Radio Control Electrics - 2004/06

114 MODEL AVIATION
THIS COLUMN INCLUDES three meet announcements,
reviews several recurring reader questions and advisories,
reminds you of a SIG that is growing in popularity, and describes
a how-to videotape that should be of particular interest to the
Scale modeler—Electric or otherwise.
Joe Beshar (198 Merritt Dr., Oradell NJ 07649; Tel.: [201] 261-
1281) wrote to tell about the eighth annual Old Time Eagles
Electric Fly-In, scheduled for Saturday, May 15, in Hope, New
Jersey. The rain date is Sunday, May 16.
I’ve been to several of these meets, and this is a fun, low-key
gathering that has been growing steadily from year to year. It
features open flying for all and an Elexaco event for the
competition minded. It will be less than a month away when you
receive this issue, so quickly get in touch with Joe for more
information. And do tell him Bob sent ya!
Brian Allen (47036 Berwick Ct., Sterling VA 20165; Tel.:
[703] 430-5849; E-mail: [email protected]) wrote to tell us
about the Loudoun County Aeromodelers Association’s 5th
Annual Electric Fly-In, scheduled for Saturday, July 24. It will be
held at the club’s flying field at Banshee Reeks Park, which is
several miles south of Leesburg.
This laid-back meet is AMA sanctioned and offers lunch, a
raffle, and vendors. You can get more info from Brian, and you
can check out the club site at www.lcaa.org.
Karl Benson (28 Cheltenham Dr., Wyomissing PA 19610;
Tel.: [610] 678-1447; Fax: [610] 678-7017) has announced this
year’s Cocalico Prop Busters Electric Fun Fly scheduled for
September 11. The meet is also open to CO2 power and offers fun
events for all. These include several mass-launch contests such as
the GWS Moth pylon race, a Wingo endurance contest, and Zagi
Bob Kopski, 25 West End Dr., Lansdale PA 19446
RADIO CONTROL ELECTRICS
Keith Shaw’s (Ann Arbor MI) gorgeous, curvaceous Bugatti 1⁄5-scale racer. The structure is largely of molded balsa.
Bob’s first RC receiver (R) and modern GWS four-channel
receiver. Former needed 67.5- and 1.5-volt batteries to operate.
combat. There are other events/judgings as well.
You can get more information from Karl, including a mailer
with map. He is friendly and is well known among East Coast Eaeromodelers
as a formidable AULD (All-Up/Last-Down
competitor). He has spent nearly two decades perfecting this
pursuit, and he is the man to beat. (Good luck!)
If you have an Electric event planned, share the information
06sig4.QXD 3/24/04 12:28 pm Page 114
with me, and I’ll pass it along in an
upcoming column. Just be sure to get me the
facts more than four months ahead of the
event date so that everyone can benefit from
adequate publication lead time.
I received the info about the Hope NJ
meet near the end of January—just days
ahead of my writing this column. As you can
see from the dates, this was cutting it close,
and the announcement herein is not as
helpful and useful as it would have been
with an additional month’s lead time.
Reader mail can be counted on for “theme”
or “repeat” questions. It seems that some
questions never go away, no matter how
many times and in how many places answers
are given. One good reason for this is the
continuing entry of new E-aeromodelers.
Another is that some details are difficult to
remember, so reminders are helpful.
Many readers truly enjoy the occasional
electronics projects that MA and I have
shared throughout the years. The most recent
is Dump’r in the October 2003 issue. Such a
project typically brings many reader letters,
and some are rewarding to me as the author.
These are from the few readers who may
have no related background but nervously
undertake such projects anyway. To those
people, nearly everything about such a
project can be a major challenge. I can’t
express enough admiration and appreciation
for those with such spirit and determination!
Consider the common question, Which
direction does a resistor go? More
experienced readers may chuckle at this, but
pretend that you are a first-timer and you’ll
appreciate the question.
Resistors have no direction; you can
install them in a circuit either way. The
pretty color code does not indicate top,
bottom, right, or left—just the resistance
value and some related information. This
same thing is true for the oft-used chokes
I’ve mentioned for solving noise problems
and some capacitors.
I need to expand on this last item because
some capacitors are polarized and do have
“direction”; that is, they must be installed
and/or wired with the correct orientation.
These parts are marked accordingly, and I
typically indicate this in my electronics
construction articles. A component with
which you must consider polarity, direction,
or orientation is semiconductors. These
include diodes, LEDs, transistors, ICs
(integrated circuits), and such, so watch out
with these parts. And of course batteries
must be hooked up correctly.
Another rather frequent reader question
concerns some battery chargers, such as the
several I’ve published through the years and
some that are commercially available. The
most recent of the former was the Small-
Pack Slow Charger in the June 2002 MA.
Many readers are forever confused by the
concept of “constant current.” They can be
so used to (so focused on) voltage that the
idea of a current source is totally alien.
Many (but not all) chargers are designed
to deliver a specific charging current no
matter the cell count, as long as it’s in the
intended design/application range. (This is
true for every one I’ve published.) So
whether you’re charging one cell or the limit
number of cells that that particular charger
allows, the selected current remains the
same.
Many readers panic when they measure
the charger output voltage in the absence of
a pack, only to find an extremely high
voltage present. Then they fearfully react
with concern for the safety of a pack they
want to charge.
Put the voltmeter away! For a properly
working constant-current (i.e., current
source) charger, this “open circuit” voltage
measurement means nothing! (Actually, it
sets the maximum number of cells—but
nothing else.) The only thing that matters is
the current present when a pack—any pack
within the design range—is in place. If you
still need assurance of proper operation, you
can connect a current meter in series with
your pack and observe the charging current
value.
All my published electronics projects
have included a necessary-parts list. This is
usually a straightforward matter, but such a
list may become problematic if a suggested
supplier goes away or discontinues a
particular part.
