Maintenance and usage thoughts for diesel fans
Also included in this column:
• Repairing broken lugs with
J.B. Weld
• Fixing stripped heads with
HeliCoil inserts
• Stop the leaks!
August 2006 87
The Engine Shop Joe Wagner | [email protected]
Brass ball retainers, as in the smaller
bearing, can induce rust by catalyzing
methanol into acid. All-steel ball bearings
don’t have that problem.
Broken engine lugs fixed with J.B. Weld. (Rebuilt Enya lug has been darkened for
contrast.) The wood “mold” on the McCoy case is ready for filling.
A PAW .40 diesel spins its 14 x 4 3-D propeller with authority
despite its mild sound. Never use ARO in a model diesel!
IN PAST COLUMNS I’ve recommended Tower Hobbies’ After Run
Oil (ARO) for keeping engines from getting sticky in long-term
storage. It certainly does that job well! However, I’ve found out the
hard way that ARO should never be used in a model diesel.
I made that mistake last fall with four of my diesels. When spring
came, none of them would start! Rinsing out their interiors with fuel
or solvents did no good. Evidently ARO contains a powerful
antioxidant that bonds to steel surfaces. Yes, it does a fine job of
preventing rust and keeping the moving parts free—but it also stops
the ether in model diesel fuel from igniting.
To get my engines running again I had to take them apart and
scour their pistons and cylinder bores thoroughly with steel wool and
WD-40. Now they’re okay; and I learned a lesson from that.
Later I took one of my old diesels that had not been run for years
out of storage. As I expected, congealed oil had made it hard to turn
over. But a squirt of fresh diesel fuel in its intake and exhaust
loosened the moving parts nicely in just a few minutes.
Modelers often use ARO in their engines to prevent rust in ball
bearings. That’s not so much of a problem anymore, though. Many
manufacturers have changed from the earlier bearings that used brass
ball retainers; now they use all-steel types. Those eliminate any
chance of brass catalyzing the methanol in glow fuel into acetic acid
and causing rust.
(It’s an excellent idea to keep all brass out of and away from glow
fuel. The Sullivan company knows that. Now it supplies nylon fuel
tubing with its tank kits, along with the traditional brass tubes.)
I like model diesels a lot for powering my RC airplanes. Their ability
to uncomplainingly swing large-diameter propellers makes them
especially suitable for today’s “3-D”-style RC flying. Diesels are
quieter than glow engines too.
08sig3.QXD 6/23/06 11:30 AM Page 8788 MODEL AVIATION
Ace’s Pipe Thread Compound seals air leaks in needle valves (such as those the Cox
Texaco .049 often suffers) and makes a good substitute for gaskets.
Clarence Lee can repair stripped glow-plug threads to be like new by installing a
HeliCoil insert such as the one shown. This is not a do-it-yourself job!
At the Toledo Show last April, Eric
Clutton—aka Doctor Diesel—demonstrated
one of the Progress Aero Works (PAW) .19s
he imports. He attached a long piece of
vinyl tubing to the engine’s muffler outlet
and submerged the other end in a bucket of
water (to avoid polluting the indoor
environment with exhaust fumes).
“It silenced the engine so effectively, I
could hear the connecting rod swishing back
and forth!” he said.
To learn more about the British-made
PAW line of model diesel engines, check
the Web page www.eifflaender.com and
Eric Clutton’s at www.cafes.net/
doctordiesel/. You can learn a lot from those
sites.
Model engines do sustain damage. CL
airplanes flown over concrete can break
pieces off their power plants in “unplanned
landings.” Yet damage such as broken
mounting lugs can be repaired fairly easily
with a product called J.B. Weld.
I’ve fixed several broken lugs for friends
throughout the years, and the repairs have
held up well. The method I use is to clean
the break and rough-file it to provide a good
bond for the J.B. Weld. Then I make a
slightly oversize wooden “mold” to fit
around the broken area and clamp that in
place. I mix the two-component material
well and fill the “mold cavity” with it.
After three or four hours the J.B. Weld
has solidified firmly enough to allow the
“mold” to be cut away. Yet at that stage the
material is still capable of being carved with
an X-Acto knife.
