BAD GUY’S ESCAPE HELICOPTER
Most LEGO websites are flooded with vehicles of positive superheroes:
Batman, Spiderman, X-Man, Y-Man, Z-Man, Whatever-Man… However equipment of bad
guys are heavily underrepresented. Therefore, hereby we represent to MOCers
community Bad Guys Escape Helicopter (BGEH). Both in Hollywood movies and in
the reality bad guys/gangsters/dictators/politicians escape on their personal
helicopter when moment of justice/revolution/NATO-bombing/IRS comes. So it is
absolutely the first item on their shopping list spending stolen/taxpayers
money.
BGEH is a twin engined, 4-seat, armed executive transport in
1:20 scale (Lego Belleville/Playmobil figure size) made of 1718 bricks
featuring:
-
2-blade, semi-rigid Hiller-Bell type main rotor
with folding blades
-
2-blade variable pitch tail rotor
-
Variable pitch elevator surface
-
Aerodynamic rotor blades with spar-and-ribs
structure
-
6-channel twin controls connected into cockpit:
cyclic pitch/roll, yaw, collective pitch, engine throttle, elevator
-
Twin M-motor electric drive
(all these features above are packed into a
self-contained Light Helicopter Module)
-
Powered cargo ramp
-
Powered rescue winch
-
Four-barrel, belt-feed rotary gun in nose turret
trainable with joystick from cockpit at -21..+26/-30..+30 degrees
-
Magazine with 100 rounds of ammo
-
Windscreen with mechanized windscreen wipers
-
Swing arm-mounted, lockable side doors
-
Lockable cockpit doors
-
Folding rear seats
-
Fully faired airframe
-
Battery pack loadable into emptied cargo space
See model and building instructions in Lego
Digital Designer (LDD): BGEH With Guide
2.Basic idea
2.1.Building BGEH was inspired
by work of several excellent MOCers:
(This part is technical and for
heli builders with at least some experience. If you do not understand
something, see: http://www.aviastar.org/theory/index.html
about basics of how helicopters work)
SgtPepper set up the mark for
high-end Lego Technic helicopter modeling with his Aerospatiale Alouette II
(about real, see: http://www.aviastar.org/helicopters_eng/snias_alu2.php
) in 2008 with almost photo-realistic modeling of airframe in scale=1:14 (see: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=316589).
But it is also very functional with electric drive and 4 channel controls in
cockpit. Unfortunately it uses 2-blade
main rotor instead of the original 3-blade with Lego swash plate drilled
through allowing it sliding on main rotor axis for collective controls.
It is interesting because Wojtek
already developed functional 3-blade rotor in his Aerospatiale Gazelle (see
real http://www.aviastar.org/helicopters_eng/gazelle.php
) in 2006, in scale=1:14, electric drive, 4 channel controls in cockpit (see http://www.brickshelf.com/cgi-bin/gallery.cgi?f=161508
), but its fenestron (ducted fan) tail rotor left unfinished.
One of the finest fenestrons in
Lego Tech heli industry can be seen at Samrotule’s Eurocopter Dauphine (see
real http://www.aviastar.org/helicopters_eng/snias_dolphin.php
), 2003 in a some what larger scale=1:10, electric drive, 4 channel controls in
cockpit, (see: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=32036
)
The closest model to my concept
is Steph77’s Bell UH-1 (see real http://www.aviastar.org/helicopters_eng/bell_204.php
) from 2012. He maintained reasonable material requirement using scale=1:18
(Lego Tech figure scale) at the price of less exact airframe. But he managed to
model one of the mechanically most complex types of rotors, the Hiller-Bell,
with electric drive, 4 channel controls in cockpit (see: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=496125
)
In terms of airframe, I owe much
inspiration to Darkenski’s Eurocopter EC145 (see real http://www.aviastar.org/helicopters_eng/eurocopter_ec-145.php
) from 2011, in scale=1:18, electric drive. It has no real controls, but its
creator met the challenge to model a modern heli airframe using large amount of
composite materials and many CAD-designed curved surfaces (see: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=462815
)
2.2.Building BGEH was inspired
by the following real helicopters:
There are 2 generations of
German-originated helicopters with so high versatility that they are used „from
tank attack to heart attack” (in roles from anti-armor to medical rescue) worldwide.
I wanted to create similarly versatile and modular craft.
MBB BO-105 from 1967 (see http://www.aviastar.org/helicopters_eng/mbb-105.php
) was twice as expensive as contemporary light helicopters with the double
capability.
MBB-Kawasaki BK 117/Eurocopter
EC145 (see http://www.aviastar.org/helicopters_eng/mbb-117.php
/http://www.aviastar.org/helicopters_eng/eurocopter_ec-145.php
) from 1999. I was especially amazed by the Kawasaki-built version, which can
have gun turret under the nose.
2.3.Innovations and
advancements of BGEH compared to contemporary models:
(In the forthcoming technical
description, functional parts of BGEH are referenced by numbers which can be
found on cutaway drawings)
GOAL 1: First Lego heli with functional
6 channel twin controls: The models shown above had all 4 channel twin
controls (2 cyclic, 1 collective, 1 yaw control). I added 5th channel of engine
throttle control by rotating knob (29)
on collective lever (28) and 6th channel controlling tail elevator surface (86)
by pitch component of yokes (30) position, just like in real helicopters.
