The new Aviastar CL engines
October 2009 97
The Engine Shop Joe Wagner | [email protected]
Also included in this column:
• Where friction on an engine
is needed
• Cox engine parts source
• Glow plug recommendation
Left: CL engines now even include fourstrokers.
This Saito .56 hauls its big Brodak
Cardinal efficiently through the sky.
Below: Differing only in height, the Aviastar
.46 and .53 are potent CL power plants.
Made in Hong Kong, they’re high-precision
products.
The compact packaging of Aviastar engines wastes little space but protects the
contents more than adequately.
WITH THIS COLUMN, I’m beginning
my 13th year writing “The Engine Shop.”
In the past dozen years, I’ve tested and
reported on more than 100 new model
airplane engines and wrote about more than
twice that number of older types.
All of that work has been highly
educational for me—and the learning
process never seems to end. Month after
month through the passing years, new
products continue coming out—and lately
those have included CL engines.
I’ve been a CL enthusiast since the
1940s. Within a few months of the end of
WW II, when production of model engines
resumed in the US, CL flying became
overwhelmingly the most popular type of
aeromodeling activity. But RC flying had
overtaken CL by the 1960s, and RC now
dominates the hobby.
But CL is making a distinct comeback.
10sig4.QXD 8/21/09 1:09 PM Page 97
98 MODEL AVIATION
Four-stroke RC-type glow plugs in twostroke
CL engines help ensure smooth rpm
transitions in the “four-two-four” running
mode that many Stunt fliers prefer.
The Aviastar .61 in action. The tall intake stack
provides excellent suction, and muffler pressure to
the tank is seldom needed.
Parts to keep many of the multitude of small Cox engines runnable, such as
the .049 reed-valve types shown, are available again.
There is good evidence of that in the
number of new designed-strictly-for-CL
engines coming onto the market. See my
article about Saito’s big four-strokers in
the August 2009 MA and Tom Dixon’s
(Marietta, Georgia) Double Star line of
two-stroke power plants that I reviewed in
a recent column.
John Brodak—America’s foremost
promoter and manufacturer in CL—now
markets a new series of CL engines: the
double-ball-bearing Aviastars. These are
ABC types, with Aluminum pistons
running in Brass sleeves that have Chromeplated
bores. Three sizes are available so
far: a .46, a .53, and a 61.
As is common with ABC engines, the
Aviastars have a noticeable “pinch” at the
top of the stroke. That’s caused by a
slightly tapered bore; it’s smaller at the
top, to allow for heat expansion when the
engine is running.
Because of that, I wasn’t able to handstart
any of the three Aviastars right out of
their boxes. The top pinch was a trifle too
draggy for hand starting to work.
However, electric starting did the job. I
followed the Aviastar break-in instructions
exactly, and after the recommended onehour
accumulated running time per engine,
I could easily hand-start all three.
For break-in, I used the larger-diameter
propellers that the instruction sheets listed
for each engine: 12 x 4 for the .46, 12 x 6
for the .53 (a longer-stroke, higher-torque
version of the .46), and 13 x 4 on the .61.
My Aviastars came packaged without
glow plugs. Tom Dixon advised me to try
Sig’s idle-bar-type plugs (item SIGGP003)
in my engines. He supplies those with all
of his Double Stars. So that’s what I did.
The Sig plugs worked fine in all three
Aviastars, even at rich needle settings.
The reason for using an RC-type plug in
a CL engine is that its heat-retaining
capability provides dependable running
during the “four-cycle/two-cycle break”
style of engine operation that many CL
Precision Aerobatics (Stunt) pilots prefer.
The engine runs rich throughout most of the
flight, only breaking into a two-cycle mode
when the model makes a rapid change of
direction. That way, the slipstream from the
sudden burst of high rpm hits the deflected
elevators and makes for sharper, more
precise cornering.
One feature of the Aviastar engines that I
particularly like is their tall intake stacks.
As I’ve written before, a long intake
passage on a model engine—front or rear
rotary, four-stroke, reed valve, or even the
old-fashioned sideport type—improves both
fuel suction and power. It does that by
increasing the momentum of the inlet air
and thereby compensating to some degree
for the pulsating intake flow into the engine.
