A monster truck with Power Puller wheels. Features 4×4 drive, three steering modes, full independent suspension, remotely controlled gearbox and lights.  

Datasheet:

Completion date: 29/05/2011
Power: electric (Power Functions)
Dimensions: length 44 studs / width 28 studs / height 31 studs
Weight: 2.113 kg
Suspension: full independent
Propulsion: 2 x PF XL geared 6.5:1 (1st gear) / 1.6:1 (2nd gear)
Motors: 3 x PF Medium, 2 x PF XL, 1 x 2838

A construction I’m definitely not happy with. It doesn’t work or look exactly how I wanted, and I couldn’t make the video the way I wanted neither. The chassis of this truck has been entirely reworked three times. The first version was using 4-link floating axles suspension from my Sandrail, but it turned out unstable and it pressed strongly on the driveshaft. I then turned to the independent suspension based on the 8297 set’s suspension components, and using knob wheels instead differentials for a better off-road performance. It proved slow and it was struggling very hard to make a turn. Eventually, the third version had differentials and increased gear reduction. It drives and turns well, but the Power Puller wheels which I wanted to own and put into use for a very long time, turned out to create an amazing amount of problems.

The chassis has 4×4 drive with the differentials enclosed in 5×7 studless frames, with universal joints and CV joints – a simple solution using specialized Lego pieces, and putting these pieces at a considerable risk of getting damaged. Each wheel is suspended on three shock absorbers: two long ones and one short one, with the short one located closed to the middle of the chassis to preserve the suspension’s long travel distance. I was prepared to see some broken CV joints, and I had spares at hand, but surprisingly not a single piece got damaged. In the centre of the chassis, there is my heavy duty 2-speed gearbox controlled by a Medium motor and a single mini linear actuator. There are two XL motors attached to the gearbox, they are coupled with knob wheels and connected to a switch inside the cabin. By turning this switch off, it is possible to shut down the main drive and play with the V8 piston engine which is coupled with the drive motors. The engine is driven by a 2838 motor reaching well over 1000 RPM, and includes a fan and a fiber optics unit. It creates interesting sound effects, especially when used with the speed control remote.

Both front and rear axles are identical. Each includes a Medium motor reduced 5:1 and controlling steering, so there is no mechanical connection between the steering of front and rear axle. Instead, the rear axle’s steering motor is connected to a switch that is motorized with another Medium motor using the spring-loaded Lego connector. Thanks to the connector, the switch returns to off position when the motor is turned off, thus allowing to switch the switch remotely through three positions. This results in three steering modes: normal steering for front axle, normal steering for two axles and crab steering for two axles.

I have spent a considerable amount of time testing the chassis and getting it to perform better, and I’m disappointed with the result. Despite the fact that the truck is relatively light and driven by two XL motors, it is slow and can get stalled on large obstacles. All because of the Power Puller wheels, which are heavy, extremely wide and with very soft tires. The amount of torque required to drive these wheels at all is shocking, and they tend to tilt a little every now and then, even though the chassis is extremely rigid and the suspension is very stable. I have tested the truck with different wheels, and changing to any other wheels resulted in an instant improvement of the overall performance, at cost of the look. It seems that the reason the Power Puller wheels are rarely seen in practical use is not only because how rare and expensive they are.

Even despite my disappointment, the truck was a valuable experience on how the 8297-based suspension behaves in extreme conditions and on how durable are the pieces it requires. While the truck itself was never intended for the Truck Trial competition, I hope to make use of this experience when building my next Truck Trial vehicle. I have also used this opportunity to work on the photos a little more, e.g. by artificially re-creating the so called ‘Michael Bay flares’

Photos:

Video:

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Successor of my 2009 tow truck model, and my most complex construction up to date. Features remote drive & steering, elevated axle #2, rear & side outriggers, automated turn signals, automated reversing lights, motorized towing arm, rotated, elevated & extended boom, dual drum winch, engine model, opened doors and bonnet, lights and custom stickers. Update: a short video in a Full HD quality added.

Datasheet:

Completion date: 11/02/2011
Power: electric (Power Functions)
Dimensions: length 97 studs / width 26 studs / height 28 studs
Weight: 5.069 kg
Suspension: none
Propulsion: 2 x PF XL motor geared 3.89:1
Top speed: 0.56 kmph
Motors: 10 x PF Medium, 2 x PF XL, 3 x 71427, 2 x micromotor

I have been planning to build a successor of my 2009 Tow Truck for quite a while, seeing the subject of large tow truck as a very attractive one. However, it was only the release of mini linear actuators in early 2011 that made me finally start it, giving me the opportunity to control all functions mechanically, without using pneumatics whatsoever. It was obvious from the very beginning that the project is going to be extremely parts-costly, and I started looking for parts I anticipated I would need already in the first half of 2010.

Initially, I was planning to build some non-existent truck in black-and-yellow livery, just like I did with my first tow truck. However, during 2010 I have started to assembly some plastic model kits in order to work on my modelling skills, and I have quickly become a big fan of Revell’s product line. It led me to discovering one of probably the most impressive models ever released by the Revell company: the Peterbilt 379 Wrecker truck. It was exactly the kind of a tow truck I wanted to build. The set itself is no longer produced and unopened boxes are very rare and very expensive. I actually had the opportunity to buy it at a relatively reasonable price, but I decided to pass, having doubts about me being able to assembly it properly. Luckily, I managed to obtain decent blueprints of this set, and they have become the basis of my Lego model.

The subject of large tow trucks is attractive to many skilled builders, and I was certainly not the first to explore it. It was therefore easy, and even reasonable, to look for a couple of inspirations. I have found three, one being the legendary Lego 5571 Giant Truck AKA Black Cat set, which – despite being a regular truck – set the standard for aesthetics and details I wanted to achieve. Again, the set is discontinued and I do not own it due to its exorbitant prices, so I was relying on plenty of photos floating around. My second inspiration was a tow truck based on the 5571 set created long time ago by Andrea Grazi and later artfully modelled by Blakbird. Andrea’s work was an impressive example of integrating plenty of functions into a model, while maintaining its 5571-like body shell uncompromising. Finally, the third inspiration came from my LUGPol fellow member, M_longer, in the form of his Kenworth W900 Rotator, which was a splendid example of building a large, functional tow truck model from a scratch.

