76 MODEL AVIATION
Joe Wagner The Engine Shop | [email protected]
Also included in this column:
• Do-it-yourself model diesel fuel
• Morgan’s new CL glow fuel
• Quirk with certain glows
Glows vs. diesels in detail
The PAW .19 (L) is a nice contrast to the Thunder Tiger .18 (R).
Take note of the diesel’s tiny muffler and tall intake.
Another excellent comparison: the newly reissued Norvel (now
NV) .40 glow (foreground) and the PAW .40. Their styling varies
much more than their performance.
Diesels have an oily, messy exhaust. However, they aren’t affected much by back
pressure, so long exhaust extensions such as this can keep a model clean without losing
performance.
THROUGHOUT THE YEARS that I’ve
been writing this column, I’ve often
mentioned the many virtues of diesel
power plants for model airplanes. But until
now I had never directly compared a diesel
with a same-size glow, spinning the samesize
propellers, on the same day. And I
hadn’t yet discussed in much detail the
minor adverse quirks of diesels and how
those can be overcome.
I’ll do that now.
For these comparative tests I chose four
of my own well-broken-in and currently
available engines: a pair of .19s and a pair
of .40s. The diesels are British-made
Progress Aero Works engines, or PAWs.
The glow .19 is a Thunder Tiger “Green
Power” .18, while its double-size glow
partner is a recently reissued Russianmade
NV (formerly Norvel) Revlite .40.
These tests were obviously not
laboratory-grade, high-precision
procedures. Instead, I carried them out
under roughly the same conditions as “the
average modeler” would at his or her local
flying field—with one major exception.
I used the same propeller on both .19s
and another for both .40s. Doing that
forced all of the engines to run at lessthan-
optimal efficiency. The diesels spun
slightly smaller propellers than they work
best with, and the glows had the opposite
handicap.
However, as experienced model fliers
know, the airplane has more influence on
optimum propeller size and pitch than the
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:30 AM Page 76
engine’s size and type. Thus all I hope to
show here is a basic relationship—not a
cast-in-concrete set of aeronautical
engineering formulas.
For the glows I used Morgan’s new
specially-blended-for-CL fuel: 15% nitro
and 22% oil (half castor and half
synthetic). The diesels ran on a
commercially prepared sport-type fuel of
30% ether, 22% castor oil, and 43%
kerosene. (The kerosene is actually
aviation-grade jet fuel.)
All of the propellers used in these tests
were Graupners: 9 x 4s for the .19s and
12 x 5s for the .40s. I hand-started all of
the engines without difficulty.
Performance differences showed up
most markedly with the .40-size power
plants. That was because, as you can
readily tell from their appearances, the
NV is a short-stroke design, intended for
maximizing rpm; the PAW is a longstroker,
built to generate torque.
Now for the numbers. The NV .40’s
reliable rpm ranged from 11,000 to 3,100,
with sound-output levels between 93 and
71 dBA. The PAW .40 spun its 12 x 5
propeller at 9,200 rpm tops and 2,200 at a
reliable idle. Its sound measured 98-78
dBA.
The engines were a mere half-ounce
apart, at 13.6 ounces for the NV (it’s
mostly aluminum) and 14.1 for the PAW.
The pair of .19s were a bit more
closely comparable, designwise. That
showed up in their performance.
The Thunder Tiger turned its 9 x 4
Graupner at 11,800 and idled at 3,100,
with a sound output ranging between 92
dBA and 78. The PAW .19 put out 9,300
top rpm, 3,100 low idle, and 90-82 dBA.
Again, the weights registered a halfounce
difference. The .19 diesel came out
to 6.9 ounces, and the glow Thunder
Tiger was 7.4 ounces.
The diesel’s advantages are no glow
April 2011 77
plugs, runs are 70% longer per ounce of
fuel, it is unaffected by humidity, the
same fuel can be used for every size
engine (and you can mix your own using
easy-to-obtain ingredients), it will spin
any-size propeller you can fit on its shaft,
and it has a small, unobtrusive muffler.