Some experimentally minded model
fliers have found that a mild supercharging
effect can be obtained from a lengthened
(tuned) intake. It’s used successfully on
racing motorcycles; why not on model
engines? Works for me.
The instruction sheets for all Aviastars
list the same practical rpm range: 1,900-
16,000. However, the usual engine speed
for use in CL aerobatic flight is 8,000-
10,000 rpm.
We don’t want our Stunt models to fly
excessively fast. Too much flight velocity
makes tight maneuvers difficult because of
the high G loads generated. That’s a major
reason for running CL Stunt engines rich
and slow.
And that’s how I tested the Aviastars. I
never tried setting their needles for
maximum shriek.
Made in China, Aviastar engines are
designed and built to metric dimensional
standards. The two smaller models have
7mm (.275 inch) crankshaft threads. The
.61 has the same-size drive-shaft diameter,
but its propeller-retaining threads and nut
are the old tried-and-true 1/4-28 US
standard.
On the topic of propeller retaining, an
Aviastar drives the propeller via a separate
slotted brass collet that fits between the
shaft itself and a tapered ID in the
propeller driver. When you tighten the
propeller nut, the collet is squeezed
between the shaft and driver, gripping
both.
Thus friction does the entire job of
transferring torque between an Aviastar’s
shaft and its propeller. Because of that,
before installing a propeller on an
Aviastar, I advise you to wipe off all traces
of oil between the mating surfaces of the
three parts: the crankshaft OD, the
propeller driver ID, and both the ID and
the tapered ID of the brass collet.
That’s one assembly where you want
and need maximum friction between the
parts. Lubrication is not required here.
And before each run, check to make
certain that your Aviastar’s propeller nut is
tightened to the maximum. You’d be
surprised how much of a power loss even a
slightly slipping propeller can cause. Not
only that, but loose propellers separate
from their engines all too often.
10sig4.QXD 8/21/09 1:10 PM Page 98
almost as big as the engines to which they
attach, yet they are not heavy. That’s
because they’re thin-walled, expansionchamber
types. They contain no internal
baffles.
The small locknut on the back end of
the screw that holds an Aviastar muffler
together is not a retaining nut. The long
fore-and-aft screw through the muffler
threads into the rear half of the assembly.
The small nut merely acts as a jam nut.
I mention that because the mufflers on
two of the Aviastars I tested weren’t quite
firmly screwed together when I received
them. I was briefly baffled when I tried to
tighten them; torquing the small outer nut
had no effect. I had to loosen this nut,
tighten the screw from the front, and
retighten the small jam nut.
Also, Aviastar mufflers come with
pressure fittings installed. For flying with
Uniflow-type tanks, this fitting isn’t
needed. The engine package contains a
machine screw to replace the pressure
fitting, thus sealing its opening.
Since the first model airplane engines
were offered for sale in America—in
1911—there have been more than 270
different American model engine
manufacturers. Of them all, the company
with by far the highest number of engines
sold was Cox.
I can’t determine exactly the total
number of Cox model engines
manufactured before the Cox Company was
sold to Estes Industries in 1996, from the
1952 Space Bug .049 to the 1996 Venom
.049, but it exceeds 12 million. Many of
those engines still exist today and can
perform as well as ever, but they
occasionally require replacement parts.
Those have been difficult to find until
recently.
However, a new source for Cox parts has
emerged. Visit Cox International for full
information about what all it has in stock. (See
the “Sources” list for contact information.)
The prices seem reasonable to me.
Not every part for every engine is
available, but as the proprietors (Bernie and
Xena) state:
“ ... we are in the process of setting up
manufacturing to continue production of
some more popular parts and accessories—
all with original Cox tooling—and partly
with former Cox OEM [original equipment
manufacturer] suppliers.”
That’s good news for the many who fly
1/2A-powered models. MA
Sources:
Saito Engines
(800) 338-4639
www.saitoengines.com
Tom Dixon
Box 671166
Marietta GA 30066
http://tomdixon.tripod.com/engines.htm
Brodak Manufacturing
(724) 966-2726
www.brodak.com
Sig Manufacturing
(800) 247-5008
www.sigmfg.com
Cox Engines
(250) 398-2600
www.coxengines.ca
Edition: Model Aviation - 2009/10
Page Numbers: 97,98,100
Edition: Model Aviation - 2009/10
Page Numbers: 97,98,100
The new Aviastar CL engines
October 2009 97
The Engine Shop Joe Wagner | [email protected]
Also included in this column:
• Where friction on an engine
is needed
• Cox engine parts source
• Glow plug recommendation
Left: CL engines now even include fourstrokers.