I do almost all the shaping of my repairs
before the J.B. Weld has fully hardened.
(That takes approximately 24 hours,
depending on temperature.) Afterward,
careful work with needle files and drills
completes the restoration job and readies
the engine for flying again.
Although it’s an uncommon difficulty,
loose glow-plug threads can spoil a model
engine’s performance. The usual sign of a
loose thread is compression leaking out
around the base of the plug.
Trying to stop the leakage by tightening
the plug really hard can strip the head
threads. Then you’re in trouble.
Replacement heads can be hard to find—
especially for older engines.
However, my old friend Clarence Lee
(who wrote the model-engine column for
Radio Control Modeler magazine for
decades, up to its recent demise, and now
writes for Model Airplane News) can fix
loose or stripped plug threads to be as good
as new. (See his ad in the “Classified Ads”
section in the back of this magazine.)
Clarence uses an ingenious but
extremely simple device called a “HeliCoil”
insert. It looks like a short, tightly wound
spring and is made from wire with a
diamond-shaped cross-section.
He starts the repair process by drilling
and tapping out the bad plug hole oversize
using a special HeliCoil tap. Then he uses
another special tool to screw the HeliCoil
insert into place.
(The insert’s diameter is visibly larger
than that of the newly tapped hole.
Therefore, the insert must compress inward
as it threads into that hole. That brings its
diameter down to the proper size, and at the
same time locks the insert firmly in place so
it cannot back out.)
In the final step, another tool is used to
break off the crossways “tang” of the
HeliCoil, so the plug can be installed.
As is evident from my description, this
kind of repair requires special procedures
and tools. I have a well-equipped
metalworking shop here—but I let Clarence
Lee solve my plug-hole problems (although
I don’t encounter many).
Probably the most common source of
unreliable model-engine performance is
leakage of one kind or another. Air will leak
08sig3.QXD 6/23/06 11:32 AM Page 8888 MODEL AVIATION
Ace’s Pipe Thread Compound seals air leaks in needle valves (such as those the Cox
Texaco .049 often suffers) and makes a good substitute for gaskets.
Clarence Lee can repair stripped glow-plug threads to be like new by installing a
HeliCoil insert such as the one shown. This is not a do-it-yourself job!
At the Toledo Show last April, Eric
Clutton—aka Doctor Diesel—demonstrated
one of the Progress Aero Works (PAW) .19s
he imports. He attached a long piece of
vinyl tubing to the engine’s muffler outlet
and submerged the other end in a bucket of
water (to avoid polluting the indoor
environment with exhaust fumes).
“It silenced the engine so effectively, I
could hear the connecting rod swishing back
and forth!” he said.
To learn more about the British-made
PAW line of model diesel engines, check
the Web page www.eifflaender.com and
Eric Clutton’s at www.cafes.net/
doctordiesel/. You can learn a lot from those
sites.
Model engines do sustain damage. CL
airplanes flown over concrete can break
pieces off their power plants in “unplanned
landings.” Yet damage such as broken
mounting lugs can be repaired fairly easily
with a product called J.B. Weld.
I’ve fixed several broken lugs for friends
throughout the years, and the repairs have
held up well. The method I use is to clean
the break and rough-file it to provide a good
bond for the J.B. Weld. Then I make a
slightly oversize wooden “mold” to fit
around the broken area and clamp that in
place. I mix the two-component material
well and fill the “mold cavity” with it.
After three or four hours the J.B. Weld
has solidified firmly enough to allow the
“mold” to be cut away. Yet at that stage the
material is still capable of being carved with
an X-Acto knife.
I do almost all the shaping of my repairs
before the J.B. Weld has fully hardened.
(That takes approximately 24 hours,
depending on temperature.) Afterward,
careful work with needle files and drills
completes the restoration job and readies
the engine for flying again.
Although it’s an uncommon difficulty,
loose glow-plug threads can spoil a model
engine’s performance. The usual sign of a
loose thread is compression leaking out
around the base of the plug.
Trying to stop the leakage by tightening
the plug really hard can strip the head
threads. Then you’re in trouble.
Replacement heads can be hard to find—
especially for older engines.
