Frequently Asked Questions - 2011/02

84 MODEL AVIATION
Please write in with your questions; that is the only way we can
keep this column format going. When referring to published questions
and answers (for follow-ups), provide the number as a reference.
Also note that references to addresses and Web sites are placed in a
group, separate from the text, at the end of this column under
“Sources.”
A new feature, “Tips,” is provided in addition to Qs and As. These
hints are numbered in the same sequence as the questions and answers.
Q483: “I heard that one of the Model Aviation columns last year
showed a neat take-off dolly for model aircraft that was constructed
from common PVC pipe and fittings. Can you locate this reference for
me and elaborate on it?”
a483: The dolly you are referring to was featured in Red Scholefield’s
battery column, on
page 104 of the
November 2009
issue. Red used the
device to support his
electric-powered
sailplane, enabling it
to take off from the
ground even though
it had no landing
gear or even wheels.
Many sailplanes
are simply handlaunched,
but Red
preferred a ground
launch. A detailed
photo published in
that column shows
the basic construction of the dolly, from
common PVC pipe and fittings.
Steerable PVC aircraft dolly
Bob Aberle | baberle@? Frequently Asked Questions optonline.net
Also included in this column:
• Metal and carbon-fiber
landing gears
• Folding propellers for small
electric models
• RC for beginners
• Follow-up connector
thoughts
Left: In the mid motor
current range of 5-10
amps, a good connector
choice is the Deans 2NR.
It is available in red or
black and is reversible.
An aeromodeler at the 2010 NEAT Fair had
this electric-ducted- fan-powered scale
Grumman F9F Panther resting on an RC dolly
made from PVC material.
The interesting part about this jet dolly is that it could be steered by the RC system
to aid in taxiing and takeoff. In the text Bob explains how to get the aircraft and the
dolly to respond to rudder commands from a single transmitter.
Right: In the December 2009 MA, “The Battery Clinic”
columnist Red Scholefield included this photo of his
electric-powered sailplane resting on an RC takeoff dolly
that he constructed from PVC pipe and fittings.
Connectors used for electric flight should be carefully selected for
the anticipated motor current. Heat from the flowing current can
melt a weak connector.
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February 2011 85
Some landing gears come in two pieces and are intended to
mount to profile-fuselage models. These are from 3D Hobby
Shop (L) and Du-Bro Products.
The BSD Micro RC folding propeller comes with a 1-inchdiameter
spinner. In some cases an adapter tube will be required
to allow the propeller hub to fit snugly on the motor shaft. Two
setscrews anchor the propeller hub to the motor shaft.
BSD Micro RC is now
importing a neat foldingpropeller
assembly designed expressly
for micro/indoor airplanes and small
park flyers. Two sizes are available, and
they cost $5 each.
These are typical carbon-fiber landing gear that you can purchase
from Esprit Model. There are two- as well as one-piece styles.
Some of these are small enough for park flyer-size airplanes.
Esprit Model was kind enough to provide a chart containing all of
the important dimensions of its various landing gears. You can find
this information on the company’s Web site, and it is helpful when
selecting gear for a specific-size and -weight aircraft.
That would have been the end of this question, except that I found
an alternative to the idea at the recent NEAT (Northeast Electric
Aircraft Technology) Fair in upstate New York. A modeler (whose
name I never learned) had a stand-off-scale, electric-ducted-fan (EDF)-
powered Grumman F9F Panther that had no landing gear. The jet is
shown resting on a dolly that was constructed from PVC pipe.
As I looked closer I saw that the structure had an RC receiver,
servo, and battery pack attached to it. The servo actually steers the
dolly, which means that it also steers the airplane while it is on the
ground. The servo output arm is connected to a single wheel located at
the rear of the dolly.
The modeler employed two RC systems—one in the F9F and the
other on the dolly—that were operated by separate transmitters. A
friend performed the ground steering with one system while he flew the
jet with the other.
I asked why he didn’t simply have two receivers working off of one
transmitter. His reply was that he thought you couldn’t bind two
receivers to one 2.4 GHz spread spectrum transmitter. I couldn’t wait
to get home to try an experiment.
I quickly set up two Spektrum AR6110 2.4 GHz receivers and
bound both to my Spectrum DX7 transmitter. To my total delight,
both receivers responded to the rudder command from the
transmitter. So now my modeler friend can taxi, takeoff, and fly
his Panther all by himself.
02sig3.QXD_00MSTRPG.QXD 12/20/10 9:30The only thing I caution you about is that
this scheme might not work with every RC
spread spectrum system. You will have to run
tests with your particular system to verify that
two receivers can be bound to one transmitter.
But this is an interesting concept. It will also
save you from a bungee-cord launch, which
sometimes can prove quite difficult.
Q484: “I’m looking for small size metal or
carbon fiber strap type main landing gears for
use on my original design park flyer and E3D
aircraft.
“I remember years ago a product line
under the company name, Hallco, that offered
a full line of aluminum landing gears that
many referred to as ‘Cessna type’ gears. These
gears were simply bolted to the bottom of the
fuselage. Integral axles came already attached
to accept the wheels.
“I’ve tried to locate this company but
suspect they are long out of business. How can
I obtain similar type gears?”
A484: I thought this answer was going to be
easy, but it proved me wrong. The Internet
search approach did not yield the Hallco
company name. But, surprisingly, several
modelers had used Hallco gears that they were
selling on eBay and some of the model
forums.
One of the nice things about Hallco gears
was that the company supplied their tread and
height, so you could judge propeller-to-ground
clearance, and a guide to the estimated model
weight that the specific gear could support.
