86 MODEL AVIATION
THIS MONTH we
are going to look at
the growth and
development of gas
ignition engines.
There has been a
large trend in recent
years to use electric
motors to power
model aircraft
instead of glow
engines. The growth
of electrics has
somewhat
overshadowed the
significant increase
in popularity of
ignition engines.
You might note
that I wrote
“ignition” rather
than “gas.” This is
because existing
ignition engines use
either methanol- or
gasoline-based
fuels. (I am
unaware of any
model engines that
use both types
because of the
effect of different
based fuels on
components such as
diaphragms, fuel
lines, and seals.)
The new popularity of ignition engines
can be attributed to many factors, including
the increased availability of purpose-built
designs for model aviation.
There was a time when a gas engine for
an RC model was really just a converted
weed whacker or chainsaw power plant.
Those who did these conversions tended to
be highly skilled.
Leave it to the creativity of modelers to
take a garden tool and make it fly an
airplane. They were mechanically oriented
people and knew how to not only make their creations work, but get
the best they could out of designs that were not that great for flying.
These “wee beasties” were often hard to start with badly timed
ignition systems and were not that great in the rpm and associated
power department.
Starting a converted gas engine was often dangerous and
occasionally downright nasty. Hand-flipping a propeller on one of
these creations often caused a backfire or premature ignition. The
piston was not far enough up the barrel and would go back the
wrong way.
Two things caused this. Sometimes, the propeller, shaft, and
piston were not moving fast enough. The other cause was the
ignition timing was fixed and too soon (advanced) for hand starting.
At normal running speeds this ignition timing was fine, but during
starting it was not very friendly!
This all changed when transistorized—aka electronic ignition
(EI)—came along. Most of these new EI systems don’t allow the
spark plug to fire unless the crankshaft is spinning at more than 300
rpm. This is equivalent to a hard flip of the propeller. If the
propeller is turned over slowly during an action such as priming the
carburetor, the spark plug will not flash.
Generally the current breed of ignition engines is now built and
designed with safety and ease of operation in mind. There are watercooled
versions for model boats. You will see ignition engines in
helicopters and remote-control cars. The airplane variants are now
lighter and more powerful than their predecessors.
Because of their origins, ignition engines were once quite large
and heavy. In the last 10 years, the weight has decreased. You can
find gas engines as small as 17cc and as large as 350cc. Giant Scale
Eric Henderson | The Engine Shop [email protected]
Ignition engines becoming more popular
Above: This DA-150 twin, preparing to
power a 140-inch Yak all the way to the
heavens, shows how far gas engines have
come.
Below: Current gas motors are compact,
and the “finger-saving” electronic ignition
systems are small and lightweight.
Below left: The same DA-50 is nestled in
the cowl of a Double Vision biplane with a
smoke nipple for excellent sky trails.
Left: An early DA-50, mounted on Merle
Hyde’s son’s Vision Design, turns a 24 x 8
carbon-fiber propeller with authority.
Also included in this column:
• Two-cycle engines
• DX8 telemetry use
08sig3.QXD_00MSTRPG.QXD 6/23/11 8:45 AM Page 86
August 2011 87
of the propeller to prime the carburetor and
they fire. You just open the choke, flip
again, and they purr to life. The typical glow
engine flight box—if there is such a thing—
has a glow igniter, an electric starter motor,
and a 12-volt battery.
The one winning fact is the cost of the
gas/ignition fuel. A gallon of glow fuel can
easily be five times the cost of a gallon of
premium and the associated two-cycle oil.
Additionally, gas engines are legendary
when it comes to their miserly fuel
consumption. This leads to smaller fuel
tanks and/or much longer flight times.
Less power comes from burning gasoline
(petrol to the rest of the world) than
methanol. In essence, methanol is alcohol,
which is poisonous to humans. Drag racing
cars use alcohol for a reason. It gives a
better power burn. However, there is still
plenty of power that can be obtained from
burning gasoline.