GOAL 2: First Lego heli with aerodynamic
rotor blades: In my vision, putting a studded bar in the airflow is funny,
but only until you play with Duplo. I simply got fed up with that Lego cannot
support us with reasonable rotor blades and come up with my solution: A
structure of blade spar (50) and ribs (51) covered with duct tape, assuming
that decals - which are regular parts in many Lego sets - could play more
important role as cover of aerodynamic surfaces.
GOAL 3: Fully faired airframe:
The usual, gridded-style look of Lego technic models looks nice at cranes,
heavy machinery and early helicopters, but it is ridiculous at modeling
streamlined, curved forms of modern heli airframes made of composite materials.
So I decided that I will maximally utilize Lego Technic fairing panels to
eliminate gaps, holes, steps, facets, etc. But the price was that I could not
tie myself strictly to model an existing helicopter. Instead I created a mix
from MBB BO105, Kawasaki BK117, and Bell Jet Ranger, but strictly adhering to
real engineering principles.
GOAL 4: Put engines where they
really are: Even at models with scale 1:14..1:10, Lego Technic electric
motors are usually put „somewhere” in the airframe, and engines are fake. This
has negative consequences: e.g. at Steph77’s UH-1, battery went in place of
engines, so electric motor went in place of controls before main rotor mast, thus
controls went into passenger deck, thus passengers most probably went into the
sea. Therefore I tried to incorporate electric motors (61) in place of
turboshaft engines.
GOAL 5: Windscreens and
glazing: Most technic models usually do not have any windscreens or
glazing. This is pretty OK. for a bulldozer, but modern helicopters with large
curved, one-piece windscreens get a distinctive „burnt-out scrap” look without
glazing. Fortunately, introducing Star Wars and other themes in Lego resulted
in variety of windscreen and canopy elements we can use with some tricks in
Technic.
GOAL 6: Modularity: At
first, this seems empty marketing slogan, as Lego by default is modular. But it
means that all stuff necessary for a twin engined electric helicopter with 6-channel twin controls in cockpit are
incorporated into a self-contained Light Helicopter Module (LHM), with which
you can build wide variety of helicopters.
GOAL 7: Reasonable materials
requirement: I reduced the scale from 1:18 (Lego Tech figure scale) to 1:20
(Lego Belleville/Playmobil figure scale). As material requirement changes in
average third power of the scale of the model it has definite positive effect
on reducing costs. Even if whole BGEH consist of 1718 bricks, the LHM - which
contains all vital parts of a helicopter – is made from only 628 bricks,
avoiding any rare or exotic parts. 1090 bricks are spent on airframe,
auxiliaries and armament… I paid the price of re-scaling in that I had to develop
compact, simplified, but still functional structure at main- and tail rotors,
which was challenging.
3.Light Helicopter Module (LHM)
See model in LDD: Light Helicopter Module
The purpose of LHM is to pack ALL
FUNCTIONALITY (except battery) of a twin-engined, electric driven Lego technic helicopter with 6-channel twin
controls in cockpit into a self-contained unit made of 628 bricks. With its
help, you can create helicopter from almost any light land/sea vehicles,
replacing their roof with LHM, if they have at least 10 studs long × 9 studs
wide × 9 studs tall internal space to accommodate cockpit and controls. To
support this, creating LHM I intentionally avoided using any exotic/rare
bricks: material requirement of core components can be found at almost anyone’s
brickshelf. Let’s see its functions more detailed:
See dynamic systems in LDD: BGEH Dynamic Systems
3.1.Main rotor
To understand why building a
compact Hiller-Bell type main rotor was a big challenge, we have to see through
types of helicopter rotors very shortly:
3.1.1.Bell-type rotor
We show an example of the most
simple helicopter rotor at SgtPepper’s Alouette II: Rotating part of swash
plate (black) is directly linked to variable pitch rotor blades with pitch rods
and ball joints (marked with red and yellow). Usually, between these rods there
is a small scissor-jack keeping rotating part of swash plate aligned with main
rotor mast, while still enabling swash plate lower/raise vertically on main
rotor mast for collective control. Static part of swash plate (grey) is linked
to:
-
its rotating part with a large diameter bearing,
-
to main rotor mast with a central ball joint,
which can also slide on main rotor mast
-
to collective and cyclic control rods (dark grey
and black) with ball joints
SgtPepper used
here the Lego Technic swash plate part, which has several problems:
-
It is bulky (6×6 studs) resulting large rotor
hub with 8 studs diameter and 13 studs tall
-
It is not designed to serve as swash plate, but
to tilt rotor as one monolith unit around main rotor mast, which is practically
unworkable and misleading. A real swash plate has ball joints of both static
and rotating part in one plane
-
Moreover, it cannot slide easily on main rotor
axis so poor MOCers have to drill it enabling collective control, which is not
really Lego-compatible move.
The same
functionality of Bell-rotor can be achieved with much more simple and compact
structure, if we omit Lego swash plate. The example is my earlier model, the oTo
Helichopper (http://www.mocpages.com/moc.php/327183):
rubber band (8) acting as a torsion spring gently forcing blades into zero
degree pitch relative to each other. Thus red pitch rods jacking on yellow
hinges are pressed down to swash plate. Swash plate here is a flat,
non-rotating plate can be tilted and lifted around main rotor axis by sliding
cardan-hinge. A 6-hole disk fixed to main rotor axis drives pitch rods, whose
lower tip slides on swash plate, thus we do not need any bearing. When swash
plate is lifted or tilted, pitch rods will increase blade pitch from zero
against the force of torsion spring. Rotor hub has 3 studs diameter and 5 studs
height (all the extra stuff outside this are to make blades foldable). Quite a
difference.
