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Star Wars Real Engineered: Multiple Troop Transport
Tilting propeller multicopter/amphibious tracked personnel carrier hybrid with 10-CH RC: air/land/sea drive, propeller folding/tilting, cargo winch, cargo ramp. Spring driven shooting armament: recoilless gun + portable light MG in retractable turret, 8 RPGs, 2 PDWs. 3 Bionicle/Technic crew, in scale 1:10
About this creation
Multiple Troop Transport converts from road- to air mode and takes off (animated)
Figure 0: Multiple Troop Transport converts from road- to air mode and takes off (animated)
See model in LDD

Multiple Troop Transport transforms from hovering to level flight (animated)
Figure 1: Multiple Troop Transport transforms from hovering to level flight (animated)
See model in LDD

Multiple Troop Transport in level flight (animated)
Figure 2: Multiple Troop Transport in level flight (animated)
See model in LDD

1 Preface for our „Star Wars Real-Engineered” mini-series

It is very clear that no one can make Sci-Fi movie without departing from existing scientific knowledge. However, it can be done in the clever way, like Stanley Kubrick’s „2001 a space odyssey”. Alternatively, it can be done unnecessarily raping very basic laws of Physics valid through the Universe - like in Babylon 5 or in Star Wars - serving the marketing needs of target audience. Our mission is trying to re-create the fanciest Star Wars-gizmos from Lego Technic using strict engineering point of view, based on current or slightly extended technology.

2 The Star Wars gizmo real-engineered: Trade Federation Multiple Troop Transport

Trade Federation Multiple Troop Transport is a heavily armored repulsorlift transport vehicle dropped by Trade Federation Landing Ships and used to transport B1 battle droids during the Clone Wars. It was designed by Doug Chiang, who created one of the most well-thought and integrated weapons system in Star Wars franchise.


Figure 3: Trade Federation Multiple Troop Transport

The Lego set 7662 modeling it is pretty austere mechanically and downsized.

This is sad because dropships/ flying troop transports capable of fast delivery of battle robots to battlefield will have practical significance in future warfare. Not in the “Marvel-franchise way”, where 10-story giant mechas are hitting each other with steel fists. But deploying small all-terrain robotic vehicles equipped with sniper/ anti-armor weapons, which can have longer mission duration than human snipers, and can cause serious disruption in communication behind enemy lines with minor force.

The really bad news about building flying Multiple Troop Transport in the reality is that by general relativity theory, gravitation is not a force - which could be repelled somehow - but special geometry of spacetime around large masses. Even antimatter has positive gravity. So repulsorlift engines are not only uninvented yet, but pretty much impossible by current fundaments of Physics.

Therefore in real engineering - with the advent of advanced LiPo battery technology - there is lot of experimenting with hybrid drone multicopter/ all terrain vehicle combos:
B-Unstoppable Flying Drone Tank, UK proved to be an early commercial success with well-balanced land- and flight performance:


Figure 4: B-Unstoppable flying Drone Tank

There are 2-3 cheaper clones of it with running 4 wheels instead of electric driven tracks. The main disadvantage of this layout is that it can have only very small airframe compared to its road gauge, as the non-foldable propellers eat tremendous space.

JJRC H40WH FPV Tank Quadcopter is more complicated but promising concept: it has retractable propeller arms, therefore road gauge does not depend on propeller diameter anymore, and it can have quite a sizeable airframe compared to its road gauge, so theoretically it can deliver battle robot cargo.


Figure 5: JJRC H40WH FPV Tank Quadcopter

From the unboxing video linked above, one can see that surprisingly enough, it is better multicopter (of course cannot reach the performance of pure multicopters) than RC car: short wheelbase + high motor torque + small mass resulting insufficient adhesion of driving wheels is not a healthy combination. Moreover, its propeller arm folding solution eats lot of space inside the airframe, and sometimes it gets stuck as propeller blades can be opened/closed only by centrifugal force. We intended to develop this concept correcting some of its deficiencies.

3 Our Multiple Troop Transport (MTT)

Our goal was to create a tilting propeller multicopter/ amphibious tracked personnel carrier hybrid, air-droppable from our previous heavy dropship, capable of carrying battle droids on its cargo deck. It is a piece of concept art - but strictly tied to real engineering principles - slightly extending the current level of technology. It contains 3890 bricks, yielding 10 RC power functions, 39 manual functions, and 24 non-working features, in scale 1:10:

Multiple Troop Transport functions overview
Figure 6: Multiple Troop Transport functions overview
See model in LDD

The aims of the model are:
- RC controlled air- and land mode
- Fast, fully RC controlled conversion between air- and land modes
- RC controlled transformation from hovering to level flight mode with tilting propeller arms
- RC controlled cargo winch and cargo ramp
- RC controlled amphibious mode with watertight lower hull + lower hatch driven by 2 screws
- Foldability into a compact boxy shape to enhance air transportability by heavy dropship
- Mid-air dropability from heavy dropship
- Box-shaped inner cargo space with maximal volume, accessible through forward/rear cargo ramps
- Dual usage with human crew/ without human crew as drone, carrying different tracked vehicles on its cargo deck
- Reasonable offroad performance on retractable tracks
- Retractable gun turret with spring driven shooting armament
- Modeling the layout of range extender hybrid drive by 2 turboshaft engines + alternator combos besides batteries
- Retractable refueling boom for mid-air refueling

Let us note that these aims are extremely challenging even in real engineering, therefore MTT is far beyond the physical tolerance of Lego bricks, although we tried our best to reinforce it. Our priority was conceptual design instead of real playability. Real multicopters are built from carbon fiber-reinforced materials, with the lightness and tensile strength ABS cannot compete.