Based on all these inspirations, my plans finally evolved towards a model of a Peterbilt 379 as close to Revell’s model as possible, in a black-and-red livery similar to that of the Lego Black Cat. It was not my goal, however, to accurately copy Revell’s model – I was using it more like a base for additions and modifications, for instance by adding extra minor details where I saw them fit, to come close to the level of detailwork shown by Andrea Grazi.

The model’s silhouette and general construction was based strictly on Revell’s blueprints – but I made it a little longer to accommodate for more motors. It is still shorter than M_longer’s model and than some existing real-life tow trucks. Anticipating the model to be really heavy, as exemplified by  M_longer’s Kenworth, I have reluctantly decided not to use a suspension system of any kind. It turned out to be the right decision, as the model’s internal space is used very sedulously and its front axle is very heavily loaded, even though it has been heavily reinforced.

As for the motors, I was initially planning on using 12 or 13 of them, but as I started to build the body frame, it became apparent that using more motors would actually keep the model smaller and less complex. This is largely because of the side outriggers slot, which traverses the very middle of the model, not only taking up a lot of space, but also requiring a massive internal frame below and above it in order to keep the model rigid. Thus, the middle section of the model had very little space left for any sort of connections between its rear and front halves, and it was an obvious choice to reduce these connections to electric wires only, using separate but coupled motors for certain functions in front and rear parts of the model rather than to try to connect these functions mechanically using driveshafts and gears. Additionally, using separate motors gave me a degree of freedom in choosing where to place certain mechanisms, as they were not connected mechanically. A very good example of it is using separate motors for steering and controlling turn signals: these two functions are coupled together, but controlled by two separate motors, because instead of connecting all the mechanic parts to a single motor, I was able to keep the steering motor very close to the front axle, gaining enough room behind it to fit in the turn signals mechanism controlled by a motor located elsewhere.

Thus, the list of motors is as follows:

1. PF Medium motor for towing arm elevation, controlled by an IR receiver
2. 71427 motor for towing fork elevation, controlled by an IR receiver
3. PF Medium motor for extending side outriggers, controlled by a manual switch
4. PF Medium motor for deploying side outriggers, controlled by a manual switch
5. 71427 motor for deploying rear outriggers, coupled with the motor #4
6. PF XL motor for drive, controlled by an IR receiver
7. PF XL motor for drive, coupled with the motor #6
8. PF Medium motor for controlling the reversing lights, coupled with the motors #6 and #7
9. Micromotor for rotating the engine fan, coupled with the motors #6, #7 and #8
10. PF Medium motor for driving the winch, controlled by an IR receiver
11. PF Medium motor for extending the boom, controlled by an IR receiver
12. PF Medium motor for rotating the superstructure, controlled by an IR receiver
13. PF Medium motor for elevating the boom, controlled by an IR receiver
14. 71427 motor for elevating axle #2, controlled by a manual switch
15. PF Medium motor for steering, controlled by an IR receiver
16. PF Medium motor for controlling the turn signals, coupled with the motor #15
17. Micromotor for rotating the steering wheel, coupled with the motors #15 and #16

So, as you can see, the model uses all 8 IR channels and 3 manual switches to control all the functions. This means there are in fact 11 separate functions, and additional motors are used to control some functions together (e.g. the drive) or to couple some functions together without using mechanical connections (e.g. turn signals).

Except for 17 motors, 4 IR receivers and 3 switches, there are 5 more switches used inside the model (1 for controlling the lightbar, 1 for the reversing lights and 3 for my improved turn signals mechanism), as well as a number of 9V wires (for two 9V switches, lightbar and micromotors), 16 PF extension wires (9 short and 7 long ones) and 22 pairs of Lego PF LEDs. All these together include nearly 19 metres of electric wires, all of which is crammed inside the model. This picture gives an exact calculation and shows what the internal space looked like after most of the wire-cramming was already finished:

This amount of electric wires not only needed a very careful planning of the entire electric installation, which is powered from two separate Lego 8878 rechargeable batteries, each independently powering two IR receivers, but it also contributes significantly to model’s weight, and it required adding special ducts and spaces for wires in the model’s internal structure. For example, the largest duct is located directly above the side outriggers slot, inside the black bulge between the sleeper and the superstructure, and the largest space for wires can be found in the upper portion of the sleeper, where it was obviously needed due to all the four IR receivers residing there.

As for the side outriggers, which puzzled some viewers, their construction is in fact fairly simple and explained on the two following pictures, that show simplified (meaning: showing all the mechanic parts but with some structural parts removed so that they don’t obstruct the view) view of a retracted and extended outrigger respectively. Note that there are two identical outriggers side-to-side, rotated 180 degrees to each other, and extending in opposite directions. Each of them is controlled by a separate pair of gears, and there is a ridge of tiles separating them. The whole construction is somewhat fragile and unable to handle high torque, but since the outriggers are not meant to lift the model off the ground, there is no high torque involved.

To finish describing the model’s internal composition, from back to front:

• the flat rear portion  of the body below the boom houses all the mechanics of the towing arm and rear outriggers, along the axle’s #2 elevation mechanism
• the ‘box’ below the superstructure houses 6 motors, most of the drivetrain, almost entire turntable with its rotation mechanism and respective motor, motors that control turn signals and boom elevation, as well as the entire side outriggers with most of their mechanics
• the superstructure houses most of the mechanics for the boom elevation, a motor that extends the boom and the winch with another motor driving it; locating the boom extension motor inside it took some precious space, but thanks to it the boom is simpler and stronger, looks better and extends to almost twice its length
• the sleeper houses no motors (but there are two PF Mediums below it, on the sides of the chassis), but four IR receivers, one 8878 battery (accessible through the sunroof on the passenger’s side), the entire reversing lights mechanism, part of the turn signals mechanism, the rest of the side outriggers mechanics and huge amount of wires; there is also one internal LED that shines through one of its side windows
• below the cabin, there is most of the turn signals mechanism, another 8878 battery sitting between the cabin and the engine compartment (accessible by opening the bonnet) and some wires; inside the cabin, there is one of the micromotors, while the other one sits inside the engine model under the bonnet

