|Contributed by: Greg Covey | Published: August 2006 | Views: 65342 | Email this Article
by: Greg Covey
Photos: Paul Weigand
Photos: "Papa Jeff" Ring
1 Pilot: Lynn Bowerman
2 Pilot: Devin McGrath
Hangar 9 ARFS
Distributed exclusively by:
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Champaign, IL 61822 USA
Tel (800) 388-4639
Superb Flying Performance
AXI motors require dual power systems
After a very successful Hangar 9 33% Edge 540 - Part
2 project, I have received many e-mails from R/Cers using
the same or similar power system in their own giant scale models.
Even a year later, the AXI 5330 motor and Jeti 90-amp ESC are
still the value frontrunners in the R/C market although many newcomers
are now challenging this position thus adding more choices for
the electric enthusiast.
On my 20lb Edge 540, I had plenty of power for sport aerobatics
with the 3500 watt burst setup. We flew demo flights using this
setup at the 2005 NEAT Fair. Now that we've done the low cost
thing to help people jump into giant scale electrics, I wanted
to double the power using two 5330 motors on a single shaft and
do some 3D flying!
There are several ways to double the motor power without using
a gearbox. My choice was to use a solution that was professionally
engineered right from the manufacturer, Model Motors, in the Czech
Republic and available through reputable vendors in the U.S like
Hobby Lobby. The solution is costly since it uses dual power systems
and requires a well designed motor mount for the tremendous power
level. No manual exists for this application so I communicated
directly with the motor designer at Model Motors for various suggestions.
My initial prop choice was to use an APC e-prop. I wanted to
display the wide dynamic range of flight that electric power systems
provide so I positioned my largest and smallest props together
at the time. My smallest prop is a U80 (or 3x1) that is used on
my 0.9oz Hangar Rat with an RFFS100 module for indoor flying.
My largest prop (at the time) was an APC 26x15 e-prop available
at Hobby Lobby.
Since the photos were taken, the APC prop was replaced by a 28x10
hallow carbon Mejzlik prop available at Desert Aircraft.
Here were some of my target goals for this project:
- 7000 watt (9h.p.) burst power level
- 22.5lb all up weight
- 3D performance
- parts available from multiple vendors
2005 came a few days early for me as my Dual AXI 5330 motor arrived
from Hobby Lobby on December 23, 2005. The single shaft, dual 5330/20
motor is available special order from Hobby Lobby for $790. Note that
the motors come bolted together to drive a single long shaft. The mounting
ears make it a near drop in replacement for a single AXI 5330 setup.
The motor Kv is 235 RPM/V and it
weighs 56oz (3.5lbs). The "Double 5330" is designed for aerobatic
flying with about a 26" prop and around 6000RPM. The recommended
max. current with a 10s LiPo is also about 70A burst per motor. As you
may be aware, my single AXI 5330 power system would burst over 100amps
to provide 3500 watts for short periods. This makes my target goal around
7000 watts (or 9.3h.p.) using the dual motor.
By positioning the new double AXI motor on top
of my existing mount, you can see that the 4-3/8" PVC pipe assembly
( called 4" ) may still work as an inexpensive mount with a few
modifications. Initially, I intended to reinforce the 4" end cap
and provide air cooling for the motor inside the PVC can.
After some discussion with my friend who is both
a modeler and a retired machinist from Eastman Kodak, we decided not
to use the PVC mount for fear that the needed cooling holes would weaken
the pipe. We have also decided not to use aluminum tubing or metal standoffs
due to the tremendous rotational torque or twisting action that could
focus forces in small areas.
Our approach will be a more traditional technique
used in giant scale engine mounting. We'll use aircraft grade birch
plywood available at most hobby shops to build a box extension that
will fit over the existing motor mount box. This box will use two layers
of 1/8" aircraft grade plywood epoxied together for tremendous
strength. Short #10 screws will connect the motor mount ears to blind
nuts on the new box front wall. The bigger box will be easier to drill
cooling holes in for the inside motor and the process will be easily
repeatable by others. I'll show the exact dimensions needed for the
box extension later on in my review.
Tthe local hobby
shops will usually carry SIG or Midwest brands aircraft grade plywood.
Tower hobbies sells the aircraft grade 1/8" birch plywood on-line.
We glued two layers of 1/8" together for a 10-ply total which is
stronger than the 5-ply 1/4" plywood.
of Plywood at Tower Hobbies
& Prop Mounting :
The Dual AXI adapter is 12mm and tapers out to 17mm.