The general
advantage of Bell-rotors is simplicity, the disadvantage is lack of any
automatic stabilization, so it is very demanding on piloting skill or requires
difficult avionics
3.1.2.Hiller-type rotor
A somewhat more complex rotor
using Flybar stabilizator (as an example, see my earlier Light Assault
Helicopter model: http://www.mocpages.com/moc.php/300772
). Flybar (grey rod) is a pendulum-like device fixed with cardan-hinges to main
rotor axis transversal to rotor blades. It tries to keep its original plane of
rotation because of its gyroscopic torque in case the helicopter is tilted by
disturbances in airflow. Changing the cyclic pitch of rotor blades through
control rods, it counterbalances tilting. In Hiller system, the pilot can shift
only the plane of rotation of flybar with collective and cyclic controls
through the swash plate, and only the flybar controls main rotor blade pitch.
It has the advantage of increased stability over the Bell-rotor, its
disadvantage is less responsive control.
3.1.3.Mixed Hiller-Bell rotor
Thus, there is
a mixed system called Hiller-Bell, which results in stable AND responsive, but
mechanically more complex rotor. We show Steph77’s UH-1 as an example: here
BOTH flybar and rotor blades are linked to swash plate with rods and ball
joints to mix manual input from pilot and gyroscopic torque of flybar in blade
pitch control. However, there is a nasty difficulty: swash plate makes
relatively big vertical movements in collective pitch control compared to fine
correction movements of flybar. Thus, while blades are connected with swash
plate with simple straight rods (black) flybar can be connected with swash
plate only with a complicated jacking mechanism (light and dark grey)
compensating vertical swash plate movement and aligning rotating part of swash
plate to rotor blades. This is the weak point in Lego Technic where minimal cross-section
of any parts is 1 stud: both for main rotor mast and small jacks, which are at
least 5 times thinner in reality. So the rotor hub will be quite bulky: 9 studs
diameter and 14 studs height.
At BGEH I
created simplified Hiller-Bell main rotor with lifting flybar: swash plate (39)
is a flat plate with a hole in the middle letting through main rotor mast (45).
It can be tilted in any direction by cyclic swing arms (38) and pushrods (24),
and lowered/lifted by collective lever (18). Flybar (40) is lowered/lifted
together with swash plate, because 2 rollers built in flybar hub (43) roll on
that. Flybar can be tilted in any direction around main rotor mast (45), which
has an ½ Bush closely rounded by flybar hub components. This solves centering
flybar on main rotor mast. Leading slides (41) and leading swing arms (42) keep
flybar strictly transversal to rotor blades, but allow its all necessary
tilting and lifting movements. Plane of rotation of flybar hub (43) is
influenced:
-
Partly by manual cyclic and collective input
from swash plate (39) through rollers.
-
Partly by gyroscopic torque of flybar masses
(40).
Blade pitch
rods (44) are linked to flybar hub (43) offset from its centerline, so they are
mixing manual - flybar torque input in proportion 60% - 40%. This solution eliminates
the need of complicated jacking mechanism between flybar and swash plate
consisting of small parts. Therefore, main rotor hub can be more compact: 8
studs diameter and 7.25 studs tall. Blade
pitch rods (44) change the pitch of blade locking sleeves (46), which nest the
inner end of blade spars (50). Rubber tie (48) acts as a torsion spring gently
forcing blades into zero degree relative pitch. This way, rollers of flybar hub
(43) are pressed down against swash plate surface (39) through blade pitch rods
(44). When swash plate is lifted or tilted, it will lift/tilt flybar against
the force of torsion spring, and flybar will increase blade pitch from zero
through pitch rods. Blades can be folded into storage position around blade
folding hinges (47) disengaging end of blade spars (50) from blade locking
sleeves (46).
3.1.4.Aerodynamic rotor blades
Rotor blades are the most controversial part of my design. I
simply got fed up with that Lego cannot provide us reasonably aerodynamic rotor
blades. They introduced specialized rotor blade component at set 8046 in 2010
but they put studs in the middle of it making it pretty ridiculous.
Building bigger blades from studded
plates and flat tiles gave trouble to every MOCer. E.g. SgtPepper wrote that
blades of Aerospatiale Alouette II were too heavy, even using 2 instead of 3…
Therefore I created structure of
blade spar (50) made of the longest Technic rod (32 studs) part and blade ribs
(51) made of „Bionic eye” part covered with duct tape:
-
These blades are aerodynamic, strong and
lightweight even at large size. They are still very far from a patented NACA
(National Advisory Committee for Aeronautics)-aerofoil section, but they made
their effect. When I prepared the open-air photos of my earlier model oTo
Helichopper http://www.mocpages.com/moc.php/327183,
there was medium wind, and blades did what they are proposed to do with
annoying flipping-flopping.
-
Most duct tapes are 48mm (2in) wide, so they can
be applied to 3 studs (24mm, 1in) wide blade ribs in 2 strips: Strip A is stickled
first by its half-line to trailing (rear) edge of the blade, and bent forward
gently to ribs. Strip B is stickled second by its half-line to leading (front)
edge of the blade, and bent backward gently to Strip A and ribs. This way
sticking upper and lower half of cover can be avoided by the elasticity of the
tape.