The model also features two ‘nods’ toward the Lego Black Cat set (other than the colours of the livery): a white cat used as the bonnet ornament, and the cabin’s doors which are unique for the Black Cat set, and which I bought when it turned out that the would perfectly match both the size & the colour theme of the cabin. As for the colours, rather than trying some fancy trails, I settled on a single large red stripe going through the entire body (and even around it, if you look at the model’s rear end), which includes four sets of little doors on the sides of the rear part of the truck. Three of these doors allow to access manual switches, while the fourth one reveals a mock-up control panel. There is also a thin red strip around the sleeper, which resulted from its internal structure: I needed to create a ‘shelf’ for IR receivers inside it, and I used a single layer of red plates for it, just to brighten it up a bit. As for the boom, I have put a lot of effort into making it perfectly smooth, with rounded edges, and I decided that some transverse black and red stripes would underline its shape nicely. The boom is internally a completely studless structure, with two ‘halves’ of studfull shell put over it, one in an upside-down position. The halves are not connected witch each other, but they are kept together by the boom’s structure and secured by large stickers on its sides. Finally, there are two small red plates on top of the cabin’s roof. This is because the original Peterbilt 379 uses distinctive rectangle-shaped hooters, and the part that modelled these ideally was a 1×2 jumper plate connected to a horizontal antenna. I wanted to have chrome hooter, to match the rest of the roof, but Lego does not chrome jumper plates and I had to have them custom chromed. The technique used for custom chroming, however, left the their bottoms chrome-less, and their bottoms would be their most visible part. So, for the lack of better options, I put two 1×2 plates to cover the bottoms of the chrome jumper plates. Note that the cabin’s roof is built to odd width, and fairly complex itself, as it includes openings not only for five LED’s wires, but also for five clips needed to hold the chrome pieces in proper position.

The model includes an extensive array of lights. There are 22 pairs of Lego LEDs (meaning 44 LEDs altogether) used for regular and decorative lights, for reversing lights and turn signals. Additionally, the lightbar uses 6 old 1×4 electric bricks with two light bulbs each, with these trans-yellow parts put over them. This idea was taken straight from M-longer’s Kenworth, except that I mounted the trans-yellow covers in a different way, and used six electric bricks rather than two. A very useful property of these bricks is that they can flash or shine continuously, depending on the polarity, without the need for any external mechanism to achieve the flashing effect. They are also very shine, with the only two drawbacks being their yellowish hue (I’ve tried to use them with trans-light-blue covers instead, and the effect was ugly) and their high power consumption when compared to LEDs.

The model was being regularly tested throughout the construction process, which – together with my preventive assumptions that it will be very heavy – paid off. Its drivetrain works flawlessly, even though it was obviously slow, which shows that the new differentials braced in the 5×7 liftarm frames can handle significant loads (there are two differentials here, as there are two driven axles, so there is an average load of 2.5 kg per a differential). The steering system, which was geared down 24:1 from the very beginning, seems to work effortlessly. The weight of the model affects the front tires, though – they are noticeably deformed by it, have a slight tendency to bend aside while turning, and make squeaking sounds when turning in place. The Lego 8878 batteries turned out to cope with the extremely complex electric system, even though I managed to completely empty one of them while testing the model. The superstructure tended to bend forward a bit with the boom fully elevated, and the side outriggers jammed from time to time, but I think these were acceptable costs of the model’s general complexity. Additionally, the linear actuators elevating the boom couldn’t fully retract or fully extend, but this was because of the boom colliding with parts of the superstructure; the connection between the boom and the superstructure had to be heavily reinforced, thus limiting boom’s movement at the cost of handling its considerable weight. It should be also noted that I have deliberately used small plastic hooks for the winch instead of big metal hooks for Lego cranes, used by both Grazi & M_longer. This is for increased realism: none of the many tow trucks I have browsed through uses hooks even remotely as large as the Lego metal ones, and none uses two sections of rope between the hook and the boom neither. Thus, the hooks I’ve chosen look much more accurate, but they are not synchronized and often hang at different heights. There is a way of keeping the drums of the winch synchronized by driving them through a differential between them, but there is no space for such a solution. Still, the boom includes a transverse pulley that can be used to keep two metal hooks connected by the same rope level, so I left this option open.

I was quite pleased with how the model turned out, considering it my most complex construction up to date.  It should be noted that it was based on my experience with my Kenworth Mammoet model rather than on those with my first tow truck. I believe it to be a mark of progress of both my technical and aesthetic skills. The only downside is that it’s my first model in 2011, and I already have little chance of building anything better this year

Work in progress photos:

Photos (caution: some large ones included):

Videos:

Click here to view the embedded video.

Click here to view the embedded video.

Media reference:

Devicenation, Geeky Gadgets, Leganerd (Italian only), Technabob, Teknolelu (Finnish only), The Awesomer, The Brothers Brick, TowTimes

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Model of an Italian WW2 military truck designed for Truck Trial races. Features 6×6 drive and full pendular suspension.

Datasheet:

Completion date: 06/08/2010
Power: electric (Power Functions)
Dimensions: length 53 studs / width 25 studs / height 33 studs
Weight: 2.166 kg
Suspension: pendular, stabilized with shock absorbers
Propulsion: 1 x PF XL motor geared down 8.337:1 (low gear) / 5:1 (high gear)
Top speed: uknown
Motors: 1 x PF XL, 2 x PF Medium

My first Truck Trial vehicle equipped with a gearbox. It caught my attention when I was looking for something more complicated after building several simple 4×4 vehicles. There were two main reasons that made me model this particular truck: its excellent approach and descent angles, and its pair of spare wheels. It was a rare solution, present in a number of WW2-era vehicles, to have a pair of spare wheels mounted on the sides of the chassis, relatively low, and with ability to rotate freely. It was helpful while climbing over obstacles, as these wheels had a good chance of preventing the chassis from getting stuck on the obstacle. For some reason, this solution apparently did not survive to this day.

