The Ohm’s Law pie chart.
A power guideline chart.
This is a quality-built Himax motor.
If you read my column, you already know that I look forward to the annual Toledo Show: R/C Model
Expo the way a kid looks forward to
Christmas. It’s always a special event and
it’s my first chance to see many of the
year’s new releases.
The event has changed throughout
the years, but it’s great, and one
of the few chances to see so many
manufacturers, distributors, and vendors
in one place. The big names are usually
there and each year, new businesses
come to show their stuff as well.
It’s almost here, so mark your calendar
to be in Toledo, Ohio, at the SeaGate
Convention Centre, April 7-9, 2017!
Tools for Free
Maybe I should have said planning
tools, but I wanted to draw you in! As
you plan your shopping trip to Toledo,
you might also be planning to build a
new, electrified model. If you’re new to
electrics, or you haven’t gotten in deep
enough to convert your own airplane,
these two charts can be a lifesaver—and
they’re absolutely free!
Many modelers don’t know Ohm’s
Law, and others don’t often think past
the volts x amps = watts portion of it.
This pie chart breaks it all down for you.
The chart also garners a lot of hate mail
whenever I reference it.
Modelers tend to change the
abbreviations to commonly used letters,
If “W” works
better for you
than “P,” then use
it! Depending on
the publication in
which the abbreviations are used, they’re
accepted or argued.
The second chart breaks down
power-to-weight planning for levels of
performance. With the improvement
of batteries, motors, and ESCs, it has
become easier and easier to achieve
whatever level you’re targeting.
Just because you can set up an
airplane for 150 watts per pound doesn’t
mean that it’s the best choice if you only
need 75 watts per pound. Why? Motors
have a best-efficiency range, and that’s
the area you want to target for your
primary flight requirements.
If you overpower an airplane and
then operate it at half throttle or less
all of the time, you’re probably running
the motor in a less-efficient range. This
causes excess heat and further decreases
efficiency. Check the manufacturer’s
recommendations for efficiency and use
that information when planning.
Buy Cheap—Buy Twice
Friend and electric guru, Keith Shaw,
has preached this for as many years as
I’ve known him. Keith knows more
about electric flight than most of us ever
will, and I’ve never seen anything that he
has built not fly spectacularly.
Keith uses good equipment—but
that doesn’t mean it’s always the most
expensive. Don’t confuse “cheap” with
“inexpensive,” although they often go
hand in hand.
The Himax motor shown in one of
the photos is relatively inexpensive,
but it’s far from cheap. The quality
of construction is evident when you
disassemble one. These Himax motors
have beautifully spaced and secured
magnets, with separators between each
magnet, to help them stay aligned and
Another photo shows a cheap
motor that was poorly constructed and
obviously came apart. The cheap motor
cost half of what the Himax motor did,
but when it self-destructed because of
poor construction, it also caused a fast
current spike that destroyed the ESC,
becoming doubly expensive.
I can only blame myself for
not following Keith’s sage advice.
I tend to experiment based on
recommendations that I receive in
87 Model Aviation APRIL 2017 www.ModelAviation.com
The Toledo Show: R/C Model Expo!