*For considerable part of rendering and artwork, very special thanks to C BigBoy99899

Multiple Troop Transport rolls on cargo ramp of heavy dropship
Figure 7: Multiple Troop Transport rolls on cargo ramp of heavy dropship
See model in LDD

We wanted MTT to be air transportable/droppable by heavy dropship, due to MTT’s limited flight range (ca. 80-100km) and altitude (ca. 200-300m). The vehicle rolls on the cargo ramp of dropship on its retractable tracks. With variable height track suspension, freeboard of vehicle can be changed from 0 to 3 studs continuously.

Multiple Troop Transport on board of heavy dropship
Figure 8: Multiple Troop Transport on board of heavy dropship
See model in LDD

When loaded into the cargo hold of dropship, crew can enter into MTT through its rear cargo ramp, from the rear part of dropship’s cargo hold.

Multiple Troop Transport is sky-craned down through bomb bay door of heavy dropship
Figure 9: Multiple Troop Transport is sky-craned down through bomb bay door of heavy dropship
See model in LDD

The dropship has motorized bomb bay doors, and the folded MTT can be lowered through that with the help of cargo winch of dropship.

Multiple Troop Transport opens propeller arms and starts it engines during drop from heavy dropship
Figure 10: Multiple Troop Transport opens propeller arms and starts it engines during drop from heavy dropship
See model in LDD

The dropship can air crane down the vehicle on a spot. Alternatively, MTT can open its propeller arms, gun turret and start its engines mid-air, then releasing itself from air crane cable. This enables the expensive dropship to launch MTT at safe distance from enemy lines and enemy AA fire.

Multiple Troop Transport opens propeller arms and starts it engines during drop from heavy dropship (animated)
Figure 11: Multiple Troop Transport opens propeller arms and starts it engines during drop from heavy dropship (animated)
See model in LDD

Air drop can be done at moderate level speed and sufficient altitude, letting MTT dive down first from the heavy downwash zone of the dropship’s large coaxial rotor, where maneuvering is extremely difficult.

Multiple Troop Transport makes low pass over water surface
Figure 12: Multiple Troop Transport makes low pass over water surface
See model in LDD

MTT can be used in beyond the horizon infiltration missions of special forces, flying below radar signals.

Multiple Troop Transport lands in desert
Figure 13: Multiple Troop Transport lands in desert
See model in LDD

The fast, automated air/land transformation enables it to utilize the „drive when you cannot fly, and fly when you cannot drive”-principle. Rivers, heavy terrain, enemy checkpoints are avoided by flying. Enemy AA-fire is avoided by driving and taking cover in terrain.

Multiple Troop Transport in road mode
Figure 14: Multiple Troop Transport in road mode
See model in LDD

MTT has boxy shaped, 8×10×41 studs sized, drive-through cargo bay accessible through front/rear foldable cargo ramps. While external dimensions of folded vehicle are merely 17×16×42.5 studs. To achieve this, all seats and equipment of crew can be easily removed to clear cargo deck. Manual flight controls are in the removable windscreen panel. Flight computer and its backup - controlling flight in unmanned drone mode – and foldable propeller arms with their motorized opening mechanism are fully integrated into 4.5 stud thick cargo bay sidewalls.

Multiple Troop Transport with open cargo ramps and cleared cargo deck
Figure 15: Multiple Troop Transport with open cargo ramps and cleared cargo deck
See model in LDD

The manually actuated gun turret is seated on a 180 degree flippable roof panel, so it can be retracted at cargo bay. It is equipped with 100mm/4” recoilless gun. The gun has rocket nozzles in its upward rotatable breech, so thrust of gun gases partially blasted backward neutralizes recoil. Therefore there is no need for heavy gun mount and recoil damper.
Multiple Troop Transport fires recoilless gun wearing auxiliary armor
Figure 16: Multiple Troop Transport fires recoilless gun wearing auxiliary armor
See model in LDD

As backward blast can damage propeller arms when recoilless gun is not axially fired, MTT can be equipped by auxiliary side armor panels. It also enhances survival of non-armored MTT in land battle. Auxiliary armor panels break off automatically at opening propeller arms. Aiming of recoilless gun is assisted by co-axial portable light machinegun auto-loaded from drum magazine. All turret mounted weapons are modeled as spring driven shooting.

Multiple Troop Transport opens propeller arms at takeoff
Figure 17: Multiple Troop Transport opens propeller arms at takeoff
See model in LDD

MTT is not intended for long range flights. It is designed for amphibious landings and short hopping flights to jump into hard-to access forward positions in mountainous terrain or in urban combat. Propeller arms are tiltable 45° forward to increase maximal speed in level flight from 100km/h (usual at vertical propeller multicopters) to 200-220km/h range.