Although the APC 26" prop looks ok in the
spinner and prop adapter, we have decided not to use it for
safety reasons. Our concern is that the prop may be severely
weakened after drilling the four holes needed to mount it on
I have decided to purchase a Mejzlik carbon 26x10
prop from Desert
Aircraft. The carbon prop will be easier to drill and retain
its strength as it has a much bigger hub area. These props from
the Czech Republic are top notch designs that have come down
in price due to competition from other manufacturers.
Motor Box Measuring:
made by Paul Weigand
After measuring the stock motor box, the new box extension
design can be started. The distance from the main fuse firewall
to the back of the spinner backplate is 13.0"
The motor mounting project began by using
two layers of 1/8" aircraft grade plywood epoxied together
for tremendous strength.. Note the plywood ring reinforcement
on the back side of the new firewall to keep the T-nuts flush
with the front side. The T-nuts are also the version that use
screws to hold them in place so that no large prongs exist to
tear and weaken the aircraft grade plywood. We also removed the
existing 5330 motor and PVC parts from the stock motor box.
Prop & Spinner Mounting:
As you can see, whenever my friend Paul Weigand gets a hold of
the project, it turns into a work of art! To create the precise
bolt pattern needed for this prop and spinner, Paul has the proper
mill and lathe needed to do the job. We are also supplying the
bolt pattern to TruTurn so others can simply order the proper
backplate for this motor.
The all aluminum TruTurn 4" Ultimate Menz spinner (p/n TT-4052-B-M-L)
weighed only 4-1/4oz compared to my 6oz red plastic cone CBA spinner.
The TruTurn spinners and Mejzlik carbon props are truely well
Here is the bolt pattern for those that wish
to make their own backplate.
New Motor Box:
The new motor box assembly seemed to work well. The outer box
was epoxied around the stock Edge 540 motor box. It's a great
honor to have a dedicated craftsmen and modeler like Paul Weigand
help me out. With the tremendous power of this double AXI 5330
motor, we wanted to make sure that there are no weak points in
The back of the motor box, once the stock firewall, has been
removed. There are large air holes in the front directly in the
air flow from the cowl openings and more on the side so some air
movement will exist. For normal flight, each motor will likely
draw only 20-30 amps so they will not produce any significant
heat. Since the workload is shared between two motors, I expect
little heating to occur unless flying a 3D routine. There is a
photo of my air exit modification after the summary section.
If you watch the videos from either my "Part 2" review
or the SKS NEAT Fair 2005 video, you will see that the Edge 540
was decently powered with only a single 5330 motor and performed
sport aerobatics quite well. The additional second motor power
will only be needed on occasion for hovering and vertical pullouts,
etc. For the most part, each motor will see only half the workload
as before for normal flying and aerobatics.
We decided to mount the two ESC?s on standoffs
so they could be wired up to the motor and mounted without the
cowl in place. We also added a hole behind the motor mount so
the wires can be attached to the ESC?s without extensions.
The cowl then slips on and the heat sinks are exposed to direct
air cooling as before.
I tested the motor/ESC wiring on one motor at a time. Also,
both ESCs programmed and worked fine by doing one at a time. It
also allowed me to test the motor direction before taping up the
connectors and trying both motors together. You want each motor
to spin counter-clockwise when viewed from the front of the plane.
I used the following setup on my Jeti Advance PLUS Programming
- Low Cut-off
- Slow down
- Brake OFF
- High Timing for Outrunners
- Linear Throttle
I added a few extra decals as I waited for my BalancePro HD
packs to arrive.
To keep the two power systems as equal as possible. my receiver
and servos are no longer fed from one of the 4s flight packs.
I now use a 2s 3300mAh Cellpro Lithium pack to feed the Power
Force Regulator. The Dean's Ultra connector plugs right into
the regulator and I can still balance the pack on every charge
using the Cellpro 4s charger.
Dual Rudder Servos:
Expert 3D pilot from Team JR, Devin McGrath, suggested that
I add a second rudder servo to handle the additional demands
of 3D maneuvers. The Hangar 9 Edge 540 is already designed to
handle a dual push-pull setup (the second servo bay is merely
The dual rudder servo system will now provide 520oz/in (260
x 2) on my 6v supply from the Power Force Regulator. A JR Matchbox
is required to keep the two servos from fighting each other
and drawing excessive current. The Matchbox also allows for
servo reversal so you don't need a special "reverse"
servo. The pushbutton setup on the JR Matchbox is very convenient!