However, duct tape is not quite a
regular Lego component… BUT:
-
Decals are already well-known technology for
Lego being part of many sets, so they could be used as structural stressed skin
components of machines instead of just being decoration.
-
They are cheap and comply children safety rules
as long as they are not enough big that kids can strangle each other with that
-
Larger areas of cover can be stickled together
from smaller standard parts
-
Duct tape material technology made serious
improvement in recent years using high tensile strength plastic foils,
water-resistant glues, sticky surfaces renewable with simply washing it with
detergent, stretchable foils keeping their shape, etc.
-
Combining decal covering with stiff/elastic rod
structures would provide excellent modeling tool for real world’s welded steel/Dural
tube structures covered with glass/carbon fiber reinforced resin: e.g. most
racing cars, rigid wing aircrafts, hovercrafts, light ships, etc.
-
Mildly curved surfaces e.g. windscreens of
cars/planes could be modeled with ease
(And Dear Lego
Guys, when you will design the next “bionic eye” part for future Godzilla/
Tyrannosaurus/ Alien/ Lady Gaga sets, can you accidentally use the shape of
NACA 712A315 aerofoil, thanks.)
3.2.Tail rotor
It is a simple two-blade
construction, where blades (67) have the same structure as main rotor blades.
Blade pitch rods (66) are connected with an assembly which has 4 ears (65) and
can slide on tail rotor shaft (120) left and right changing blade pitch. This
slide is controlled by pitch control lever (63) which forces a roller (64) in
the gap between the ears (65). Tail rotor is protected from hitting the ground
by a Bell Jet Ranger-style vertical stabilizer surface.
3.3.Transmission and engines
Main rotor is geared to tail
rotor at 36:100 ratio in two-step reduction gearing assembled from Z12 and Z20
conical gears (111, 112). Two M-sized electric motors (61) are geared to main
rotor 1:1. This is because M motors already have built-in reduction gearing,
and two of them have enough total torque to drive main rotor 1:1. (But, in case
of using motor without internal reduction gearing, gearing ratio can be changed
to 36:100 easily just switching the Z20 conical and Z12 half-conical gear with
each other at the motor.) Motors are connected with main rotor reduction gearing
through short (2 studs) cross-axles, which have two Z12 half conical gears,
this leaves 1 stud gaps between main rotor assembly and engines. It is usual
gearing layout at real battle helicopters (e.g. AH-64 Apache), because the
distance between engine and main rotor reduction gearing prevents single
explosive shell taking out both of them in the same time. At LHM, I use this 1
stud gap to lead control rods of yaw (23), elevator (87), 2 engine throttles
(26, 91) lead through from forward to back side of main rotor in a compact way.
Without the gap, it would be troubleful.
3.4.Controls
(Note: handles of functionally
working controls are built in yellow color in the model.)
With the trick described above, I
could solve all controls with control rods avoiding usage of control wires.
SgtPepper at Alouette II and Steph77 at UH-1 used wires for yaw control, as the
real aircrafts use them. I also used them at my previous model oTo Helichopper http://www.mocpages.com/moc.php/327183
but their usage proved very troubleful in Lego Technic. Parts made of ABS
easily twist and bend when control wires are correctly tensioned making them
loose and useless.
3.4.1.Channel 1-2: Cyclic pitch/roll
Tilting twin yokes (30) are
synchronized by roll synchronizer rod (30) and pitch synchronizer shaft (124).
It will change position of lower cyclic control swing arms (131), which transmit
control through ball joints (108) to lower cyclic control pushrods (130). These
will rotate cyclic swing arms (21) through cyclic control hinges (132). Cyclic swing
arms will push/pull upper cyclic control rods (24), which will tilt swash plate
(39) through its swing arms (38).
3.4.2.Channel 3: Yaw control
Yaw control pedals (31) move yaw
control sliding block (121), making lower yaw control rod (123) sliding
forward/backward through slide (122). This moves small yaw control swing arm
(126), which is fixed on a cross-axle in the cushion part of the left pilots
seat together with medium yaw control swing arm (127). It moves vertical yaw
control pushrod (129) through ball joint (128). It moves upper yaw control swing
arm (22) through yaw control hinge (133). The swing arm moves upper yaw control
rod (23) through a ball joint. Upper rod (23) will transmit yaw control to the
tail to tail rotor pitch lever (63).
3.4.3.Channel 4: Collective pitch
Raising collective control lever
(28) will rotate it around its pivot (125), pulling downward a 2-part
collective pushrod (18, 109). It will raise collective lever (18) rotating it
around its pivot (20). Collective lever (18) will lift swash plate (39), and
flybar (40), which will increase blade pitch collectively.
3.4.4.Channel 5: Engine throttles
Turning throttle control knob
(29) on collective control lever (28) will rotate lower throttle swing arm
(107), which will move upper throttle swing arm (89) through a vertical pushrod
and its ball joints. This swing arm will turn engine throttle pivot axis (135),
where there are two smaller swing arms (25, 107) fixed on its both ends. Small swing
arms will move upper throttle control pushrods (26, 91) both for left and right
engine. Pushrods move engine air intake nozzles (60) for throttle control.
