CellMeter: a self-powered, portable battery-checking device
April 2008 87
? Frequently Asked Questions Bob Aberle | [email protected]
Also included in this column:
• Paper models
• Ignition-engine noise and
spread spectrum RC
systems
• Giant Scale and scalereference
data
• Contrarotating propellers
• Follow-up to bolt cutters
• Follow-up to Li-Poly
batteries in RC transmitters
Fiddlers Green offers one free paper model—the Piper J-3 Cub—which you can
download from the Web site.
The top of Jack Hiner’s Playboy Cabin
Old-Timer with the wing removed. At
right is a Spektrum 2.4 GHz spread
spectrum receiver with the antenna wire
hanging out either side.
Hobby Lobby sells these two
CellMeters: the two- to
eight-cell version (top)
and the two- to
four-cell unit.
Q339: “I noticed an interesting new item on
the Hobby Lobby website called a
‘CellMeter’ for lithium polymer battery
packs. I already have a display similar to
this meter on my Li-Poly battery charger.
Why would I want this type of device?”
A339: That’s a good question. The
CellMeter has an LCD screen and allows
you to determine the amount of charge
remaining in your Li-Poly battery pack and
whether the cells in that pack essentially
have the same voltage, indicating that the
pack is “balanced.”
You can obtain this same feature in
several of the new Li-Poly chargers on the
market, but all of those must be powered
from a 12-volt source such as your car
battery. The difference with the CellMeter is
that it is self-powered; therefore, it is
portable. It is intended for use on the
04sig3.QXD 2/25/08 12:14 PM Page 87
site for a reasonable fee and then turned out
on your computer ink-jet printer. The
aircraft include such categories as Airships,
Bombers, Early Flying Machines,
Helicopters, Light Aircraft, Racers,
Trainers, and many more. The site offers
one free download for a paper-model
version of the Piper J-3 Cub.
Take the time to search around this site
because it contains so much information.
Micro-airplane enthusiasts will love all the
scale detail, three-views, and photos. There
are even flying models made from paper.
There is too much to describe here, but I
strongly suggest that you look up the
Fiddlers Green Web site. You won’t be
sorry!
Q341: “I’ve been flying in Society of
Antique Modeler contests for many years.
Some of my planes are powered by original
and replica ignition engines and some by
electric motors. In either case I have
experienced problems with electrical noise
interfering with my RC receiver.
“I heard recently that the new 2.4 GHz
spread spectrum radios eliminate those
problems. What’s the true story?”
A341: Many fliers are currently using
spread spectrum RC systems with the large
1/4 and 1/3-scale aircraft that are powered by
large ignition engines and are experiencing
no interference problems. The literature
about these systems concentrates on many
advantages, but it has not made a strong
point on noise interference.
From what I hear, electrical noise-type
interference does not happen when using a
2.4 GHz spread spectrum radio. If I’m
wrong, please write in with your comments.
I asked Jack Hiner, noted Society of
Antique Modelers (SAM) and AMA Nats
Electrics competitor, about his experiences.
He indicated that many SAM Ignition fliers
have switched to 2.4 GHz spread spectrum
and now have no interference problems. He
mentioned that several fliers who could not
fly at all on 72 MHz now fly, with no
problems, on 2.4 GHz.
The message seems clear. The muchhigher-
frequency spread spectrum radio
systems are opening many new doors to
Old-Timer competition fliers.
Another advantage is that you can fly
when you want. If you note thermal activity,
you don’t have to wait for the frequency
pin; you can fly right away and take
advantage. I haven’t heard these particular
spread spectrum advantages mentioned
before.
Q342: “I’ve progressed enough in the
hobby to want to try a large or giant scale
RC aircraft. Can you provide some
reference information to help me get
started?”
A342: A good place to start is MA’s “Radio
Control Giants” column, written by fellow
Long Islander, Sal Calvagna. Sal has been
writing this column for years. I’m sure what
I’m about to offer has already been
mentioned there.