However, my old friend Clarence Lee
(who wrote the model-engine column for
Radio Control Modeler magazine for
decades, up to its recent demise, and now
writes for Model Airplane News) can fix
loose or stripped plug threads to be as good
as new. (See his ad in the “Classified Ads”
section in the back of this magazine.)
Clarence uses an ingenious but
extremely simple device called a “HeliCoil”
insert. It looks like a short, tightly wound
spring and is made from wire with a
diamond-shaped cross-section.
He starts the repair process by drilling
and tapping out the bad plug hole oversize
using a special HeliCoil tap. Then he uses
another special tool to screw the HeliCoil
insert into place.
(The insert’s diameter is visibly larger
than that of the newly tapped hole.
Therefore, the insert must compress inward
as it threads into that hole. That brings its
diameter down to the proper size, and at the
same time locks the insert firmly in place so
it cannot back out.)
In the final step, another tool is used to
break off the crossways “tang” of the
HeliCoil, so the plug can be installed.
As is evident from my description, this
kind of repair requires special procedures
and tools. I have a well-equipped
metalworking shop here—but I let Clarence
Lee solve my plug-hole problems (although
I don’t encounter many).
Probably the most common source of
unreliable model-engine performance is
leakage of one kind or another. Air will leak
08sig3.QXD 6/23/06 11:32 AM Page 88
Edition: Model Aviation - 2006/08
Page Numbers: 87,88,90
Edition: Model Aviation - 2006/08
Page Numbers: 87,88,90
Maintenance and usage thoughts for diesel fans
Also included in this column:
• Repairing broken lugs with
J.B. Weld
• Fixing stripped heads with
HeliCoil inserts
• Stop the leaks!
August 2006 87
The Engine Shop Joe Wagner | [email protected]
Brass ball retainers, as in the smaller
bearing, can induce rust by catalyzing
methanol into acid. All-steel ball bearings
don’t have that problem.
Broken engine lugs fixed with J.B. Weld. (Rebuilt Enya lug has been darkened for
contrast.) The wood “mold” on the McCoy case is ready for filling.
A PAW .40 diesel spins its 14 x 4 3-D propeller with authority
despite its mild sound. Never use ARO in a model diesel!
IN PAST COLUMNS I’ve recommended Tower Hobbies’ After Run
Oil (ARO) for keeping engines from getting sticky in long-term
storage. It certainly does that job well! However, I’ve found out the
hard way that ARO should never be used in a model diesel.
I made that mistake last fall with four of my diesels. When spring
came, none of them would start! Rinsing out their interiors with fuel
or solvents did no good. Evidently ARO contains a powerful
antioxidant that bonds to steel surfaces. Yes, it does a fine job of
preventing rust and keeping the moving parts free—but it also stops
the ether in model diesel fuel from igniting.
To get my engines running again I had to take them apart and
scour their pistons and cylinder bores thoroughly with steel wool and
WD-40. Now they’re okay; and I learned a lesson from that.
Later I took one of my old diesels that had not been run for years
out of storage. As I expected, congealed oil had made it hard to turn
over. But a squirt of fresh diesel fuel in its intake and exhaust
loosened the moving parts nicely in just a few minutes.
Modelers often use ARO in their engines to prevent rust in ball
bearings. That’s not so much of a problem anymore, though. Many
manufacturers have changed from the earlier bearings that used brass
ball retainers; now they use all-steel types. Those eliminate any
chance of brass catalyzing the methanol in glow fuel into acetic acid
and causing rust.
(It’s an excellent idea to keep all brass out of and away from glow
fuel. The Sullivan company knows that. Now it supplies nylon fuel
tubing with its tank kits, along with the traditional brass tubes.)
I like model diesels a lot for powering my RC airplanes. Their ability
to uncomplainingly swing large-diameter propellers makes them
especially suitable for today’s “3-D”-style RC flying. Diesels are
quieter than glow engines too.
08sig3.QXD 6/23/06 11:30 AM Page 8788 MODEL AVIATION
Ace’s Pipe Thread Compound seals air leaks in needle valves (such as those the Cox
Texaco .049 often suffers) and makes a good substitute for gaskets.