Gas engines require an ignition system to
provide a spark to ignite the gas/air fuel mix
when it is compressed by the piston. The EI
systems need a power source and employ a
small battery pack that stays with the
airplane for the entire flight. Magneto-based
systems that do not need a battery still exist,
but they need a mechanical way to advance
and retard the ignition for starting.
Ignition engines run at lower rpm, but
compensate with better lugging power
(torque). They willingly turn larger or
higher-pitch propellers than their glow
counterparts. They also will idle at slow and
reliable speeds. They don’t tend to cool off,
load-up, and die like their glow plug
counterparts.
Another reason for their increase in
popularity is that the knowledge base of
operation has increased. The basic setup for
an ignition engine is not the same as a glow
airplanes can now be pulled vertically with
ease.
Smaller, 40- to 60-size RC aircraft,
powered by glow engines, can now reap the
benefits of ignition engines. One not-soobvious
benefit of a gas engine is that the
exhaust burns much hotter than the glow
fuel counterparts. This makes fitting smoke
systems a breeze. Squirt some kerosene into
a gas engine exhaust system and you will
have white smoke billowing everywhere.
One sidebar-type question often asked is,
“Why are model gas engines predominantly
two-cycle?” It is most likely an issue of
lubrication.
There are plenty of four-cycle, gasfueled
engines in the world. Most of us
drive one! The lubrication for model twoand
four-cycle engines is typically included
in the fuel. Full-size four-cycle engines
usually use an oil-feed system with some
kind of sump and pump. Not the most
practical or lightest system for a model
engine.
The advantages of ignition over glow or
electric power can be argued, depending
upon personal taste. For the sake of
observation rather than argument, here are a
few of the positive points that have
contributed to the growth of the gas engine
movement. I did write “gas” this time
because the majority of ignition engines use
a two-cycle gasoline/oil mixture. (I can cite
the YS 170 ignition engine as a current
exception.)
The most obvious advantage of a gaspowered
airplane can be seen at the flying
field. If you look at what a gas jockey takes
compared with a glow engine user, you will
only see a small gas can and most likely a
heavy leather glove. That’s it!
Most gas engines only need a few flicks
engine. It can take up to five hours to break
in a two-cycle gas engine. During this
break-in period, the accumulated experience
of a glow plug veteran often gets in the way.
Glow plug gurus just can’t leave the fuel
mixture needles alone. They hear a gurgle
or a misfire and immediately think “adjust
the mixture!” Generally it is not the fuel-toair
ratio that needs to be changed.
They should be referring to the manual
to check the oil-to-gasoline mix charts. The
manufacturer already knows what the right
fuel/oil mix should be once the engine is
broken-in.
Getting a gas ignition engine to run
smoothly could be as simple as using less oil
in the gasoline. This is pretty counterintuitive
for an experienced glow guy!
For example, reducing a 30:1 break-in
fuel/oil to 40:1 will often let a coughing gas
engine run smoothly. If the engine is fully
broken in and the fuel mix is dialed in
correctly you may never have to change your
carburetor’s original high-or-low needle
settings. If you do, it will usually be a very
small change.
Reducing the oil content produces more
power. Oil does not combust as does
gasoline. In the same space more oil equals
less combustion and provides less power.
Less oil means there is more gasoline and air
in the combustion chamber, so you will get a
bigger and better bang! Of course you still
need some oil to lubricate the moving parts.
More on the DX8 Telemetry Use: In the
review of the O.S. FS-95V ringed four-stroke
engine, I made a slight departure from the
more traditional test mount and fitted a
Spektrum radio system. The new Spektrum
DX8 telemetry module was employed with
rpm and temperature sensors fitted to the
engine.
This same system has some super benefits
when fitted to a model airplane. You can tell
the radio to set off an alarm when the engine
is not running. This is great when you are
flying at a busy field or at a large meet such
as a Giant Scale event.
The DX8 will beep if you set the low rpm
alarm level to zero. You can turn the alarm
off by touching the “clear” button to avoid
being distracted during the mandatory
landing that will follow.
A temperature reading that is too high can
also be used in a similar way. I can think of
Left: This little piece of heat-shrink tubing contains a
heat sensor that could save you thousands of dollars.