I found a Web site Joe Huntly created
known as “Completely Scale RC.” When I
went there I was referred to Joe’s new site:
“Great War R/C.” I suspect that the title
comes from a warbird-type theme.
Joe’s site offers such categories as
“Scale Tips” and has an extensive list of
“Important Links.” That alone should keep
you busy for sometime.
On this same subject, I received an
updated catalog from Bob Banka who
operates Bob’s Aircraft Documentation. His
88 MODEL AVIATION
Left: A closer look shows a 4-40
hex bolt ready to be cut off. The
bolt threads into the tool. When
removed after cutting, the tool
smoothes the thread end.
Above: The Buchanan multipurpose
tool can cut bolts and then
smooth the threads. It also
serves as a wire stripper and
cutter, and it can crimp wire to
terminal connectors.
flightline prior to launching your aircraft.
As Hobby Lobby puts it, “Never launch
a plane with a near empty battery pack
again.” If you normally obtain several
flights on a single charge, this meter can
quickly help you determine, on the
flightline, when it is time to go back on the
charger.
The CellMeter comes in two types: a
two- to four-cell version and a two- to eightcell
version. These units are somewhat
expensive, at $90 and $120 respectively.
The CellMeter can quickly determine the
state of charge of your Li-Poly battery pack
and express it as a percentage. It can also
tell you the voltage of each cell in your pack
(provided that your pack has a balanced
node connector). If all the cells in the pack
have approximately the same voltage, the
pack is considered “balanced.”
The 2.5mm connector pin spacing on the
CellMeter 4 connects directly to PolyQuest,
Art-Tech, RCer, RICCS, and E-Sky Li-Poly
packs. Special adapters are available for
Thunder Power/Flight Power battery packs.
The CellMeter is a quality product! If
your current charger tells you all the
information I have outlined, you probably
don’t need the CellMeter unless you want to
make a check out on the flightline.
However, if your charger is of the basic
variety, without an LCD screen, the
CellMaster may prove to be an asset to your
Li-Poly charging process.
Q340: “I have heard that paper aircraft
models are still in existence. If that is true
I’d like to learn of some references and
where I might purchase some of these
models. I see a wonderful opportunity to use
these planes with my grandchildren for
educational purposes.”
A340: I have read some Web-site threads on
one of the model forums concerning paper
models. The one that was mentioned was
Fiddlers Green Paper Models.
On the Web site select “Aircraft” or
“Fun Stuff.” From what I gather, these
paper airplanes can be downloaded from the
Bob Banka’s 300-page scale-reference
catalog is available on a disc for $5 postpaid.
Every Scale builder/flier should have this!
04sig3.QXD 2/25/08 12:14 PM Page 88
almost-300-page reference catalog has been
growing for years. He offers both photo
packs (called Foto Paaks) and three-view
line drawings. Bob has indicated that he has
more than 400,000 photos on file and more
than 39,000 drawings in stock.
The Bob’s Aircraft Documentation
catalog is a bargain at $10. Bob also offers
his entire catalog on a single CD for just $5
postpaid in the US, Canada, and Mexico.
This is a must for the Scale enthusiast.
Q343: “This isn’t really a question but
thought I might share this with you and
your readers. I came upon a thread on a
recent RCGroups forum concerning how to
90 MODEL AVIATION
build your own contra-rotating prop
assembly. You might want to pass this on.”
A343: This really isn’t an answer, but I do
encourage readers to write in with ideas and
suggestions to supplement my Q/A format.
That specific RCGroups Web site covers
an inexpensive contrarotating propeller
assembly for electric motors that costs no
more than approximately $50 and requires no
special machining. It is just a matter of
bolting the parts together.
The concept was developed by
“turbodriven.” I wish I had a name for this
forum “handle.” Whoever the person is, he
did an excellent job. I was unable to pull
photos and diagrams off the site to show in
this column, so you must look it up on your
own. The information presented should be
easy to follow.