Multiple Troop Transport in mountain hopping mission
Figure 18: Multiple Troop Transport in mountain hopping mission
See model in LDD

Folding propeller arms and boxy cargo bay have rather ineffective shape aerodynamically. This results in high energy consumption of electric motors in propeller arms and very short range, even considering the very latest LiPo battery technology. Therefore, MTT has only limited LiPo battery capacity, allowing short silent sneaking in road mode/ landing /take off. For sustained operation, it is equipped with hybrid drive: besides batteries, there are conventional jet fuel tanks in the floor and 2 turboshaft engine + alternator range extender units in sidewalls.

Multiple Troop Transport in mid-air refueling, rear view
Figure 19: Multiple Troop Transport in mid-air refueling, rear view
See model in LDD

In any amphibious combat situation, one of the most critical factors is to get enough fuel enough fast to the battlefield without established supply network. Therefore MTT is equipped with extendable refueling boom, allowing its fast mid-air refueling, instead of slow and vulnerable land refueling.

Multiple Troop Transport in night mid-air refueling
Figure 20: Multiple Troop Transport in night mid-air refueling
See model in LDD

MTT’s multicopter layout and foldable cargo ramps allow performing special tasks, which cannot be performed easily by helicopters. E.g. aerial minesweeping of land mines using on-board mini excavator arm. As the vehicle does not touch ground during hovering in ground effect, it is less likely to trigger mines. In drone mode no human crew is endangered during minesweeping:

Multiple Troop Transport in aerial land mine sweep
Figure 21: Multiple Troop Transport in aerial land mine sweep
See model in LDD

Motorized cargo winch and watertight lover hatch allows MTT to perform rescue airlift operations:

Multiple Troop Transport in rescue airlift, bottom view
Figure 22: Multiple Troop Transport in rescue airlift, bottom view
See model in LDD

There are 4 downward looking cameras and searchlights to support this activity:

Multiple Troop Transport in rescue airlift, top view
Figure 23: Multiple Troop Transport in rescue airlift, top view
See model in LDD

Winch cable is very close to Center of Gravity (COG) of the craft, ensuring neutral behavior during airlift.

Multiple Troop Transport in rescue airlift, bottom view (animated)
Figure 24: Multiple Troop Transport in rescue airlift, bottom view (animated)
See model in LDD

The small dimensions of the vehicle allow to pick up only one person, e.g. a pretty female superagent, who stole the plans of Sowatian nuclear warheads from the laptop of ruthless Sowatian dictator after spending an exhausting night with him, and escaped in a liferaft from his superyacht during a gale. Of course we cannot rule out that some members of rescue crew will try to take advantage on the confined situation:

Multiple Troop Transport lifts victim on board through bottom hatch
Figure 25: Multiple Troop Transport in lifts victim on board through bottom hatch
See model in LDD

MTT has 2 jetissonable inflatable life rafts at its outer sidewalls to facilitate easier airlift of persons or equipment from sea:

Multiple Troop Transport recovers sniper in rebreather set with the help of its jetissonable life rafts
Figure 26: Multiple Troop Transport recovers sniper in rebreather set with the help of its jetissonable life rafts
See model in LDD

MTT has watertight lower hull with standard displacement of 0.7 metric tons. This is sufficient to provide buoyancy, but not enough stabile because of its shallow draft. Fully equipped MTT can ditch only on very calm water surface with propellers working at slow rpm, providing necessary stability during floating:

Multiple Troop Transport floats on calm water surface with propellers rotating low rpm
Figure 27: Multiple Troop Transport floats on calm water surface with propellers rotating low rpm
See model in LDD

With propeller arms and armament removed, MTT can cross relatively calm water surfaces. It is propelled by 2 detachable, electric driven screws at its rear:

Multiple Troop Transport after emergency landing on stormy sea, with propeller arms and armament jettisoned
Figure 28: Multiple Troop Transport after emergency landing on stormy sea, with propeller arms and armament jettisoned
See model in LDD

Cargo bay of MTT is air conditioned by 2 small A/C units placed in the sidewalls. It allows completing missions with human crew in cold weather conditions:

Multiple Troop Transport in winter mission
Figure 29: Multiple Troop Transport in winter mission
See model in LDD

4 Technical details of Multiple Troop Transport

*This part is technical. If you do not understand how multicopter controls do work, you can find an excellent summary at Wikipedia

**In the forthcoming technical description, functional parts of Multiple Troop Transport are referenced by numbers which can be found on technical drawings attached

***Parts of Multiple Troop Transport are color-coded by their function:
- Yellow: Manual controls
- Gray/Black: Static parts
- White: Dynamic parts
- Blue: Folding seat of pilots
- Red: Fire extinguishers
- Dark green: Shaped charges in RPGs

Multiple Troop Transport systems overview
Figure 30: Multiple Troop Transport systems overview
See model in LDD

Multiple Troop Transport modules overview
Figure 31: Multiple Troop Transport modules overview
See model in LDD


Multiple Troop Transport flight cutaway view
Figure 32: Multiple Troop Transport flight cutaway view
See model in LDD

4.1 Air drivetrain

Flight mode drivetrain
Figure 33: Flight mode drivetrain
See model in LDD

As TLG LPF L-motors are rather bulky and week compared to modern brushless electric motors, we could not build MTT with its real configuration (8 motors for 8 propellers in 4 arms, providing redundancy). Instead of it, one LPF L-motor per propeller arm drives 2 propellers through triplet of Z12 half beveled gears. It gives less realistic quadcopter control and it has no any redundancy, but requires only 4 channels from 2 LPF SmartHubs instead of 8. Moreover, propellers have very limited tolerance of centrifugal force in such a small size, even we tried our best to reinforce propeller hubs.