This Saito .56 hauls its big Brodak
Cardinal efficiently through the sky.
Below: Differing only in height, the Aviastar
.46 and .53 are potent CL power plants.
Made in Hong Kong, they’re high-precision
products.
The compact packaging of Aviastar engines wastes little space but protects the
contents more than adequately.
WITH THIS COLUMN, I’m beginning
my 13th year writing “The Engine Shop.”
In the past dozen years, I’ve tested and
reported on more than 100 new model
airplane engines and wrote about more than
twice that number of older types.
All of that work has been highly
educational for me—and the learning
process never seems to end. Month after
month through the passing years, new
products continue coming out—and lately
those have included CL engines.
I’ve been a CL enthusiast since the
1940s. Within a few months of the end of
WW II, when production of model engines
resumed in the US, CL flying became
overwhelmingly the most popular type of
aeromodeling activity. But RC flying had
overtaken CL by the 1960s, and RC now
dominates the hobby.
But CL is making a distinct comeback.
10sig4.QXD 8/21/09 1:09 PM Page 97
98 MODEL AVIATION
Four-stroke RC-type glow plugs in twostroke
CL engines help ensure smooth rpm
transitions in the “four-two-four” running
mode that many Stunt fliers prefer.
The Aviastar .61 in action. The tall intake stack
provides excellent suction, and muffler pressure to
the tank is seldom needed.
Parts to keep many of the multitude of small Cox engines runnable, such as
the .049 reed-valve types shown, are available again.
There is good evidence of that in the
number of new designed-strictly-for-CL
engines coming onto the market. See my
article about Saito’s big four-strokers in
the August 2009 MA and Tom Dixon’s
(Marietta, Georgia) Double Star line of
two-stroke power plants that I reviewed in
a recent column.
John Brodak—America’s foremost
promoter and manufacturer in CL—now
markets a new series of CL engines: the
double-ball-bearing Aviastars. These are
ABC types, with Aluminum pistons
running in Brass sleeves that have Chromeplated
bores. Three sizes are available so
far: a .46, a .53, and a 61.
As is common with ABC engines, the
Aviastars have a noticeable “pinch” at the
top of the stroke. That’s caused by a
slightly tapered bore; it’s smaller at the
top, to allow for heat expansion when the
engine is running.
Because of that, I wasn’t able to handstart
any of the three Aviastars right out of
their boxes. The top pinch was a trifle too
draggy for hand starting to work.
However, electric starting did the job. I
followed the Aviastar break-in instructions
exactly, and after the recommended onehour
accumulated running time per engine,
I could easily hand-start all three.
For break-in, I used the larger-diameter
propellers that the instruction sheets listed
for each engine: 12 x 4 for the .46, 12 x 6
for the .53 (a longer-stroke, higher-torque
version of the .46), and 13 x 4 on the .61.
My Aviastars came packaged without
glow plugs. Tom Dixon advised me to try
Sig’s idle-bar-type plugs (item SIGGP003)
in my engines. He supplies those with all
of his Double Stars. So that’s what I did.
The Sig plugs worked fine in all three
Aviastars, even at rich needle settings.
The reason for using an RC-type plug in
a CL engine is that its heat-retaining
capability provides dependable running
during the “four-cycle/two-cycle break”
style of engine operation that many CL
Precision Aerobatics (Stunt) pilots prefer.
The engine runs rich throughout most of the
flight, only breaking into a two-cycle mode
when the model makes a rapid change of
direction. That way, the slipstream from the
sudden burst of high rpm hits the deflected
elevators and makes for sharper, more
precise cornering.
One feature of the Aviastar engines that I
particularly like is their tall intake stacks.
As I’ve written before, a long intake
passage on a model engine—front or rear
rotary, four-stroke, reed valve, or even the
old-fashioned sideport type—improves both
fuel suction and power. It does that by
increasing the momentum of the inlet air
and thereby compensating to some degree
for the pulsating intake flow into the engine.