Follow-up to Q/A 311 (August 2007 MA,
page 93): A reader supplied a suggestion for
cutting bolts using a Dremel cutoff wheel
and then using a T-nut to smooth the ends of
the bolt heads. Several readers responded,
relating that they used various multipurpose
tools that are capable of cutting off bolts,
smoothing threads, stripping wire, cutting
wire, and crimping terminals to wires.
I purchased one such tool at The Home
Depot; it is by Buchanan (item 770414) and
sells for roughly $6. I found a comparable
tool at RadioShack called the Kronus 4-Way
Crimping Tool (catalog number 64-2984),
for $6.99.
I admit that the Buchanan tool did the job,
but considerable energy was required to cut
through a bolt. However, the extra features it
offered made it more than worth the $7 price.
Another variation of this same type of
product is the Klein Multi-Purpose 6-in-1
Tool (Klein part number 1000), which sells
for $17.49. Although it’s more expensive, it
appears to be capable of heavy-duty service.
I found this tool at The Home Depot as well.
Follow-up to Q/A 316 (MA, October 2007,
page 89): Don Armstrong, an AMA member
and regular “Frequently Asked Questions”
reader, E-mailed me a very interesting
comment concerning the use of Li-Poly in
RC transmitters. When I wrote that answer I
was thinking strictly of the transmitter lowvoltage
alarm going off at something near
8.8 volts.
However, Don claimed that he and
many of us have walked away from a stillturned-
on transmitter (in the car, in the
shop, or even at the flying field) and never
heard the alarm. That being the case, the
Li-Poly batteries go all the way down and
are quickly ruined.
Don pointed out that if Li-Polys are used,
a low-voltage cutoff will have to be
developed for this specific application. Also,
that cutoff must work only after an alarm
goes off. Otherwise, if the power goes off
with no warning and your model is still in the
air, goodbye airplane!
It’s something to think about! I apologize
for missing this extraordinarily important
point.
Please write in with your questions; that is
the only way we can keep this column format
going. Provide the number when referring to
published Q/As (for follow-ups). MA
Sources:
Bob’s Aircraft Documentation
(714) 979-8058
www.bobsairdoc.com
CellMeter:
Hobby Lobby
(866) 933-5972
www.hobby-lobby.com/cellmeter.htm
Contrarotating propeller assembly (on
RCGroups)
www.rcgroups.com/forums/showthread.php?
p=8241939#post8241939
Fiddlers Green Paper Models
www.fiddlersgreen.net
Free paper Piper J-3 Cub download
www.wsam.net/freebees/PIPERCUB/
regular/regular.pdf
Great War R/C
www.proflooney.net/
04sig3.QXD 2/25/08 12:15 PM Page 90
Edition: Model Aviation - 2008/04
Page Numbers: 87,88,90
Edition: Model Aviation - 2008/04
Page Numbers: 87,88,90
CellMeter: a self-powered, portable battery-checking device
April 2008 87
? Frequently Asked Questions Bob Aberle | [email protected]
Also included in this column:
• Paper models
• Ignition-engine noise and
spread spectrum RC
systems
• Giant Scale and scalereference
data
• Contrarotating propellers
• Follow-up to bolt cutters
• Follow-up to Li-Poly
batteries in RC transmitters
Fiddlers Green offers one free paper model—the Piper J-3 Cub—which you can
download from the Web site.
The top of Jack Hiner’s Playboy Cabin
Old-Timer with the wing removed. At
right is a Spektrum 2.4 GHz spread
spectrum receiver with the antenna wire
hanging out either side.
Hobby Lobby sells these two
CellMeters: the two- to
eight-cell version (top)
and the two- to
four-cell unit.
Q339: “I noticed an interesting new item on
the Hobby Lobby website called a
‘CellMeter’ for lithium polymer battery
packs. I already have a display similar to
this meter on my Li-Poly battery charger.
Why would I want this type of device?”
A339: That’s a good question. The
CellMeter has an LCD screen and allows
you to determine the amount of charge
remaining in your Li-Poly battery pack and
whether the cells in that pack essentially
have the same voltage, indicating that the
pack is “balanced.”
