REVIEW
words/PICTURES: Jon Tanner
Diabolo 550
Minicopter designed their 550 Diabolo to be light, strong, very aerobatic all
with 6S LiPo power
5
50-size models are so very convenient
being small enough to fit easily in the
car yet can have a ‘big model’ feel in the
air and 6S LiPo power provides plenty
of power at reasonable cost – that’s a winning
formulae that Minicopter’s Diabolo 550 exemplifies!
Minicopter has been manufacturing top quality
helicopters for many years, its owner, Gerd
Guzicki is a terrific engineer and original thinker,
for example he pioneered the Moving Flybar
concept in the Minicopter Joker patenting the
design with Jan Henseleit who was working on
the same idea at the same time in his Three Dee
NT. I well remember the 60-sized Joker that I
reviewed in 2002, this was powered by a 1.4 kW
motor running on 30-32 NiCad cells, how things
have changed… I converted this Joker to be one
of my first LiPo powered models using 2 x 5S
packs and putting it into an A109 body resulting
in 20+ minute flights!
More recently in 2010, Minicopter started the
Diabolo range of flybarless models with the specific
aim of producing top quality 3D/speed models but
retaining the ability to be flown sedately at lower
rotor rpm. The Diabolo range is a development of
the Joker retaining the 2-stage drive train and belt
drive tail rotor etc. but is taller and narrower making
it more aerodynamic.
The Diabolo started with a 700-size model able
to run 690 – 750 mm rotor blades, it was later
stretched to the Diabolo 800 Plus, turning 750 to
830 mm main blades. The Diabolo S is the limited
production (50 units) speed version that Miles
Dunkel used to win the 2014 IRCHA Speed Cup
(unlimited) with an average speed of 270 kph/167
mph. Then there is the Triabolo, introduced in 2014,
which, not surprisingly, has a 3 blade rotor head…
2015 now sees the introduction of the Diabolo
550 and Gerd is rightfully proud that it follows the
Diabolo line and as with all his models, is of all
German manufacture with much of the machining
performed in his own workshop.
The box
contains all
the parts; you
choose the
boom colour
and canopy
All nicely packaged – I got a present of an adjustable spanner!
34
Diabolo 550
Machined main gear with
spiral cut teeth – the faint ‘X’
is uppermost – that is a
10 mm main shaft
The Diabolo 550
Ordering a Diabolo is an experience in itself
because when you start to place your order you
have to specify your choice of the basic #5000
kit, the #5010 Combo Set 1 that includes the
X-Nova 4020-1000 ‘Diabolo Edition’ motor
and Zeal 80 or 85 mm tail rotor blades, or the
#5020 Combo Set 2 that adds a pair of Zeal
‘Energy’ 550 main blades. You are then able
to personalise your kit by choosing the canopy
colour, a flat or glossy black windshield that can
be factory attached, choose your decal sheet
and then your choice of tailboom that can be
black anodised or wrapped in white, yellow,
orange or green. In addition there are some
special canopies available – one of which you
see here. So already you have a personalised
model that makes it a bit special…
I chose the basic kit with the black boom and
initially ordered the white canopy with carbon
look screen and ‘Stripes’ decals. Gerd then
advised me that he had a short run of their
‘show’ canopy, so I quickly swapped to one of
those, which you’ll see from the photos was an
excellent decision! I subsequently ordered the
X-Nova 4020-1000 ‘Diabolo Edition’ motor that
is ideal with a special shaft and shorter wires plus
a 20T pinion to fit to it. A Kontronik Jive 100+ LV
ESC completed the drive system.
The model uses mini size servos with MKS9767
or Futaba BLS173SV for cyclics and a MKS9780
or Futaba BLS 251/256 for the tail being listed.
I chose the MKS that is available as a Combo
Pack making them a good value choice. The full
spec of the model is as follows.
The model spec:
Rotor diameter: 1.25 m (blade length: 550 mm)
Weight completed without battery: from 2.1 kg
Tail rotor diameter: 240 mm (blade length: 80 mm)
Length with hood: 106 cm
Length without hood: 99 cm
Height: 32 cm
Rail width 18 cm
Battery compartment: 5
4 mm high, 52 mm wide
Rotor rotation: right
Two-stage with quiet helical gearbox
Smooth-running belt drive the tail rotor
Easy battery installation with ‘O’ ring fixing for
high centre of gravity
X-Nova 4020-1000 ‘Diabolo Edition’ with the
Kontronik Jive 100+ LV ESC
The layshaft is
also 10 mm,
note the spiral
cut gears and
tail belt pulley
First job is screwing the two bearing blocks to
the 2 mm carbon sideframes, which introduces
you to the precision of the Diabolo… The holes
for the M3 screws are precisely 3 mm so the
M3 screws are a snug fit in them and hence the
bearing blocks are precisely positioned. Note that
the sideframes are handed… Next we have the
first of the gears, which is a machined 62T spiral
cut gear; it’s 11 mm deep and so is very strong.
