Model of a Scania R500 truck modified as a racing version. Features full suspension, powerful propulsion system with two independently powered RC motors, lights, custom stickers, cabin with full interior and opened doors.

Datasheet:

Completion date: 05/07/2010
Power: electric (Power Functions)
Dimensions: length 48 studs / width 18 studs (not including the side mirrors) / height 27 studs
Weight: 1.86 kg
Suspension: front – independent / rear – dragged axle
Propulsion: 2 x RC buggy motors powered from separate batteries through separate IR receivers, geared down 1.66:1
Top speed: 7.92 kmph
Motors: 2 x RC, 1 x PF Medium

I’m really fond of modern Scania trucks. I have built a model of a Scania dumper truck in 2009, which – while being technically simple – has gathered a significant acclaim because of the quality of its aesthetics and because of the number of details incorporated. I was not fully happy with it, however, because I found the cabin’s look inaccurate and simplified. This was the primary reason why I started to toy with an idea of building a much more accurate Scania model in a racing truck version. Right from the very beginning I wanted it to be red with some chrome and metallic silver elements, which is why I was not convinced of realizing this model, as it had to be expensive to build. Over the time, however, I have gathered a number of chrome and metallic silver elements, and I have determined that it would take less red parts that I initially thought, as Scanias usually have their lower part of the cabin plain black.

Building this model became eventually achievable when I designed the complete exterior of its cabin using the MLCad software and when I bought four metallic silver wheels (to go along with the two I already had). With MLCad model serving as a very accurate shipping list, it became only a matter of time before the red racing Scania would be built.

I have built a number of racing trucks before, which provided a significant building experience. Based on it, I didn’t want to focus just on the aesthetic side of the model – I wanted it to perform well too. The key to surpass the performance of any of my earlier racing truck was the use of RC buggy motors for propulsion, as they offer somewhat more mechanical power than PF XL motors do, and they are also more suitable for fast vehicles, with less gearing or no gearing whatsoever needed. To use two RC motors at the same time while keeping the model’s weight reasonable I had to use the 8878 battery as a power supply. Since it was downright impossible to power two RC motors to a single battery because of their extremely high power consumption, I had to no other choice but to get a second 8878 battery. Thus, the model needed some serious investments before I even started to build it.

The model’s chassis was initially built with both RC motors using no gearing whatsoever – both motors were simply connected directly to the rear axle. Thanks to their convenient shape, it was possible to use them as the main bearing structure for the whole rear suspension which dramatically increased the internal space available inside the chassis. Thanks to it, chassis housed not only two 8878 batteries and two IR receivers, but also PF Medium motor for the steering, with all these elements located between the front and rear axle.  The use of two IR receivers was necessary – since the drive motors were independently powered, they couldn’t be connected electrically and the only connection between them was rigid rear axle. With the initial rear axle set-up it was possible to use a differential between the motors but I dropped this idea for two reasons: firstly, a rigid axle was more efficient (no elements prone to slipping) and much less prone to a mechanical failure, and secondly the rear wheels had only limited traction while turning, since majority of the model’s weight was located above the front axle.

The independent front suspension was based strictly on my previous experiences with the models of racing trucks and used a blend of suspension components from the Lego sets 8448 and 8297. To handle the weight of the cabin, the front suspension was made very stiff, with two hardest shock absorbers set almost vertically above each front wheel. I have also used thin wedge belt wheels between the actual wheels and the chassis to prevent the expensive metallic silver wheels from rubbing away against the chassis – as it already occurred earlier, with slower and lighter racing truck models. The steering system had to be adjusted to the speed and the weight of the model, which is why it used a relatively insignificant gear reduction and no safety clutch whatsoever.

As for the aesthetic side, I came to think that the main disadvantage of my Scania dumper model was the fact that its distinctive front grill was completely flat, with air intakes simply marked with bricks of a different colour. Therefore I have put a lot of effort into inventing a system of recessed air intakes, which was eventually achieved with the use of 2×2 tiles. With plenty of internal space available in the cabin, this system could be used with a relative ease, providing an excellent aesthetic effect, as anticipated. Other than that, the cabin houses not only its own interior, but also a PF switch which controls all the lights (the lights are coupled with the drive motors and go brighter as the truck speeds up, so the switch is used primarily to turn this feature off when not needed, and thus to save energy which is so highly demanded by the RC motors). With 10 PF LEDs installed in the cabin, the switch takes a lot of space to contain 10 PF plugs with their respective wires. I was able to fit it in efficiently by mounting it on its side, so that the plugs are kept horizontally below where passenger’s seat would be located normally.