Clarence Lee can repair stripped glow-plug threads to be like new by installing a
HeliCoil insert such as the one shown. This is not a do-it-yourself job!
At the Toledo Show last April, Eric
Clutton—aka Doctor Diesel—demonstrated
one of the Progress Aero Works (PAW) .19s
he imports. He attached a long piece of
vinyl tubing to the engine’s muffler outlet
and submerged the other end in a bucket of
water (to avoid polluting the indoor
environment with exhaust fumes).
“It silenced the engine so effectively, I
could hear the connecting rod swishing back
and forth!” he said.
To learn more about the British-made
PAW line of model diesel engines, check
the Web page www.eifflaender.com and
Eric Clutton’s at www.cafes.net/
doctordiesel/. You can learn a lot from those
sites.
Model engines do sustain damage. CL
airplanes flown over concrete can break
pieces off their power plants in “unplanned
landings.” Yet damage such as broken
mounting lugs can be repaired fairly easily
with a product called J.B. Weld.
I’ve fixed several broken lugs for friends
throughout the years, and the repairs have
held up well. The method I use is to clean
the break and rough-file it to provide a good
bond for the J.B. Weld. Then I make a
slightly oversize wooden “mold” to fit
around the broken area and clamp that in
place. I mix the two-component material
well and fill the “mold cavity” with it.
After three or four hours the J.B. Weld
has solidified firmly enough to allow the
“mold” to be cut away. Yet at that stage the
material is still capable of being carved with
an X-Acto knife.
I do almost all the shaping of my repairs
before the J.B. Weld has fully hardened.
(That takes approximately 24 hours,
depending on temperature.) Afterward,
careful work with needle files and drills
completes the restoration job and readies
the engine for flying again.
Although it’s an uncommon difficulty,
loose glow-plug threads can spoil a model
engine’s performance. The usual sign of a
loose thread is compression leaking out
around the base of the plug.
Trying to stop the leakage by tightening
the plug really hard can strip the head
threads. Then you’re in trouble.
Replacement heads can be hard to find—
especially for older engines.
However, my old friend Clarence Lee
(who wrote the model-engine column for
Radio Control Modeler magazine for
decades, up to its recent demise, and now
writes for Model Airplane News) can fix
loose or stripped plug threads to be as good
as new. (See his ad in the “Classified Ads”
section in the back of this magazine.)
Clarence uses an ingenious but
extremely simple device called a “HeliCoil”
insert. It looks like a short, tightly wound
spring and is made from wire with a
diamond-shaped cross-section.
He starts the repair process by drilling
and tapping out the bad plug hole oversize
using a special HeliCoil tap. Then he uses
another special tool to screw the HeliCoil
insert into place.
(The insert’s diameter is visibly larger
than that of the newly tapped hole.
Therefore, the insert must compress inward
as it threads into that hole. That brings its
diameter down to the proper size, and at the
same time locks the insert firmly in place so
it cannot back out.)
In the final step, another tool is used to
break off the crossways “tang” of the
HeliCoil, so the plug can be installed.
As is evident from my description, this
kind of repair requires special procedures
and tools. I have a well-equipped
metalworking shop here—but I let Clarence
Lee solve my plug-hole problems (although
I don’t encounter many).
Probably the most common source of
unreliable model-engine performance is
leakage of one kind or another. Air will leak
08sig3.QXD 6/23/06 11:32 AM Page 8888 MODEL AVIATION
Ace’s Pipe Thread Compound seals air leaks in needle valves (such as those the Cox
Texaco .049 often suffers) and makes a good substitute for gaskets.
Clarence Lee can repair stripped glow-plug threads to be like new by installing a
HeliCoil insert such as the one shown. This is not a do-it-yourself job!
At the Toledo Show last April, Eric
Clutton—aka Doctor Diesel—demonstrated
one of the Progress Aero Works (PAW) .19s
he imports. He attached a long piece of
vinyl tubing to the engine’s muffler outlet
and submerged the other end in a bucket of
water (to avoid polluting the indoor
environment with exhaust fumes).
“It silenced the engine so effectively, I
could hear the connecting rod swishing back
and forth!” he said.