MTT is basically controlled by (N3, N4) duplex flight computers with GPS receiver and laser-gyroscopes, built in sidewalls as non-working features. There are optional (N1) pitch/roll and (N2) yaw/throttle control joysticks for manual control built in removable windscreen panel as non-working features.

In the reality, folding propeller arms and boxy cargo bay have rather ineffective shape aerodynamically. This results in high energy consumption of electric motors in propeller arms and very short range, even considering the very latest LiPo battery technology. Therefore, MTT has only limited LiPo battery capacity, allowing short silent sneaking in road mode/ landing /take off.

 Turbo generator unit
Figure 34: Turbo generator unit
See model in LDD

For sustained operation, it is equipped with hybrid drive: besides batteries, there are conventional jet fuel tanks in the floor and 2 turboshaft engine + alternator range extender units in sidewalls modeled as non-working features.

Turbo generator unit (animated)
Figure 35: Turbo generator unit (animated)
See model in LDD

Jet fuel of turbo generators can be filled through (D8) refueling cap or extendable mid-air refueling booms.

4.2 Propeller folding mechanism

Propeller arms folding mechanism
Figure 36: Propeller arms folding mechanism
See open model in LDD
See closed model in LDD

In real engineering, there would be separate servo motors for opening each propeller arms. But, TLG PF servo motor is so uncompact (3×6×5studs) that this was not an option for us. Therefore we used 2 (F1) LPF2 M-motors, controlled by (F0) LPF2 SmartHub, driving (F4) worm+Z8 gear combos of propeller arm folding jacks through (F2, F3, F7) driveshafts, which are built inside the left/right walls of cargo bay.

Propeller arms folding mechanism (animated)
Figure 37: Propeller arms folding mechanism (animated)
See open model in LDD
See closed model in LDD

4.3 Propeller tilting mechanism

Propeller arms tilting mechanism
Figure 38: Propeller arms tilting mechanism
See model in LDD

45° forward tiltable propellers facilitate higher speed level flight of MTT than vertical propeller quadcopters, as the sizeable airframe/hull can stay leveled. This reduces drag and results in better gun platform in flight. TLG servo motors are too bulky to integrate them into propeller arms, therefore we used a nasty trick: 4 arms are tilted by 4 (T3) integrated LPF L-Motors, and (T5, T6) stops placed on stator/tilting part of arm ensure that it can rotate only from 0°..+45°. 4 tilting motors are attached to propeller arm folding jacks with 4×2 explosive bolts (modeled as non-working feature from ‘Technic axle M3 with stop’). This enables MTT to jettison propeller arms in emergency e.g. at ditching into water.

Propeller arms tilting mechanism (animated)
Figure 39: Propeller arms tilting mechanism (animated)
See model in LDD

4.4 Land/Sea drivetrain

Amphibious tracked cargo platform
Figure 40: Amphibious tracked cargo platform
See model in LDD

Although wheeled chassis can be built more light, simple and cheap, than tracked, large steerable wheels necessary for reasonable offroad performance eat up huge space. Therefore we opted for a very lightly built tracked platform, which has Z8 + worm drive of left/right (D6) rear driving sprockets and Z20/Z12 drive of (D5) detachable screws by (D2) 2 LPF2 M-motors controlled by (D1) LPF2 SmartHub 5.

Land/Sea drivetrain
Figure 41: Land/Sea drivetrain
See model in LDD

As we wanted minimal interruption of watertight lower hull, we discarded the traditional torsion bar + Z-arm suspension. There are left/right (S4) retractable spring struts made from 2 steel springs from ‘Shock absorber’, placed between double row of (S5) Z16 track rollers and twin narrow tracks made from ‘Motorcycle chain’. They are controlled by (S3) Z8 + worm gear combos placed on (S2) suspension height regulator shafts.

Variable height suspension
Figure 42: Variable height suspension
See model in LDD

(S9) idler wheels are pressed by (S8) track tension regulator springs controlled by (S6) track tension regulator knob via (S7) Z8 + worm gear combo, to compensate changing of track tension because of variable height suspension. This enables the vehicle to change its freeboard from 0 studs to 3 studs continuously and „sit down” during airlift to fit in cargo space of dropship.

Variable height suspension (animated)
Figure 43: Variable height suspension (animated)
See model in LDD

4.5 Cargo systems

Cargo systems overview
Figure 44: Cargo systems overview
See model in LDD

(R2) LPF2 M-Motor drives (R3) winch cable spool at 1:1, and it has de-clutchable drive of (R6) rear cargo ramp via Z8 + worm gear combo. Clutching of ramp is controlled by ‘Technic axle 4M with stop’ at the rear of vehicle. Winch cable can be lead through (R9, R10, R12, R13) several pulleys forward (to winch MTT stuck)/ backward (to winch other vehicle into cargo deck)/ downward (airlift through (R11) watertight lower hatch). Rear cargo ramp has (R7) extendable end to reach ground level even at fully extended track suspension). There are left/right (R16) cable locks of external airlift cables by dropship, which can be handled from cockpit.

