his Ag Wagon.
any color to
help mask it.
On the left is
right is the
plug used for
6S packs in
to a plate with
Velcro on the
two one-wrap straps around
the packs and plate.
Because this is the building issue, I thought I’d offer a few tips to help answer some questions I have received regarding safety issues when building electrics.
When I showed some arming switches in the June 2013
issue, I received many emails from modelers interested in
knowing more. This caught me slightly by surprise, but there
was a clear interest in learning more about how to employ
There were also some home-brewed “solutions” to making a
system safer with the LiPo pack plugged into the ESC. Some
were interesting and some were scary! I’ll put this as simply
as I can: there is only one way to ensure a motor/propeller is
safe—disconnect the battery from the ESC!
Before you get up in arms over “loss-of-signal” protection
and other features built into the ESCs, let me clarify. There
are many safety measures built into our modern ESCs to help
prevent accidental startups, but manufacturers agree that the
surest way is to disconnect the battery. That is what an arming
switch does and my current favorite is the ArmSafe system
It adds very little wire to the system if done properly and
can be inconspicuously installed. In one of the photos is my
97-inch RC Guys Ag Wagon powered by a Rimfire 50cc motor
using a 12S LiPo pack. The 10-gauge wire in the ArmSafe
system I selected handles it with ease and allows me to get the
aircraft ready in the pits.
I know it’s safe until I plug the arming plug in at the
flightline. I took an extra arming plug and wired an antispark
device across the poles so I can charge the caps with that and
then quickly replace it with the real arming plug.
Securing the Motor Battery
I got to watch an accomplished pilot recover his aircraft
after its 14S LiPo pack exited the aircraft in the middle of
an outside snap. That was impressive and so was his safely
recovering the airplane without further damage. The lesson
from this is simple: be sure to build in some way of securing
your motor pack!
In the photos, you’ll see how I try to build my large electric-powered models so I can easily remove the packs or use them
in another airplane. This setup is two 6S packs in series to form
the 12S pack for my Ag Wagon and Waco UPF- 7. I build a
hardwood support into the back of the firewall and then find a
spot to secure a plate with blind nuts for the other end of the
Because I’m wiring them in series, this allows me to do
that in the open and then slide the plate into the front mount
and secure the back with socket-head bolts. It takes less than a
minute to do and everything is solid.
The packs are mounted on the plate with Velcro and further
secured with one-wrap straps around them and the plate. When
105 Model Aviation OC TOBER 2013 www.ModelAviation.com