You can obtain this same feature in
several of the new Li-Poly chargers on the
market, but all of those must be powered
from a 12-volt source such as your car
battery. The difference with the CellMeter is
that it is self-powered; therefore, it is
portable. It is intended for use on the
04sig3.QXD 2/25/08 12:14 PM Page 87
site for a reasonable fee and then turned out
on your computer ink-jet printer. The
aircraft include such categories as Airships,
Bombers, Early Flying Machines,
Helicopters, Light Aircraft, Racers,
Trainers, and many more. The site offers
one free download for a paper-model
version of the Piper J-3 Cub.
Take the time to search around this site
because it contains so much information.
Micro-airplane enthusiasts will love all the
scale detail, three-views, and photos. There
are even flying models made from paper.
There is too much to describe here, but I
strongly suggest that you look up the
Fiddlers Green Web site. You won’t be
sorry!
Q341: “I’ve been flying in Society of
Antique Modeler contests for many years.
Some of my planes are powered by original
and replica ignition engines and some by
electric motors. In either case I have
experienced problems with electrical noise
interfering with my RC receiver.
“I heard recently that the new 2.4 GHz
spread spectrum radios eliminate those
problems. What’s the true story?”
A341: Many fliers are currently using
spread spectrum RC systems with the large
1/4 and 1/3-scale aircraft that are powered by
large ignition engines and are experiencing
no interference problems. The literature
about these systems concentrates on many
advantages, but it has not made a strong
point on noise interference.
From what I hear, electrical noise-type
interference does not happen when using a
2.4 GHz spread spectrum radio. If I’m
wrong, please write in with your comments.
I asked Jack Hiner, noted Society of
Antique Modelers (SAM) and AMA Nats
Electrics competitor, about his experiences.
He indicated that many SAM Ignition fliers
have switched to 2.4 GHz spread spectrum
and now have no interference problems. He
mentioned that several fliers who could not
fly at all on 72 MHz now fly, with no
problems, on 2.4 GHz.
The message seems clear. The muchhigher-
frequency spread spectrum radio
systems are opening many new doors to
Old-Timer competition fliers.
Another advantage is that you can fly
when you want. If you note thermal activity,
you don’t have to wait for the frequency
pin; you can fly right away and take
advantage. I haven’t heard these particular
spread spectrum advantages mentioned
before.
Q342: “I’ve progressed enough in the
hobby to want to try a large or giant scale
RC aircraft. Can you provide some
reference information to help me get
started?”
A342: A good place to start is MA’s “Radio
Control Giants” column, written by fellow
Long Islander, Sal Calvagna. Sal has been
writing this column for years. I’m sure what
I’m about to offer has already been
mentioned there.
I found a Web site Joe Huntly created
known as “Completely Scale RC.” When I
went there I was referred to Joe’s new site:
“Great War R/C.” I suspect that the title
comes from a warbird-type theme.
Joe’s site offers such categories as
“Scale Tips” and has an extensive list of
“Important Links.” That alone should keep
you busy for sometime.
On this same subject, I received an
updated catalog from Bob Banka who
operates Bob’s Aircraft Documentation. His
88 MODEL AVIATION
Left: A closer look shows a 4-40
hex bolt ready to be cut off. The
bolt threads into the tool. When
removed after cutting, the tool
smoothes the thread end.
Above: The Buchanan multipurpose
tool can cut bolts and then
smooth the threads. It also
serves as a wire stripper and
cutter, and it can crimp wire to
terminal connectors.
flightline prior to launching your aircraft.
As Hobby Lobby puts it, “Never launch
a plane with a near empty battery pack
again.” If you normally obtain several
flights on a single charge, this meter can
quickly help you determine, on the
flightline, when it is time to go back on the
charger.
The CellMeter comes in two types: a
two- to four-cell version and a two- to eightcell
version. These units are somewhat
expensive, at $90 and $120 respectively.