When I attempted to locate current
suppliers for these gear, in many cases little
dimensional or model weight data was
provided. But I eventually located a few
supply sources.
Several of the gear were the metal type
fabricated from hard (resilient) aluminum and
dural, while others were molded from woven
carbon fiber and resin (or epoxy). Esprit
Model has an excellent selection of carbonfiber
landing gears and provides all necessary
data, including saddle width, height, and tread
for the entire series.
The basic strap-type landing gear is one
piece and usually bolts to the bottom of the
fuselage. Two-piece landing-gear assemblies
are intended to be mounted to the sides of a
profile fuselage. Du-Bro item 943 is a good
example of that type. Axle shafts are used on
many of these gears for wheel attachment.
A good way to locate landing gears is to
visit the Web site of a major mail-order house,
such as Tower Hobbies, Horizon Hobby,
Hobby Lobby International, or Sig
Manufacturing. When you get to the home
page, type “landing gear” into the search box.
You might be surprised by what comes up.
Be patient, because there are many landing
gears out there.
Another long-trusted source for landing
gear is TnT Landing Gear Products. Tom
Kroggel has been custom-making support
products for models for years, and the
company is worth a try, although I don’t think
it has parts for foamies yet.
I’ve listed a few Web site addresses in the
“Sources” section to get you started. If you
find other worthwhile sources for these gears
for small aircraft, please share that info; I
would be happy to write a follow-up on this
subject.
Q485: “I’m looking for a small diameter
folding prop for use with my indoor, electric
powered, endurance aircraft. I want the prop
to fold back against the fuselage sides after I
shut down the motor. This will tend to reduce
drag when not under power and give me the
cleanest possible glide.
“I’ve tried several commercially available
folding props and found them so stiff that the
blades refuse to fold back in the wind stream.
Have you come across any props that fold
freely?”
A485:Many indoor and micromodel fliers
have been on the lookout for such a propeller.
As you point out, some are so stiff that they
won’t fold, while others are too heavy for
micro applications.
Having propeller blades that fold easily
will definitely reduce drag after the motor is
shut down. Bob Selman of BSD Micro RC
has found an interesting new folding propeller
assembly that he is now importing from the
Far East.
He has two sizes available, although the
sizes are similar. They measure 4.5 inches in
diameter by 3 inches in pitch and 5.1 inches in
diameter by 3.1 inches in pitch. These
assemblies come with a 1-inch-diameter
spinner, and the entire assembly (blades, hub,
and spinner) weighs only 4.3 grams (0.15
ounce).
This type of assembly is intended
exclusively for electric power applications and
primarily for small micro/indoor aircraft.
These propeller blades fold freely and
smoothly, to the point where they stay folded
until power is applied.
The propeller hub has a 1.5mm hole and
employs two setscrews. If your motor shaft is
anything but that 1.5mm diameter, you will
need to use some sort of adapter.
My motor shaft on a 7mm geared pager
motor had a 2mm-diameter shaft. Luckily this
is a popular-size motor, and Bob provides a
small machined length of tubing that allows
the 1.5mm propeller to slide onto the 2mm
motor shaft.
These folding propeller assemblies sell for
$5. They are perfect for my pager motor and
several ParkZone RTF motors, such as those
used in the Sukhoi and P-51 Mustang. I’ve
listed the BSD Micro RC contact info under
“Sources.”
T486: I do a lot of Web site “surfing” to get
ideas and answers for this column, and
something interesting often pops up. By
accident I found a Web site that modeler Gary
Dyrkacz created, called Radio Control for
Beginners.
In his relatively brief text, Gary covers
such subjects as who can fly RC, whether or
not you need to be an engineer to fly RC, what
kinds RC aircraft are available, and what you
need for RC flight. It’s down-to-earth and
basic writing, but it is exactly what you
would want to show a person who asks
“What’s this model airplane stuff all about?”
I was impressed enough with Gary’s
writing to place several copies in the glove
compartment of my car. Along with that I
have a brief information sheet about the
AMA, including the Academy’s Web site
address and a membership application.
When an interested spectator
approaches me at the flying field, he or she
gets a copy of this material—as an
introduction—and an invitation to attend
our next regular club meeting.
Follow-Up From MA: An important photo
was accidentally omitted from Bob’s
December 2010 column. It was for
question-and-answer 475 (on page 91), and
the subject related to the current carrying
capabilities of the various connectors used
in electric flight.
We are including that picture here. It
was important because it provided a
“visual identification” of the various
connectors that Bob was discussing in that
column.
Also in A475, Editor Michael Ramsey
added a comment concerning the Deans
two-pin micro connectors. A photo of that
connector is included here as well. Be
advised that it falls into the same 5- to 10-
amp category as the Deans four-pin
connector does.
Please accept our apologies in this
matter. MA
Sources:
3D Hobby Shop
(830) 990-6978
www.3dhobbyshop.com
Tower Hobbies
(800) 637-6050
www3.towerhobbies.com
Sig Manufacturing
(641) 623-5154
www.sigmfg.com
Du-Bro Products
(800) 848-9411
www.dubro.com
Esprit Model
(321) 729-4287
www.espritmodel.com
Hobby King
(800) 607-5803
www.hobbyking.com
TnT Landing Gear Products
(419) 868-5408
www.tntlandinggear.com
W.S. Deans
(714) 828-6494
www.wsdeans.com
Radio Control for Beginners
http://home.comcast.net/~dyrgcmn/RC/Rcpa
ge1.html
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