Truck 6x4 with Rolloader Crane (2012 - 2013)


Building instructions (PDF)
(775 pages)
Example instructions (PDF)
Parts Inventory:
(4.475 parts)

Credit card and Paypal


See PDF for Bricklink XML upload procedure

Remote Controlled: Power Functions

Trailers with a rolloader crane are mostly used to transport pallets with stones. The interesting parts of these trailers are the (steered) twin-wheels and the rolloader crane, able to ride on the trailer platform to pick the right pallet for unloading. The trucks pulling these trailers are common 6x4 driven trucks, nothing special.

A rolloader crane trailer was already a couple of years on my mind; however the main requirement for the trailer was one or more steered rear wheels which I never got to work properly. In real life rear steering of a trailer is accomplished by 1) a cable connection between the kingpin and the rear wheel, 2) a bar connection between a modified kingpin and the rear wheel, or 3) by hydraulics and an electronic unit that measures the steering degree of the truck. All methods are not suited for applying in LEGO®, mainly due to the fact that LEGO® is not stiff enough. There is always some clearance, resulting in the inability to have the steered rear wheel in 'auto-center' position after passing curves.

However, with the launch of the Power Functions Servo motor I could overcome the 'auto-center' position challenge, which I will explain later.

Other requirements: ability to load/unload pallets with DUPLO® bricks and an unique 'orange/lime' color scheme of both the truck and trailer whereof I got inspired by the truck fleet of a Dutch 'special and heavy transport' company named 'Van der Vlist Group' (see middle picture underneath). About this color scheme, I guess it is a personal thing that you will really like or strongly dislike! In my honest opinion, it gives the truck just that little bit 'muscle and power' or race-truck lookalike.

The truck is remote controlled, which was just a 'copy/paste/modify' exercise of the Truck 8x4 of the Lowloader designed in 2010.

It took about 12 months to design and is the largest MOC I ever designed (4.475 parts). The long development time is because I had to wait for the new Power Functions Servo motor to be available on Bricklink and to figure out how the rear trailer wheel steering could work reliable, even when fully loaded with pallets. As well, some orange parts are scarce and therefore not easy to get against a reasonable price in the quantity I needed (1x5/1x9/1x11 beams, 5x11 panels, angle connector #2, etc).

I hope you like the result.

Remark: The truck has no 'evil plans' or intensions of 'criminal activities' like the 'Squidman' character in the LEGO® Space Police theme. J


The dimensions of the total combination (Truck and Trailer with Crane):
* Length: 88 cm
* Height: 25 cm
* Width: 14,5 cm
* Weight: 4,7 kg (including batteries & pallets)

* Cargo lenght: 12 pallets
* Cargo height: pallets with 2˝ DUPLO® bricks
* Cargo weight: 1,0 kg (tested)

* Total number of parts: 4.475
  - Truck 6x4 = 1.877
  - Trailer = 1.798
  - Rolloader crane = 482
  - Clamp, grabber, duplo pallets = 318


Photo-shoot (The Netherlands):
* Delivering pallets in the 'Noord-oost Polder' agriculture district



Other colors ?!
Examples of the Stone Trailer Truck with 'less fancy' colors... see more at the end of this page.












Truck 6x4 (Remote or manual controlled)
The truck 8x4 (see elsewhere on this site) was the basis for the design process of this truck 6x4, which means that most of the functionalities are the same. The only minor challenge was to relocated the PF M-motor to the side due to the shorter chassis base. I did consider to swap the PF M-motor for a PF Servo motor, but it was not possible to have the PF Servo motor directly connected to the front wheels gear rack. E.g., a couple of gears need to be applied that will cause - even with a PF Servo motor - a slightly misaligned auto-center function. So, I trust one have the right 'finger-spitzen' feeling to control the PF M-motor. J

The technic functions are: single axle steering, working V8 engine, differentials on both rear axles, PF head-lights and PF XL-motor for driving / PF M-motor for steering. Cosmetic changes applied (compared to the dump truck 10x4 and truck 8x4 lowloader) are adding a 4 spot light unit on the roof instead of 3 lights, reconstruct the bumper unit with a bull-bar and foglights, and adding the 'green squidman aliens' on the sunscreen!












Drive train: The same PF XL-motor drive train used as in the Truck 8x4 lowloader which proofed to be reliable in driving a trailer with heavy cargo. The force of the PF XL-motor is geared down in a two stages to the both differentials which drives the 4 rear twin wheels. The whole drive train is equipped with twin gears on each axle to apply the force from gear-axle to gear-axle. These twin gears are used to prevent damage to the gear tooth.
As remote control unit, my strong recommendation is to use only the 8879 'IR speed remote control' unit due to it's ability to control the speed of the PF XL-motor in multiple steps. Just applying 'full speed' on the PF XL-motor in a 'stand-still' position of the total combination will result in too much stress on the whole drive train (as is done with the 8885 'IR remote control', that lacks the speed control).

5th wheel: Simple construction made of technic triangles whereof the trailer's kingpin axle locks in. But, important to have the ability to fit a technic turntable - connected at the trailer - in such a matter that the steering position of the truck in relation with the trailer position can be 'measured'. See more details at the trailer section.