The few drawbacks of model diesel
engines seem minor by comparison.
One problem that many people
complain about is the dark, greasy
exhaust. The exhaust needn’t be dark;
that’s an indication of excess
compression. It causes extra stress and
heat, and it steals power.
But the exhaust doesn’t have to spray
rearward over the airplane. Diesels are
tolerant of exhaust back pressure anyway,
and PAWs in particular will readily accept
extensions that carry the exhaust well
behind and below the aircraft without
significantly reducing power output.
You might have heard that model
diesels always require hand-starting.
That’s to eliminate the chance of
hydraulic lock during electric starting
procedures, which damages the moving
parts.
That problem can be averted in various
ways. The most convenient is probably to
mount the engine with its cylinder pointed
sideways.
However, even with an upright or
inverted cylinder, if you initiate electric
starting with a dry (nonflooded) engine
and begin cranking with the compression
backed way off, you can slowly ease the
compression up until the engine fires.
After that, running adjustments proceed as
usual.
If you want to mix your own diesel
fuel, any John Deere dealership sells
spray cans of Starter Fluid. That’s as good
in model fuel as pure ether, except that it
doesn’t evaporate so quickly.
There are ways of extracting the fluid
from the cans without resorting to spray.
One is to place the John Deere can in a
freezer overnight, and then puncture a small
hole in the upper part of the can to let the
propane propellant dissipate.
After that, you can enlarge the hole with
something such as an awl, add a similar hole
as an air vent, and then pour the fluid into a
glass container.
I like to use a straight-sided jam jar in
which to measure and mix diesel. A length
of tape on its outside surface can be marked
in increments to represent the proportions of
22% castor, 43% kerosene, and 30% ether
(using the generic names of the ingredients),
for making each jarful of fuel.
The biggest tricks in operating model
diesel engines are in avoiding flooding and
making “incremental adjustments” between
compression and needle settings. That’s
what provides the smoothest, most efficient
operation.
As a diesel engine warms up, its
compression ordinarily needs to be lowered
a smidgen to prevent preignition, which is
the mixture firing while the piston is still on
its way up the bore. After reducing
compression, you lean out the mixture a bit.
Doing that generates more heat, which calls
for further reducing the compression.
Generally approximately three back-andforth
adjustment sequences will be needed
to completely fine-tune your diesel’s needle
and compression settings.
While I was running the performance
comparisons for this column, I ran into a
puzzling problem that I’ve occasionally
encountered through the years with my
spark and glow model engines. And,
coincidentally, that same week I received
an e-mail from a reader who had
experienced exactly the same difficulty.
I’ll condense and paraphrase what Abe
Gallas (Kansas City, Missouri) asked in
his message.
All it takes to home-brew fuel for model
diesels: castor oil from the drugstore, lamp
oil from Walmart, John Deere Starting
Fluid, and a modified jam jar.
This is Morgan Fuel’s
new glow fuel for CL
flying. CL engines
do run better and
last longer with an
optimized blend of
fuel.
This shot of the NV .40 running brings to mind an odd
phenomenon—one that has caused Joe and other model fliers to
scratch their heads before figuring it out.
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:31 AM Page 77
“In preparing to run one of my glow
engines, I made a battery pack of two D-size
cells in parallel. I put an alligator clip on each
terminal of this battery pack, plus an alligator
clip on ‘ground’ and the top of the glow plug.
“The plug did not light. I then used a
commercial glow clip, and the plug lit right
up. I was using the same battery setup, so
electrically the circuit was the same. I asked
several modelers for an opinion as to why the
first arrangement did not work, and none of
them had a clue. Do you?”
This problem results from the fact that
oxidized aluminum is electrically
nonconductive. (This fact is what makes
electrolytic capacitors possible.)