The gear is screwed to the aluminium hub and an
‘X’ marks the top side. The main shaft is 10 mm
and a spacer tube sits above the gear hub;
thin shim washers are included to eliminate any
endplay in the shaft.
Everything is so precise; the gear mesh is not
adjustable and doesn’t need to be
Building
A small booklet is included showing the
construction pictures, while the Minicopter
website has the full manual as a download, which
I did and printed out the English text section to
use with the booklet.
The combo pack of MKS servos even included
a tube of grease!
Servos need to be fitted before joining the
frames, note the plastic spacers to position them
Elevator servo secures to the upper bearing
block with a spacer block at the bottom
35
Diabolo 550
20T pinion used with this 1000 kV X-Nova motor
Kontronik include a resistor kit that eliminates
the spark when connecting a LiPo; the resistor
is inside the heatshrink wrap
Plenty of room for a big
motor and the ESC tray
is perfectly positioned
Rear view of the frame assembly
The layshaft is next; it too is 10 mm and a 16T
steel pinion gear fixed to the top drives the main
gear. Under this is the 20T tail drive pulley, which
too is secured with setscrews onto flats on the
shaft. The first stage gear is another machined
gear, with 51T spiral cut teeth and this is fitted to
the freewheel hub; thus during an auto the main
rotor drives the layshaft but not the first stage
gear. Aluminium bearing blocks carry the layshaft
top and bottom – when you secure it to the
sideframe, don’t forget the tail drive belt…
You need to fit the eCCPM servos to the frames
before they are joined. The MKS 9767 and 9780
are aluminium cased HV servos, making them
distinctive, as does the radius case end – they
are a perfect fit for the model. Spacers are
included in the kit that positions the servo arms
in precisely the right position. You will see in the
photo that the elevator servo screws direct to the
upper bearing block with a spacer for securing its
bottom to the sideframe; additional washers are
supplied to help correctly position your choice of
servo if required.
You’re advised to first join the frames using
the bearing blocks and then sand the corners of
the frames where cables run, before adding the
other carbon plates and frames spacers. You
will find drilled holes for cable ties to help route
the servo leads and a rubber grommet protects
the elevator servo lead where it passes through
the frame. Three of the spacers act as battery
supports and so have silicone tube over them to
provide protection. The resulting frame assembly
is as rigid and strong as you could ever expect
while at the same time being compact and light.
Drive
36
‘Single Arm Control’ uses this rigid arm to drive
the inner swashplate ring while…
… this adjustable link has a turnbuckle for
precise tracking adjustment
The bearing stack fits to the 8 mm spindle with
the blade grips sliding over it, secured with 4
screws into the black collar
Tail housing is supplied like this as a matched
set
My original plan was to fit a Kontronik PYRO
650-103 motor, however I found that the motor
mount was not drilled for this motor, which is
when I ordered the X-Nova 4020-1000 ‘Diabolo
Edition’, which does fit! The difference is that the
mount is drilled for M3 holes at 25 mm centres,
while the PYRO fixing is M4 at 30 mm centres.
I used a 20T pinion gear, while 18T – 22T are
available to suit different set ups. With the gear
attached, the motor is fitted and the backlash
adjusted as per the excellent instructions. The
gear ratio using the 20T pinion is 1:9.88, which
with the 1000 kV motor running on 6S LiPo pack
gives an estimated max rpm of about 2250 rpm.
Needless to say the KONTRONIK JIVE 100+
LV ESC would be retained! An aside here is that
KONTRONIK now include a resistor kit with the
JIVE. Rather than fit this to the battery lead, I
prefer to fit these to the red ESC input wire, so
one kit does every battery pack… The photo
shows how it is fitted and the idea is that when
the pack is connected, a small amount of current
first goes to the ESC through the resistor that
charges the large capacitors before the main lead
is connected. This protects the ESC from the
‘crack’ and helps safeguard it.
Diabolo 550
The size of the spacer you see on the output side is chosen for the
specific set so no shimming is required
The simplest and maybe the best tail pitch rod support I’ve seen
Rotor Head Assembly
The swashplate is very elegant with the inner
‘ring’ having just two sculptured arms for the
blade pitch links, only one of which drives the
inner ring and is why Minicopter calls this ‘Single
Rod Control’ and it’s subject of a Patent Pending.