Engine temperature, rpm, and ignition
battery maximums and minimums are
now yours to know.
Below: The telemetry module of a Spektrum DX8
radio can now tell you what is going on with your
engine in the air.
08sig3.QXD_00MSTRPG.QXD 6/23/11 8:46 AM Page 87
four occasions where I could have saved an
engine if I had known that it had reached a
critical head temperature. A setting of 200° F
would be a good place to start. Once again,
you can turn off the alarm while you try to
land. You can also throttle back and/or put
the airplane into a shallow dive to see if the
engine cools down and the alarm turns itself
off.
One really cool thing that you can do is fit
a voltage tap to show the state of your
ignition battery. This channel is normally
used to monitor a Li-Poly electric motor
flight pack, but that would not be required on
a gas airplane.
The condition of the ignition pack is
normally an unknown to the pilot. With the
DX8 telemetry you could now see the
condition while the engine is at rest, running,
and in the air. It is good data for safety and
airplane survival. This instrumentation can,
will, and should change the longevity of your
airplanes and maybe the use of your hobby
credit cards. Just ask your spouse! MA
Sources:
O.S. Engines
(217) 398-8970
www.osengines.com
Spektrum
Edition: Model Aviation - 2011/08
Page Numbers: 86,87,88
Edition: Model Aviation - 2011/08
Page Numbers: 86,87,88
86 MODEL AVIATION
THIS MONTH we
are going to look at
the growth and
development of gas
ignition engines.
There has been a
large trend in recent
years to use electric
motors to power
model aircraft
instead of glow
engines. The growth
of electrics has
somewhat
overshadowed the
significant increase
in popularity of
ignition engines.
You might note
that I wrote
“ignition” rather
than “gas.” This is
because existing
ignition engines use
either methanol- or
gasoline-based
fuels. (I am
unaware of any
model engines that
use both types
because of the
effect of different
based fuels on
components such as
diaphragms, fuel
lines, and seals.)
The new popularity of ignition engines
can be attributed to many factors, including
the increased availability of purpose-built
designs for model aviation.
There was a time when a gas engine for
an RC model was really just a converted
weed whacker or chainsaw power plant.
Those who did these conversions tended to
be highly skilled.
Leave it to the creativity of modelers to
take a garden tool and make it fly an
airplane. They were mechanically oriented
people and knew how to not only make their creations work, but get
the best they could out of designs that were not that great for flying.
These “wee beasties” were often hard to start with badly timed
ignition systems and were not that great in the rpm and associated
power department.
Starting a converted gas engine was often dangerous and
occasionally downright nasty. Hand-flipping a propeller on one of
these creations often caused a backfire or premature ignition. The
piston was not far enough up the barrel and would go back the
wrong way.
Two things caused this. Sometimes, the propeller, shaft, and
piston were not moving fast enough. The other cause was the
ignition timing was fixed and too soon (advanced) for hand starting.
At normal running speeds this ignition timing was fine, but during
starting it was not very friendly!
This all changed when transistorized—aka electronic ignition
(EI)—came along. Most of these new EI systems don’t allow the
spark plug to fire unless the crankshaft is spinning at more than 300
rpm. This is equivalent to a hard flip of the propeller. If the
propeller is turned over slowly during an action such as priming the
carburetor, the spark plug will not flash.
Generally the current breed of ignition engines is now built and
designed with safety and ease of operation in mind. There are watercooled
versions for model boats. You will see ignition engines in
helicopters and remote-control cars. The airplane variants are now
lighter and more powerful than their predecessors.
Because of their origins, ignition engines were once quite large
and heavy. In the last 10 years, the weight has decreased. You can
find gas engines as small as 17cc and as large as 350cc. Giant Scale
Eric Henderson | The Engine Shop [email protected]
Ignition engines becoming more popular
Above: This DA-150 twin, preparing to
power a 140-inch Yak all the way to the
heavens, shows how far gas engines have
come.