The CellMeter can quickly determine the
state of charge of your Li-Poly battery pack
and express it as a percentage. It can also
tell you the voltage of each cell in your pack
(provided that your pack has a balanced
node connector). If all the cells in the pack
have approximately the same voltage, the
pack is considered “balanced.”
The 2.5mm connector pin spacing on the
CellMeter 4 connects directly to PolyQuest,
Art-Tech, RCer, RICCS, and E-Sky Li-Poly
packs. Special adapters are available for
Thunder Power/Flight Power battery packs.
The CellMeter is a quality product! If
your current charger tells you all the
information I have outlined, you probably
don’t need the CellMeter unless you want to
make a check out on the flightline.
However, if your charger is of the basic
variety, without an LCD screen, the
CellMaster may prove to be an asset to your
Li-Poly charging process.
Q340: “I have heard that paper aircraft
models are still in existence. If that is true
I’d like to learn of some references and
where I might purchase some of these
models. I see a wonderful opportunity to use
these planes with my grandchildren for
educational purposes.”
A340: I have read some Web-site threads on
one of the model forums concerning paper
models. The one that was mentioned was
Fiddlers Green Paper Models.
On the Web site select “Aircraft” or
“Fun Stuff.” From what I gather, these
paper airplanes can be downloaded from the
Bob Banka’s 300-page scale-reference
catalog is available on a disc for $5 postpaid.
Every Scale builder/flier should have this!
04sig3.QXD 2/25/08 12:14 PM Page 88
almost-300-page reference catalog has been
growing for years. He offers both photo
packs (called Foto Paaks) and three-view
line drawings. Bob has indicated that he has
more than 400,000 photos on file and more
than 39,000 drawings in stock.
The Bob’s Aircraft Documentation
catalog is a bargain at $10. Bob also offers
his entire catalog on a single CD for just $5
postpaid in the US, Canada, and Mexico.
This is a must for the Scale enthusiast.
Q343: “This isn’t really a question but
thought I might share this with you and
your readers. I came upon a thread on a
recent RCGroups forum concerning how to
90 MODEL AVIATION
build your own contra-rotating prop
assembly. You might want to pass this on.”
A343: This really isn’t an answer, but I do
encourage readers to write in with ideas and
suggestions to supplement my Q/A format.
That specific RCGroups Web site covers
an inexpensive contrarotating propeller
assembly for electric motors that costs no
more than approximately $50 and requires no
special machining. It is just a matter of
bolting the parts together.
The concept was developed by
“turbodriven.” I wish I had a name for this
forum “handle.” Whoever the person is, he
did an excellent job. I was unable to pull
photos and diagrams off the site to show in
this column, so you must look it up on your
own. The information presented should be
easy to follow.
Follow-up to Q/A 311 (August 2007 MA,
page 93): A reader supplied a suggestion for
cutting bolts using a Dremel cutoff wheel
and then using a T-nut to smooth the ends of
the bolt heads. Several readers responded,
relating that they used various multipurpose
tools that are capable of cutting off bolts,
smoothing threads, stripping wire, cutting
wire, and crimping terminals to wires.
I purchased one such tool at The Home
Depot; it is by Buchanan (item 770414) and
sells for roughly $6. I found a comparable
tool at RadioShack called the Kronus 4-Way
Crimping Tool (catalog number 64-2984),
for $6.99.
I admit that the Buchanan tool did the job,
but considerable energy was required to cut
through a bolt. However, the extra features it
offered made it more than worth the $7 price.
Another variation of this same type of
product is the Klein Multi-Purpose 6-in-1
Tool (Klein part number 1000), which sells
for $17.49. Although it’s more expensive, it
appears to be capable of heavy-duty service.
I found this tool at The Home Depot as well.
Follow-up to Q/A 316 (MA, October 2007,
page 89): Don Armstrong, an AMA member
and regular “Frequently Asked Questions”
reader, E-mailed me a very interesting
comment concerning the use of Li-Poly in
RC transmitters. When I wrote that answer I
was thinking strictly of the transmitter lowvoltage
alarm going off at something near
8.8 volts.