Many model-engine cases are aluminum;
when those are anodized (which is an
oxidative process), their surfaces might as
well have been made from wood, as far as
electrical conductivity goes.
Yes, electricity travels readily via
nonoxidized aluminum, such as where a
glow plug hole has been drilled and tapped
through otherwise anodized metal. But
hooking up a glow plug lead to the outer
surface of an engine’s case—i.e.,
“ground”—won’t light the plug if that case
has been anodized. Anodizing encapsulates
the case in an insulating skin. MA
Sources:
Progress Aero Works
www.eifflaender.com
Thunder Tiger
(217) 398-8970
www.ttamerica.com
Model Engine Collectors Association
www.modelenginecollectors.org
78 MODEL AVIATION
- SECURE SHOPPING WITH OUR ONLINE CATALOG -
www.fiberglassspecialtiesinc.com
[email protected]
Phone (479) 359-2429 Fax (479) 359-2259
Hours: Monday - Friday 9 to 5 CST
15715 Ashmore Dr., Garfield, Arkansas 72732
LARGEST
COLLECTION OF
EPOXY GLASS
COWLS & WHEEL
PANTS IN THE WORLD!
SINCE
1977!
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:32 AM Page 78
Edition: Model Aviation - 2011/04
Page Numbers: 76,77,78
Edition: Model Aviation - 2011/04
Page Numbers: 76,77,78
76 MODEL AVIATION
Joe Wagner The Engine Shop | [email protected]
Also included in this column:
• Do-it-yourself model diesel fuel
• Morgan’s new CL glow fuel
• Quirk with certain glows
Glows vs. diesels in detail
The PAW .19 (L) is a nice contrast to the Thunder Tiger .18 (R).
Take note of the diesel’s tiny muffler and tall intake.
Another excellent comparison: the newly reissued Norvel (now
NV) .40 glow (foreground) and the PAW .40. Their styling varies
much more than their performance.
Diesels have an oily, messy exhaust. However, they aren’t affected much by back
pressure, so long exhaust extensions such as this can keep a model clean without losing
performance.
THROUGHOUT THE YEARS that I’ve
been writing this column, I’ve often
mentioned the many virtues of diesel
power plants for model airplanes. But until
now I had never directly compared a diesel
with a same-size glow, spinning the samesize
propellers, on the same day. And I
hadn’t yet discussed in much detail the
minor adverse quirks of diesels and how
those can be overcome.
I’ll do that now.
For these comparative tests I chose four
of my own well-broken-in and currently
available engines: a pair of .19s and a pair
of .40s. The diesels are British-made
Progress Aero Works engines, or PAWs.
The glow .19 is a Thunder Tiger “Green
Power” .18, while its double-size glow
partner is a recently reissued Russianmade
NV (formerly Norvel) Revlite .40.
These tests were obviously not
laboratory-grade, high-precision
procedures. Instead, I carried them out
under roughly the same conditions as “the
average modeler” would at his or her local
flying field—with one major exception.
I used the same propeller on both .19s
and another for both .40s. Doing that
forced all of the engines to run at lessthan-
optimal efficiency. The diesels spun
slightly smaller propellers than they work
best with, and the glows had the opposite
handicap.
However, as experienced model fliers
know, the airplane has more influence on
optimum propeller size and pitch than the
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:30 AM Page 76
engine’s size and type. Thus all I hope to
show here is a basic relationship—not a
cast-in-concrete set of aeronautical
engineering formulas.
For the glows I used Morgan’s new
specially-blended-for-CL fuel: 15% nitro
and 22% oil (half castor and half
synthetic). The diesels ran on a
commercially prepared sport-type fuel of
30% ether, 22% castor oil, and 43%
kerosene. (The kerosene is actually
aviation-grade jet fuel.)
All of the propellers used in these tests
were Graupners: 9 x 4s for the .19s and
12 x 5s for the .40s. I hand-started all of
the engines without difficulty.