Below: Current gas motors are compact,
and the “finger-saving” electronic ignition
systems are small and lightweight.
Below left: The same DA-50 is nestled in
the cowl of a Double Vision biplane with a
smoke nipple for excellent sky trails.
Left: An early DA-50, mounted on Merle
Hyde’s son’s Vision Design, turns a 24 x 8
carbon-fiber propeller with authority.
Also included in this column:
• Two-cycle engines
• DX8 telemetry use
08sig3.QXD_00MSTRPG.QXD 6/23/11 8:45 AM Page 86
August 2011 87
of the propeller to prime the carburetor and
they fire. You just open the choke, flip
again, and they purr to life. The typical glow
engine flight box—if there is such a thing—
has a glow igniter, an electric starter motor,
and a 12-volt battery.
The one winning fact is the cost of the
gas/ignition fuel. A gallon of glow fuel can
easily be five times the cost of a gallon of
premium and the associated two-cycle oil.
Additionally, gas engines are legendary
when it comes to their miserly fuel
consumption. This leads to smaller fuel
tanks and/or much longer flight times.
Less power comes from burning gasoline
(petrol to the rest of the world) than
methanol. In essence, methanol is alcohol,
which is poisonous to humans. Drag racing
cars use alcohol for a reason. It gives a
better power burn. However, there is still
plenty of power that can be obtained from
burning gasoline.
Gas engines require an ignition system to
provide a spark to ignite the gas/air fuel mix
when it is compressed by the piston. The EI
systems need a power source and employ a
small battery pack that stays with the
airplane for the entire flight. Magneto-based
systems that do not need a battery still exist,
but they need a mechanical way to advance
and retard the ignition for starting.
Ignition engines run at lower rpm, but
compensate with better lugging power
(torque). They willingly turn larger or
higher-pitch propellers than their glow
counterparts. They also will idle at slow and
reliable speeds. They don’t tend to cool off,
load-up, and die like their glow plug
counterparts.
Another reason for their increase in
popularity is that the knowledge base of
operation has increased. The basic setup for
an ignition engine is not the same as a glow
airplanes can now be pulled vertically with
ease.
Smaller, 40- to 60-size RC aircraft,
powered by glow engines, can now reap the
benefits of ignition engines. One not-soobvious
benefit of a gas engine is that the
exhaust burns much hotter than the glow
fuel counterparts. This makes fitting smoke
systems a breeze. Squirt some kerosene into
a gas engine exhaust system and you will
have white smoke billowing everywhere.
One sidebar-type question often asked is,
“Why are model gas engines predominantly
two-cycle?” It is most likely an issue of
lubrication.
There are plenty of four-cycle, gasfueled
engines in the world. Most of us
drive one! The lubrication for model twoand
four-cycle engines is typically included
in the fuel. Full-size four-cycle engines
usually use an oil-feed system with some
kind of sump and pump. Not the most
practical or lightest system for a model
engine.
The advantages of ignition over glow or
electric power can be argued, depending
upon personal taste. For the sake of
observation rather than argument, here are a
few of the positive points that have
contributed to the growth of the gas engine
movement. I did write “gas” this time
because the majority of ignition engines use
a two-cycle gasoline/oil mixture. (I can cite
the YS 170 ignition engine as a current
exception.)
The most obvious advantage of a gaspowered
airplane can be seen at the flying
field. If you look at what a gas jockey takes
compared with a glow engine user, you will
only see a small gas can and most likely a
heavy leather glove. That’s it!
Most gas engines only need a few flicks
engine. It can take up to five hours to break
in a two-cycle gas engine. During this
break-in period, the accumulated experience
of a glow plug veteran often gets in the way.
Glow plug gurus just can’t leave the fuel
mixture needles alone. They hear a gurgle
or a misfire and immediately think “adjust
the mixture!” Generally it is not the fuel-toair
ratio that needs to be changed.
They should be referring to the manual
to check the oil-to-gasoline mix charts. The
manufacturer already knows what the right
fuel/oil mix should be once the engine is
broken-in.