An important thing to know is that the real racing trucks are usually subjected to very radical visual modifications which make them look pretty much unlike any stock vehicle. Being a huge fan of the original Scania design, I wanted to avoid this. Therefore my approach was to use a stock Scania R500 as the model’s point of reference, with a few typically racing elements added so as to minimize their impact on the model’s look. Eventually, it ended up with five such elements: the four extra headlights (which are not really used for racing, but I viewed it as an opportunity to experiment with the PF LEDs a bit), the racing air intake on top of the roof, the engine moved back from under the cabin, the large spoiler instead of a fifth wheel, and a custom rear bumper. Additionally, the cabin’s interior has been arranged in a ‘racing’ fashion, with a mock-up of two blue N2O bottles replacing the passenger’s seat and with a distinctive safety net in the driver’s window. The net itself is not a Lego element – I made it as a sticker, by printing a black square with a dark grey grid on it, carefully cutting it to net-like shape with a modelling scalpel, and then painting its other side black with a felt-tip pen (I could also print the black square on both sides of the same sheet, but since large portion of it was meant to be cut out, it felt like a waste of ink). Eventually, the paper net was fixed to the door with a thin stripes of a Scotch tape on its edges.

The other, more traditional stickers, have also been intended to reflect the racing ‘nature’ of the model, with the most obvious example being a note in front of the driver’s window that says “Tävlingsfordon”, which is Swedish for “Racing vehicle” (all stickers use Swedish as a nod to Scania’s country of origin). The sticker above the windshield says “Sagodjur”, which can be translated as “Griffon” (the animal used as Scania’s brand mark) and which was intended to look like driver’s nickname, while both front and rear registration plates feature a miniature Scania’s griffon head and a number 5AR13L, which is an obvious reference to my own nickname.

As the model was getting close to its final weight, the propulsion system started to show signs of weakness. To solve this, I have moved the rear axle back a little while keeping the motors intact, and  added a 1.66:1 gear reduction between the motors and the axle, with gear wheels doubled to handle the significant torque. It has greatly improved the overall performance of the model by making it faster and decreasing its accelerating and braking times, but it also made the chassis seem a bit longish and it made the rear suspension very soft. The manoeuvrability of the model, on the other hand, was not noticeably affected by this change. I have ran a number of tests with Lego speedometer mounted on the truck and the top speed it recorded was 7.92 kmph. This is more than any of my earlier racing trucks could achieve, but I feel like it could be surpassed by this very model. The model clearly has plenty of power in the drivetrain and appears to best build up its speed in long runs. It led me to believe that it could break 8 kmph given a long section of a perfectly smooth floor (unlike the floor I had to run tests on). Anyway, 7.92 kmph is a fairly good result, as it requires model’s wheels to rotate at over 600 RPM (that is 10 rotations per second) and – given the model’s 1:17 scale – corresponds with the speed of 135 mph in the real life.

The truck was highly acclaimed for its aesthetics and performance, both emphasized by the video which took me 4 hours straight to produce. It was my second construction to use a slow motion footage (shot with Casio Exilim FS-10), and my first construction to be accompanied by 1200×800 px photos rather than usual 800×600 px, as I really liked the look of the model and the results of its photo-session.

The model will be kept intact at least until a public event that takes place on July 10th, giving my fellow LUGPol members the chance to see, and perhaps even to drive it.

Photos:

Work in progress photos:

Video:

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Media reference:

Legocn.net (Chinese only), Mancave (Dutch only), Town Truck Brick! (Spanish only)

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Small model of the iconic Peterbilt 359 truck, inspired by the HTC races organized by the DoubleBrick community. Features pendular rear suspension, openable bonnet, engine’s model and lights.

Datasheet:

Completion date: 14/01/2010
Power: electric (Power Functions)
Dimensions:  length 49 studs / width 13 studs / height 23 studs
Weight: 0.96 kg
Suspension: front: none / rear: pendular stabilized with rubber axle joiners
Motors: 1×71427, 2x PF Medium

This is a rare example of a construction inspired entirely by a competition specific for a given community. Namely, it was inspired by the Hard Truck Contest invented and successfully introduced by the DoubleBrick community. The exact description of the contest can be found via respective link, it suffices to say that the contest brings together small models of trucks (usually 14 studs wide), built with an accuracy and attention to details that make them a wonder to behold. I’ve spent some time watching the videos from the HTC races not to follow the course of the competition, but to simply enjoy the view of the beautiful models. I was hoping to get the builders from my country interested in similar races, and the best way to get their attention seemed to build a prototypical vehicle.

Having previously built model of the Kenworth W900, I have chosen another one of the most iconic American trucks, the legendary Peterbilt 359. When scaled accordingly to the size of the wheels used in HTC races, it turned out to be just 12 studs wide. The original HTC vehicles are 14 studs wide – I don’t know the reasons for which such a standard was accepted, perhaps it was simply more convenient or based on trucks with different wheels size, but I decided to take the challenge of building a 12 studs wide model. And it was quite a challenge – it was my goal to use identical wheels on all axles, which meant that I only had 6 studs of width available to make the front axle steered (original HTC trucks often use narrower front wheels).