However, Don claimed that he and
many of us have walked away from a stillturned-
on transmitter (in the car, in the
shop, or even at the flying field) and never
heard the alarm. That being the case, the
Li-Poly batteries go all the way down and
are quickly ruined.
Don pointed out that if Li-Polys are used,
a low-voltage cutoff will have to be
developed for this specific application. Also,
that cutoff must work only after an alarm
goes off. Otherwise, if the power goes off
with no warning and your model is still in the
air, goodbye airplane!
It’s something to think about! I apologize
for missing this extraordinarily important
point.
Please write in with your questions; that is
the only way we can keep this column format
going. Provide the number when referring to
published Q/As (for follow-ups). MA
Sources:
Bob’s Aircraft Documentation
(714) 979-8058
www.bobsairdoc.com
CellMeter:
Hobby Lobby
(866) 933-5972
www.hobby-lobby.com/cellmeter.htm
Contrarotating propeller assembly (on
RCGroups)
www.rcgroups.com/forums/showthread.php?
p=8241939#post8241939
Fiddlers Green Paper Models
www.fiddlersgreen.net
Free paper Piper J-3 Cub download
www.wsam.net/freebees/PIPERCUB/
regular/regular.pdf
Great War R/C
www.proflooney.net/
04sig3.QXD 2/25/08 12:15 PM Page 90
Edition: Model Aviation - 2008/04
Page Numbers: 87,88,90
CellMeter: a self-powered, portable battery-checking device
April 2008 87
? Frequently Asked Questions Bob Aberle | [email protected]
Also included in this column:
• Paper models
• Ignition-engine noise and
spread spectrum RC
systems
• Giant Scale and scalereference
data
• Contrarotating propellers
• Follow-up to bolt cutters
• Follow-up to Li-Poly
batteries in RC transmitters
Fiddlers Green offers one free paper model—the Piper J-3 Cub—which you can
download from the Web site.
The top of Jack Hiner’s Playboy Cabin
Old-Timer with the wing removed. At
right is a Spektrum 2.4 GHz spread
spectrum receiver with the antenna wire
hanging out either side.
Hobby Lobby sells these two
CellMeters: the two- to
eight-cell version (top)
and the two- to
four-cell unit.
Q339: “I noticed an interesting new item on
the Hobby Lobby website called a
‘CellMeter’ for lithium polymer battery
packs. I already have a display similar to
this meter on my Li-Poly battery charger.
Why would I want this type of device?”
A339: That’s a good question. The
CellMeter has an LCD screen and allows
you to determine the amount of charge
remaining in your Li-Poly battery pack and
whether the cells in that pack essentially
have the same voltage, indicating that the
pack is “balanced.”
You can obtain this same feature in
several of the new Li-Poly chargers on the
market, but all of those must be powered
from a 12-volt source such as your car
battery. The difference with the CellMeter is
that it is self-powered; therefore, it is
portable. It is intended for use on the
04sig3.QXD 2/25/08 12:14 PM Page 87
site for a reasonable fee and then turned out
on your computer ink-jet printer. The
aircraft include such categories as Airships,
Bombers, Early Flying Machines,
Helicopters, Light Aircraft, Racers,
Trainers, and many more. The site offers
one free download for a paper-model
version of the Piper J-3 Cub.
Take the time to search around this site
because it contains so much information.
Micro-airplane enthusiasts will love all the
scale detail, three-views, and photos. There
are even flying models made from paper.
There is too much to describe here, but I
strongly suggest that you look up the
Fiddlers Green Web site. You won’t be
sorry!
Q341: “I’ve been flying in Society of
Antique Modeler contests for many years.
Some of my planes are powered by original
and replica ignition engines and some by
electric motors. In either case I have
experienced problems with electrical noise
interfering with my RC receiver.
“I heard recently that the new 2.4 GHz
spread spectrum radios eliminate those
problems. What’s the true story?”