Technically, the Fiat was supposed to continue and develop the solutions from my two previous Truck Trial vehicles – Hummer H1 and Jeep Wrangler Rubicon. It was built around a brand new studless chassis, unlike the two mentioned vehicles which had studfull chassis. It was also equipped with a simple linear 2-speed gearbox that was controlled remotely with an extra PF Medium motor, and it had unusual rear axle with 4 wheels. While the original vehicle has three regular axles, I decided to combine the two rear axles into a single pendular module that would have 4 wheels suspended on it. It has two advantages: firstly, while the module itself has a transverse pendular suspension, the wheels had a longitudinal one, so their flotation was better that it would be in case of two separate pendular axles. Secondly, a combined module needed much less space inside the chassis, thanks to which I was able to put the model’s battery behind it and the gearbox in front of it. Finally, the Fiat’s chassis used pendular axles mounted on the large Technic turntables, with both drive and steering transferred through the middle of these (drive transferred through a solid driveshaft and steering transferred by an empty differential sitting on it), which eliminated the problem of shock absorbers pressing on the driveshaft and thus creating a significant friction on it. Using the turntables resulted in slightly worse ground clearance, but has greatly improved the structural robustness.

The gearbox was made of a module attached to the PF XL motor, that was supposed to slide inside the chassis back and forth by a single stud, thus shifting the gear. By attaching the drive motor to it, I was able to eliminate a complex transmission system between the fixed motor and the sliding gearbox (this idea was first presented by  Emilus). The gearbox has a very sturdy structure and performed well during the initial test. Only double bevel gear wheels were used inside it, to minimize the problems with engaging/disengaging.

The model was equipped with a single body, which was completed just hours before the race. Despite appearing tall, the body has relatively low centre of gravity thanks to an openwork structure above the cabin and the cargo box. I didn’t have time to care about details such as doors, but at least I made the windshield able to be folded down, just like in the real truck. The cabin had a very basic interior and a simple inline piston engine driven from the driveshaft.

The truck’s performance in the race was arguable. On one hand it has shown good agility, surprising stability and I was able to drive it with great precision. On the other, it was pestered by constant problems with the gearbox, because the gears inside it started to slide along the axle under stress. I was able to temporarily fix it with tweezers until at some point the axle popped out of the drive motor and there was no way to put it back in without taking major portion of the body apart. It has forced me to give up and withdraw from the race.

At first I felt like fixing the gearbox would solve the model’s only problem, resulting in an excellent Truck Trial vehicle. Thus I was obviously planning to use it in the next race. Unfortunately, as I started to rework the gearbox, more problems occurred. The redesigned gearbox needed serious modifications of the chassis. Once the chassis was completed, the rear axle and the drivetrain started to fail. I have made several attempts at solving these problems, until I noticed that the knob wheels in the rear axle’s drivetrain are being worn down very quickly, most likely because of the resistance generated by four wheels. At this point I decided to give up on the truck, on assumption that combining two rear axles with large tires into a single module with drive transferred to by just a pair of knob wheels was a bad idea. The combined resistance of four wheels was simply too much for the knob wheels to handle.

The model became quite popular with the other Truck Trial contestants because of its unusual look and wheels set-up. It became known as “the revenge of Mussolini”, and my decision to give up on raised many protests.

Photos:

Video:

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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:

Click here to view the embedded video.

Media reference:

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

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My first Truck Trial vehicle for 2010. Features 6×6 drive and full independent suspension.

Datasheet:

Completion date: 10/04/2010
Power: electric (Power Functions)
Dimensions: length 66 studs / width 25 studs / height 31 studs
Weight: 2.624 kg
Suspension: full independent with swinging half-axles
Motors: 1 x PF Medium, 2 x PF XL

My first 2010 Truck Trial vehicle had a rather difficult creating process. Even though I started to build it more than a month before the race, the final version was created under two weeks time. It was mainly because of the chassis, which wasn’t stiff enough to handle the torque of two PF XL motors, and got completely rebuilt three times.

The goal of the Tatra was to have a realistic suspension with swinging half-axles which are typical for all Tatra trucks. It was achieved by removing differentials and transferring the drive with the knob wheels. The modern Tatras have their half-axles offset a bit – this was not modelled in order to keep the steering system simple and sturdy.

The steering system was located entirely between axles 1 and 2 and consisted of two complex sliding beams with links. The beams were sliding in different directions for axle 1 and 2 and were controlled by a driveshaft whose direction of rotation was inverted in between these axles. Because of insufficient internal space both beams were given the same gear ratio, resulting in an identical steering lock of both axles.

The drivetrain was kept as simple as possible, and the main portion of it, including the drive motors, was located between axles 2 and 3. Both drive motors were located between two stringers of the vehicle’s frame, one behind the other, and were not connected directly but by a common driveshaft located beneath them. Since the space between axles 1 and 2 was occupied by the steering system, an extra driveshaft was needed to transfer the drive to axle 1. It was located above the axles, under the cabin, and it transferred the drive to a V12 piston engine located inside the cabin as well. Thus the transmission of the axle 1 was located in front of it and in order to prevent such a vital mechanism from damage, a cover made of liftarms was installed before the axle.

The body of the truck was rather simple, with the cabin built almost exclusively with the new Technic panels to reduce its weight. The cargo case was simple and shallow, and there was a transportation handle built into vehicle’s frame behind the cabin – a solution I’ve used in some of my earlier Truck Trial vehicles, and which proved very useful as every Truck Trial race involves a lot of carrying the vehicles around. The cabin had a safety cage built on it, which was meant to give it extra stiffness and a more Tatra-like look, as the real Tatras participating Truck Trial races are always equipped with distinctive external safety cages.

The Tatra suffered from the same thing that most of my earlier Truck Trial vehicles did – insufficient amount of testing. The problem with this kind of vehicles is that they can be only fully tested once finished, because test are most revealing at full vehicle’s weight. As you can guess this implies that a finished vehicle has to be taken back apart if it fails tests, and to avoid this arduous procedure it is a common practice to test just the chassis alone with extra load on it simulating the anticipated body’s weight. It doesn’t always work as it’s difficult to precisely anticipate the final weight of the body if it wasn’t built yet, and it’s almost impossible to simulate its exact weight distribution. I have to admit that being short on time, I have only given a minimal amount of testing to the final version of the Tatra – this was also because I was afraid of damaging it right before the race.