3.4.5.Channel 6: Elevator pitch
Vertical elevator pushrod (101)
is linked to lower swing arm of right yoke (131) to receive pitch component of
yoke’s movement. Pushrod (101) will move upper elevator swing arm (88), which
moves upper elevator pushrod (87) through a ball joint. Pushrod (87) transmits
elevator control to tail, changing pitch of elevator surface (86).
4.Airframe
I tried to create streamlined,
faired and lightweight airframe, maximally utilizing Technic fairing panels and
flexible rods, and Star Wars windscreen elements
4.1.Windscreens and wipers
Windscreens
are made from part „Screen bowed 4×8×2” connecting them with part „Fric/stump
with crosshole” to Technic airframe structure. Windscreen wipers were inspired
by Darkenski’s EC-145. There wipers are static and do not follow lines of
windscreen very well.
Therefore, I
placed a mechanics for them from two Z16 gears at the front edge of head
instrument panel, which ensures correct movement of elastic wiper arms.
4.2.Cockpit doors
They are the weakest part of my
design as I could not find any glazing matching their shape. Part „Gate 4×8”
has correct size and half-rounded shape, but it is not available in transparent
color. Part „Door for wall element” available in transparent, but it is too
long. Of course I could cover cockpit doors with transparent duct tape any
time, just like rotor blades, but it would be too easy solution without
challenge. To compensate my reluctance, I equipped cockpit doors with lock,
inner- and outer opening knobs (82, 117), and rear view, truck-style side
mirrors (118) (they are used to check rotors and rescue winch crane during
flight). (Note: at top corner of doors, there should be part „angle element 0
degrees”, just LDD could not match it with flexible frame, even using flex and
match tools. Pity. In the reality, of course it is not an issue.)
4.3.Side cargo doors
See model with doors open and
blades folded in LDD: BGEH Doors Open
In the
reality, most helicopters have side cargo doors backward sliding on rails. However,
this is a trap in Technic, as minimal thickness of any door built from more
parts is 1 stud. So it will create a very nasty and disproportional 1 stud step
on the side of a 9-11 studs wide cabin as we can see it at Darkenski’s EC-145:
Therefore, I
placed 8×11 stud sized side cargo doors on 6×2 stud, L-shaped swing arms (57),
which can rotate 180 degrees: when they are in forward position, doors are
locked, PERFECTLY IN LINE with cabin wall, and cushioned top of swing arms
serve as arm stands for back seats. When swing arms are backward, they extract
side doors from cabin wall 2 studs and move them backward 10 studs. Each cargo
doors have two „train windows” and between them there are latch-type door locks
with inner and outer opening ears (99)
4.4.Cargo ramp
Light and medium sized
helicopters usually do not have lifting cargo ramp, just 2 streamlined
„clamshell doors” made of glass fiber reinforced resin. However, modeling
clamshell doors in Technic is troubleful as we can see in Darkenski’s EC-145:
there are quite a gaps around door where poor rescued guy and its casevac can
fall off in sharp turns…
Therefore, I
decided to build a two-piece, liftable, powered cargo ramp, which is mechanically
more challenging than clamshell doors, but it can be faired easier with existing
Technic panels. The ramp consists of two jacking pieces, the larger lower (71)
and the smaller upper (72) part to better follow streamlining of the end of the
cabin. Ideally, ramp should be lifted by a separate electric motor, but even
the smallest type of Technic motor is too bulky and heavy for this – we have
not enough space there. Therefore lower shaft of tail rotor reduction gearing
(112) is extended backward and continued in an universal joint (113). This
transmits drive to a ½ conical gear (114), which can slide on a short axle,
forced by lift drive clutch lever (116) and pushrod (73). When the pushrod is
pressed backward (accessible from left rear seat), gear (114) is connected with
lifting gear and axis (115), which has ramp lifting hinges (74) at its right
and left ends. Rotating 2 hinges pull 4 swing arms of ramp parts (75) through 4
pushrods (76) and ramp is lifted. Ramp lock rod (95) has a hook catching the
left hinge (74), locking ramp in closed position. Pulling ramp lock rod to the
left (accessible from right rear seat), the hook disengages, and ramp parts go
down in line with cargo space floor by their own weight.
The big
challenge in building this was that lifting mechanism could be 1 stud wide on
both sides to preserve 7 studs × 6 studs maximal cargo gauge using the ramp. The
maximal cargo size can be loaded with ramp lowered is 7 studs wide × 6 studs
tall × 24 studs long. Such an oversized cargo can be fixed to hooks (140) on
ramp floor. When ramp is lifted, main cargo area can still accommodate cargo 7
studs wide × 7 studs tall × 11 studs long, as side doors have bigger maximal
gauge than the ramp.
See model with empty deck in LDD: BGEH Empty Deck
See model with empty deck in LDD: BGEH Empty Deck
4.5.Rescue winch
It is nearly the same story as cargo ramp: powering it would require a separate electric motor, but there is not enough space for that. So winch gets its lift/lower drive connecting left/ or right ½ conical gears (92) placed on spool axis with a swing arm to forward stage of tail rotor reduction gearing (111). This device eats only 1 studs space on main cargo space roof. Rope is lead from winch to crane arm (93) between throttle control rods (91) of right engine, which has rollers to drive rope. Crane arm (93) can be rotated 90 degrees above cabin roof to reduce drag when it is not used.