Rear cargo ramp (animated)
Figure 45: Rear cargo ramp (animated)
See model in LDD

4.6 Navigation systems

Navigation systems overview
Figure 46: Navigation systems overview
See model in LDD

Besides duplex (N3, N4) flight computers used in drone mode, there are (N6, N7, N8, N9) flight instruments for manual control grouped in the detachable windscreen module. As vision from MTT’s cockpit is inferior, it is equipped with “glass cockpit” system, consisting of several (N15, N16, N18, N28) positionable cameras and (N17, N27) searchlights. There are (N10) retractable pitot tubes for level flight and (N25) retractable VHF aerials for land mode.

4.7 Crew and Accrual systems

Crew and Accrual systems
Figure 47: Crew and Accrual systems
See model in LDD

In human troop transport mode, 3 crew members, 2 Personal Defense Weapons, 6 spare shells for recoilless gun are squeezed on cargo deck. (H1) Bionicle/Technic pilots with 5-finger palms have (H3) helmet displays connected to „glass cockpit” camera system.

Crew and Accrual systems
Figure 48: Cockpit view
See model in LDD

4.8 Armament

Armament overview
Figure 49: Armament overview
See model in LDD

4.8.1 Retractable gun turret

Retractable gun turret overview
Figure 50: Retractable gun turret overview
See model in LDD

MTT has (W60) 180 degree flippable panel in its cabin roof with a roof hatch door just before that. This allows the manual controlled machine gun turret with recoilless gun and coaxial portable machine gun to be retracted into cargo hold.

Turret opening sequence
Figure 51: Turret opening sequence
See model in LDD

Azimuth control of turret is made by (W62) Z8 gear connected to (W63) turret turntable made from ‘Turntable 7M’. Elevation control is made by (W67, W68, W69) worm+Z8 gear combo, driven by an axis located centrally on turntable. Upper part of the turret can be lifted 1 stud on 2 slides, allowing much higher (+37°) maximal elevation of turret-mounted weapons.

Retractable gun turret (animation)
Figure 52: Retractable gun turret (animation)
See model in LDD

In retracted position, weapons are on the left/right side of navigator’s head. Turret can be opened also when the vehicle hangs on cargo winch cable of dropship.

MTT folded cutaway view showing retracted gun turret
Figure 53: MTT folded cutaway view showing retracted gun turret
See model in LDD

4.8.2 100mm recoilless gun
As MTT has only very light armor, providing some degree of splinter protection, it is no match for any Armored Fighting Vehicle (AFV). Therefore it needs some light Anti-Armor support. Recoilless guns mean cheap and compact solution: their breach have several small rocket nozzles and perforated propellant cases, letting some part of propellant gases backward. The generated thrust neutralizes recoil force of shooting an otherwise conventional grenade. This way, heavy trunnion and recoil dumper can be omitted, and barrel can be more thin-walled. The price is that range is reduced to 40% of normal projectile.

MTT Recoilless gun
Figure 54: MTT Recoilless gun
See model in LDD

In TLG parts we have nothing even close to thin-walled long barrels, probably due to children safety, to prevent building any serious shooting weapons. We circumvented the problem pulling series of ‘Life belt’ parts onto 24 studs long ‘Outer cable’, whose tension provides some degree of structural stiffness for the resulting barrel with 10mm inner bore.

MTT Recoilless gun (animated)
Figure 55: MTT Recoilless gun (animated)
See model in LDD

We designed (W36) swinging breech with 4 nozzles inside. 8mm (in real size 80mm) grenades consists of (W32) 8 propellant springs pulled on (W34) flying spigot type bolt made from ‘Standard 53mm’. (W33) trigger of loaded propellant is hit by (W39) trigger lever of gun barrel to break it off and release propellant springs for shooting.

4.8.3 LM-7B portable light machinegun

In retracted position, turret-mounted light machinegun has to fit into 3×4×16 stud space. To make it spring driven shooting and auto-loaded in such a compact layout, it requires some not fully TLG-conform solutions: (W15) Propellant springs are from disassembling TLG part ‘Shock absorber’ (as LDD cannot draw steel springs, we denote them with ‘Corrugated pipe 2 studs’, which has similar size and shape). Projectiles are non-TLG parts as Lego does not produce reasonably small parts due children safety reasons, moreover ABS material is not enough heavy to be efficient projectile. Therefore 1.5×5mm projectiles are made from copper electric wiring can be found in any hardware store. Mass of the projectile is so small that it can fly stabile flight path even without spin stabilization because of the density and drag of air. Drum magazines are not very popular in modern automatic weapons (although they were used extensively between WWI and WWII), but building from Lego Technic, they provide much more compact and easily moveable ammo feed than box magazines or belt feed. Z-16 gear from TLG ‘Gear shift’ rounded by ‘Tire 24×7mm’ can hold 16 rounds. (LDD cannot draw the tire pulled on Z-16 gear, so we mock it with the red rubber ring as placeholder).

Firing cycle of LM7B light machinegun
Figure 56: Firing cycle of LM7B light machinegun
See model in LDD

The weapon is equipped with optical sight, tripod adapter and Cradle Grenade Launcher (CGL) shooting 8×53mm flying spigot type grenade with the help of 2 propellant springs.