Some experimentally minded model
fliers have found that a mild supercharging
effect can be obtained from a lengthened
(tuned) intake. It’s used successfully on
racing motorcycles; why not on model
engines? Works for me.
The instruction sheets for all Aviastars
list the same practical rpm range: 1,900-
16,000. However, the usual engine speed
for use in CL aerobatic flight is 8,000-
10,000 rpm.
We don’t want our Stunt models to fly
excessively fast. Too much flight velocity
makes tight maneuvers difficult because of
the high G loads generated. That’s a major
reason for running CL Stunt engines rich
and slow.
And that’s how I tested the Aviastars. I
never tried setting their needles for
maximum shriek.
Made in China, Aviastar engines are
designed and built to metric dimensional
standards. The two smaller models have
7mm (.275 inch) crankshaft threads. The
.61 has the same-size drive-shaft diameter,
but its propeller-retaining threads and nut
are the old tried-and-true 1/4-28 US
standard.
On the topic of propeller retaining, an
Aviastar drives the propeller via a separate
slotted brass collet that fits between the
shaft itself and a tapered ID in the
propeller driver. When you tighten the
propeller nut, the collet is squeezed
between the shaft and driver, gripping
both.
Thus friction does the entire job of
transferring torque between an Aviastar’s
shaft and its propeller. Because of that,
before installing a propeller on an
Aviastar, I advise you to wipe off all traces
of oil between the mating surfaces of the
three parts: the crankshaft OD, the
propeller driver ID, and both the ID and
the tapered ID of the brass collet.
That’s one assembly where you want
and need maximum friction between the
parts. Lubrication is not required here.
And before each run, check to make
certain that your Aviastar’s propeller nut is
tightened to the maximum. You’d be
surprised how much of a power loss even a
slightly slipping propeller can cause. Not
only that, but loose propellers separate
from their engines all too often.
10sig4.QXD 8/21/09 1:10 PM Page 98
almost as big as the engines to which they
attach, yet they are not heavy. That’s
because they’re thin-walled, expansionchamber
types. They contain no internal
baffles.
The small locknut on the back end of
the screw that holds an Aviastar muffler
together is not a retaining nut. The long
fore-and-aft screw through the muffler
threads into the rear half of the assembly.
The small nut merely acts as a jam nut.
I mention that because the mufflers on
two of the Aviastars I tested weren’t quite
firmly screwed together when I received
them. I was briefly baffled when I tried to
tighten them; torquing the small outer nut
had no effect. I had to loosen this nut,
tighten the screw from the front, and
retighten the small jam nut.
Also, Aviastar mufflers come with
pressure fittings installed. For flying with
Uniflow-type tanks, this fitting isn’t
needed. The engine package contains a
machine screw to replace the pressure
fitting, thus sealing its opening.
Since the first model airplane engines
were offered for sale in America—in
1911—there have been more than 270
different American model engine
manufacturers. Of them all, the company
with by far the highest number of engines
sold was Cox.
I can’t determine exactly the total
number of Cox model engines
manufactured before the Cox Company was
sold to Estes Industries in 1996, from the
1952 Space Bug .049 to the 1996 Venom
.049, but it exceeds 12 million. Many of
those engines still exist today and can
perform as well as ever, but they
occasionally require replacement parts.
Those have been difficult to find until
recently.
However, a new source for Cox parts has
emerged. Visit Cox International for full
information about what all it has in stock. (See
the “Sources” list for contact information.)
The prices seem reasonable to me.
Not every part for every engine is
available, but as the proprietors (Bernie and
Xena) state:
“ ... we are in the process of setting up
manufacturing to continue production of
some more popular parts and accessories—
all with original Cox tooling—and partly
with former Cox OEM [original equipment
manufacturer] suppliers.”
That’s good news for the many who fly
1/2A-powered models. MA
Sources:
Saito Engines
(800) 338-4639
www.saitoengines.com
Tom Dixon
Box 671166
Marietta GA 30066
http://tomdixon.tripod.com/engines.htm
Brodak Manufacturing
(724) 966-2726
www.brodak.com
Sig Manufacturing
(800) 247-5008
www.sigmfg.com
Cox Engines
(250) 398-2600
www.coxengines.ca
Edition: Model Aviation - 2009/10
Page Numbers: 97,98,100
The new Aviastar CL engines
October 2009 97
The Engine Shop Joe Wagner | [email protected]
Also included in this column:
• Where friction on an engine
is needed
• Cox engine parts source
• Glow plug recommendation
Left: CL engines now even include fourstrokers.