4.6.Toilette module
It is nearly the same story as cargo ramp: powering it would require a separate electric motor, but there is not enough space for that. So winch gets its lift/lower drive connecting left/ or right ½ conical gears (92) placed on spool axis with a swing arm to forward stage of tail rotor reduction gearing (111). This device eats only 1 studs space on main cargo space roof. Rope is lead from winch to crane arm (93) between throttle control rods (91) of right engine, which has rollers to drive rope. Crane arm (93) can be rotated 90 degrees above cabin roof to reduce drag when it is not used.
4.6.Toilette module
Most bad
guys/gangsters/dictators/politicians consider themselves immortal gods, or at
least semi-gods who can do anything without any consequences. So they won’t
eat, wear, drink what ordinary people do. And they will not use public
restrooms… Therefore a decent personal helicopter should provide all these
amenities on luxury level. Toilette module is a lightweight structure can be
easily fixed and removed from main cargo space floor including toilette (54), hand
wash basin (53), cabinet (52), entrance door (98). On the outer wall of the
module facing towards back seats (56) has LCD TV (55) (made from part „train
window”, whose back is covered with parts „container door”), intercom (100) and
A/C unit (96). When toilette module is installed on cargo space floor, it locks
left cargo door in closed position. So one cannot suddenly open it revealing
the „big man” in desperate need… Toilette outer window has darkened glazing,
but it is still the toilette with the greatest view on the face of the Earth.
4.7.Folding back seats
The primary
motivation behind torturing and massacring ten thousands of innocent people - regularly
made by bad guys - is to accumulate enough money and power to hunt down most
expensive girls and top models. (e.g. Kaddafi’s amazon bodyguards, Silvio
Berlusconi’s unga-bunga parties, Saddam’s lovers, etc.). Or, hunt down not-so
expensive girls, after lot of alcohol (e.g. Dominique Strauss-Kahn). A personal
aircraft – as a symbol of status and power – can be an excellent device for womanizing
activity if it provides discrete environment (e.g. Catherin Hepburn and Howard
Hughes in PYB Catalina hydroplane in the movie Aviator). Therefore, back seats
can be folded backward to create double bed releasing locking handles (58) and
flipping down locking ears (59). Still with this help, life can be a boring
routine for bad guy’s girlfriend aboard BGEH: morning – poison gas bombing of a
rebel mountain village, noon – skiing in Swiss Alps, evening – cocktail party
with celebs in Hamburg. To create some excitement, lid of toilette (144) is
foldable and toilette paper roll (145) is rollable, providing excellent battlefield
for women’s hysteria.
Lego Technic battery pack is too
bulky and heavy to build in fixed somewhere in the airframe in scale 1:20. It
would totally destroy styling. But BGEH can carry it as cargo when cargo deck
is cleared. I will wait with integration of battery pack into the structure
until Lego develops more compact, light, higher capacity and rechargeable Li-Po
battery pack. This way, they could reach at least the technology level of cheap
mass-produced Chinese mobile phones…
4.9.Fuel tanks
In the reality, kerosene fuel of turboshaft engines is stored in the 2 large hollow spaces (2×7×11 studs) of cargo deck floor and lower cargo ramp floor can be filled trough cap (139).
4.10.Landing skid
In most Lego Tech heli models landing skids are parallel with plane of main rotor disk area. However in the reality, cabin and rotor is put on skids somewhat backward tilted to make autorotation crash landing easier. I used 3.75 degrees backward tilting on skids (35) at BGEH. Moreover, it is important, because rear end of cargo ramp can touch ground, when lowered in level with cargo deck floor. This makes loading and unloading easier.
5.Armament
Sooner or later, moment of justice/the good guy/revolution/the next bad guy comes for every bad guy, when survival depends on BGEH. Don’t repeat the mistake of Fantomas, who built a jet-powered, flying Citroen DS-19, but forget to put there any armament. Pity.
4.9.Fuel tanks
In the reality, kerosene fuel of turboshaft engines is stored in the 2 large hollow spaces (2×7×11 studs) of cargo deck floor and lower cargo ramp floor can be filled trough cap (139).
4.10.Landing skid
In most Lego Tech heli models landing skids are parallel with plane of main rotor disk area. However in the reality, cabin and rotor is put on skids somewhat backward tilted to make autorotation crash landing easier. I used 3.75 degrees backward tilting on skids (35) at BGEH. Moreover, it is important, because rear end of cargo ramp can touch ground, when lowered in level with cargo deck floor. This makes loading and unloading easier.
5.Armament
Sooner or later, moment of justice/the good guy/revolution/the next bad guy comes for every bad guy, when survival depends on BGEH. Don’t repeat the mistake of Fantomas, who built a jet-powered, flying Citroen DS-19, but forget to put there any armament. Pity.