LM7B Light machinegun animated
Figure 57: LM7B Light machinegun animated
See model in LDD

4.8.4 Twin 160mm RPG quad launchers

Firing cycle of RPG launcher
Figure 58: Firing cycle of RPG launcher
See model in LDD

The main difficulty creating any decent looking RPG launchers from Lego is the complete lack of thin long barrels with 1 stud inner diameter (probably due to children safety reasons). Any of such a barrel solution from TLG parts will result in nearly 3 stud outer diameter, which would look terrible. Therefore we invented pseudo-tube launcher. 16×112mm RPG projectile is placed among 4 parallel ‘Technic cross axles 12M’ spaced 1 stud vertical/horizontal gaping as quadruple launch rails. This will result in reasonably sized launcher. Technically, real RPG launchers could be built this way also, but hot propellant gases would roast personnel to death. To create simple and compact launcher, our RPG has flying spigot type bolt: it flies out together with the projectile, leaving propellant springs behind.

RPG launcher (animated)
Figure 59: RPG launcher (animated)
See model in LDD

4.8.5 Personal Defense Weapons

Firing cycle of Personal Defense Weapon
Figure 60: Firing cycle of Personal Defense Weapon
See model in LDD

Although light machinegun in gun turret is portable, it takes a while to bring it into manual action e.g. in an ambush situation, where it cannot shoot immediate surroundings of MTT. So it was necessary to deploy compact Personal Defense Weapons (PDW) for crew. The problem is that the only empty space left for them in cockpit at the legs of crew is only 8 studs long across the cargo bay width. Lack of space required unconventional weapon layout: (W53) rotating type bolt consists of a ‘Rapier’ connected to ‘Technic cross axle with stop 8 studs’. The bolt slides in fixed breech block, while (W52) drum magazine and (W54) 2 8×16mm propellant springs are pulled on bolt sequentially. Drum magazine is rotated during firing cycle by the friction of propellant springs placed on rotating bolt. (W57) ratchet ensures that magazine can rotate only counter-clockwise, and it is aligned with (W50) barrel correctly at shooting.

Personal Defense Weapon (animated)
Figure 61: Personal Defense Weapon (animated)
See model in LDD

5 Transported vehicles by Multiple Troop Transport

5.1 Trackboard personal tracked offroad vehicle

TrackBoard personal tracked offroad vehicle overview
Figure 62: TrackBoard personal tracked offroad vehicle overview
See model in LDD

We got the idea to build this compact vehicle from Electric military dirt bikes, which became more frequently used in recent years as the effect of advanced LiPo battery technology. They can handle extremely rough terrain and narrow gauge forest trails, moreover carry weapons, ammunition, supplies besides the rider. They are also fairly silent to serve Special Forces in surprise attack/ ambush situations. But, they have one serious disadvantage: riding bike on rough terrain requires most of the time 2 hands, so it is impossible to make aimed shoot from a moving bike, leaving its rider defenseless.

TrackBoard personal tracked offroad vehicle functions overview
Figure 63: TrackBoard personal tracked offroad vehicle functions overview
See model in LDD

Civilian recreation vehicles Flux Design Track 1 and Scarpar Electric Skateboard gave us the inspiration to solve this problem using a small tracked vehicle, which can be ridden and controlled like a snowboard, leaving hands free for handling submachine gun or Personal Defense Weapon when moving.
TrackBoard personal tracked offroad vehicle cutaway view
Figure 64: TrackBoard personal tracked offroad vehicle cutaway view
See model in LDD

Squeezing steerable electric driven tracks in 4×4.5 studs (in real size: 32×36cm /1’×1’1.5”) narrow gauge requires special layout. Tandem placed (D2) 2 LPF2 M-motors drive forward/rear axles respectively via (D3) ‘Z12 half beveled gear’ sets at gearing ratio 1:1. (D4) driving sprockets made from ‘Z24 gear’ are placed on axles echeloned, driving 1 stud wide tracks made from ‘Motorcycle chain’. Echelon placed idler wheels are made from (D5) ‘Z24 Technic coupling gears’. They are disassembled and their steel plates are bent a little bit to make the coupling weaker than TLG factory setting. (This is not destruction of the brick, just an adjustment). This way, motors can easily drive tracks separately at steering (even allowing to make turn on spot with considerable friction). But there is a soft mechanical synchronization between left/right tracks, improving directional stability of the vehicle, which is by default inferior because of narrowly placed tracks. At the top side of the vehicle, there are 2 (C1) moveable steering/accelerator/brake pedals as non-working feature. 2-channel RC control is made by (D1) LPF2 SmartHub, placed as the backpack of the rider, fixed with harness made from ‘Motorcycle chain’. In case accident, electric cables get detached from backpack, preventing the vehicle run away from rider. Besides backpack, the rider is equipped with the usual Special Forces equipment:
- 1 SM-14 spring driven shooting submachine gun, auto-loaded from drum magazine for 16 1.5×5mm projectiles made from ‘Z16 running gear’ and ‘Tire 24×7mm’, equipped with 24mm optical sight and gun lamp,
- 2 spare drum magazines,
- 1 PDW-2 spring driven shooting Personal Defense Weapon, auto-loaded from drum magazine for 16 1.5×5mm projectiles made from ‘Z16 running gear’ and ‘Tire 24×7mm’, equipped with 24mm optical sight and gun lamp,
- 1 fragmentation hand grenade,
- 1 HE hand grenade,
- 1 combat knife,
- UHF field radio set on harness,
- Helmet with IR camera, display, microphone, headlamp,
- Canned food and drink on harness.
2 crew members with 2 Trackboard can be squeezed on cargo deck of MTT.