Performance differences showed up
most markedly with the .40-size power
plants. That was because, as you can
readily tell from their appearances, the
NV is a short-stroke design, intended for
maximizing rpm; the PAW is a longstroker,
built to generate torque.
Now for the numbers. The NV .40’s
reliable rpm ranged from 11,000 to 3,100,
with sound-output levels between 93 and
71 dBA. The PAW .40 spun its 12 x 5
propeller at 9,200 rpm tops and 2,200 at a
reliable idle. Its sound measured 98-78
dBA.
The engines were a mere half-ounce
apart, at 13.6 ounces for the NV (it’s
mostly aluminum) and 14.1 for the PAW.
The pair of .19s were a bit more
closely comparable, designwise. That
showed up in their performance.
The Thunder Tiger turned its 9 x 4
Graupner at 11,800 and idled at 3,100,
with a sound output ranging between 92
dBA and 78. The PAW .19 put out 9,300
top rpm, 3,100 low idle, and 90-82 dBA.
Again, the weights registered a halfounce
difference. The .19 diesel came out
to 6.9 ounces, and the glow Thunder
Tiger was 7.4 ounces.
The diesel’s advantages are no glow
April 2011 77
plugs, runs are 70% longer per ounce of
fuel, it is unaffected by humidity, the
same fuel can be used for every size
engine (and you can mix your own using
easy-to-obtain ingredients), it will spin
any-size propeller you can fit on its shaft,
and it has a small, unobtrusive muffler.
The few drawbacks of model diesel
engines seem minor by comparison.
One problem that many people
complain about is the dark, greasy
exhaust. The exhaust needn’t be dark;
that’s an indication of excess
compression. It causes extra stress and
heat, and it steals power.
But the exhaust doesn’t have to spray
rearward over the airplane. Diesels are
tolerant of exhaust back pressure anyway,
and PAWs in particular will readily accept
extensions that carry the exhaust well
behind and below the aircraft without
significantly reducing power output.
You might have heard that model
diesels always require hand-starting.
That’s to eliminate the chance of
hydraulic lock during electric starting
procedures, which damages the moving
parts.
That problem can be averted in various
ways. The most convenient is probably to
mount the engine with its cylinder pointed
sideways.
However, even with an upright or
inverted cylinder, if you initiate electric
starting with a dry (nonflooded) engine
and begin cranking with the compression
backed way off, you can slowly ease the
compression up until the engine fires.
After that, running adjustments proceed as
usual.
If you want to mix your own diesel
fuel, any John Deere dealership sells
spray cans of Starter Fluid. That’s as good
in model fuel as pure ether, except that it
doesn’t evaporate so quickly.
There are ways of extracting the fluid
from the cans without resorting to spray.
One is to place the John Deere can in a
freezer overnight, and then puncture a small
hole in the upper part of the can to let the
propane propellant dissipate.
After that, you can enlarge the hole with
something such as an awl, add a similar hole
as an air vent, and then pour the fluid into a
glass container.
I like to use a straight-sided jam jar in
which to measure and mix diesel. A length
of tape on its outside surface can be marked
in increments to represent the proportions of
22% castor, 43% kerosene, and 30% ether
(using the generic names of the ingredients),
for making each jarful of fuel.
The biggest tricks in operating model
diesel engines are in avoiding flooding and
making “incremental adjustments” between
compression and needle settings. That’s
what provides the smoothest, most efficient
operation.
As a diesel engine warms up, its
compression ordinarily needs to be lowered
a smidgen to prevent preignition, which is
the mixture firing while the piston is still on
its way up the bore. After reducing
compression, you lean out the mixture a bit.
Doing that generates more heat, which calls
for further reducing the compression.
Generally approximately three back-andforth
adjustment sequences will be needed
to completely fine-tune your diesel’s needle
and compression settings.