A341: Many fliers are currently using
spread spectrum RC systems with the large
1/4 and 1/3-scale aircraft that are powered by
large ignition engines and are experiencing
no interference problems. The literature
about these systems concentrates on many
advantages, but it has not made a strong
point on noise interference.
From what I hear, electrical noise-type
interference does not happen when using a
2.4 GHz spread spectrum radio. If I’m
wrong, please write in with your comments.
I asked Jack Hiner, noted Society of
Antique Modelers (SAM) and AMA Nats
Electrics competitor, about his experiences.
He indicated that many SAM Ignition fliers
have switched to 2.4 GHz spread spectrum
and now have no interference problems. He
mentioned that several fliers who could not
fly at all on 72 MHz now fly, with no
problems, on 2.4 GHz.
The message seems clear. The muchhigher-
frequency spread spectrum radio
systems are opening many new doors to
Old-Timer competition fliers.
Another advantage is that you can fly
when you want. If you note thermal activity,
you don’t have to wait for the frequency
pin; you can fly right away and take
advantage. I haven’t heard these particular
spread spectrum advantages mentioned
before.
Q342: “I’ve progressed enough in the
hobby to want to try a large or giant scale
RC aircraft. Can you provide some
reference information to help me get
started?”
A342: A good place to start is MA’s “Radio
Control Giants” column, written by fellow
Long Islander, Sal Calvagna. Sal has been
writing this column for years. I’m sure what
I’m about to offer has already been
mentioned there.
I found a Web site Joe Huntly created
known as “Completely Scale RC.” When I
went there I was referred to Joe’s new site:
“Great War R/C.” I suspect that the title
comes from a warbird-type theme.
Joe’s site offers such categories as
“Scale Tips” and has an extensive list of
“Important Links.” That alone should keep
you busy for sometime.
On this same subject, I received an
updated catalog from Bob Banka who
operates Bob’s Aircraft Documentation. His
88 MODEL AVIATION
Left: A closer look shows a 4-40
hex bolt ready to be cut off. The
bolt threads into the tool. When
removed after cutting, the tool
smoothes the thread end.
Above: The Buchanan multipurpose
tool can cut bolts and then
smooth the threads. It also
serves as a wire stripper and
cutter, and it can crimp wire to
terminal connectors.
flightline prior to launching your aircraft.
As Hobby Lobby puts it, “Never launch
a plane with a near empty battery pack
again.” If you normally obtain several
flights on a single charge, this meter can
quickly help you determine, on the
flightline, when it is time to go back on the
charger.
The CellMeter comes in two types: a
two- to four-cell version and a two- to eightcell
version. These units are somewhat
expensive, at $90 and $120 respectively.
The CellMeter can quickly determine the
state of charge of your Li-Poly battery pack
and express it as a percentage. It can also
tell you the voltage of each cell in your pack
(provided that your pack has a balanced
node connector). If all the cells in the pack
have approximately the same voltage, the
pack is considered “balanced.”
The 2.5mm connector pin spacing on the
CellMeter 4 connects directly to PolyQuest,
Art-Tech, RCer, RICCS, and E-Sky Li-Poly
packs. Special adapters are available for
Thunder Power/Flight Power battery packs.
The CellMeter is a quality product! If
your current charger tells you all the
information I have outlined, you probably
don’t need the CellMeter unless you want to
make a check out on the flightline.
However, if your charger is of the basic
variety, without an LCD screen, the
CellMaster may prove to be an asset to your
Li-Poly charging process.
Q340: “I have heard that paper aircraft
models are still in existence. If that is true
I’d like to learn of some references and
where I might purchase some of these
models. I see a wonderful opportunity to use
these planes with my grandchildren for
educational purposes.”
A340: I have read some Web-site threads on
one of the model forums concerning paper
models. The one that was mentioned was
Fiddlers Green Paper Models.
On the Web site select “Aircraft” or
“Fun Stuff.” From what I gather, these
paper airplanes can be downloaded from the
Bob Banka’s 300-page scale-reference
catalog is available on a disc for $5 postpaid.
Every Scale builder/flier should have this!