As the idea of making the front axle suspended seemed mad, I focused on the rear axles’ suspension. Since the axles are based on the 5×7 open liftarm frames with differentials inside, it was natural to make them pendular. Concerned about the truck’s stability at high speeds, I have used rubber axle joiners as the suspension stabilizers – they were simply attached to the truck’s frame above the rear axles, and acted as shock absorbers whenever the suspension changed its angle. It should be noted that it’s an obvious solution to use some sort of a simple supporting structure between the frames of axle #2 and #3, but I wanted to model the original wheel span, and the model was simply too small to add an extra space for such a structure. It has slightly degraded its performance – the driveshaft connecting axles #2 and #3 is being pressed by the truck’s weight, and hence the truck is somewhat slowed down.

I have started to built this model with its both ends, separately with front and rear axles. It resulted in an uncommon frame design – the front half of the frame is purely brick-built, while the rear one is 100% liftarmic. Both halves are connected under the sleeper module, but the rear half lacks the stiffness typical for bricks.

The chassis design is pretty typical – both drive motors are located in front of the rear axles, and the steering motor is located behind the front one. Due to limited length of the chassis, I have used  a 71427 motor for steering. It’s located below, and partially inside the cabin, while the drive motors have been hidden under the mock-ups of the side fuel tanks. The final drivetrain’s gear ratio is 1:1.43.

Extra attention was given to the bonnet – I wanted it to be openable and to have a model of the engine underneath it, just like I’ve seen in the original HTC models, but I also wanted to take one more step and use PF lights in the headlights. It was eventually achieved by resizing the bonnet’s width from 7 to 6 studs. This is wrong in terms of the scale, but it makes the bonnet much more structurally solid.

I have deeply enjoyed building this model – perhaps partially because it took just roughly 4 days to complete. It was a valuable experience, showing that e.g. brick-built exterior may look pretty but is quite heavy – this is a really small model, but it weights almost 1 kg (just to give you a point of reference, 1 kg is a minimum required vehicle’s weight according to the rules of Polish Truck Trial). Still, it was reasonably fast and fun to play with, despite its pretty limited functionality.

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Video:

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Another take on racing trucks. Features fully modular design, return-to-center steering system, full suspension, speedometer and lights.

Datasheet:

Completion date: 20/01/2009
Power: electric (Power Functions)
Dimensions:  length 43 studs / width 18 studs / height 25 studs
Weight: 1.69 kg
Suspension:  front – pendular without shock absorbers/ rear –  dragged axle
Motors: 1 x PF Medium, 2 x PF XL

After a long break, I’ve come back to the subject of the racing trucks. I wanted something faster and better-looking than my two previous trucks, something that I could call ultimate in terms of performance. The only way to achieve the latter goal was, in my opinion, a fully modular design. Therefore, the truck was built out of three basic modules: a cabin, front part of the chassis with the entire steering system, and rear part of the chassis with entire drivetrain and detachable battery box. Thus it was quite easy to make adjustments to the drivetrain and the steering system.

The drivetrain was powered by two PF XL motors connected by a rigid axle (one of them with polarity switched). The rear axle was driven via a small number of double bevel gears, and a chain that transferred the drive to a 4-studs wide differential. The construction of the rear axle was quite uncommon: its structure consisted of several axles and Technic triangles, the differential was moved to the side, and the space gained this way was occupied by a Lego speedometer sensor. The axle was suspended on two stiff shock absorbers, and given a very small travel distance.

The steering system used the mini pendular steered suspension module developed shortly earlier, with the rubber band layout that enabled return-to-center steering. This function lacked some precision, limited steering lock and disabled the proportional steering, but it served its essential purpose.

The modular design involved a single disadvantage – a necessity to locate most of the PF elements behind the cabin, so that they could be easily accessed when e.g. the steering motor had to be disconnected along with the front chassis module. It has significantly degraded the aesthetic impression given by the truck’s cab.

The performance of the truck was way below my expectations. The drivetrain provided excellent speed when the truck’s weight was only a little bit over 1 kilogram, but with the final weight of 1.69 kg the speed was only half as good. After adjusting the gear ratio I was only able to draw close to 4 kmph (compared to the initial 7 kmph of the 1-kilogram heavy chassis). Therefore, despite a number of innovative features and the satisfactory look of the truck, I considered it a major disappointment. It made me think that perhaps the assumed scale of the vehicle and the final weight it imposed were too high for the PF system to provide a decent speed. Certainly a smaller, lighter and suspensionless truck could run much faster.