During the race, the model experienced two problems – the first was a failing transmission to the front axle, which snapped. There were also minor problems with axle 3, which meant that only the middle axle worked at full efficiency, and it didn’t really help while climbing obstacles. The reason was a faulty construction of the chassis – the suspension itself worked fine, all the snapping occurred in the transmission system inside the chassis. The second problem was sideways stability. While building this model, I have given a lot of attention to make sure its weight distribution prevents it from falling forwards or backwards – and I succeeded. The sideways stability, on the other hand, proved much below what could be expected. It seems that the problem was not related with this particular vehicle but with this type of suspension in general, as exemplified by another Tatra model, the T813 built by Lomero and used in the same race. His Tatra had the same suspension type while keeping a considerably lower silhouette which suggested a better stability. Surprisingly, it kept tumbling over a couple of times per each section of the race. It convinced me that it’s practically impossible to model the Tatras’ suspension system in such a way that the resulting model is stable.

Finally, the model’s drivetrain was pretty much obsolete in terms of the rules used in Polish Truck Trial. The rules take power-to-weight ratio of each individual vehicle into account in order to prevent builders from winning by simply adding more drive motors. Each vehicle is given its own points conversion rate based on its power-to-weight ratio, which basically means that you can win with a vehicle that can race despite having a very low power-to-weight ratio (resulting in high points conversion rate) or with a vehicle that has a high power-to-weight ratio but is very fast and can complete the race in short time. Tatra was neither of these cases – it had a relatively high power-to-weight ratio because of two PF XL motors, while not being really fast. The current tendency among the top Truck Trial builders is to use complex gearboxes with 3 or even 4 gears available. Thus even a truck which is much heavier than Tatra can be driven by a single PF XL motor whose gear ratio is changed as needed by the means of the remotely controlled gearbox. This results in a models that are slow but still capable, while having an extremely high points conversion rate. Two good examples of such trucks are Emilus’ GINAFs and Atr’s Volvo – both being large, heavy, and driven by a single motor.

Upon observing the race, I’ve decided to abandon the Tatra project. While the transmission problems could be solved given a sufficient amount of testing, the suspension system would still not provide satisfying stability. With the next race being only two weeks away, I decided that I would focus on building a new, small, lightweight and efficient vehicle rather than fixing Tatra. This is also the reason not to document the Tatra’s technical solutions – I think it’s better to build something more successful and then document it once it’s solutions are proven in a race. Right not I have a complete front suspension of my next Truck Trial vehicle, which looks very promising, and if it succeeds in the race, I intend to publish a complete instruction for it.

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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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Model of a dump truck based on Scania CB8x4. Features full suspension, two axles steered with a different steering lock, elevated cargo case, full interior, lights and custom stickers.

Datasheet:

Completion date: 23/11/2009
Power: electric (Power Functions)
Dimensions:  length 68 studs / width 20 studs / height 29 studs
Weight: 3.35 kg
Suspension:  independent on axles 1&2, double pendular on axles 3&4
Motors: 1×71427, 1x PF Medium, 2x PF XL

My first model after a short break. It was supposed to be relatively simple technically, but elaborated aesthetically. Basically, I wanted to built an improved version of my 8-wheeled dump truck created 2 years earlier, and my very good source of inspiration was Scania tractor unit by Pedro Agnelo. It was Pedro’s great work that made me want to built an entirely black truck with some dark gray elements. The trick that makes cabin’s door open easily (double opposing hinges) is also takes from Pedro’s model.

The first and second axle have been fitted with an independent suspension based on the 8297 set’s components. Both axles have been suspended on shock absorbers, with the axle #1 using doubled shock absorbers to support cabin’s weight. This solution – a very hard suspension of the front axle – made the entire model very stable; almost unbelievably stable for a model driven by pendular axles. The steering system was controlled by a 71427 motor located in front of the axle #1 (a place where a PF Medium motor was too long to fit in), with the usual 9:1 gear reduction and a safety clutch. Both front axles are steered by a single common steering shaft, which was a very good solution for two reasons. Firstly, it kept the steering systems of both axles synchronized at all times, and secondly if any of the steered wheels became stuck or reached the maximum steering lock, the whole steering system of both axles stopped without losing its synchronicity. The ratio of the steering lock of the two axles was 2:1, and it was achieved by using gear wheels of different size for steering. Two IR receivers have been hidden between the mudguards of the two front axles.

Axles #3 and #4 have been suspended on a special pendular module with a transverse and longitudinal swivel points.  Both axles have been pendular with a longitudinal swivel point, so that one wheel could rise above the other. Both axles have been attached to a central structure with a transverse swivel point, so that one axle could rise above the other. It was a compact and strong suspension system with a very good off-road performance, but it was unsprung which resulted in its poor stability as well as in the tendency for the wheels to slip under the torque (the suspension would rise one wheel off the ground if a sufficiently high torque was applied). Moreover, the truck suffered from a disadvantageous weight distribution: axles #1 and #2, which were not driven, handled most of its weight. Therefore the truck performed better while driving backwards than forwards, and some extra load above the rear axles was needed to improve its traction.

The drivetrain was unusual and realistic at the same time. There was a driveshaft connecting axle #3 with the motors in the chassis, but since the height of the axle  wasn’t constant due to the suspension type, it needed an extendable section. It was located between two universal joints and consisted of a number of wedge belt wheels connected by short axles. This is an old solution, found e.g. in the linear gearboxes, but it worked perfectly well here, even though it was handling a serious amount of torque.

It should be mentioned that the gear reduction in the drivetrain was really minimal, and the truck’s speed dependend heavily on the raw power of two PF XL motors. This approach has paid off – the truck was faster that my previous Kenworth Mammoet driven by two PF XLs too, despite being much heavier. However, when some demanding obstacles have been met, the motors would become so strained that they made the Lego battery go off for a moment.

The truck’s cabin housed the drive motor, full sets of lights including rooflights, and the battery along with a full interior that included a detailed cockpit, a steering wheel, seats, pedals, and even flags on the rear wall. The doors could be easily opened thanks to the double opposing hinges system invented by Pedro Agnelo. I have initially thought about using the cabin to house an automated trafficators system, but since I didn’t have a sufficient amount of lights, so I’ve decided to use it for an interior instead. The cabin couldn’t be lifted and its bonnet was fixed, not openable. The ‘Paul’ badge visible in front part of the cabin’s interior is a nod to the recent Lego 8258 set, which is a 4-axle truck too, and which has stickers with driver’s name intended to go in the very same place (the interesting thing is that set contains a number of badges with various names to pick from, including Paul as well as Wabra – the set designer’s surname). One thing I wasn’t happy about was the use of stickers to imitate the air intakes on the sides of the front Scania logo. I’ve decided to use stickers because I couldn’t find any brick of appropriate shape, but the result was way below my expectations.