5.1.Four-barrel 12.7mm(0.5in)
rotary gun in nose turret
See gun turret in LDD: Nose Gun Turret
This gun is modeled after the Russian diminutive of the famous American M61 Vulcan 6-barrel rotary gun, which was used in Mil MI-24 battlefield helicopters. It is little bit oversized for a light helicopter. I paid the price of it in limited arcs of fire (-21..+26 degrees vertically and -30..+30 degrees horizontally), but creating it was challenging. Belt of 12.7mm (0.5in) ammo is modeled with motorcycle chain parts (Note: In LDD, this type of chain cannot be twisted, but it tolerates that pretty well in reality). To save space, I omitted parts of gun behind its rotor (151): bolts, springs, catches, etc. Gun turret can be controlled with joystick from cockpit through laying pushrod (152), which rotates trunnion directly. Training is made by training pushrod (153) rotating training lever (7), which drives training transmission gear (105) through rotating axis of trunnion. Gear (104) rotates training gear of gun (105). Behind fixing hardpoints of turret (154) there is a magazine for belt of 100 rounds (106). Belt is extracted from magazine by extractor gear (155) and received at gun by receiver gear (5), which is driven by gun rotor (151). This type of gun has firing rate of 4000 shots/min in the reality, so it can empty the whole magazine in a 1.5 second-burst, but I had no more space for magazine, and motorcycle chain is not very compact.
See gun turret in LDD: Nose Gun Turret
This gun is modeled after the Russian diminutive of the famous American M61 Vulcan 6-barrel rotary gun, which was used in Mil MI-24 battlefield helicopters. It is little bit oversized for a light helicopter. I paid the price of it in limited arcs of fire (-21..+26 degrees vertically and -30..+30 degrees horizontally), but creating it was challenging. Belt of 12.7mm (0.5in) ammo is modeled with motorcycle chain parts (Note: In LDD, this type of chain cannot be twisted, but it tolerates that pretty well in reality). To save space, I omitted parts of gun behind its rotor (151): bolts, springs, catches, etc. Gun turret can be controlled with joystick from cockpit through laying pushrod (152), which rotates trunnion directly. Training is made by training pushrod (153) rotating training lever (7), which drives training transmission gear (105) through rotating axis of trunnion. Gear (104) rotates training gear of gun (105). Behind fixing hardpoints of turret (154) there is a magazine for belt of 100 rounds (106). Belt is extracted from magazine by extractor gear (155) and received at gun by receiver gear (5), which is driven by gun rotor (151). This type of gun has firing rate of 4000 shots/min in the reality, so it can empty the whole magazine in a 1.5 second-burst, but I had no more space for magazine, and motorcycle chain is not very compact.
5.2.Six TOW missiles
TOW stands for Tube-launched,
Optical-targeted, Wire guided anti-armor missile developed by Hughes Aircraft
in 1971 and continuously improved since that. Its advantages are relative
cheapness and accessibility. As it is re-engineered and manufactured by Iran
also, it is an everyday commodity on illegal weapons market for bad guys. As the
missile is controlled during its flight by electric signals traveling on a
double piano wire spooling down from a coil, it is relatively safe against
Electronic Counter Measures (ECM). Disadvantages are limited range by wire
(max. 3750m), limited speed to prevent tearing the wire (187m/sec in average) ,
limited armor piercing (630 mm) by 3.1 kg HE warhead, and the biggest one:
launching platform has to keep target in line of sight during whole flight time
of missile (max. 20secs) being an easy target itself for AA guns. Its
semi-automatic optical guidance requires a gyro-stabilized periscope sight (15)
with an ocular (85). At helicopters it is usually placed at cockpit roof, this
way at least the cabin of the helicopter can be behind some cover during
targeting. Modeling the missile launch tubes (80) in scale 1:20 was not an
issue, as their real diameter (0.15m, 6”) matches pretty well with 1 stud
diameter-tube parts.
Missile
weapons can be attached to retractable side weapons consoles (79) on both
sides. When they are employed, they lock side cargo doors in closed position,
but cargo deck is still accessible through cargo ramp.
5.3.Two Hellfire missiles
Hellfire is a more modern and
potent fire-and-forget weapon with semi-active laser homing produced by Lockheed
Martin. Thus, it is much more hard to access for bad guys. I included it
because of modeling challenge: the missile is launched from short rails, and I
wanted to solve it as it is. The key was „Tacho 8”, an 8-winged
stabilizator-like part (161), which has small T-hooks at the end of wings.
These hooks can go between rails of „1×2 plate with rail” parts (162) in the
reality, even if LDD cannot handle this. The difficulty was that rails had to
be spaced in a distance, which did not match any standard Lego part size.
Therefore, I hanged assembled rails with parts „1×1 plate with holder” on
4-stud cross-rods named „Lightsword” (165). This way, gap between rails can be
freely adjusted to safely hook missiles (97) by T-hooks.
6.Dimensions of BGEH:
Main rotor diameter: 69 studs/
552mm/ 21.73” in real size: 11.04m / 36’ 2.36”
Main rotor disc area: 3739.28
sqstuds/ 0.239sqm / 370.93sqinch in real size: 95.72sqm/ 1029sqfeet
Tail rotor diameter: 16 studs/
128mm/ 5.04” in real size: 2.56m / 8’ 4.72”
Tail rotor disc area: 201.06
sqstuds/ 0.013sqm / 19.94sqinch in real size: 5.147sqm/ 55.33sqfeet
Distance between main- and tail
rotors: 39 studs/ 312mm/ 12.28” in real size: 6.24m / 20’ 5.51”
Height: 25.25 studs/ 202mm/ 7.95”
in real size: 4.04m / 13’ 2.95”
Cabin size: 11studs/ 88mm/ 3.46”wide × 12studs/ 96mm/ 3.78” tall × 44studs/ 352mm/ 13.86” long in real size: 1.76m/
5’ 9.25” wide × 1.92m/ 6’ 3.54” tall × 7.04m/
23’ 0.98” long
Largest loadable cargo size (with
lowered cargo ramp): 7studs/ 56mm/
2.20”wide × 6studs/ 48mm/ 1.89”
tall × 24studs/ 192mm/ 7.56” long
in real size: 1.12m/ 3’ 8.07” wide × 0.96m/
3’ 1.77” tall × 3.84m/ 12’ 7.09”
long
Minimal storage space of BGEH
with folded blades, without armament: 15 studs/ 120mm/ 4.72”wide × 26.25 studs/ 210mm/ 8.27” tall × 73 studs/ 584mm/ 22.99” long in real size: 2.40m/
7’ 10.43” wide × 4.20m/ 13’ 9.25” tall × 11.68m/
38’ 3.54” long
7.Unsolved problems and shortcomings
- There is only one collective
lever/throttle control for 2 pilots, so one of them should be left-handed: This
was not because technical limitations, but I wanted to keep 9 studs internal
gauge of cockpit. Wider cockpit can be done with twin collective lever.