Getting a gas ignition engine to run
smoothly could be as simple as using less oil
in the gasoline. This is pretty counterintuitive
for an experienced glow guy!
For example, reducing a 30:1 break-in
fuel/oil to 40:1 will often let a coughing gas
engine run smoothly. If the engine is fully
broken in and the fuel mix is dialed in
correctly you may never have to change your
carburetor’s original high-or-low needle
settings. If you do, it will usually be a very
small change.
Reducing the oil content produces more
power. Oil does not combust as does
gasoline. In the same space more oil equals
less combustion and provides less power.
Less oil means there is more gasoline and air
in the combustion chamber, so you will get a
bigger and better bang! Of course you still
need some oil to lubricate the moving parts.
More on the DX8 Telemetry Use: In the
review of the O.S. FS-95V ringed four-stroke
engine, I made a slight departure from the
more traditional test mount and fitted a
Spektrum radio system. The new Spektrum
DX8 telemetry module was employed with
rpm and temperature sensors fitted to the
engine.
This same system has some super benefits
when fitted to a model airplane. You can tell
the radio to set off an alarm when the engine
is not running. This is great when you are
flying at a busy field or at a large meet such
as a Giant Scale event.
The DX8 will beep if you set the low rpm
alarm level to zero. You can turn the alarm
off by touching the “clear” button to avoid
being distracted during the mandatory
landing that will follow.
A temperature reading that is too high can
also be used in a similar way. I can think of
Left: This little piece of heat-shrink tubing contains a
heat sensor that could save you thousands of dollars.
Engine temperature, rpm, and ignition
battery maximums and minimums are
now yours to know.
Below: The telemetry module of a Spektrum DX8
radio can now tell you what is going on with your
engine in the air.
08sig3.QXD_00MSTRPG.QXD 6/23/11 8:46 AM Page 87
four occasions where I could have saved an
engine if I had known that it had reached a
critical head temperature. A setting of 200° F
would be a good place to start. Once again,
you can turn off the alarm while you try to
land. You can also throttle back and/or put
the airplane into a shallow dive to see if the
engine cools down and the alarm turns itself
off.
One really cool thing that you can do is fit
a voltage tap to show the state of your
ignition battery. This channel is normally
used to monitor a Li-Poly electric motor
flight pack, but that would not be required on
a gas airplane.
The condition of the ignition pack is
normally an unknown to the pilot. With the
DX8 telemetry you could now see the
condition while the engine is at rest, running,
and in the air. It is good data for safety and
airplane survival. This instrumentation can,
will, and should change the longevity of your
airplanes and maybe the use of your hobby
credit cards. Just ask your spouse! MA
Sources:
O.S. Engines
(217) 398-8970
www.osengines.com
Spektrum
Edition: Model Aviation - 2011/08
Page Numbers: 86,87,88
86 MODEL AVIATION
THIS MONTH we
are going to look at
the growth and
development of gas
ignition engines.
There has been a
large trend in recent
years to use electric
motors to power
model aircraft
instead of glow
engines. The growth
of electrics has
somewhat
overshadowed the
significant increase
in popularity of
ignition engines.
You might note
that I wrote
“ignition” rather
than “gas.” This is
because existing
ignition engines use
either methanol- or
gasoline-based
fuels. (I am
unaware of any
model engines that
use both types
because of the
effect of different
based fuels on
components such as
diaphragms, fuel
lines, and seals.)
The new popularity of ignition engines
can be attributed to many factors, including
the increased availability of purpose-built
designs for model aviation.
There was a time when a gas engine for
an RC model was really just a converted
weed whacker or chainsaw power plant.
Those who did these conversions tended to
be highly skilled.
Leave it to the creativity of modelers to
take a garden tool and make it fly an
airplane. They were mechanically oriented
people and knew how to not only make their creations work, but get
the best they could out of designs that were not that great for flying.
These “wee beasties” were often hard to start with badly timed
ignition systems and were not that great in the rpm and associated
power department.
Starting a converted gas engine was often dangerous and
occasionally downright nasty. Hand-flipping a propeller on one of
these creations often caused a backfire or premature ignition. The
piston was not far enough up the barrel and would go back the
wrong way.