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Video:

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Model of a racing truck inspired by Volvo FH12. Features full suspension, lightweight body and lights.

Datasheet:

Completion date: 27/08/2008
Power: electric (Power Functions)
Dimensions:  length 45 studs / width 19 studs / height 25 studs
Weight: 1.58 kg
Suspension: front independent / rear dragged axle
Motors: 5 x PF Medium

Promptly after my first racing truck was completed, I started to build a completely new one, trying to eliminate all the flaws I have noticed in the first one. The result is a truck, which is much lighter, though almost identical in size, more stable and slightly faster. The dimensions and the look were based on the Volvo FH12 this time. The drivetrain was entirely different, with 4 PF Medium motors connected directly to a common drive shaft. Thus, I intended to test whether or not a greater number of weak motors performs better that the few strong ones. The rear axle was driven via an universal joint and the new type of the differential. Instead of pendular rear suspension, I have used a dragged rear axle to improve the truck’s stability at the cost of its off-road performance, which was not much needed. The front suspension, though still independent, was rebuilt from a scratch. All the 8435 set components were removed, and replaced by a combination of the 8297 and 8448 suspension parts, which offered slightly larger steering lock and much better robustness. The chassis was much less massive and used panels and axles instead of bricks to save on weight. The spoiler was replaced by a trailer catch, just to compare the aesthetic effect, as both solutions are present in the real truck racing. The chassis housed a vertical battery box behind the front axle, while the IR receiver was moved to the cabin. The cabin had some basic interior, and its front wall was made from vertical plates instead bricks, again – to save on weight. For the same reason the number of lights was significantly limited, and the lights off/on switch completely removed.

The truck still had the excellent manoeuvrability of its predecessor, this time supported by much lighter body and better weight distribution. The drivetrain’s performance was clearly worse, it could barely hold all the torque, and the improvement of truck’s speed was possible only thanks to the smaller weight. Given full weight of the previous truck, the drivetrain would probably completely fail.

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My first racing truck. Features full suspension, dual motor drive, and lifted cabin.

Datasheet:

Completion date: 16/08/2008
Power: electric (Power Functions)
Dimensions:  length 47 studs / width 18 studs / height 26 studs
Weight: 1.92 kg
Suspension: front independent / rear pendular with shock absorbers
Motors: 1 x PF Medium, 2 x PF XL

In August 2008, I’ve come across the European truck racing, and this sport appeared to me as very potent in the terms of a LEGO Technic competition. To try out some assumptions of such a competition, and demonstrate my idea, I have built an exemplary truck.

The assumptions of the LEGO Truck Trial competition were as follows:
- trucks scaled to the 62.4 x 20 S wheels, or different wheels of similar size
- maximum width of a vehicle: 19 studs, exluding side mirrors
- full suspension on all axles
- at least one axle driven, at least one axle steered
- must refer to an existing racing truck; therefore I’ve assumed that truck with more than 3 axles won’t be used, as there are no such trucks in the real sport
- no weight limits, and unlimited number of motors used to drive

The idea, presented at LugPOL, prompted several builders to build their own racing trucks, most of which did not comply with the assumed rules (a lot of people complained about the suspension system requirement, which I have viewed as crucial for realism). As of the end of 2008, not a single contest took place.

The truck was driven by two PF XL motors connected by an adder. The rear axle was driven via the new type of differential from the 8297 set, and had pendular suspension stabilized by shock absorbers. The front axle was not driven, and had an independent suspension based on the components from the 8435 set, with very hard shock absorbers (to support the weight of the cabin and to improve stability of the truck, which could rely on the rear axle only). The dimensions and the look of the truck have been to a large extent based on layout of Scania R 340. The battery box was located above the front axle, and the cabin could be lifted to access the box. The truck was equipped with a large array of lights, both front and rear. The IR receiver was located in the chassis and well exposed.

For the lack of any official contest, the truck went through a lot of test-driving. It performed well, with a drivetrain which provided speed below my expectation, but proved entirely capable of handling all the torque involved in driving such a heavy vehicle. Because of the large accelerating gear ratio in the drivetrain, the truck suffered from a large inertia while stopping. I have assumed that a braking manoeuvre must be used to eliminate that, namely the motors were switched to reverse to stop the truck. Again, the drivetrain endured a huge torque generated while stopping truck this way, and since that time, I required all my racing trucks to be able to endure such a manoeuvre.

The disadvantages of the truck was a significant weight, and a tall center of gravity, which did not cause any trouble here, but I have anticipated that it would, if the truck was faster. Moreover, there was a noticeable part wear in the front suspension, which resulted probably from the large weight of the vehicle, located mainly on the front axle.

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Video:

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