it comes to making electric conversions easier, I am always eager
to use new products in my next project. This month's column shows
a few of these items that have helped make it easier for me to fly
electric and "arm the big boys".
some plane designs, it is particularly difficult to access the battery
packs without making extensive modifications. This scenario is often
seen on scale warbirds where you don't want to detract from the
look of the plane or weaken the fuselage by cutting the frame for
a hatch. On smaller electrics, connecting the battery to arm the
plane before flight is acceptable. When you start getting into larger
electrics and glow conversions, it is often difficult to gain access
to the battery connections for arming the plane. Further, it is
just plain dangerous to leave it armed even though the Electronic
Speed Control (ESC) keeps the motor off when there is a Loss-Of-Signal
(LOS) from the transmitter.
many years, the only convenient arming system that I used on electric
conversions was developed by Tom Cimato of MaxCim
Motors. Adding a MaxCim Charging Harness allowed me to safely
arm the plane at the flight line as well as re-charge the batteries
while keeping the wing on. I
found these features to be invaluable for full day events. You can
set up your planes in the morning and keep flying or recharging
all day. You simply taxi into the pits and plug in your charger
after a cooling period.
MaxCim Charging Harness on the right was modified to use Dean's
Ultra connectors, a 40-amp ATO-style fuse, and a single battery
connection. My hope was that someday this type of charging
harness would be sold to R/Cers for easy recharging of the
battery packs in the plane.
ATO fuse moves from the 'Operate' to the 'Charge' position
to connect the charge jack and disconnect the battery from
the controller. This assembly allowed me to mount my Hangar
9 Corsair F4U wing once in the morning of an R/C event
and simply taxi into the pits for a recharge. At the time,
it was a true convenience for arming the system and charging
NiCd or NiMH packs.
MPI 6790 Arming Switch
Products International (MPI) has a new part called the 6970
Arming Switch. In addition to adding safety to your power
system by keeping the motor disarmed until you reach the
flight line, the Arming Switch allows you to easily disconnect
the ESC (by unplugging it outside the fuselage) to recharge
batteries in the plane. The assumptions here are when using
LiPo packs, you have access to the node connector and use
a balancer or balancing charger for safety.
using two packs in series, you can also use the 6970 Arming
Switch to disconnect the two packs so that they can be charged
at the same time (by separate chargers) without having a
ground fault issue. Simply install the 6970 receptacle into
the fuselage side and connect it in-between the battery
and ESC. No soldering needed!
MPI Arming Switch mounted easily in the soft thick balsa area
of the P-51D fuselage.
wiring harness for my Hangar 9 P-51D conversion
is greatly simplified by the new 6970 Arming Switch from MPI.
It can be mounted right in the fuselage and will either arm or
disable my entire power system with a single plug. Since the black
plastic housing pulls apart to expose the receptacle, the 6970
Arming Switch can be mounted from either the inside or outside
of the fuselage. By having access to the balance (or node) connectors,
I can recharge both packs right in the plane without removing
the wing. I don't even need an additional On/Off switch to the
receiver. The Sermos (a.k.a. PowerPole) connectors on the 6970
Arming Switch can handle about 50amps continuous current and about
100amps peak current for short bursts. This capability makes it
a good solution for most electric conversion applications.
re-wired my MPI Arming Switch to eliminate a pair of Dean's
Ultra connectors. Since I was using two 5-cell Lithium packs
in series to obtain a 10-cell total Lithium voltage, I also
needed an On/Off switch in-line with the UBEC
A future column will discuss series and parallel packs.
photos by "Papa Jeff" Ring
MPI 6970 Arming Switch is much less noticeable than the MaxCim
Charging Harness so it is a favorable choice on scale models
like the Hangar
9 P-51D and Corsair F4U. The evolution of the arming switch
(and arming higher voltage ESCs) still has a way to go but we
are now seeing new products on the market that address these
Battery Disconnect Switches
I cannot find a product I need for electric flight, or the product
is more expensive than expected, I often go outside the R/C industry
to look for what I need to get the job done. This situation arose
when I needed to enable a 200amp power system for my 1/3 scale
Clipped Wing Cub. I had a motor and controller that can draw up
to 200 amps but no product to help me properly arm the system.
I discovered that Battery Disconnect Switches were a common product
in motorcycle racing, RVs, and campers.
100amp to 500amp "Little Switch" from Flaming River
Industries (shown above) is available in a simple switch-only
form for $20 or with mounting plate, hardware, and rubber seals
for $28. I purchased mine from a known good source like Summit
my application, the mounting plate was not needed as the switch
was mounted to the fuselage wall of a third scale Cub. The rubber
cover is really meant to keep the switch clean in racing environments
where oil, fuel, or dirt can more easily come in contact with
the switch. To keep the switch from protruding too far, I made
a thick washer from the foam flooring I used to line my trailer
floor. These flooring pieces can be purchased at most home improvement
stores and cut easily with a razor knife.
procedure to arm my third scale Cub power system (on the
right) is to first throw the anti-spark toggle switch and
a few seconds later insert the removable key and turn it
to arm the system. This also locks the key in place for
combination of the anti-spark switch on the Jeti SPIN200
ESC and the Battery Disconnect Switch make this 6000 watt,
200amp power system easy and safe to enable at the flight
of all, the 14s power system is armed spark-free!