The technic specifications of the 'Truck 6x4':
* 3 axle truck, single steered
* Remote controlled, ability to switch to manual operation
* Working V8 engine, including fan
* differential unit on 2nd and 3rd axle, interconnected
* Headlights equipped with Power Functions LED's

Non-technic functions are:
* Cabin doors open & close
* Cabin can be opened for engine access
* Raise-able wind deflector
* Open/close of panels covering fuel tank and air filter unit
* Towbar

Details applied:
* Green squidman aliens on the sun-screen
* Dashboard with coffee machine and coffee cups (standard feature)
* Fuel tank and air filter unit covered with panels
* Additional fuel tanks and air filters on top of chassis
* air compressors between rear wheels
* Fire extinguisher, exhaust pipe
* 4 Spotlights, flashlights, horns and airco-unit on cabin roof
* Bull bar


The dimensions of the 'Truck 6x4' are:
* Length: 41 cm
* Width: 14,5 cm
* Height: 21 cm
* Weight: 2,0 kg (including batteries)

* Number of parts: Unknown












Switch to manual operation (and vice-versa):
The truck can be operated with a remote control unit or manually. The reasons for applying this feature is to make this model attractive to a broad audience. Especially young kids like to push the truck around, whereof older kids (and AFOL's) like the remote control.












Switch driving mode:
At the left picture, the truck is set to manual operation (both gears shift aside). For remote controlled operation, shift both 16 tooth gears to the middle.

Switch steering mode:
At the right picture, the truck is set to manual operation. Shift the 8-tooth gear to the right to couple the motor to the steering-train.


The truck is equipped with a tow-bar. This means that - for example - the drawbar trailer can be connected.



The trailer took much more time to design, especially the rear wheel steering mechanism. The trailer's chassis itself was a straight forward build and relative easy. A small challenge - but not difficult - was how to connect the hinges of the swing panels (both sides 6) in such a way that the rolloader crane is still able to ride on the platform when the panels are swinged down.

A worm gear design is used for the parking stand being able to lift a loaded trailer of the truck's 5th wheel. And, after decoration as cupboard's, airtanks, rear side with 'alien squidman', there was even space left to add a spare wheel winch mechanism just before the front twin wheels. The spare wheel can be reeled by turning the little light bluish gray bush/axle just at the right side of the cupboards (see picture below).

The color scheme was not that easy. First I started with the light bluish gray panels of the #8110 Unimog (12 in there!) because these panels are commonly used on real life stone trailers.... but it did not match nicely with the orange/lime truck. So, I decided to apply the color scheme of the truck even on the trailer... which is of course unusual but a relieve compared to the traditional yellow/black, gray/black or red/black colors Lego® uses.

So how does the rear steering works? A technic turntable (with inner axle) is used as kingpin to couple on the truck's 5th wheel. The turntable is locked on the truck in such a way that it's gear 'measures' the position of the truck irw the trailer. The turntable's gear position is passed via chains to a 2nd technic turntable in the inner middle of the trailer. That turntable passes (with a fixed inner axle) the position to an PF Rechargable Battery Box's motor speed control. The motor speed control dial can turn 90 degrees in both directions in 7 steps and therefore precisely being able to control the PF Servo Motor in the same way. The PF Servo Motor drives a traditional double 1x4 gear rack, passing it's output to a technic turntable whereof the rear twin wheels are mounted.

Remark: I tried a 3rd steered rear twin wheel but the PF Servo Motor was not powerfull to operate a double steered twin-wheel setup.













The technic specifications of the 'Trailer' are:
* 2 axle assembly, all with twin-wheels
* Rear axle steered, controlled by a PF Rechargeable Battery Box motor
  speed control dial icw the PF Servo motor
* Trailer stand mechanism
* Spare wheel lifting winch

Non-technic functions are:
* all panels swing for unloading pallets
* Cupboard stowing units at both sides

Details applied:
* Green squidman alien at the rear side
* air compressors on rear wheel steering unit





The dimensions of the 'Trailer' are:
* Length: 65 cm
* Height: 25 cm (incl. crane)
* Width: 14,5 cm
* Weight: 2,4 kg (incl. PF rechargable battery)

* Cargo lenght: 12 pallets
* Cargo height: pallets with 2˝ DUPLO® bricks stacked
* Cargo weight: 1,0 kg

* Number of parts: Unknown






Rolloader Crane
The crane is able to ride on the trailer forwards until the first 2 panels. Both sides of the crane chassis do have 2 wheels with arms that lock under the trailer bed to prevent skipping off the trailer when pallets are loaded/unloaded. The crane itself consists of 2 boom's powered by PF Linear Actuators that are operated with levers on the fixed boom of the chassis. The 2nd boom section is able to extract ~ 7 studs. As such the crane has a reach to unload pallets 22 cm away from the trailer's side. Details applied are chairs to reach the operator's seat, and a fuel tank.

Compromise: According to the scale of the truck & trailer, the rolloader crane is actually 3 studs 'too high'. Translation to original sizes it means that the top of the crane in folding position is ~ 4,35 meters, whereof in The Netherlands the governmental regulation is max 4,00 meters.
In the first designs I used the mini Linear Actuator to comply to the scale, but in no way the mini LA's could handle the load of pallets with DUPLO® bricks. So, I had to make a compromise, playability and functionality in favor of sticking to the scale.












Clamp or grabber. The crane can be equipped with a clamp or grabber that are easy to change.

The clamp legs are operated manually by a mini Linear Actuator. The legs lock into the pallets on both sides of the pallets (e.g. the forklift side and the 1x8 technic brick side). The clamp has a mini technic turntable being able to rotate the pallet.
The grabber is just a copy of the Technic LEGO® #42006 excavator set and modified to operate manually.













The technic specifications of the 'Rolloader Crane' are:
* 1st and 2nd boom power by PF Linear Actuator
* 2nd boom extension ~7 studs
* Ability to unload pallets 22 cm away of the trailer's side

Non-technic functions are:
* Ride on the trailer until first 2 swing panels
* Slewing angle: 360 degrees with no limits

Details applied:
* Stairs to reach operators seat
* Fuel tank
* Flash lights

Number of parts: Unknown



Big 'THANK YOU' to Steve for checking the BI's (yes, faults were in there) and providing the constructive feedback out of the USA!