This idea is different and makes perfect sense
as it eliminates stress that can be induced
with a design using two fixed drive link when
the feathering shaft moves in its dampers. The
photographs show one rod is a fixed length using
two ball races to mount to the blade pitch arm
and so drives the swashplate using a heavy-duty
ball link. The other link is more conventional but is
uses a turnbuckle to join the heavy-duty links, so
there is no excuse for anything other than perfect
tracking!
Minicopter FBL rotor heads are all similar in
design; the 550 uses an 8 mm spindle carried
in hard dampers in the aluminium head block.
Two high quality radial bearings with a thrust
race between carry the machines blade grip. The
difference to many designs is that the bearing
stack is assembled onto the spindle with a collar
and the blade grip then slides over the stack and
is secured to the collar with M3 screws. Again
the fit is precise with very tight tolerances – the
manual advises you may need to heat the blade
grip if it feels too tight on the bearing stack!
The fit of the rotor head to the mainshaft is also
a very precise interference fit – it is so accurate
that you must not twist the hub as it slides on,
use a drop of oil to help if needed. A special
screw is used to secure the head block and you’ll
see that the hub does not clamp to the shaft – it
is so accurate, it doesn’t need to be clamped –
Minicopter consider that a clamping screw is only
needed if the fit is loose and that means it isn’t as
accurate as it could be!
Mini V-BAR used with two Spektrum satellite
receivers
As per the main rotor grips, the tail grips slide
over the bearing stack and are secured with
screws into the collar
Finished tail rotor assembly is refined and
functional, note the ‘Chinese Weights’
The last comment on this section is the
swashplate to servo links; all three are direct
and parallel to the shaft, although the roll rods
do angle in slightly to the swashplate. A set of
optional ‘forked’ servo arms are available that fit
either side of the ball holding it totally securely.
Tail
Before getting to the tail there is the
undercarriage, which is all aluminium and very
functional! The only observation is that the
rear hoop is taller than the front to give more
ground clearance for the tail rotor. The next job
Lovely looking canopy
37
Diabolo 550
Useful swashplate leveller is supplied to set zero pitch
38
LiPo pack retained with large ‘O’ rings
Very compact two-stage drive train produces a very neat set of mechanics…
…that is very narrow; the canopy is only
110 mm wide
Lots of Opti Power protection
Ultra-Guard to guard against an ESC failure…
…and BEC Guards to protect the BEC!
is pretty unusual as it’s removing some of the
anodising from the front of the boom so as to
ensure conductivity. I assume this is to ‘earth’
the boom and tail housing to dissipate any
static electricity that might be generated by the
tail belt. Radio interference caused by static
discharges from rotating belts seem to be
much rarer nowadays, but I’m all for reducing
any risk.
The metal boom clamps are slid onto the
boom, which with the belt fed through it is fitted
between the frames. If you are using a mini size
servo for tail control, then it will fit in the right
sideframe and so the boom clamp clamping
screws need to be on the left – it’s the other way
round if you’re using a standard size servo.
The tail gear housing is supplied with the
pulley, spacer and shaft as a matched set, so
there shouldn’t be any shimming required making
assembly that much simpler, and you get it, more
precise! (The manual shows an additional washer
in the assembly, which is no longer needed, as
the spacer is the precise width for this set).
The pulley is secured with two setscrews, so it’s
very secure. The tail fin is screwed to the housing
with a long screw running thought holes in the
boom and into the bellcrank bracket. That leaves
tensioning the belt and adding the boom stays
plus the pitch rod guides that are really neat as
they are short pieces of tube secured with large
‘O’ rings – simple and far more effective than a
lot of moulded supports I’ve seen.
The tail rotor is again all-metal with the grips
supported on the usual two radial bearings and
a thrust race. As with the main rotor head, the
bearing stack is assembled onto the hub, the
grips slide over and are each retained with two
M2.5 screws. The pitch slider is conventional
with articulated links to the grips and a single ball
operates it via the ball raced bellcrank.
For many years Minicopter have utilised ‘propeller
moment weights’ (AKA Chinese weights), on the
tail grips and do so on the 550. In this case they are
short aluminium tubes either side of the tail blade
retaining screw and their function is to reduce the
load on the tail servo. Final jobs for the tail are the
carbon pushrod and boom stays.
Diabolo 550
Final Bits
My canopy arrived ready to fit – even the front
canopy holders were in place. These slide over
the front canopy posts, while its rear is retained
with the usual stand-offs and ‘P’ clips for added
security. Instructional videos on the Minicopter
website show how to apply the stickers yourself.