This Saito .56 hauls its big Brodak
Cardinal efficiently through the sky.
Below: Differing only in height, the Aviastar
.46 and .53 are potent CL power plants.
Made in Hong Kong, they’re high-precision
products.
The compact packaging of Aviastar engines wastes little space but protects the
contents more than adequately.
WITH THIS COLUMN, I’m beginning
my 13th year writing “The Engine Shop.”
In the past dozen years, I’ve tested and
reported on more than 100 new model
airplane engines and wrote about more than
twice that number of older types.
All of that work has been highly
educational for me—and the learning
process never seems to end. Month after
month through the passing years, new
products continue coming out—and lately
those have included CL engines.
I’ve been a CL enthusiast since the
1940s. Within a few months of the end of
WW II, when production of model engines
resumed in the US, CL flying became
overwhelmingly the most popular type of
aeromodeling activity. But RC flying had
overtaken CL by the 1960s, and RC now
dominates the hobby.
But CL is making a distinct comeback.
10sig4.QXD 8/21/09 1:09 PM Page 97
98 MODEL AVIATION
Four-stroke RC-type glow plugs in twostroke
CL engines help ensure smooth rpm
transitions in the “four-two-four” running
mode that many Stunt fliers prefer.
The Aviastar .61 in action. The tall intake stack
provides excellent suction, and muffler pressure to
the tank is seldom needed.
Parts to keep many of the multitude of small Cox engines runnable, such as
the .049 reed-valve types shown, are available again.
There is good evidence of that in the
number of new designed-strictly-for-CL
engines coming onto the market. See my
article about Saito’s big four-strokers in
the August 2009 MA and Tom Dixon’s
(Marietta, Georgia) Double Star line of
two-stroke power plants that I reviewed in
a recent column.
John Brodak—America’s foremost
promoter and manufacturer in CL—now
markets a new series of CL engines: the
double-ball-bearing Aviastars. These are
ABC types, with Aluminum pistons
running in Brass sleeves that have Chromeplated
bores. Three sizes are available so
far: a .46, a .53, and a 61.
As is common with ABC engines, the
Aviastars have a noticeable “pinch” at the
top of the stroke. That’s caused by a
slightly tapered bore; it’s smaller at the
top, to allow for heat expansion when the
engine is running.
Because of that, I wasn’t able to handstart
any of the three Aviastars right out of
their boxes. The top pinch was a trifle too
draggy for hand starting to work.
However, electric starting did the job. I
followed the Aviastar break-in instructions
exactly, and after the recommended onehour
accumulated running time per engine,
I could easily hand-start all three.
For break-in, I used the larger-diameter
propellers that the instruction sheets listed
for each engine: 12 x 4 for the .46, 12 x 6
for the .53 (a longer-stroke, higher-torque
version of the .46), and 13 x 4 on the .61.
My Aviastars came packaged without
glow plugs. Tom Dixon advised me to try
Sig’s idle-bar-type plugs (item SIGGP003)
in my engines. He supplies those with all
of his Double Stars. So that’s what I did.
The Sig plugs worked fine in all three
Aviastars, even at rich needle settings.
The reason for using an RC-type plug in
a CL engine is that its heat-retaining
capability provides dependable running
during the “four-cycle/two-cycle break”
style of engine operation that many CL
Precision Aerobatics (Stunt) pilots prefer.
The engine runs rich throughout most of the
flight, only breaking into a two-cycle mode
when the model makes a rapid change of
direction. That way, the slipstream from the
sudden burst of high rpm hits the deflected
elevators and makes for sharper, more
precise cornering.
One feature of the Aviastar engines that I
particularly like is their tall intake stacks.
As I’ve written before, a long intake
passage on a model engine—front or rear
rotary, four-stroke, reed valve, or even the
old-fashioned sideport type—improves both
fuel suction and power. It does that by
increasing the momentum of the inlet air
and thereby compensating to some degree
for the pulsating intake flow into the engine.
