Minicopter Diabolo blows away the competition 2012/07

Hi, and warm greetings on your
return to the helipad. My friend,
Santiago Panzardi, is providing
the content for this month’s column.
Santiago wrote an excellent piece in
the December 2011 issue of MA, about
the Speed Cup at the 2011 International
Radio Controlled Helicopter Association
(IRCHA) Jamboree. He is back this
month to detail an interesting and
exciting new product: the Minicopter
Diabolo helicopter. Thanks again,
Santiago, for taking the time to write
about it.
Specifi cations
• Rotor diameter: 1.56 to 1.68 meters;
(blade length: 690 to 750mm)
• Weight with 12s/5000: 4.8 to 5.2 kg
(10.5 to 11.4 pounds)
• Two-stage gear, helical spur gear
• Gear ratio, fi rst stage: 1:3.1 to 1:4.13;
second stage: 1:3.17
• Belt-driven tailrotor: with automatic
tension control
• Tail gear ratio: 4.75:1
• Tail rotor diameter: 290 to 300mm
(11.4 to 11.8 inches)
• Length with canopy: 1.38 meters
(54.3 inches)
• Height: 39 cm (15.3 inches)
• Landing gear width: 22 cm (8.66
inches)
• Tailboom diameter: 30mm (1.18
inches)
• Battery tray: 68 (74)mm high, 64mm
wide
Introduction
Last year I had the privilege of
bringing back the Speed runs to the
IRCHA Jamboree, where we witnessed
some brave pilots  ying various exotic
and common helicopters, different
power schemes, head setups, and
brands.
This was also the big debut for the new model coming
from a well-established small company in Germany called
Minicopter. The new 3-D speed offering was the Diabolo.
How did it fare? It won.
The Diabolo is not a one-trick pony; it is a capable 3-D
machine that delivers fantastic performance with head speeds
as low as 1600 rpm and mind-blowing aerobatics at higher
head speeds. Attention to detail is evident in the smooth and
efficient powertrain—encased in a rigid,
simple, and lightweight structure—
allowing this model to fly smoother and
faster using less power than your average
RC helicopter. You may think every 3-D
helicopter boasts such claims these days.
This one is different.
Chassis and Assembly
The Diabolo uses a two-stage gear
train with helical cut gears and pinion
capable of withstanding the new crop
of 10,000-watt-peak motors. Gear
ratios range from roughly 9.8:1 to 13:1.
Below the main gears is a belt-driven tail
with an unusual and clever automatic
tensioning system with a dampener. A
spring oil shock presses against the idler
pulley to keep optimum tension on the
belt, and dampens slapping during quick
loading and unloading of the tail rotors
in demanding 3-D rigors.
The boom diameter is larger than
most at 30mm, adding rigidity and
allowing space to use larger tail pulleys
for improved belt contact. The boom
enhances in-flight visibility and is long
enough to accommodate up to 750mm
blades, making this a truly flexible
700mm to 750mm-size machine.
The battery tray easily fits larger 14S
and 16S packs with a little effort. Battery
packs are held in place with large O-rings
acting as rubber bands and connected to
shaped frame pegs. A battery tray plate is
provided to slide both packs in and out
at once, but I found fitting one pack at a
time is just as easy.
There are only five pushrods used in
the entire model. The rotor head control
arrangement is direct servo-to-swash.
The 3mm pushrods have captive ball
links, which will hold nearly anything in
place. The carbon frames extend high,
separating the main shaft bearing blocks
with little cantilevering above the upper
bearing support.
The contoured swash is 120°
collective cyclic pitch mixing layout
with servos using 18.5mm arms, keeping
the control rod angles to a minimum
while allowing plus or minus 15° of
pitch and more than 8° of cyclic without
binding. Three-millimeter bolts fasten
the swashplate servos to the frame’s
integral aluminum lugs.
Radio, Motor, and Electronics Setup
I chose Futaba BLS253 servos for
this model because of their reliability,
speed, high resolution, and lower power
consumption than most servos in their
class. I also used a Futaba 6008HS
receiver, BLS251 servo for the tail
control, and a Mikado mini VBar 5.2
flybarless (FBL) unit.
The receiver and FBL unit are
mounted on the rear, behind the
swashplate and next to the rear
swashplate servo. It’s a compact and
clean installation, but any adjustment to
the rear servo arm requires the modeler
to undo the gyro mounting plate, or
detach the swashplate autorotation
bracket.
I had two motors lined up for
propulsion: a Scorpion HK4035-500
(3500 watt) for 3-D and sport flying,
and a Xera 4530-500 capable of
delivering steady 5000 watts (10,000-
watt peak) for demanding speed runs.
The standard 19t pinion was a good
pairing with these motors. When
combined with a Kontronik 120a Jive
ESC, it yielded a 1600 to 2100 usable
rotor rpm range.
A small, low-internal-resistance NiMH
battery is used in parallel with the BEC,
providing extra power when needed and
a fail-safe in case of main battery or ESC
malfunction. All flights were done with
the smaller Scorpion.
After the transmitter, ESC, and FBL
unit were programmed, I fitted a set of
Edge 693 FBL blades and walked out for
a quick test hover in the backyard snow.
The brief hover was uneventful and gave
me an idea of which rates to try. After
a safety inspection, I headed out for the
big maiden flight.
Upon arriving at the field, I began
receiving comments about the striking
appearance of the Diabolo, and the
beautiful canopy graphics designed by
Minicopter. Various friends were ready
with cameras to capture the magic of
the first flight.
Flying
Final preflight inspection completed
and batteries connected, I spooled up
and up it went. One crowd comment
dominated for the first two minutes:
“This is the quietest, smoothest
helicopter we ever heard.”
The model felt solid and light. I
revved up to roughly 1750 rpm and
did a few passes at what I intended to
be medium speed. The Diabolo began
to reveal its character: slippery in the
air. I upped the idle to 2, which at the
time was approximately 1875 rpm and
plus or minus 12° of collective, and I
let it stretch its legs. The speed of this
helicopter is mind blowing.
I have flown thousands of times at the
Dayton (Ohio) Wingmasters field, and
have a good reference for speed. I knew
this model was cruising at close to 100
mph, yet it made only a whisper.
Next, I proceeded to try some Tic-
Tocks and Rainbows with little collective
input. Axial rolls and flips were accurate
and centered. Gigantic high-speed loops
were simple tasks for this helicopter.
For the second flight session, I
tweaked the FBL unit and increased
the rpm to 2030, still limiting plus or
minus 12° of collective. For the fourth
and fi fth fl ights, I asked a friend, who
is an accomplished 3-D pilot, to put
it through its paces. His immediate
comments were about how effortless
and fast it fl ew, even at 1850 rpm doing
piro-funnels and fast tumbling, rolling
loops. It fl ew on rails. And then there
was that “speed thing.”
Summary
The Diabolo has the distinction of
being a fast model, but it also performs
any maneuver quietly and remarkably
well. The lightweight model’s effi cient
design sets the bar for future model
helicopters.