Arming a 1/3 scale Cub
U.S. General Battery Cut-off Switch from Harbor Freight
is only $6. It can handle 100amps continuous @ 12 volts
or 1000amp surge for 10 seconds and comes with two keys.
someone looking to make their own arming device, Powerwerx
sells sets of Powerpole connectors that vary in current handling
capability from 15amps up to 350amps. Chassis mount housings are
also available in multiple sets of connectors that could be mounted
inside or through a fuselage wall.
"Jones Witch" from VampowerPro.com
is a switch mechanism that enables the battery in an airplane
by inserting a plunger when you are ready to fly. It has a positive
locking mechanism that offers a bit of resistance when the plunger
is pulled so it doesn't accidentally shut off.
the small plunger head shows outside the model and these devices
are rated to handle over 100 amps with bursts to 180 amps for
using larger electric or glow conversion models, the easier
you can arm and disarm the power system, the safer you make
it. Never completely rely on the ESC to keep the motor off
when the power system is armed and always alert people around
you when they approach an armed prop. Unlike a gas or glow-powered
plane, a stopped but armed electric prop is a tremendous
safety hazard! A faulty ESC, receiver glitch, or bumping
the left stick are all possibilities for an accident. When
you fly electric, fly clean, fly quiet, and fly safe!
This section of AMP'D covers some of the
questions that our readers have sent in and I thought
would be interesting for others.
Jeff asks: "My ESC doesn't
have an anti-spark feature. How can I get my battery
connection to stop sparking when I first plug it into
Greg: Many of my ESCs also sparked
when I connect more than a 5s LiPo supply to them. The
Jeti SPIN200 ESC that I am using was the first one I
had seen with a built-in anti-spark feature. Is is fairly
simple to make your own anti-spark feature by using
a 50-100ohm 1/2w-1w resistor. Shown above are three
size resistors compared to a penny. These parts can
be purchased at your local Radio Shack.
The resistor can be wired in series, as
shown above, to the plus side of the battery to ESC
connection. This can be done with a second parallel
set of connectors or a switch. Simply plug in the anti-spark
connector first and then the normal battery connection
to the ESC, about a second later. You can use thinner
wires for the anti-spark connection like those commonly
seen on Lithium battery balance plugs.
Frank asks: "I plan on using
two AXI 4120/18s, APC 13x8 electric props and two Jeti
77-Amp ESCs in a Top Flite Cessna 310. I was wondering
if it is okay to use one battery pack (actually 2 Flightpower
3700mah 6-cell packs in parallel)? The batteries would
be installed in the fuselage. Is it better to install
each pack in the nacelle, one for each ESC?"
Greg: Jeti recommends using a separate
pack for each motor/ESC combination. The reason is to
eliminate the motor noise of the second motor so that
the ESC can properly detect the position of the magnets
on the outrunner case. On my dual
AXI 5330 setup and my twin AXI 4120 powered P-82
Twin Mustang, I used separate packs. That being
said, on smaller models like the new E-flite P-38
Lightning 400 ARF, it uses a single LiPo pack for
both ESCs. I have not seen a problem with the power
system on this model.
Where the packs get installed doesn't really matter.
As long as the noisy Motor to ESC wires are short, the
battery lines to the ESC can be long.
I consider a "ParkFlyer" is generally anything
less than two pounds that is hand launched, or ROG's
(rises off ground) with landing gear. What I consider
to be the limitations for a Parkflyer, have not so much
to do with the size of the plane (or Jet) but how that
plane is flown in the "Park" like setting.
This whole topic of what is a parkflyer boils down to
what you can sensibly and safely fly in a particular
area, given the amount of space, and who is there with
you. My website has a page called Sensible
Flying Tips that covers this topic in more detail.
should point out that the flyer must also determine
if it is Legal to fly in their area, if it's public,
or have the owner's permission if they are flying on
private ground. Somebody owns or has rights to everything,
and that perfect flying field you found may have an
irate owner attached to it. Flyers need to check with
the Parks Department or local Police before flying anything.
(One good way to convince someone to let you fly is
to show them your AMA Card, and explain the Insurance
coverage you have.)
If people want to establish "What is a ParkFlyer"
they should look at setting up a reasonable Maximum
Limit to Overall Size, "Watts per Pound" and
Aircraft Speed, and let everyone design Parkflyers and
ParkJets around those parameters.
Once you have that established, then you can look at
a minimum "Flying Space" requirement. Anything
within the Maximum Limit can be flown as a ParkFlyer,
and anything over the limit should be restricted to
an AMA approved flying field..(Regardless of what powers
it, or how it's built, Except for Powerless Gliders).
have a great start to your column, best of luck!!!
RCParkflyer @ RCGroups & RCUniverse
Parkjetsflyer @ Wattflyer
writes: You address a topic which many marketing folks would
rather not discuss. I appreciate your candor. No one in our hobby,
young and old alike should be fooled by the 'Parkflyer' bullet on
the box of so many models these days. Whenever anyone puts anything
in the air with a spinning prop, regardless of power system/ energy
output, we must have an inherent mind for the safety of others who
may be around. Your points really hit home here in California at our
crowded Electrics only RC field that we share with many hikers, bikers
and future R/C'rs.