Note that the new JR DS8611a digital servo design has an incredible
320oz/in. torque on a 6v supply. This increase in output torque
is now the standard servo when ordering a DS8611.
I re-tapped the stock 4-40 holes in the Edge 540
canopy for 6-32 so I can use the nylon thumbscrews from Home
Depot. No more tools needed at the flight line!
Dual Rudder Linkage:
My dual rudder servo project started by removing
the existing control horn and installing the threaded rod that
also comes in the Hangar 9 (HAN3614) 8-32 Swivel Clevis Horn
kit. It's a dual kit so you get two of everything and then a
choice of threaded rods or screws. I also used a second Hangar
9 (HAN3557) Titanium Pro-Link 4-40 x 5" and another (HAN3616)
4-40 HD Ball Link.
HD Power System:
My existing battery packs were re-configured
into 6s2p and 4s2p BalancePro HD packs. These are older Kokam
2100mAh (20C) cells that were rated at a 20C discharge rate
or 80amps in my 2p configuration. They never sold well due
to their weight and shape that we called "Pop Tarts"
after the famed breakfast food. The cells were discontinued
and I was fortunite to be able to mix some left over stock
with my pre-enjoyed packs.
Each 10s configuration weighs 55oz for a total
battery weight of 110oz or 6.9lbs. Every pack gets plugged
into a BalancePro HD 6s Discharge Protection Module (DPM)
with the optional LED/Speaker modules. The 6s and 4s Dean's
Ultra connectors will plug into a Series Connector Module
so there is a complete 10s power supply for each motor. The
throttle channel output from the receiver is then split using
a "Y" adapter cable and then daisy-chained through
each set of DPMs on its way to the ESC.
If the 4200mAh capacity (for each motor) is
not enough flight time, or the 80 burst rate is not sufficient,
I will then upgrade to the new 5AH cells also rated at 20C
discharge. Since I originally started this project in late
2005, I have acquired several new 5AH packs for comparison.
Upon measuring the weight of the old 4s packs and my new 4s
20C 5000mAh pack, I determined that the drop-in weight loss
will be an incredible 21oz (1-1/4lb) by switching to the new
BalancePro HD 5AH cells. Further, the 20% increase in rated
flight time will likely provide 6-8 minute flights. Something
to look forward to (and save for) in the 2007 season.
I wired up my Series Adapter Modules after splitting a single
Connector Module from FMA Direct into several double sections
with a Dremel tool. These adapters are used to wire my 6s and
4s packs into a single 10s pack.
Both motors were tested individually and then together. Note
that the LED/Speaker modules from the DPMs are placed near the
big opening in the cowl (when it is attached). My initial flight
test will have the DPMs disconnected from the throttle channel
(like the heli guys use it) so that only an audible alarm will
sound if the packs have a problem with discharge current or
duration. The DPM control lines will then be attached in series
with the ESCs and throttle channel after the first few flights.
Initial Power Test:
The inside of the fuselage shows my 4 BalancePro HD DPMs set
on an angle bracket for easy connection/disconnection of the
4 batteries. The receiver and servos are powered by a separate
2-cell Cellpro 3300mAh pack feeding the FMA Power Force Regulator.
When I initially tested the power system with the prop installed,
it was scary powerful! My intent was to measure the current
so I left the cowl off for access to the ESC using my wattmeter.
I never went above 1/2 throttle because the power felt so strong
I was afraid that the anchor would pull out or break. Perhaps
when I have a group of people at the field, I will revisit the
current measurement since it is easy to remove the spinner,
prop, and cowl.
Even with10lb weights on the anchor, the plane looked like
it was moving. The grass was bent straight back behind the plane.
The prop and spinner appeared perfectly balanced as there was
little vibration. I'm ready to test fly!
I was fortunate to have Team Futaba's Dan Landis
and his father, Richard (left) fly the Edge 540 during one of
the local summer events where Dan was a guest demonstrator.
Both Dan and his Dad are very knowledgeable on high power electric
flight systems. After test flying the Edge 540, Dan offered
several suggestions for fine tuning the power system. Standing
next to me is my friend, Paul Weigand, who designed the motor
The original test flight using the Dual AXI powered
Edge 540 used a Mekzlik 26x10 hallow carbon prop. We measured
the current to be about 63 amps per motor which provided about
4500 watts total. Although it flew well, the Mejzlik 26"
prop was not big enough to bring the real power of this system
out. While this is more power than my previous single (low cost)
AXI 5330 system, it was not sufficient for 3D maneuvers.