04sig3.QXD 2/25/08 12:14 PM Page 88
almost-300-page reference catalog has been
growing for years. He offers both photo
packs (called Foto Paaks) and three-view
line drawings. Bob has indicated that he has
more than 400,000 photos on file and more
than 39,000 drawings in stock.
The Bob’s Aircraft Documentation
catalog is a bargain at $10. Bob also offers
his entire catalog on a single CD for just $5
postpaid in the US, Canada, and Mexico.
This is a must for the Scale enthusiast.
Q343: “This isn’t really a question but
thought I might share this with you and
your readers. I came upon a thread on a
recent RCGroups forum concerning how to
90 MODEL AVIATION
build your own contra-rotating prop
assembly. You might want to pass this on.”
A343: This really isn’t an answer, but I do
encourage readers to write in with ideas and
suggestions to supplement my Q/A format.
That specific RCGroups Web site covers
an inexpensive contrarotating propeller
assembly for electric motors that costs no
more than approximately $50 and requires no
special machining. It is just a matter of
bolting the parts together.
The concept was developed by
“turbodriven.” I wish I had a name for this
forum “handle.” Whoever the person is, he
did an excellent job. I was unable to pull
photos and diagrams off the site to show in
this column, so you must look it up on your
own. The information presented should be
easy to follow.
Follow-up to Q/A 311 (August 2007 MA,
page 93): A reader supplied a suggestion for
cutting bolts using a Dremel cutoff wheel
and then using a T-nut to smooth the ends of
the bolt heads. Several readers responded,
relating that they used various multipurpose
tools that are capable of cutting off bolts,
smoothing threads, stripping wire, cutting
wire, and crimping terminals to wires.
I purchased one such tool at The Home
Depot; it is by Buchanan (item 770414) and
sells for roughly $6. I found a comparable
tool at RadioShack called the Kronus 4-Way
Crimping Tool (catalog number 64-2984),
for $6.99.
I admit that the Buchanan tool did the job,
but considerable energy was required to cut
through a bolt. However, the extra features it
offered made it more than worth the $7 price.
Another variation of this same type of
product is the Klein Multi-Purpose 6-in-1
Tool (Klein part number 1000), which sells
for $17.49. Although it’s more expensive, it
appears to be capable of heavy-duty service.
I found this tool at The Home Depot as well.
Follow-up to Q/A 316 (MA, October 2007,
page 89): Don Armstrong, an AMA member
and regular “Frequently Asked Questions”
reader, E-mailed me a very interesting
comment concerning the use of Li-Poly in
RC transmitters. When I wrote that answer I
was thinking strictly of the transmitter lowvoltage
alarm going off at something near
8.8 volts.
However, Don claimed that he and
many of us have walked away from a stillturned-
on transmitter (in the car, in the
shop, or even at the flying field) and never
heard the alarm. That being the case, the
Li-Poly batteries go all the way down and
are quickly ruined.
Don pointed out that if Li-Polys are used,
a low-voltage cutoff will have to be
developed for this specific application. Also,
that cutoff must work only after an alarm
goes off. Otherwise, if the power goes off
with no warning and your model is still in the
air, goodbye airplane!
It’s something to think about! I apologize
for missing this extraordinarily important
point.
Please write in with your questions; that is
the only way we can keep this column format
going. Provide the number when referring to
published Q/As (for follow-ups). MA
Sources:
Bob’s Aircraft Documentation
(714) 979-8058
www.bobsairdoc.com
CellMeter:
Hobby Lobby
(866) 933-5972
www.hobby-lobby.com/cellmeter.htm
Contrarotating propeller assembly (on
RCGroups)
www.rcgroups.com/forums/showthread.php?
p=8241939#post8241939
Fiddlers Green Paper Models
www.fiddlersgreen.net
Free paper Piper J-3 Cub download
www.wsam.net/freebees/PIPERCUB/
regular/regular.pdf
Great War R/C
www.proflooney.net/
04sig3.QXD 2/25/08 12:15 PM Page 90