While I was running the performance
comparisons for this column, I ran into a
puzzling problem that I’ve occasionally
encountered through the years with my
spark and glow model engines. And,
coincidentally, that same week I received
an e-mail from a reader who had
experienced exactly the same difficulty.
I’ll condense and paraphrase what Abe
Gallas (Kansas City, Missouri) asked in
his message.
All it takes to home-brew fuel for model
diesels: castor oil from the drugstore, lamp
oil from Walmart, John Deere Starting
Fluid, and a modified jam jar.
This is Morgan Fuel’s
new glow fuel for CL
flying. CL engines
do run better and
last longer with an
optimized blend of
fuel.
This shot of the NV .40 running brings to mind an odd
phenomenon—one that has caused Joe and other model fliers to
scratch their heads before figuring it out.
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:31 AM Page 77
“In preparing to run one of my glow
engines, I made a battery pack of two D-size
cells in parallel. I put an alligator clip on each
terminal of this battery pack, plus an alligator
clip on ‘ground’ and the top of the glow plug.
“The plug did not light. I then used a
commercial glow clip, and the plug lit right
up. I was using the same battery setup, so
electrically the circuit was the same. I asked
several modelers for an opinion as to why the
first arrangement did not work, and none of
them had a clue. Do you?”
This problem results from the fact that
oxidized aluminum is electrically
nonconductive. (This fact is what makes
electrolytic capacitors possible.)
Many model-engine cases are aluminum;
when those are anodized (which is an
oxidative process), their surfaces might as
well have been made from wood, as far as
electrical conductivity goes.
Yes, electricity travels readily via
nonoxidized aluminum, such as where a
glow plug hole has been drilled and tapped
through otherwise anodized metal. But
hooking up a glow plug lead to the outer
surface of an engine’s case—i.e.,
“ground”—won’t light the plug if that case
has been anodized. Anodizing encapsulates
the case in an insulating skin. MA
Sources:
Progress Aero Works
www.eifflaender.com
Thunder Tiger
(217) 398-8970
www.ttamerica.com
Model Engine Collectors Association
www.modelenginecollectors.org
78 MODEL AVIATION
- SECURE SHOPPING WITH OUR ONLINE CATALOG -
www.fiberglassspecialtiesinc.com
[email protected]
Phone (479) 359-2429 Fax (479) 359-2259
Hours: Monday - Friday 9 to 5 CST
15715 Ashmore Dr., Garfield, Arkansas 72732
LARGEST
COLLECTION OF
EPOXY GLASS
COWLS & WHEEL
PANTS IN THE WORLD!
SINCE
1977!
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:32 AM Page 78
Edition: Model Aviation - 2011/04
Page Numbers: 76,77,78
76 MODEL AVIATION
Joe Wagner The Engine Shop | [email protected]
Also included in this column:
• Do-it-yourself model diesel fuel
• Morgan’s new CL glow fuel
• Quirk with certain glows
Glows vs. diesels in detail
The PAW .19 (L) is a nice contrast to the Thunder Tiger .18 (R).
Take note of the diesel’s tiny muffler and tall intake.
Another excellent comparison: the newly reissued Norvel (now
NV) .40 glow (foreground) and the PAW .40. Their styling varies
much more than their performance.
Diesels have an oily, messy exhaust. However, they aren’t affected much by back
pressure, so long exhaust extensions such as this can keep a model clean without losing
performance.
THROUGHOUT THE YEARS that I’ve
been writing this column, I’ve often
mentioned the many virtues of diesel
power plants for model airplanes. But until
now I had never directly compared a diesel
with a same-size glow, spinning the samesize
propellers, on the same day. And I
hadn’t yet discussed in much detail the
minor adverse quirks of diesels and how
those can be overcome.
I’ll do that now.
For these comparative tests I chose four
of my own well-broken-in and currently
available engines: a pair of .19s and a pair
of .40s. The diesels are British-made
Progress Aero Works engines, or PAWs.