Some experimentally minded model
fliers have found that a mild supercharging
effect can be obtained from a lengthened
(tuned) intake. It’s used successfully on
racing motorcycles; why not on model
engines? Works for me.
The instruction sheets for all Aviastars
list the same practical rpm range: 1,900-
16,000. However, the usual engine speed
for use in CL aerobatic flight is 8,000-
10,000 rpm.
We don’t want our Stunt models to fly
excessively fast. Too much flight velocity
makes tight maneuvers difficult because of
the high G loads generated. That’s a major
reason for running CL Stunt engines rich
and slow.
And that’s how I tested the Aviastars. I
never tried setting their needles for
maximum shriek.
Made in China, Aviastar engines are
designed and built to metric dimensional
standards. The two smaller models have
7mm (.275 inch) crankshaft threads. The
.61 has the same-size drive-shaft diameter,
but its propeller-retaining threads and nut
are the old tried-and-true 1/4-28 US
standard.
On the topic of propeller retaining, an
Aviastar drives the propeller via a separate
slotted brass collet that fits between the
shaft itself and a tapered ID in the
propeller driver. When you tighten the
propeller nut, the collet is squeezed
between the shaft and driver, gripping
both.
Thus friction does the entire job of
transferring torque between an Aviastar’s
shaft and its propeller. Because of that,
before installing a propeller on an
Aviastar, I advise you to wipe off all traces
of oil between the mating surfaces of the
three parts: the crankshaft OD, the
propeller driver ID, and both the ID and
the tapered ID of the brass collet.
That’s one assembly where you want
and need maximum friction between the
parts. Lubrication is not required here.
And before each run, check to make
certain that your Aviastar’s propeller nut is
tightened to the maximum. You’d be
surprised how much of a power loss even a
slightly slipping propeller can cause. Not
only that, but loose propellers separate
from their engines all too often.
10sig4.QXD 8/21/09 1:10 PM Page 98
almost as big as the engines to which they
attach, yet they are not heavy. That’s
because they’re thin-walled, expansionchamber
types. They contain no internal
baffles.
The small locknut on the back end of
the screw that holds an Aviastar muffler
together is not a retaining nut. The long
fore-and-aft screw through the muffler
threads into the rear half of the assembly.
The small nut merely acts as a jam nut.
I mention that because the mufflers on
two of the Aviastars I tested weren’t quite
firmly screwed together when I received
them. I was briefly baffled when I tried to
tighten them; torquing the small outer nut
had no effect. I had to loosen this nut,
tighten the screw from the front, and
retighten the small jam nut.
Also, Aviastar mufflers come with
pressure fittings installed. For flying with
Uniflow-type tanks, this fitting isn’t
needed. The engine package contains a
machine screw to replace the pressure
fitting, thus sealing its opening.
Since the first model airplane engines
were offered for sale in America—in
1911—there have been more than 270
different American model engine
manufacturers. Of them all, the company
with by far the highest number of engines
sold was Cox.
I can’t determine exactly the total
number of Cox model engines
manufactured before the Cox Company was
sold to Estes Industries in 1996, from the
1952 Space Bug .049 to the 1996 Venom
.049, but it exceeds 12 million. Many of
those engines still exist today and can
perform as well as ever, but they
occasionally require replacement parts.
Those have been difficult to find until
recently.
However, a new source for Cox parts has
emerged. Visit Cox International for full
information about what all it has in stock. (See
the “Sources” list for contact information.)
The prices seem reasonable to me.
Not every part for every engine is
available, but as the proprietors (Bernie and
Xena) state:
“ ... we are in the process of setting up
manufacturing to continue production of
some more popular parts and accessories—
all with original Cox tooling—and partly
with former Cox OEM [original equipment
manufacturer] suppliers.”
That’s good news for the many who fly
1/2A-powered models. MA
Sources:
Saito Engines
(800) 338-4639
www.saitoengines.com
Tom Dixon
Box 671166
Marietta GA 30066
http://tomdixon.tripod.com/engines.htm
Brodak Manufacturing
(724) 966-2726
www.brodak.com
Sig Manufacturing
(800) 247-5008
www.sigmfg.com
Cox Engines
(250) 398-2600
www.coxengines.ca