TrackBoard personal tracked offroad vehicle loaded into MTT
Figure 65: TrackBoard personal tracked offroad vehicle loaded into MTT
See model in LDD

5.2 Battle Droid/ Explosive Ordnance Disposal Robot

Mechas, Terminator, Trade Federation Battle Droids and all kinds of humanoid battle robots are typical products of “Hollywood science”. In the reality, human-like body is not really optimized for warfare with rapid shooting weapons:
- When moving fast (running), it shows large ballistic silhouette, and cannot make well-aimed shots with high recoil weapons, as it is supported by ground only in 1 point (or 0).
- When showing small ballistic silhouette (sneaking), it cannot move fast, and firing angles are limited (cannot shoot upward, backward).
That’s how trench warfare was born in WWI, resulting several millions of casualties in stalemates.
Therefore our battle robot design is inspired by real prototypes. Talon Robots Maars was taken to Iraq in 2006 for limited field trials:


Figure 66: Talon Robots MAARS

Remotec Andros was the first Explosive Ordnance Disposal (EOD) robot, which was used to kill a heavily armed criminal with 1 pound of C4 charge in
Dallas policemen shooting at July 8, 2016:


Figure 67: Remotec ANDROS

We merged their most important common features together and developed further in our design:
- Compact tracked running gear providing all-terrain capacity with air transportability
- Rotating gun turret for wide firing angles
- Man-portable weapons to aid infantry in emergency
- Foldability to provide small ballistic silhouette and passing through small gaps even in high speed mode
- Carry multiple weapon systems, allowing proportional response on threats
- Foldable robotic arms for EOD activity
- Ability to carry human rider in emergency

MTT unloads battle droids on battlefield
Figure 68: MTT unloads battle droids on battlefield
See model in LDD

We developed tracked chassis airliftable by MTT in 8×6×20 studs size, driven by 2 LPF2 M-Motors via RC of 1 LPF2 SmartHub. It also contains manual rescue winch driven by Z8 + worm gear combo, azimuth gear of gun turret (another Z8 + worm gear), and foldable driver’s seat.

Battle Droid functions overview
Figure 69: Battle Droid functions overview
See model in LDD

Base plate of gun turret serves EOD activity: it has 2 foldable robotic arms, searchlights, downward looking/panoramic cameras modeled as non-working features.

Battle Droid cutaway view
Figure 70: Battle Droid cutaway view
See model in LDD

Upper part of gun turret is liftable 4 studs with the help of parallelogram planar linkage and mini linear actuator made from worm gear + technic bush combo. This allows wider elevation angles, and enables to quick pop up weapons from cover, fire, and pull back. Elevation gear is solved with Z8 + worm combo. At the top of it, there is a foldable top camera/searchlight mount, combined with a rangefinder. Carried weapons are:
- 1 LM-7C spring driven shooting man-portable light machine gun, auto-loaded from drum magazine for 16 1.5×5mm projectiles made from ‘Z16 running gear’ and ‘Tire 24×7mm’, equipped with 24mm optical sight, gun lamp, and 5 8×53mm spring driven shooting cradle grenades with flying spigot type bolt,
- 1 spare drum magazine,
- 1 spring driven shooting man-portable RPG launcher with 16×104mm RPG.
- 1 rapid firing grenade launcher with barrel made from ‘Life belts’ pulled on ‘Outer cable 160mm’, fed from box magazine made from ‘Technic beam with studs 6M’, containing 5 8×53mm grenades with flying spigot type bolt.

2 Battle Droids tandem loaded into MTT
Figure 71: 2 Battle Droids tandem loaded into MTT
See model in LDD

Battle droids can be rolled onto cargo deck of MTT in tandem through rear cargo ramp (windscreen panel removed in this configuration). Alternatively, MTT can transport 1 human crew, 1 battle droid and 1 pallet of box magazines for grenade launcher.

3 Plane view of Battle Droid
Figure 72: 3 Plane view of Battle Droid
See folded model in LDD
See opened model in LDD
See high elevation model in LDD
See low elevation model in LDD

5.3 Foldable Bucket Machine

Unloading Foldable Bucket Machine from MTT
Figure 73: Unloading Foldable Bucket Machine from MTT
See model in LDD

The compact airliftable tracked chassis can be used for various roles with small modifications. We created folding bucket machine making the track drive of chassis de-clutchable: Z8 gears of driving sprockets can be pulled aside from worm gears of LPF2 M-Motors. There are 2 clutchable actuator levers of bucket arm also solved with slideable Z8 gears. So LPF2 M-Motors can drive the bucket arm through a linkage, instead of driving the tracks. Actuation of the bucket is manual, with the help of a linear actuator.

Foldable Bucket Machine functions overview
Figure 74: Foldable Bucket Machine functions overview
See model in LDD

The bucket arm linkage has special geometry, allowing to be folded it backward with some manual help (marked with red on functional overview figure).