- Cyclic and collective controls are interlinked: changing collective pitch will influence cyclic pitch also and should be compensated on yokes. This is because there was not enough space for 4 dislinker levers in the already crowded controls housing. It is the price of the 1:20 scale.
- Tail rotor is too close to main rotor and too close to ground, and disturbs usage of cargo ramp: Bell Jet Ranger-style straight tail boom should be replaced with angled tail boom and universal joint on tail rotor transmission shaft, even it will increase minimal storage size.
- There are no flapping hinges and yaw dampers in main rotor. BGEH is already too big and too heavy using semi-rigid rotor.
- Correct gearing ratio between main- and tail rotor should be 10:100 instead of 36:100
- There are no centrifugal clutches between engines and main rotor gearing, which would prevent stalling engines destroying inertia of the autorotating main rotor.
- Gearing ratio of cargo ramp lift and rescue winch is insufficient: both of them should use clutchable worm drive, but there was not enough space for that.
- Cargo doors can flip-flop in rotor downwash when their swing arms left half-open: there was not enough space left for secondary swing arms securing it.
- Cargo ramp tends to jam at lowering, when there is not enough weight on that
- Cockpit doors have no glazing.
8.Building guides
See building guide: BGEH With Guide
Complexity of BGEH put guide-generating algorithm of LDD on hard testing. This algorithm most probably starts from center of gravity of the model, and seemingly tries to group similar parts in each others proximity into sub-modules. Also it seemingly checks collisions of sub-modules during assembly at some level, but no fully. However, the fully faired design confused up it totally:
- Cyclic and collective controls are interlinked: changing collective pitch will influence cyclic pitch also and should be compensated on yokes. This is because there was not enough space for 4 dislinker levers in the already crowded controls housing. It is the price of the 1:20 scale.
- Tail rotor is too close to main rotor and too close to ground, and disturbs usage of cargo ramp: Bell Jet Ranger-style straight tail boom should be replaced with angled tail boom and universal joint on tail rotor transmission shaft, even it will increase minimal storage size.
- There are no flapping hinges and yaw dampers in main rotor. BGEH is already too big and too heavy using semi-rigid rotor.
- Correct gearing ratio between main- and tail rotor should be 10:100 instead of 36:100
- There are no centrifugal clutches between engines and main rotor gearing, which would prevent stalling engines destroying inertia of the autorotating main rotor.
- Gearing ratio of cargo ramp lift and rescue winch is insufficient: both of them should use clutchable worm drive, but there was not enough space for that.
- Cargo doors can flip-flop in rotor downwash when their swing arms left half-open: there was not enough space left for secondary swing arms securing it.
- Cargo ramp tends to jam at lowering, when there is not enough weight on that
- Cockpit doors have no glazing.
8.Building guides
See building guide: BGEH With Guide
Complexity of BGEH put guide-generating algorithm of LDD on hard testing. This algorithm most probably starts from center of gravity of the model, and seemingly tries to group similar parts in each others proximity into sub-modules. Also it seemingly checks collisions of sub-modules during assembly at some level, but no fully. However, the fully faired design confused up it totally:
- First, during 370 steps, it
builds all the internals of the helicopter, then puts it aside.
- Second, it builds up the „empty skin” of fairing elements in more than 200 steps.
- In the final, 618th step, it tries to pull the whole „skin” on internals in one step, just like a robe, which is funny, but totally impractical. You may use the building guides of sub-models (e.g. LHM) instead of this.
9.Recommendation
The idea of this twin-engined, twin-controlled helicopter is born on the same day as my twin sons – Daniel and Szilard – so I recommend it to them.
10.To be continued…
My next Lego Technic heli has 6-blade main rotor with 148 studs (1.18m, 3’10”) diameter. So stay tuned…
- Second, it builds up the „empty skin” of fairing elements in more than 200 steps.
- In the final, 618th step, it tries to pull the whole „skin” on internals in one step, just like a robe, which is funny, but totally impractical. You may use the building guides of sub-models (e.g. LHM) instead of this.
9.Recommendation
The idea of this twin-engined, twin-controlled helicopter is born on the same day as my twin sons – Daniel and Szilard – so I recommend it to them.
10.To be continued…
My next Lego Technic heli has 6-blade main rotor with 148 studs (1.18m, 3’10”) diameter. So stay tuned…