To learn more about the British-made
PAW line of model diesel engines, check
the Web page www.eifflaender.com and
Eric Clutton’s at www.cafes.net/
doctordiesel/. You can learn a lot from those
sites.
Model engines do sustain damage. CL
airplanes flown over concrete can break
pieces off their power plants in “unplanned
landings.” Yet damage such as broken
mounting lugs can be repaired fairly easily
with a product called J.B. Weld.
I’ve fixed several broken lugs for friends
throughout the years, and the repairs have
held up well. The method I use is to clean
the break and rough-file it to provide a good
bond for the J.B. Weld. Then I make a
slightly oversize wooden “mold” to fit
around the broken area and clamp that in
place. I mix the two-component material
well and fill the “mold cavity” with it.
After three or four hours the J.B. Weld
has solidified firmly enough to allow the
“mold” to be cut away. Yet at that stage the
material is still capable of being carved with
an X-Acto knife.
I do almost all the shaping of my repairs
before the J.B. Weld has fully hardened.
(That takes approximately 24 hours,
depending on temperature.) Afterward,
careful work with needle files and drills
completes the restoration job and readies
the engine for flying again.
Although it’s an uncommon difficulty,
loose glow-plug threads can spoil a model
engine’s performance. The usual sign of a
loose thread is compression leaking out
around the base of the plug.
Trying to stop the leakage by tightening
the plug really hard can strip the head
threads. Then you’re in trouble.
Replacement heads can be hard to find—
especially for older engines.
However, my old friend Clarence Lee
(who wrote the model-engine column for
Radio Control Modeler magazine for
decades, up to its recent demise, and now
writes for Model Airplane News) can fix
loose or stripped plug threads to be as good
as new. (See his ad in the “Classified Ads”
section in the back of this magazine.)
Clarence uses an ingenious but
extremely simple device called a “HeliCoil”
insert. It looks like a short, tightly wound
spring and is made from wire with a
diamond-shaped cross-section.
He starts the repair process by drilling
and tapping out the bad plug hole oversize
using a special HeliCoil tap. Then he uses
another special tool to screw the HeliCoil
insert into place.
(The insert’s diameter is visibly larger
than that of the newly tapped hole.
Therefore, the insert must compress inward
as it threads into that hole. That brings its
diameter down to the proper size, and at the
same time locks the insert firmly in place so
it cannot back out.)
In the final step, another tool is used to
break off the crossways “tang” of the
HeliCoil, so the plug can be installed.
As is evident from my description, this
kind of repair requires special procedures
and tools. I have a well-equipped
metalworking shop here—but I let Clarence
Lee solve my plug-hole problems (although
I don’t encounter many).
Probably the most common source of
unreliable model-engine performance is
leakage of one kind or another. Air will leak
08sig3.QXD 6/23/06 11:32 AM Page 88
Edition: Model Aviation - 2006/08
Page Numbers: 87,88,90
Maintenance and usage thoughts for diesel fans
Also included in this column:
• Repairing broken lugs with
J.B. Weld
• Fixing stripped heads with
HeliCoil inserts
• Stop the leaks!
August 2006 87
The Engine Shop Joe Wagner | [email protected]
Brass ball retainers, as in the smaller
bearing, can induce rust by catalyzing
methanol into acid. All-steel ball bearings
don’t have that problem.
Broken engine lugs fixed with J.B. Weld. (Rebuilt Enya lug has been darkened for
contrast.) The wood “mold” on the McCoy case is ready for filling.
A PAW .40 diesel spins its 14 x 4 3-D propeller with authority
despite its mild sound. Never use ARO in a model diesel!
IN PAST COLUMNS I’ve recommended Tower Hobbies’ After Run
Oil (ARO) for keeping engines from getting sticky in long-term
storage. It certainly does that job well! However, I’ve found out the
hard way that ARO should never be used in a model diesel.
I made that mistake last fall with four of my diesels. When spring
came, none of them would start! Rinsing out their interiors with fuel
or solvents did no good. Evidently ARO contains a powerful
antioxidant that bonds to steel surfaces. Yes, it does a fine job of
preventing rust and keeping the moving parts free—but it also stops
the ether in model diesel fuel from igniting.