The cargo case was elevated by two linear actuators driven by a single PF Medium motor located above the second axle. A 3:1 gear reduction was used, but no clutch, since the amount of torque required to lift the case up would make any clutch slip. Please note the very robust way in which the actuators have been attached to the chassis – it was intended to limit the torque losses caused by the actuators bending under the load. Moreover, they needed little space inside the chassis – basically just some openings in the mudguards of axle #3.

The cargo case was large, robust and heavy. I wanted its sides to be perfectly studless and to look interesting, which was achieved with a modular system of tiles. The system itself was just two layers of tiles thick, but to obtain proper stiffness the sides of the case have been made up to five layers thick. It could be built practically up to any length or height too. I believe the look of the case sides was worth the final, surprisingly high weight of the model.

I was pleased with the model despite its technical simplicity. While it was not large enough to house e.g. a gearbox, it was still quite functional, it looked very well, and its mechanical elements have been nearly invisible. Despite some rear suspension problems the truck was relatively fast and handled very well. I believe the key feature of this model was the realistic look, which is more than I need to justify the mediocre number of its technical features.

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Media reference:

Bricks’n'Gears, Fascinating LEGO Model Of The Day, kockak.hu

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My fourth Trial Truck vehicle. Features 6×6 drive, two axles with different steering lock, full independent suspension and front winch with a quick release lever. The first vehicle powered by the Lego 8878 battery in Polish Truck Trial.

Datasheet:

Completion date: 05/09/2009
Power: electric (Power Functions)
Dimensions:  length 53 studs / width 27 studs / height 24 studs
Weight: 1.875 kg
Suspension:  full independent
Motors: 1x PF Medium, 1x PF XL

My another attempt to create a successful Truck Trial vehicle. Having my previous experiences with Unimog U900 and Star 266 in mind, I focused on a vehicle that would be small, light, low and simple. I have chosen to model the Alvis Stalwart truck because it was one of the shortest off-road vehicles with three axles. I liked the idea of having six wheels so close to each other, because if offered good traction and good weight distribution.

The chassis was complex but compact, built almost exclusively with liftarms. It consisted of two steered axles both of which were copies of the module I have used in the front axle of my earlier Hellbender model. The third axle was not steered. The intervals between all three axles were identical, which meant that the second axle was supposed to have 50% of the first axle’s steering lock.

The problem was that two aforementioned modules  were located in ‘mirrored’ positions in order to simplify the drivetrain. Therefore the steering driveshaft had to have its direction of rotation reverted between the modules. It was achieved with a simple setup of small bevel gears, but it also created a significant backlash. Initially there was 16-teeth gear in the first axle’s rack & pinion mechanism, and an 8-teeth gear in the second axle’s one. In theory it provided the desired difference in steering locks of two axles, but in practice that difference was heavily degraded by the backlash. I have solved it eventually replacing the 16-teeth gear in the front axle with a 12-teeth one. Coupled with the backlash, it created just about the perfect steering lock difference.

The drivetrain was somewhat complex, with two separate driveshafts for the third axle and for the two first ones. The model was driven by a single PF XL motor located just above the third axle, and the 8878 battery was located at the very rear end of the chassis – together with the PF XL motor it counterbalanced the weight of the cabin.  I expected the front winch to be a very important part of the vehicle – it was driven by the drive motor through a driving ring with a quick release lever. When the lever was engaged, the winch was driven accordingly to the direction of vehicle’s movement. When the lever was disengaged, the winch was disconnected from the motor and the string could be quickly extended by hand. There was a number of pulleys used inside the chassis to reduce the friction of the string, and the entire winch was enclosed within model’s frame. The winch proved so powerful and robust that when forced to stop, the string split before there was any mechanical damage.

The model was a bit heavier than expected, but it had a very good weight distribution and the suspension worked flawlessly with its weight. It was also quite manoeuvrable and very, very stable. I expected the low ground clearance to be a problem, but it was helped by the bottom of vehicle which was covered by a protective layer of smooth liftarms, so that the model could slide over obstacles to some extent. The main problem of the vehicle was failing drivetrain plus non-lockable differentials. A lot of slip situations occured, and the drivetrain would snap when a really high torque was needed. It could have been helped by the use of the winch, but it worked way below the vehicle’s travelling speed, which proved fatal – the winch was simply to slow to take the load off the wheels. It would work much better if the release mechanism disengaged wheels from the drivetrain as the winch was engaged.

The model has lost its first and only race, but in some aspects it performed much better than any of my previous trucks – it remained stable at all times, it did not suffer any damage despite the use of many delicate parts such as CV joints or universal joints, and it did not formally malfunction – it simply suffered from the drivetrain being unable to handle high torque. It was also acclaimed by other Truck Trial builders for capturing the original vehicle’s look, which kind of surprised me. Moreover, the experimental use of the 8878 battery turned out to be a success – the model’s performance was not degraded, while its weight with a traditional battery box would exceed 2 kilograms.

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Media reference:

Mao de ABS (Spanish only)

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Model of the Kenworth W900 in a version customized by the Mammoet company. Features full pendular suspension, functional steering wheel, R4 piston engine, openable bonnet, sleeper’s roof and doors, remotely controlled front and rear lights, automated reverse lights and trafficators, remotely locked catch and custom stickers. My first construction powered by the Lego 8878 rechargeable battery.

Datasheet:

Completion date: 29/06/2009
Power: electric (Power Functions)
Dimensions:  truck – length 75 studs / width 19 studs / height 26 studs, trailer - length 111 studs / width 18 studs / height 12 studs
Weight: truck – 2.66 kg, trailer – 0.709 kg
Suspension:  truck – full pendular, trailer – none
Motors: 2 x 71427, 1 x PF Medium, 2 x PF XL

Kenworth W900 is one of the most iconic US-type trucks, and the Mammoet is one of the most impressive companies ever, handling stuff like transportation of bridges or houses on a daily basis. Moreover, it is a Dutch company, just like the Lego, and it uses almost entirely black livery for its vehicles which is very appealing for me. Finally, the Mammoet fleet, which consists of some of the world’s biggest and most powerful vehicles in their class, contains a number of customized vehicles, which makes them even more interesting.