The glow .19 is a Thunder Tiger “Green
Power” .18, while its double-size glow
partner is a recently reissued Russianmade
NV (formerly Norvel) Revlite .40.
These tests were obviously not
laboratory-grade, high-precision
procedures. Instead, I carried them out
under roughly the same conditions as “the
average modeler” would at his or her local
flying field—with one major exception.
I used the same propeller on both .19s
and another for both .40s. Doing that
forced all of the engines to run at lessthan-
optimal efficiency. The diesels spun
slightly smaller propellers than they work
best with, and the glows had the opposite
handicap.
However, as experienced model fliers
know, the airplane has more influence on
optimum propeller size and pitch than the
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:30 AM Page 76
engine’s size and type. Thus all I hope to
show here is a basic relationship—not a
cast-in-concrete set of aeronautical
engineering formulas.
For the glows I used Morgan’s new
specially-blended-for-CL fuel: 15% nitro
and 22% oil (half castor and half
synthetic). The diesels ran on a
commercially prepared sport-type fuel of
30% ether, 22% castor oil, and 43%
kerosene. (The kerosene is actually
aviation-grade jet fuel.)
All of the propellers used in these tests
were Graupners: 9 x 4s for the .19s and
12 x 5s for the .40s. I hand-started all of
the engines without difficulty.
Performance differences showed up
most markedly with the .40-size power
plants. That was because, as you can
readily tell from their appearances, the
NV is a short-stroke design, intended for
maximizing rpm; the PAW is a longstroker,
built to generate torque.
Now for the numbers. The NV .40’s
reliable rpm ranged from 11,000 to 3,100,
with sound-output levels between 93 and
71 dBA. The PAW .40 spun its 12 x 5
propeller at 9,200 rpm tops and 2,200 at a
reliable idle. Its sound measured 98-78
dBA.
The engines were a mere half-ounce
apart, at 13.6 ounces for the NV (it’s
mostly aluminum) and 14.1 for the PAW.
The pair of .19s were a bit more
closely comparable, designwise. That
showed up in their performance.
The Thunder Tiger turned its 9 x 4
Graupner at 11,800 and idled at 3,100,
with a sound output ranging between 92
dBA and 78. The PAW .19 put out 9,300
top rpm, 3,100 low idle, and 90-82 dBA.
Again, the weights registered a halfounce
difference. The .19 diesel came out
to 6.9 ounces, and the glow Thunder
Tiger was 7.4 ounces.
The diesel’s advantages are no glow
April 2011 77
plugs, runs are 70% longer per ounce of
fuel, it is unaffected by humidity, the
same fuel can be used for every size
engine (and you can mix your own using
easy-to-obtain ingredients), it will spin
any-size propeller you can fit on its shaft,
and it has a small, unobtrusive muffler.
The few drawbacks of model diesel
engines seem minor by comparison.
One problem that many people
complain about is the dark, greasy
exhaust. The exhaust needn’t be dark;
that’s an indication of excess
compression. It causes extra stress and
heat, and it steals power.
But the exhaust doesn’t have to spray
rearward over the airplane. Diesels are
tolerant of exhaust back pressure anyway,
and PAWs in particular will readily accept
extensions that carry the exhaust well
behind and below the aircraft without
significantly reducing power output.
You might have heard that model
diesels always require hand-starting.
That’s to eliminate the chance of
hydraulic lock during electric starting
procedures, which damages the moving
parts.
That problem can be averted in various
ways. The most convenient is probably to
mount the engine with its cylinder pointed
sideways.
However, even with an upright or
inverted cylinder, if you initiate electric
starting with a dry (nonflooded) engine
and begin cranking with the compression
backed way off, you can slowly ease the
compression up until the engine fires.
After that, running adjustments proceed as
usual.
If you want to mix your own diesel
fuel, any John Deere dealership sells
spray cans of Starter Fluid. That’s as good
in model fuel as pure ether, except that it
doesn’t evaporate so quickly.