To get my engines running again I had to take them apart and
scour their pistons and cylinder bores thoroughly with steel wool and
WD-40. Now they’re okay; and I learned a lesson from that.
Later I took one of my old diesels that had not been run for years
out of storage. As I expected, congealed oil had made it hard to turn
over. But a squirt of fresh diesel fuel in its intake and exhaust
loosened the moving parts nicely in just a few minutes.
Modelers often use ARO in their engines to prevent rust in ball
bearings. That’s not so much of a problem anymore, though. Many
manufacturers have changed from the earlier bearings that used brass
ball retainers; now they use all-steel types. Those eliminate any
chance of brass catalyzing the methanol in glow fuel into acetic acid
and causing rust.
(It’s an excellent idea to keep all brass out of and away from glow
fuel. The Sullivan company knows that. Now it supplies nylon fuel
tubing with its tank kits, along with the traditional brass tubes.)
I like model diesels a lot for powering my RC airplanes. Their ability
to uncomplainingly swing large-diameter propellers makes them
especially suitable for today’s “3-D”-style RC flying. Diesels are
quieter than glow engines too.
08sig3.QXD 6/23/06 11:30 AM Page 8788 MODEL AVIATION
Ace’s Pipe Thread Compound seals air leaks in needle valves (such as those the Cox
Texaco .049 often suffers) and makes a good substitute for gaskets.
Clarence Lee can repair stripped glow-plug threads to be like new by installing a
HeliCoil insert such as the one shown. This is not a do-it-yourself job!
At the Toledo Show last April, Eric
Clutton—aka Doctor Diesel—demonstrated
one of the Progress Aero Works (PAW) .19s
he imports. He attached a long piece of
vinyl tubing to the engine’s muffler outlet
and submerged the other end in a bucket of
water (to avoid polluting the indoor
environment with exhaust fumes).
“It silenced the engine so effectively, I
could hear the connecting rod swishing back
and forth!” he said.
To learn more about the British-made
PAW line of model diesel engines, check
the Web page www.eifflaender.com and
Eric Clutton’s at www.cafes.net/
doctordiesel/. You can learn a lot from those
sites.
Model engines do sustain damage. CL
airplanes flown over concrete can break
pieces off their power plants in “unplanned
landings.” Yet damage such as broken
mounting lugs can be repaired fairly easily
with a product called J.B. Weld.
I’ve fixed several broken lugs for friends
throughout the years, and the repairs have
held up well. The method I use is to clean
the break and rough-file it to provide a good
bond for the J.B. Weld. Then I make a
slightly oversize wooden “mold” to fit
around the broken area and clamp that in
place. I mix the two-component material
well and fill the “mold cavity” with it.
After three or four hours the J.B. Weld
has solidified firmly enough to allow the
“mold” to be cut away. Yet at that stage the
material is still capable of being carved with
an X-Acto knife.
I do almost all the shaping of my repairs
before the J.B. Weld has fully hardened.
(That takes approximately 24 hours,
depending on temperature.) Afterward,
careful work with needle files and drills
completes the restoration job and readies
the engine for flying again.
Although it’s an uncommon difficulty,
loose glow-plug threads can spoil a model
engine’s performance. The usual sign of a
loose thread is compression leaking out
around the base of the plug.
Trying to stop the leakage by tightening
the plug really hard can strip the head
threads. Then you’re in trouble.
Replacement heads can be hard to find—
especially for older engines.
However, my old friend Clarence Lee
(who wrote the model-engine column for
Radio Control Modeler magazine for
decades, up to its recent demise, and now
writes for Model Airplane News) can fix
loose or stripped plug threads to be as good
as new. (See his ad in the “Classified Ads”
section in the back of this magazine.)
Clarence uses an ingenious but
extremely simple device called a “HeliCoil”
insert. It looks like a short, tightly wound
spring and is made from wire with a
diamond-shaped cross-section.
He starts the repair process by drilling
and tapping out the bad plug hole oversize
using a special HeliCoil tap. Then he uses
another special tool to screw the HeliCoil
insert into place.
(The insert’s diameter is visibly larger
than that of the newly tapped hole.