There is one obvious point of reference for this model, that is my Tow Truck, completed almost a year earlier. I have assumed that it would be difficult to exceed its level of technical complexity, and if I tried to, it would most likely result in a vehicle of even bigger size and similiar look. That is why Kenworth was meant to be simplier and built with more focus on its aesthetic side.

First thing about the aesthetics are somewhat missed proportions – although according to Mammoet’s blueprints only the bonnet is 2 studs too long, and the rest of dimensions is more or less correct. Nevertheless, the truck looks long and narrow. I have recreated Mammoet’s livery on the body, but not on the bumpers, preferring to keep them free from paint job. Instead, they were fitted with small warning badges, and on the front bumper has a set of guards that Mammoet company uses in trucks intended to push some loads. There are no warning lights, either. I’ve put a lot of work into the bonnet, which can be opened up together with the front mudguards, which is a realistic solution unlike the one used in my earlier Tow Truck. The sleeper was made taller to fit the mechanics in, the catch was increased in size to achieve more accurate shape, and rear mudguards were added.

The model was designed for use with a standard Power Functions battery box, and only in the last stage of building it received the Lego 8878 rechargeable battery instead. The battery decreased sleeper’s height and truck’s weight (by considerable 160 grams) while not impacting the performance in any apparent way.

The suspension system consisted of three simple pendular modules, with axles #2 and #3 using my 3-studs wide differential bracings, each stabilized by four hardest 6.5L shock absorbers available to handle the truck’s weight and load. The front axle had no shock absorbers at all, because too much place was taken by the bonnet and front mudguards. Since the entire suspension is pendular, the truck is susceptible to a transverse tilt resulting from the driveshaft’s load, but it is greatly limited by the hard shock absorbers.

The model is driven by two PF XL motors facing each other and connected by four bevel gears. I have tested this setup before, and I liked how simple and effective it was. Additionally, the use of two motors facing each other substantially reduces the strain on the drivetrain. When I tested it with a single motor, it had a tendency to pull the driveshaft down or up if it was not reinforced properly. With two motors, the driveshaft remains in place because while one motor pulls it up, the other pulls it down. One of the four bevel gears is an idler gear, used only to keep the other three gears in place. It can be easily noticed that the motors would look better if they were located along the body – they would then look just like the fuel tanks. It’s a nice solution, but it makes the vehicle’s frame and transmission much more complex, and so I gave it up. I have to mention that the truck turns surprisingly smoothly, most likely thanks to the long span between the steered axle and the driven axles. And it feels very pleasant and realistic to drive it with the speed control-enabled 8879 handset.

It may come as a surprise, but there is no gearbox whatsoever. I’ve done a lot of tests with a linear 3-speed manual gearbox, which seemed most adequate due to it size and robustness, but it proved somewhat loose and the model performed much better with no gearbox. I intended to use the speed control feature anyway, so the gearbox was eventually removed.

The catch lock mechanism is very simple and compact. It uses a worm gear to hold the trailer in place, and a linear clutch to avoid damage. It was located just above the last axle, which is why I’ve used a custom casing (the standard Lego casing wouldn’t fit in), and it was driven by a motor located in the chassis, directly in front of the second axle.

Slightly in front of the second axle, there is also the steering system’s power output, intended to be connected to the trailer’s own steering system to couple it with the truck’s steering. I have tested a trailer with such a system, but I eventually faced the choice whether to make the trailer with steered axles or to make the trailer which is strong and looks realistic. I have chosen the latter.

Between the fuel tanks, there is a reverse lights activator in the chassis. It consists of a single PF switch whose movement is limited to a neutral and one extreme position , and which is connected to the driveshaft through a clutch. The reverse lights are powered from the same output as the drive engine, thanks to which they go out as the truck stops.

The doors of the cab can be fully opened after removal of their side bars. Inside the cab, there is a functional steering wheel and a simple cockpit. There are no seats, because the respective space is occupied by the trafficators mechanism. I will now explain how it works. Imagine a PF light powered through a PF switch – it blinks as the switch’s position changes. Such a motion can be easily motorized by means of an eccentric mechanism – that kind of solution was already used in the forementioned Tow Truck, and can be well seen in my Snowgroomer. Now, imagine a ratchet that is sensitive to the direction of rotation – it has been used in my direction sensitive gearbox. We can attach the motor to the ratchet, and then prepare two separate eccentric mechanisms with two separate PF switches and two separate set of lights (of any size – in fact, I would make the rear trafficators work too if I had 9 lights instead of just 7). It will result in a mechanism when only one eccentric mechanism is driven at a time, and it changes as the direction of rotation of the steering motor changes. Thus, it is perfectly possible to use the steering motor for it, as it can easily control one more mechanism, and I have used a separate motor here only to be able to locate the trafficators mechanism independently of the steering motor’s location. The trafficators’ lights are powered from the same output as the steering motor, so they go out when it stops working, regardless of the wheels’ position.

One drawback of this solution is that the eccentric mechanism remains in whatever position it was when the ratched moved to the other one. It means that there is a high risk of having all trafficators come up at the same time, because the ones that should be off will have the PF switch stopped in ‘on’ position. It can be prevented with rubber bands that pull the eccentric mechanisms to a specific position once they no longer mesh with the ratchet, but I did not use such means of prevention because of the available space limitations. Please note that the truck already houses approximately 5 meters of electric wire.

Under the bonnet, there is a R4 piston engine with moving pistons and rotating front fan. It is small because of the limited space under the bonnet which results from its specific construction. As you can see on the photo below, there is an interesting area near the front axle where the model’s smooth external surface ends and a Technic structure can be seen beneath it.

Finally, the trailer. I wanted it to wear a different colour scheme. Trailers of this type usually have red and white warning stripes on the edges of main platform. I didn’t have the needed number of red and white parts, and I disliked the look of these colours combined so I replaced them with two shades of grey. The trailer has no steering system nor suspension of any kind, and it is attached to the truck in a fairly simply way. I have to admit that the truck took a terrible amount of work to build and I really didn’t like the idea of even more work with the trailer, especially since it was difficult to show or film together with the truck due to its length. Therefore the trailer is an addition to the truck rather than a proper model.