Two things caused this. Sometimes, the propeller, shaft, and
piston were not moving fast enough. The other cause was the
ignition timing was fixed and too soon (advanced) for hand starting.
At normal running speeds this ignition timing was fine, but during
starting it was not very friendly!
This all changed when transistorized—aka electronic ignition
(EI)—came along. Most of these new EI systems don’t allow the
spark plug to fire unless the crankshaft is spinning at more than 300
rpm. This is equivalent to a hard flip of the propeller. If the
propeller is turned over slowly during an action such as priming the
carburetor, the spark plug will not flash.
Generally the current breed of ignition engines is now built and
designed with safety and ease of operation in mind. There are watercooled
versions for model boats. You will see ignition engines in
helicopters and remote-control cars. The airplane variants are now
lighter and more powerful than their predecessors.
Because of their origins, ignition engines were once quite large
and heavy. In the last 10 years, the weight has decreased. You can
find gas engines as small as 17cc and as large as 350cc. Giant Scale
Eric Henderson | The Engine Shop [email protected]
Ignition engines becoming more popular
Above: This DA-150 twin, preparing to
power a 140-inch Yak all the way to the
heavens, shows how far gas engines have
come.
Below: Current gas motors are compact,
and the “finger-saving” electronic ignition
systems are small and lightweight.
Below left: The same DA-50 is nestled in
the cowl of a Double Vision biplane with a
smoke nipple for excellent sky trails.
Left: An early DA-50, mounted on Merle
Hyde’s son’s Vision Design, turns a 24 x 8
carbon-fiber propeller with authority.
Also included in this column:
• Two-cycle engines
• DX8 telemetry use
08sig3.QXD_00MSTRPG.QXD 6/23/11 8:45 AM Page 86
August 2011 87
of the propeller to prime the carburetor and
they fire. You just open the choke, flip
again, and they purr to life. The typical glow
engine flight box—if there is such a thing—
has a glow igniter, an electric starter motor,
and a 12-volt battery.
The one winning fact is the cost of the
gas/ignition fuel. A gallon of glow fuel can
easily be five times the cost of a gallon of
premium and the associated two-cycle oil.
Additionally, gas engines are legendary
when it comes to their miserly fuel
consumption. This leads to smaller fuel
tanks and/or much longer flight times.
Less power comes from burning gasoline
(petrol to the rest of the world) than
methanol. In essence, methanol is alcohol,
which is poisonous to humans. Drag racing
cars use alcohol for a reason. It gives a
better power burn. However, there is still
plenty of power that can be obtained from
burning gasoline.
Gas engines require an ignition system to
provide a spark to ignite the gas/air fuel mix
when it is compressed by the piston. The EI
systems need a power source and employ a
small battery pack that stays with the
airplane for the entire flight. Magneto-based
systems that do not need a battery still exist,
but they need a mechanical way to advance
and retard the ignition for starting.
Ignition engines run at lower rpm, but
compensate with better lugging power
(torque). They willingly turn larger or
higher-pitch propellers than their glow
counterparts. They also will idle at slow and
reliable speeds. They don’t tend to cool off,
load-up, and die like their glow plug
counterparts.
Another reason for their increase in
popularity is that the knowledge base of
operation has increased. The basic setup for
an ignition engine is not the same as a glow
airplanes can now be pulled vertically with
ease.
Smaller, 40- to 60-size RC aircraft,
powered by glow engines, can now reap the
benefits of ignition engines. One not-soobvious
benefit of a gas engine is that the
exhaust burns much hotter than the glow
fuel counterparts. This makes fitting smoke
systems a breeze. Squirt some kerosene into
a gas engine exhaust system and you will
have white smoke billowing everywhere.
One sidebar-type question often asked is,
“Why are model gas engines predominantly
two-cycle?” It is most likely an issue of
lubrication.