Three large ‘O’ rings loop under the LiPo pack and
over stand-offs, which hold the pack against the
previously installed spacers with silicone tubing to
protect the pack. It would be nice to see a more
elegant method of retaining the pack…
I chose to use a Mikado Mini V-Bar fitted with
two Spektrum Satellite receivers bound to my
JR DSX12 transmitter. Set up of the V-Bar was
as usual straightforward and I used the supplied
swashplate leveller to level precisely… The pitch
range was set to the suggested limits of ±12º,
and each flight mode was set for my preferred
set up. I also set the V-Bar response to my usual
non-aggressive style. The Kontronik JIVE 100+
LV ESC was set to the Governor mode and the
throttle curves were set at 70% in normal, 75% in
idle up 1 and 85% in idle up 2, which also has a
full 3D set up of ±11.5º.
As I’m using the BEC that is built into the JIVE
to power the radio, I added an OptiPOWER
Ultra-Guard 430 – just in case as they say, and
while I was about it, I fitted two BEC Guards to
protect the BEC against any possible back EMF
(two are needed because the JIVE includes a
slave BEC supply). The last bits of the package
were rotor blades and I chose Switch Premium
Carbon 553 mm main blades and a pair of their
matching 86 mm tail blades.
Flights
It’s no secret that I don’t do 3D flying preferring
more scale and conventional aerobatics… So
as I have some OptiPOWER 4300 mAh 6S I
decided to use these for the initial flights. And
what a pleasurable anti-climax the first and all
subsequent flights were! I’d spent a lot of time
flying larger scale machines, which can tend to
feel a bit imprecise and I’d forgotten how nice it
is to fly a smaller, well set up pod ‘n boom model.
The Diabolo 550 feels absolutely rock solid
and totally locked in, it’s instantly clear that the
combination of MKS servos with the Mini V-Bar
is top class and that the X-Nova motor provides
plenty of brute power.
The model is remarkably quiet in flight, all
thanks to the very smooth running spiral cut
gears that are perfectly meshed. The model is
certainly very agile, but not overly with my set
up, it is also very quick and will eat up the sky if
you let it. A big plus to me is its visibility – thanks
to the canopy design that stands out well. This
is one of those models that makes you smile.
It’s very capable and yet not intimidating and
the only risk is that you could easily get over
confidant, however the control response is so
quick and precise any correcting control input will
have an immediate response.
For me it’s a lovely machine to fly, it’s small
enough to take everywhere; the 4300 mAh packs
give an easy 6+ minute flight all of which make
it an instant favourite… But that’s me, and you’ll
be interested in a more 3D orientated view of its
capabilities, so I lent it to Kevin Targett together
with a selection of OptiPOWER flight packs…
Ready for a solid evening’s practice. I just need to make sure I avoid the hay bales!
Kevin’s Thoughts…
I was excited to receive the Diabolo 550 to
check out after Jon had built it. First impressions
are that it is a very solid helicopter with wellmachined metal parts and thick carbon frame for
a rigid and accurate set-up. The two-stage drive
train makes for a very compact layout and it has
helical cut gears everywhere making it very quiet.
The belt driven tail can be run quite loose whilst
not allowing any slip. This leads to a quieter and
more efficient tail drive with less wear on the tail
case bearings.
Initially I assumed it was a DFC head but then
noticed the standard pitch link on the other side.
This is an interesting concept, which allows
a very simple set up without one of the major
mechanical disadvantages of the DFC design.
At ~2.4 kg minus battery (~3 kg with battery) it is
still a very light helicopter for the size, despite the
rugged construction.
There is very little slop (if any) in any of the
linkages, which results in a very accurate flying
model. I did find some movement in the tail blade
within the tail grip, but adding 0.15 mm shims for
the Switch tail blades to keep the tail grip sides
parallel easily solved this.
The Xnova motor certainly feels like it should
be powerful and has a very pronounced cogging
effect. This makes it hard to turn when you rotate
the blades in reverse (against the one-way bearing).
Be careful of your knuckles as you do this because
the very sturdy swashplate anti-rotation guide
is close to the blade grips (I have lost an undue
amount of skin on my knuckles to this!).
The battery tray mount, using rubber straps,
is not my favourite design but is effective. The
slots and bands provided need a minimum
battery height of 47 mm, which means that a
lot of the smaller lighter packs need packing out
slightly. Even some of the larger packs like the
OptiPOWER 6S 5000 30C need a small amount
of packing. The heavier packs need to be
mounted all the way back in the frames and even
then can lead to a slightly nose heavy finish. The
model seems to have been designed around the
6S 4300 size pack weighing about 670 g.