Therefore, the insert must compress inward
as it threads into that hole. That brings its
diameter down to the proper size, and at the
same time locks the insert firmly in place so
it cannot back out.)
In the final step, another tool is used to
break off the crossways “tang” of the
HeliCoil, so the plug can be installed.
As is evident from my description, this
kind of repair requires special procedures
and tools. I have a well-equipped
metalworking shop here—but I let Clarence
Lee solve my plug-hole problems (although
I don’t encounter many).
Probably the most common source of
unreliable model-engine performance is
leakage of one kind or another. Air will leak
08sig3.QXD 6/23/06 11:32 AM Page 8888 MODEL AVIATION
Ace’s Pipe Thread Compound seals air leaks in needle valves (such as those the Cox
Texaco .049 often suffers) and makes a good substitute for gaskets.
Clarence Lee can repair stripped glow-plug threads to be like new by installing a
HeliCoil insert such as the one shown. This is not a do-it-yourself job!
At the Toledo Show last April, Eric
Clutton—aka Doctor Diesel—demonstrated
one of the Progress Aero Works (PAW) .19s
he imports. He attached a long piece of
vinyl tubing to the engine’s muffler outlet
and submerged the other end in a bucket of
water (to avoid polluting the indoor
environment with exhaust fumes).
“It silenced the engine so effectively, I
could hear the connecting rod swishing back
and forth!” he said.
To learn more about the British-made
PAW line of model diesel engines, check
the Web page www.eifflaender.com and
Eric Clutton’s at www.cafes.net/
doctordiesel/. You can learn a lot from those
sites.
Model engines do sustain damage. CL
airplanes flown over concrete can break
pieces off their power plants in “unplanned
landings.” Yet damage such as broken
mounting lugs can be repaired fairly easily
with a product called J.B. Weld.
I’ve fixed several broken lugs for friends
throughout the years, and the repairs have
held up well. The method I use is to clean
the break and rough-file it to provide a good
bond for the J.B. Weld. Then I make a
slightly oversize wooden “mold” to fit
around the broken area and clamp that in
place. I mix the two-component material
well and fill the “mold cavity” with it.
After three or four hours the J.B. Weld
has solidified firmly enough to allow the
“mold” to be cut away. Yet at that stage the
material is still capable of being carved with
an X-Acto knife.
I do almost all the shaping of my repairs
before the J.B. Weld has fully hardened.
(That takes approximately 24 hours,
depending on temperature.) Afterward,
careful work with needle files and drills
completes the restoration job and readies
the engine for flying again.
Although it’s an uncommon difficulty,
loose glow-plug threads can spoil a model
engine’s performance. The usual sign of a
loose thread is compression leaking out
around the base of the plug.
Trying to stop the leakage by tightening
the plug really hard can strip the head
threads. Then you’re in trouble.
Replacement heads can be hard to find—
especially for older engines.
However, my old friend Clarence Lee
(who wrote the model-engine column for
Radio Control Modeler magazine for
decades, up to its recent demise, and now
writes for Model Airplane News) can fix
loose or stripped plug threads to be as good
as new. (See his ad in the “Classified Ads”
section in the back of this magazine.)
Clarence uses an ingenious but
extremely simple device called a “HeliCoil”
insert. It looks like a short, tightly wound
spring and is made from wire with a
diamond-shaped cross-section.
He starts the repair process by drilling
and tapping out the bad plug hole oversize
using a special HeliCoil tap. Then he uses
another special tool to screw the HeliCoil
insert into place.
(The insert’s diameter is visibly larger
than that of the newly tapped hole.
Therefore, the insert must compress inward
as it threads into that hole. That brings its
diameter down to the proper size, and at the
same time locks the insert firmly in place so
it cannot back out.)
In the final step, another tool is used to
break off the crossways “tang” of the
HeliCoil, so the plug can be installed.
As is evident from my description, this
kind of repair requires special procedures
and tools. I have a well-equipped
metalworking shop here—but I let Clarence
Lee solve my plug-hole problems (although
I don’t encounter many).
Probably the most common source of
unreliable model-engine performance is
leakage of one kind or another. Air will leak
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