If you are absolutely sure (fully
knowledgeable) about what you’re doing,
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06sig4.QXD 3/24/04 12:29 pm Page 116
118 MODEL AVIATION
you can likely find a suitable alternative
supplier or component on your own.
However, if you aren’t capable of doing this,
I must caution you about what several
readers have learned the hard way:
advertised “equivalent” or “substitute” parts
are not always so! Please inquire of me (with
an SASE), and I’ll do my best to assist.
Recent years have brought a common
question that is associated with the rapid
growth of small-model interest and NiMH
batteries. Many fliers have experienced
shorter than expected flights because of
premature ESC shutdown. Numerous readers
have described this same thing, inquiring
what might be wrong with their ESC, pack,
charger, or whatever.
In most of these cases, the problem
turned out to be that the NiMH pack, unlike a
similar Ni-Cd pack, was unable to sustain
terminal voltage for the particular motor
current drain. Then the ESC cutoff function
“thought” the pack was nearing empty, so it
shut down the motor to preserve power for
the radio. The ESC did what it was supposed
to do—but for the wrong reason!
It’s been a common experience that
NiMH packs of the same or even higher
nominal capacity as the Ni-Cd packs they
replaced are simply unable to “hold up” their
terminal voltage for the same motor current
demand.
Common occurrences of this are found
in six- and seven-cell systems with ESCs
that cut off near 5.5 volts. Many readers
have found that everything works okay
right after charge and/or at reduced throttle,
but as soon as power is increased, cutoff
occurs. This is usually because NiMH
packs have more internal resistance and,
despite being fully charged, appear to the
ESC as one that is getting low. The effect is
most pronounced a minute or so into the
flight at high throttle.
I know that many have been
disappointed to find that the “better” NiMH
pack they thought they had let them down
in this manner. Some have solved this
problem by adding another cell as a way to
keep the pack voltage high enough; thus a
six-cell Ni-Cd would be replaced with a
seven-cell NiMH. Another option is to use
higher-capacity (or better-quality) cells
with lower internal resistance.
If you seem to be getting short flights
(premature ESC shutdown), this may be the
cause, so you can proceed accordingly.
The Vintage Radio Control Society
(VR/CS) is an AMA SIG that, as the name
suggests, is dedicated to early RC model
designs. What is interesting is that many
who participate in this activity are flying
electric-powered versions of these long-ago
airplanes.
VR/CS activities are for RC designs
predating January 1, 1970. These
(numerous) models are considered “vintage”
and fit within the organization’s focus. In a
sense, this is another nostalgia activity and
is appealing to many “mature”
aeromodelers.
Representative designs include such old
greats as Hal deBolt’s famous Live Wire
series, the Esquire, the Trixter Beam, the
Square Hare, and dozens more. VR/CS
meets include such challenging events as
Rudder Only. (At one time there was an
AMA RC event called Rudder Only—and
that’s how it was flown!)
I find that many readers enjoy the fond
memories associated with this venture—
especially the part about combining these
oldest RC designs with the newest power
systems: electric. For an example, look at
Weldon Smith’s Electric Zephyr in the
August 2003 MA. He first flew this basic
design approximately 42 years ago, and now
he does so again—quietly. I’ve witnessed it!
Vintage designs are now flown with
contemporary radios, but one photo shows
an early RC receiver—my first. It is a
Citizen-Ship, single-channel, superregenerative
operating on 27 mHz. If the
“glass bottle” looks alien to you, it’s a
vacuum tube, and it needed many batteries
to operate. The relay output was capable of a
simple on-off operation. Push the transmitter
button, and the actuator (not a servo!) would
move the rudder—hopefully—full throw!
This receiver is 50 years old this year,
and I flew it in my first RC model: a wetpowered
Trixter Beam. My goal is to fly it
in a vintage Beam again—this time with
electric power, of course.
You can get more information about the
VR/CS from Membership Chairman Scott
Wallace at 3621 Matthews Dr., Endwell NY
13760; E-mail: [email protected]. You
can also check out www.vintagerc
society.org/—a nice place to visit. The
society publishes a bimonthly magazine, and
membership costs $20 annually. VR/CS
rules specifically allow electric power. If
this sounds appealing, please check into this
SIG.
A photo this month shows an absolutely
gorgeous 1⁄5-scale Bugatti racer rendered by
the well-known Keith Shaw of Ann Arbor,
Michigan. This design was years in the
works, and it includes a custom-built
“transmission” (gearbox) that couples the
Astro 40 motor to the counter-rotating
propellers.
Other specifics include the model’s 65-
inch wingspan and an area of approximately
800 square inches. Energy storage is 24
CP1700s, and the all-up weight is 9.5
pounds. The finish is all MonoKote.
The beautiful, shapely Bugatti was built
using balsa molding techniques, which
brings me to a nifty how-to video entitled
Balsa Molding Techniques, produced by
Robin’s View Productions (Box 68,
Stockertown PA 18083; Tel.: [610] 746-
0106). This 105-minute video details the
processes and practices of molding balsa in
straight and compound-curve applications.
(Yes, you can make balsa bend both ways at
the same time!)
I’ve been an aeromodeler for more than
50 years, and I did not fully appreciate the
details of this application/technology until I
saw the Bugatti and the tape and put the two
together. If you’ve been stalled while
building a curvaceous Scale project, check
out this video.
Robin’s View has several other
aeromodeling tapes, covering such topics as
Lost Foam wing building (a high-precision
technique) and covering with Japanese
tissue—a nearly lost skill.
Thus ends another column. Please include
an SASE with any correspondence for
which you’d like a reply. Everyone so doing
does get one! In the meantime, many happy
electric landings, everyone! MA
or
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