Flying
The Diabolo 550 took off into a very stable hover
even at the fairly low head speed of about 1600
rpm that I had set for my Normal mode. Increasing
the throttle curve to give about 2050 rpm provided
a very nice set up for smooth 3D. Increasing it a
bit further to 2150 allows for any manoeuvre to
be flown and feels much like any 700-size model I
have flown. The tail control power is exceptionally
good on this model, which is often lacking on
smaller models. I wasn’t able to make the tail
blow out or pause even during some very high
collectively loaded pirouetting manoeuvres.
For most pilots the 1000 kV motor and 20 tooth
pinion is an excellent set-up for long flight times
whilst providing the performance required at a
wide range of head speeds. To get a governed
head speed of 2200-2500 rpm for hard smack
3D you would need to either increase the pinion
size or choose a slightly higher kV motor, which
of course means that flight time would suffer.
I flew twelve flights back to back, getting
between three and eight minutes flight times
depending on the battery size (6S 3500 to
5000 mAh) and head speed (1600-2150 rpm).
The motor and speed controller only got warm
during this and with the built-in BEC I didn’t need
to worry about charging receiver packs. Even
flying with a head speed of 1600 rpm the model
behaves extremely well and is perfectly capable of
soft 3D. You can achieve over 10 minute flights at
1600 rpm using a 6S 5000 mAh pack flying 3D.
The extra weight of the 5000 mAh packs is
barely noticeable on this model and the VBar
handles the slight nose heavy centre of gravity
with ease. The extra 30 seconds of flight time
and slightly better governor performance is worth
having at the high head speeds. It would be a very
good model to fit a capacity meter and telemetry
unit to maximise flight times depending on the
battery and head speed used for each flight.
Head Speed
1600
1950
2100
Flight Time (mins)
3500
4300
mAh
mAh
7.5
9.5
4.5
5.5
3.5
4.25
5000
mAh
11
6.25
5
39
Diabolo 550
Data log of a 4 minute 3D flight on a 6S 5000 pack at 2100 rpm, showing
good governor performance and only 3000 mA used
Data log of a 5 minute 3D flight on a 6S 4300 pack at 1600 rpm, showing
good governor performance and only 1770 mA used, so plenty more
capacity left for longer flight times
Head speed vs. flight time for different pack
capacities for my typical 3D flight. Times will vary
depending style of flight and battery C rating or age.
The canopy is plain white with vinyl decals
applied including a carbon effect windshield. This
feels high quality and shows up really well in the
air with its bright, uncluttered design. The shape
is distinctive as the big Diabolo’s baby brother,
so would make a great addition to the fleet. The
canopy is a little difficult to fit, but pushing full
down elevator and full negative collective does
make it a bit easier.
Overall it is an extremely accurate flying model
and the lightweight design allows for great
performance at a wide range of head speeds.
The power and size to weight ratio feels great
in the air with very positive stops and minimal
flybarless tuning needed to operate with a range
of styles, making it a perfect practice machine.
The size and quiet nature of the model allows
you to fly the model in more areas. This, with
the ability to use the same packs as a 700
class helicopter, allows for easily getting a lot of
valuable flights in. This is one helicopter that Jon
is going to have difficulty getting back! MHW
Spec
First flight and totally locked in, and looking suitably menacing…
PRODUCT Diabolo 550
MARKETPLACE 550-size 3-D and Sports
MANUFACTURER Minicopter,
Rheinstahlring 47, 34246 Vellmar, Germany
Tel: +49 (0) 561 988 2800.
Web: www.minicopter.de
MAIN ROTOR DIAMETER 1,250 mm
TAIL ROTOR DIAMETER 240 mm
OVERALL LENGTH 1,060 mm
WEIGHT (including blades) 2460 g
ALL-UP WEIGHT (with 6S 4600 mAh
LiPo)
3133 g
MAIN GEAR RATIO (with supplied 20T
pinion)
9.88:1
TAIL GEAR RATIO (engine to tail)1:4.3
CONTROL REQUIREMENTS Heli. Radio with 120º eCCPM and SAS
POWER REQUIREMENT 6S LiPo and
550 class heli motor
CURRENT EU Price ex. Shipping: #5000 basic kit,
€799.00
#5010 Combo Set 1 €949.00
#5020 Combo Set 2 €999.00
We Used
The canopy shows up well from all perspectives
40
X-Nova 4020-1000 ‘Diabolo Edition’
motor, KONTRONIK JIVE 100+ LV ESC,
MKS Combo containing three MKS9767
and a MKS9780 tail servo, Mini V-Bar with
Spektrum Satellite Rx’s, JR DSX12 Tx,
OptiPOWER 6S mAh LiPo packs, UltraGuard and BEC Guards