There are plenty of four-cycle, gasfueled
engines in the world. Most of us
drive one! The lubrication for model twoand
four-cycle engines is typically included
in the fuel. Full-size four-cycle engines
usually use an oil-feed system with some
kind of sump and pump. Not the most
practical or lightest system for a model
engine.
The advantages of ignition over glow or
electric power can be argued, depending
upon personal taste. For the sake of
observation rather than argument, here are a
few of the positive points that have
contributed to the growth of the gas engine
movement. I did write “gas” this time
because the majority of ignition engines use
a two-cycle gasoline/oil mixture. (I can cite
the YS 170 ignition engine as a current
exception.)
The most obvious advantage of a gaspowered
airplane can be seen at the flying
field. If you look at what a gas jockey takes
compared with a glow engine user, you will
only see a small gas can and most likely a
heavy leather glove. That’s it!
Most gas engines only need a few flicks
engine. It can take up to five hours to break
in a two-cycle gas engine. During this
break-in period, the accumulated experience
of a glow plug veteran often gets in the way.
Glow plug gurus just can’t leave the fuel
mixture needles alone. They hear a gurgle
or a misfire and immediately think “adjust
the mixture!” Generally it is not the fuel-toair
ratio that needs to be changed.
They should be referring to the manual
to check the oil-to-gasoline mix charts. The
manufacturer already knows what the right
fuel/oil mix should be once the engine is
broken-in.
Getting a gas ignition engine to run
smoothly could be as simple as using less oil
in the gasoline. This is pretty counterintuitive
for an experienced glow guy!
For example, reducing a 30:1 break-in
fuel/oil to 40:1 will often let a coughing gas
engine run smoothly. If the engine is fully
broken in and the fuel mix is dialed in
correctly you may never have to change your
carburetor’s original high-or-low needle
settings. If you do, it will usually be a very
small change.
Reducing the oil content produces more
power. Oil does not combust as does
gasoline. In the same space more oil equals
less combustion and provides less power.
Less oil means there is more gasoline and air
in the combustion chamber, so you will get a
bigger and better bang! Of course you still
need some oil to lubricate the moving parts.
More on the DX8 Telemetry Use: In the
review of the O.S. FS-95V ringed four-stroke
engine, I made a slight departure from the
more traditional test mount and fitted a
Spektrum radio system. The new Spektrum
DX8 telemetry module was employed with
rpm and temperature sensors fitted to the
engine.
This same system has some super benefits
when fitted to a model airplane. You can tell
the radio to set off an alarm when the engine
is not running. This is great when you are
flying at a busy field or at a large meet such
as a Giant Scale event.
The DX8 will beep if you set the low rpm
alarm level to zero. You can turn the alarm
off by touching the “clear” button to avoid
being distracted during the mandatory
landing that will follow.
A temperature reading that is too high can
also be used in a similar way. I can think of
Left: This little piece of heat-shrink tubing contains a
heat sensor that could save you thousands of dollars.
Engine temperature, rpm, and ignition
battery maximums and minimums are
now yours to know.
Below: The telemetry module of a Spektrum DX8
radio can now tell you what is going on with your
engine in the air.
08sig3.QXD_00MSTRPG.QXD 6/23/11 8:46 AM Page 87
four occasions where I could have saved an
engine if I had known that it had reached a
critical head temperature. A setting of 200° F
would be a good place to start. Once again,
you can turn off the alarm while you try to
land. You can also throttle back and/or put
the airplane into a shallow dive to see if the
engine cools down and the alarm turns itself
off.
One really cool thing that you can do is fit
a voltage tap to show the state of your
ignition battery. This channel is normally
used to monitor a Li-Poly electric motor
flight pack, but that would not be required on
a gas airplane.
The condition of the ignition pack is
normally an unknown to the pilot. With the
DX8 telemetry you could now see the
condition while the engine is at rest, running,
and in the air. It is good data for safety and
airplane survival. This instrumentation can,
will, and should change the longevity of your
airplanes and maybe the use of your hobby
credit cards. Just ask your spouse! MA
Sources:
O.S. Engines
(217) 398-8970
www.osengines.com
Spektrum