There are ways of extracting the fluid
from the cans without resorting to spray.
One is to place the John Deere can in a
freezer overnight, and then puncture a small
hole in the upper part of the can to let the
propane propellant dissipate.
After that, you can enlarge the hole with
something such as an awl, add a similar hole
as an air vent, and then pour the fluid into a
glass container.
I like to use a straight-sided jam jar in
which to measure and mix diesel. A length
of tape on its outside surface can be marked
in increments to represent the proportions of
22% castor, 43% kerosene, and 30% ether
(using the generic names of the ingredients),
for making each jarful of fuel.
The biggest tricks in operating model
diesel engines are in avoiding flooding and
making “incremental adjustments” between
compression and needle settings. That’s
what provides the smoothest, most efficient
operation.
As a diesel engine warms up, its
compression ordinarily needs to be lowered
a smidgen to prevent preignition, which is
the mixture firing while the piston is still on
its way up the bore. After reducing
compression, you lean out the mixture a bit.
Doing that generates more heat, which calls
for further reducing the compression.
Generally approximately three back-andforth
adjustment sequences will be needed
to completely fine-tune your diesel’s needle
and compression settings.
While I was running the performance
comparisons for this column, I ran into a
puzzling problem that I’ve occasionally
encountered through the years with my
spark and glow model engines. And,
coincidentally, that same week I received
an e-mail from a reader who had
experienced exactly the same difficulty.
I’ll condense and paraphrase what Abe
Gallas (Kansas City, Missouri) asked in
his message.
All it takes to home-brew fuel for model
diesels: castor oil from the drugstore, lamp
oil from Walmart, John Deere Starting
Fluid, and a modified jam jar.
This is Morgan Fuel’s
new glow fuel for CL
flying. CL engines
do run better and
last longer with an
optimized blend of
fuel.
This shot of the NV .40 running brings to mind an odd
phenomenon—one that has caused Joe and other model fliers to
scratch their heads before figuring it out.
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:31 AM Page 77
“In preparing to run one of my glow
engines, I made a battery pack of two D-size
cells in parallel. I put an alligator clip on each
terminal of this battery pack, plus an alligator
clip on ‘ground’ and the top of the glow plug.
“The plug did not light. I then used a
commercial glow clip, and the plug lit right
up. I was using the same battery setup, so
electrically the circuit was the same. I asked
several modelers for an opinion as to why the
first arrangement did not work, and none of
them had a clue. Do you?”
This problem results from the fact that
oxidized aluminum is electrically
nonconductive. (This fact is what makes
electrolytic capacitors possible.)
Many model-engine cases are aluminum;
when those are anodized (which is an
oxidative process), their surfaces might as
well have been made from wood, as far as
electrical conductivity goes.
Yes, electricity travels readily via
nonoxidized aluminum, such as where a
glow plug hole has been drilled and tapped
through otherwise anodized metal. But
hooking up a glow plug lead to the outer
surface of an engine’s case—i.e.,
“ground”—won’t light the plug if that case
has been anodized. Anodizing encapsulates
the case in an insulating skin. MA
Sources:
Progress Aero Works
www.eifflaender.com
Thunder Tiger
(217) 398-8970
www.ttamerica.com
Model Engine Collectors Association
www.modelenginecollectors.org
78 MODEL AVIATION
- SECURE SHOPPING WITH OUR ONLINE CATALOG -
www.fiberglassspecialtiesinc.com
[email protected]
Phone (479) 359-2429 Fax (479) 359-2259
Hours: Monday - Friday 9 to 5 CST
15715 Ashmore Dr., Garfield, Arkansas 72732
LARGEST
COLLECTION OF
EPOXY GLASS
COWLS & WHEEL
PANTS IN THE WORLD!
SINCE
1977!
04sig3x.QXD_00MSTRPG.QXD 2/22/11 11:32 AM Page 78