Foldable Bucket Machine cutaway view
Figure 75: Foldable Bucket Machine cutaway view
See model in LDD

The foldable driver’s seat is set higher than at battle robot, resulting in better overall vision, as small ballistic silhouette is not an issue here.

Foldable Bucket Machine loaded into MTT
Figure 76: Foldable Bucket Machine loaded into MTT
See model in LDD

Folded bucket machine can be rolled onto cargo deck of MTT through rear ramp together with 1 human crew and 1 PDW. At the front of airliftable tracked chassis, there is a lock fixing it to the cargo deck floor, preventing its movement during airlift.

3 Plane View of Foldable Bucket Machine
Figure 77: 3 Plane View of Foldable Bucket Machine
See lowered bucket model in LDD
See medium positioned bucket model in LDD
See folded bucket model in LDD


Building instructions
Download building instructions (LEGO Digital Designer)

Comments

 I made it 
  May 21, 2018
Quoting Oliver Becker Hats off, Gabor! There's no one who puts so much effort in showing detailed construction and function in his MOCs like you do! Your enthusiasm for technical stuff is smiling out of every pore here... One little remark: in Figure 27 it has to be called: heads off... ;)
Thanks. About floating on water surface with slow running propellers: the guy in the jet-ski is not neccessarily decapitated, as opened rear cargo ramp is between rear propellers. But it is risky. The problem is that the whole craft is downsized very strongly to fit in the large dropship. I considered this feature for an upsized version, and REALLY calm conditions. I am already working on a huge dropship (you will see some details very soon), which can accomodate normal sized version of MTT.
 I made it 
  May 21, 2018
Quoting Justin Li Ok wow...the amount of detail and complexity here is just crazy.
Thanks.
 I like it 
  May 21, 2018
Hats off, Gabor! There's no one who puts so much effort in showing detailed construction and function in his MOCs like you do! Your enthusiasm for technical stuff is smiling out of every pore here... One little remark: in Figure 27 it has to be called: heads off... ;)
 I like it 
  May 21, 2018
Ok wow...the amount of detail and complexity here is just crazy.
 I made it 
  May 17, 2018
Quoting Doug Hughes As usual, this is totally nuts and amazing! Such technical details and really fantastic designs and drawings to go along with it!
Thanks.
 I like it 
  May 17, 2018
As usual, this is totally nuts and amazing! Such technical details and really fantastic designs and drawings to go along with it!
 I made it 
  May 17, 2018
Quoting BATOH rossi as always I can not even comment ... simply great!
Thanks.
 I like it 
  May 17, 2018
as always I can not even comment ... simply great!
 I made it 
  May 17, 2018
Quoting Nick Barrett Wow. So many brilliant systems in one machine, and you seem to have it all beautifully integrated. Amazing work.
Thanks.
 I like it 
  May 17, 2018
Wow. So many brilliant systems in one machine, and you seem to have it all beautifully integrated. Amazing work.
 I made it 
  May 16, 2018
Quoting Jesse Horn You are a total Genius
Thanks. If I were a genius, I could build it for real. I'm just a dreamer, trying to play somewhat realistic dreams.
 I made it 
  May 16, 2018
Quoting Digital Dreams One day there is going to be a class action lawsuit against you for all the minds you have blown.
Unfortunately, number of the people who have mind worth to blow is rapidly decreasing. Trump, Putin, Brexit, Erdogan are now the symptoms of it. Later they will become reasons of it.
 I like it 
  May 16, 2018
One day there is going to be a class action lawsuit against you for all the minds you have blown.
 I made it 
  May 16, 2018
Quoting P. Andrei The thinking that went into this is insane. Last thing I was expecting to see was a giant transport helicopter to go with it.
Thanks.
Gabor Pauler
 I like it 
Keith Goldman
  May 15, 2018
That is a stunning amount of work and it’s almost overwhelming in one post like this. I don’t know where to start...just awesome.
 I like it 
  May 15, 2018
You are a total Genius
 I like it 
  May 15, 2018
The thinking that went into this is insane. Last thing I was expecting to see was a giant transport helicopter to go with it.
 I made it 
  May 15, 2018
Quoting Pico van Grootveld Jaw dropped. This is like a whole essay man! Wow is an understatement!!
Thanks.
 I made it 
  May 15, 2018
Quoting Master Shifu Leo J Comprehensive is an understatement.
Thanks.
 I made it 
  May 15, 2018
Quoting Keith Goldman That is a stunning amount of work and it’s almost overwhelming in one post like this. I don’t know where to start...just awesome.
Thanks.
 I made it 
  May 15, 2018
Quoting Michiel Norp Lego Skunk works in action, and rescuing a nice girl.
Thanks. Well, my girl figures are really in interanational photo model tallnes range, therefore cockpit of MTT looks very confined. With an average tallnes of woman it is not so critical.
 I made it 
  May 15, 2018
Quoting Seaman SPb Fantastic work!
Thanks.
 I like it 
  May 15, 2018
Jaw dropped. This is like a whole essay man! Wow is an understatement!!
 I like it 
  May 15, 2018
Comprehensive is an understatement.
 I like it 
  May 15, 2018
Lego Skunk works in action, and rescuing a nice girl.
 I like it 
  May 15, 2018
Fantastic work!
 
By Gabor Pauler
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