Edge 540 Mejzlik 26" Prop video.
We succesfully tested the Dual AXI powered Edge 540, and, although
it flew well with sport aerobatics, the Mejzlik 26" prop
was not big enough to bring out the real power of this system.
I measured about 63amps per motor and about 4500 watts total.
While this is more power than my previous single AXI 5330 system,
it was not sufficient for 3D. Since I am not taxing any part of
my setup, we decided that my next change will be to try a Mejzlik
28" prop and raise the ground clearance of the gear mains
by an inch. On the video, you can hear the impressive amount of
air moved by the 26" prop.
Edge 540 Mejzlik 28" Prop video.
The new Mejzlik 28x10 prop proved to be a winner
by providing my Edge 540 with 3D power. The current measured 83amps
on both motors and the plane can now hover and has unlimited vertical.
We video taped Team JR's Devin McGrath practicing on the Edge
540 for his demo at the upcoming 2006 NEAT Fair. Now that we have
a larger prop and increased aileron gain, the power level and
roll rate look good. Devin wants more elevator throw as he had
difficulty holding the hover in wind. I realized that my limited
30 degree elevator throw had never been increased for 3D flying.
These type of iterative changes are a normal process for fine
tuning a plane to your preference.
Here are the final numbers...at least for the 2006 season.
Multiply 36v (10s voltage under load) x 83amps (measured) = 2988
watts (confirmed by wattmeter). The result is 3000w x 2 motors
= 6000w = 8h.p.
My best estimate when adding up the weight changes from the
single AXI to the double AXI power system has the all-up weight
at 22.5lbs which gives me a power level of 266w/lb. If I replace
my rather heavy and older 2p 2100mAh cells with newer 1p 5000mAh
cells, I can drop 21oz (or 1-1/4lbs) while increasing the flight
time by 20%. This would increase the power level to about 282w/lb.
The additional 3/4" extension to the gear mains really helped
the ground clearance using the 28x10 Mejzlik prop.
As I watched Team JR's Devin McGrath fly the Edge 540 well beyond
my own skills, I can't help but think what new electric flight
technology is just around the corner. Over the winter months,
I will likely replace my older worn out cells with newer, lighter
cells that will increase performance and flying time. I can now
safely recharge and balance my LiPo packs in the plane using the
BalancePro HD 6s chargers from FMA Direct. Newer 12s (12-cell
LiPo) ESCs are already on the market and we know that Jeti is
testing their own 12s and 15s ESC designs in Europe. We have also
heard reports of people breaking the 10,000 watt power level.
The possibilities for electric flight are endless and it is an
exciting part of the hobby to help push the envelope and work
with others that share your enthusiam.
Gear Mains Extension:
I made a 3/4" extension to my gear mains out of a
solid piece of oak finishing wood. This will mostly negate the added
1" from the new 28x10 Mejzlik carbon prop. I then cut the front
section off the cover plate now that the gear mains are flush with the
On a tip from Team Futaba's Dan Landis, I installed dual
10-amp Power Force regulators to provide more current to the dual rudder
servos. The regulators are positive controlled and they will work fine
with common ground. Since they are push type only, they can also be
paralleled on the positive side too. The second regulator tip from Dan
is an easy solution to eliminate blowback on my two rudder servos.
To keep things cool during the heavy demands of 3D flying,
it is important to have good air flow. I cut the covering away from
the bottom side of the fuselage for an air exit. This allows the incoming
air from the cowl through the holes in the firewall to flow through
the plane during flight.
Distributed Exclusively in the U.S.A. by:
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4105 Fieldstone Road
Champaign, IL 61822
Ph: (800) 338-4639
Toll Free: (800) 338-4639
Fax: (217) 352-6799
5716A Industry Lane
Frederick, MD 21704
Sales: 800-343-2934 or 301-668-7614
Franklin Pike Cr.
Brentwood, TN 37027
1815 South Research Loop
Tucson, Arizona 85710
JR Digital Servos and Matchboxes
Exclusively in the U.S.A. by:
Horizon Hobby, Inc
4105 Fieldstone Road
Champaign, IL 61822
Ph: (800) 338-4639
Toll Free: (800) 338-4639
Fax: (217) 352-6799
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Deer Park, Texas 77536
The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.
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