remove. They rely therefore on
fuel cooling to augment the air-cooling. In the case of high
performance diesels, they are set to give regular misfiring
to give an occasional cooling stroke. With all this in mind
all you need to understand are the things that affect your
thermal cycle enabling you to reach optimum
performance.

These are:

Ignition timing

Fuel consumption

Fuel content

Propeller load

Compression

Plug (glow)

Compression setting (diesel)

Fuel feed


Cooling
Type of event


As you can see, there are quite a few and you may be able
to think of even more. Not surprisingly the fuel content and
ignition timing are major factors in our motor operations.
For whatever RPM you are operating at there is an ideal
timing for combustion to start. Too late (retarded) is never
harmful but not powerful. Too early (advanced) is
dangerous and can lead to permanent damage,
overheating and other nasty things. In all the large engine
research I have done, increasing the temperature of the
gas in the combustion chamber advances the ignition
point. That is, hotter plug earlier fire, increased
compression earlier fire (increased compression = more
heat). Of course too hot means pre ignition. That is real
bad news, as now the ignition is so early it is fighting the
motor. Remember that all things that affect temperature
affect timing and timing when ideal is good but early is bad
and late is slow.

In general when the fuel starts to run too hot then within a
matter of seconds everything goes bad quickly. Often you
see racing diesels burn down or fall over within a lap or
two. It is the rapid build up of earlier and earlier ignition
that causes the fast overheat as it builds on itself, even
though the motor may have appeared to be running well
for twenty laps or so beforehand. Obviously the thermal
cycle was not stable. Importantly don’t let the heat build
even slowly as you will suddenly get to a point of no return.
Speed engines do the same thing hence the need to play
with the fuel and compression settings.

In modern large engine management systems combustion
is very tightly controlled by fuel quantity both for pollution
and temperature. With unleaded fuel pre-ignition sets on
very easily and very fine control is needed to keep the
engine running well. A standard practice is that if the
engine load increases (i.e. go uphill) but nothing else then
the fuel ratio is increased to compensate for the slight
temperature increase that would otherwise occur. For our
model engines it is exactly the same. All motors will
increase in temperature with increasing load, because
relative to the prior load the ignition point has advanced
and, if not relieved could run away.

Interestingly Team racers held up in traffic burn down for
that reason. A setting with less compression gives less
overall performance but will withstand the traffic or slow
pilot problems. In general a Stunter increases power
during manoeuvres because firstly the temperature rises
due to slight leaning of the mixture in turn advancing the
ignition which causes more of the too rich mixture to burn,
causing more heat to be generated. We have the potential
for a runaway. Quite often if the manoeuvres last for too
long then the engine might continue to run hot and fast for
the rest of the tank full. Now your arm gets sore from
hanging on to a heavy model that is flying too fast. Speed
motors simply get to hot and slow down. In all cases once
the motor is too hot the pre-ignition is quite audible and
with a little observation you can learn to recognise this.

HOW DO WE FIX THIS?
Temperature control is every thing, but the majority of our
planes have very poor cooling management. Most
stunters have no cooling management at all, just a motor

either in the open or prettily cowled. Speed models appear
to have very little cooling and although most team racers
have shrouding to force cooling air to pass through the
fins, it is not just the cylinder that needs to run at the
correct temperature. Although the cylinder produces the
most heat the temperature of the entire engine needs to be
correct. The temperature of the fuel mix in the combustion
chamber determines the ignition point if nothing else is
changing. The crankcase temperature also affects the
mixture temperature. An F2C racer could come down
overheating (over compressed as recognised by the
mechanic). Pouring cold fuel or water on only the crank
case is usually sufficient to cure this, or using a different
fuel mixture with .05% less DII would also work. In both
cases the ignition timing has been retarded. Another
consideration is that the fuel mixture is not adjustable in
flight yet it has the greatest effect on temperature.

The answer for maximum performance and flexibility is
that the conditions must be provided for a constant thermal
cycle. It is not much use having a racer that is hotter at the
end of the tank then at the beginning. You cannot achieve
its ultimate performance this way. The same goes for a
Stunter or Speed model. The fastest speed models (at
least the ones that I saw at the world champs) are the ones
that don’t sag in the last two timed laps.

I have listed all the things that affect the thermal cycle.
Since there are so many, how can we get to the best
compromise? It is a combination of weight, drag,
propeller, fuel and cooling in all cases. Find a propeller
and fuel combination that gives an even run, then use a
fully cowled engine compartment where you can control
the cooling temperature independently to the parts that
matter. Separate the air to the carbie, crankcase and
cylinder. Control the flow of air over these parts by
changing the outlet vents. By making the air cooling the
adjustable part and fixing everything else you can get
more flexible settings. National’s winner David Campbell’s
F2C relies on outlet air restriction to generate heat rather
than compression. His view is that by using the air to get
to the right temperature a less critical setting is achieved
giving greater tolerance in traffic. At the Busselton
nationals I timed his model in the final. At times it was
doing 17.8 seconds for 10 laps at other times it was doing

19.2 but it sang like a bird all the time. I have the prop he
used with me now. The tips were damaged partway
through the race and a considerable amount was missing.
In fact most racers missing that much prop would have
cooled down and gone slow. It did not seem to slow
Campbell’s racer, and in fact the Brits were dead set
better. How does Campbell control the cooling? By a
piece of sticking tape over a portion of the air exhaust duct.
Of course compression ratio (or compression setting) has
its effect but this should always be used to set the timing
not wound up to get motor temperature. This should be
controlled through the outlet ducts.

There are many fuel factors to consider also. Nitro
methane when added to glow fuel greatly increases the
combustion temperature because more fuel mixture is
burnt and this generally requires a reduction in
compression ratio to remain stable. Diesel Ignition
Improver (DII) advances the timing when the motor gets
hotter, while xylene has a mild retarding effect. You may


find it interesting to learn more about fuels and fuel mixes
so that you can experiment with ratios knowingly.

The big difference between the real world and us is that
petrol engines are usually spark ignition thereby having
good control over the ignition point and of course most use
water cooling which is about 100 times more efficient than
air. While full size diesel engines use the injector timing
and quantity to set the ignition point.

The information that I have given you is just the tip of an
iceberg, but hopefully there is enough to whet your
appetite to know more. All types of powered models can
benefit from the technique of controlled cooling, all you
need to do is think through how your engine run behaves
and start to diagnose from there.

Good Luck. Hans Bertina

I'm betting you are the so and so who writes my taxation clauses