Overall, the model enjoyed a fairly good reception, despite many people pointing the proportions issue out. The trafficators feature was widely acclaimed, and there was even a number of people who were very critical about the proportions and accuracy of the truck, but still regarded it as an impressive model. Few people declared that the focus on the truck’s aesthetic aspect was much greater than expected of me, and that its functionality was degraded because of this.

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Media reference:

Bricks ‘n’ Gears, kockak.hu, TechnicBRICKs

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An experimental halftrack vehicle. Features three types of suspension, a 4-speed manual gearbox and openable doors.

Datasheet:

Completion date: 13/04/2009
Power: electric (Power Functions)
Dimensions:  length 54 studs / width 17 studs / height 16 studs
Weight: 1.41 kg
Suspension:  front – independent / rear –  torsion bars + pendular bogie
Motors: 1 x PF Medium, 1 x PF XL

Having built a dozen or more tracked vehicles, I eventually felt compelled to try a halftrack. Halftracks are an interesting blend of tracked and wheeled vehicles, combining the advantages of both. Namely, they perform better off-road with tracks than typical wheeled vehicles, and they can steer much easier than typical tracked vehicles thanks to the wheels (which results in a simplier construction rather than in a better performance).

There is a number of problems involved in building a halftrack, and I was curious as to how they would affect a small, lightweight model. Basically, the real halftracks often have the front wheels driven for better traction and better steering. There is usually a differential between the tracks, which serves the same purpose, and some of the heavy German halftracks were fitted with automatic brakes that would slow down one track while turning.

There was a single technical solution that greatly affected the look of the vehicle: the torsion bars. I was earlier suggested to try this kind of suspension, popular even in heavy tanks of the WW2, but it did not occur to me at that time how to make such a bar bend without sustaining any damage. Only sometime later it hit me that the elastic 16-studs long axles from the Jumping Giant would be an ideal and natural choice. It’s just their limited length that was not ideal, and hence the width of the entire vehicle was limited by the transverse 16-studs long axles used as torsion bars.

With the vehicle’s body only 16 studs wide I’ve given up the intent to make the front wheels driven. Instead, they were just fitted with a simple independent suspension, and the suspension of the tracks was complemented by a central pendular bogies because I only had two axles that could serve as torsion bars. The drive was transferred through the usual 4-speed manual gearbox I’ve used many times before to the tracks’ front return rollers without the use of a differential. I have assumed that it would be catastrophic to drive a lightweight vehicle with a slippery tracks via a differential – the slip situation would be more than likely to happen.

Eventually, the vehicle had a surprisingly efficient steering system – which was due to the tracks’ poor traction rather that to its construction. The turning radius was even slightly better than it would be with two regular rear axles instead of tracks. I suppose that given a sufficient speed it could be a great drifting truck.

As for the look of the truck – I had no clear idea what should it look like, but I definitely didn’t want it to look like German military halftracks of the WW2, which are often considered iconic for this type of vehicle. That is why I pursued the look of a vintage truck, which eventually proved to have a lot in common with the US Army’s halftracks (M3 and its successors in particular). Still, I was unhappy about the bonnet which had to be tall and wide to cover the shock absorbers of the front suspension. Actually, the front of the truck was so massive that its center of gravity ended up below the cab – despite the fact that all motors and the battery box were located between the tracks. I felt that the back of the truck should be openable, but that was impossible because of the battery box being fixed there. The battery box and the motors were left uncovered deliberately: this way they could appear to be the truck’s load, and the cargo space seemed much larger than it would with these parts covered up.

The truck was technically very compact, which resulted in some limitations. There was no place for working lights nor for the reinforced drivetrain, the latter resulting in an inconsiderable vehicle’s top speed.  The suspension system, however, worked pretty well. The torsion bars functioned in a proper and realistic way, even though they were probably too weak to support the entire truck’s weight. Still, there was a margin of calibration available, as I created a 2 studs long ‘torsion space’ – that is a space between the actual suspension and the point where the torsion bars were fixed to the chassis. If this space was reduced to a single stud, the suspension could probably handle a significant weight. Tests with the gearbox proved the torsion bars to be a bit unreliable; they tended to produce vibrations at lower speeds and worked smoothly only at the higher ones. I suppose that this effect is proportional to the size of tracks’ links, which means that the newer tracks system would require even higher speed to run smoothly with this suspension system.

Although I have initially considered it a minor, highly experimental project, the Crusader performed almost flawlessly and was more fun to drive than many more advanced vehicles. Moreover, to my sincere surprise its aesthetic aspect was much acclaimed at the LUGPol and beyond.

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Media reference:

Klocki, The Brothers Brick

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My third, unsuccessful Trial Truck. Features 4×4 drive, full indepent suspension and R6 piston engine.

Datasheet:

Completion date: 31/03/2009
Power: electric (Power Functions)
Dimensions:  length 46 studs / width 25 studs / height 31 studs
Weight: 1.95 kg
Suspension:  full independent
Motors: 1 x PF Medium, 1 x PF XL

An unfortunate result of my attempt to enter 2009 Truck Trial season with a brand new vehicle. It was intended to be small, lightweight and as simple as possible. Therefore I’ve decided to model the shortest version of the legendary Unimog truck being produced at the time.

The truck was built in a traditional way, with layers of bricks and plates reinforced by vertical liftarms. There were no differentials at all and the suspension utilized the 8880 set’s suspension components, replacing the universal joints with knob wheels as the universal joints get damaged in the Truck Trial quite often. The number of motors and electric components was limited to a single battery box and a single IR receiver controlling drive & steering. For the sake of stability both battery box and the drive motor were located low under the chassis, with the battery box moved close to the rear axle in order to compensate for the cabin’s weight. I have initially intended to build the cabin with liftarms and panels, but I didn’t really like the look of it and eventually chose to build a ‘fullbrick’ cab. I have, however, failed to maintain the proportions and the resulting cabin was too tall and placed a bit too high.

The decision about the cabin has dramatically increased truck’s weight – from approx. 1 kg with bare chassis and 1.4 kg with cargo platform to the final 1.95 kg. It had a great impact on the stability and performance of the model. Eventually it turned out that the truck was having serious problems with everything but driving straight ahead. A meticulous analysis revealed that it was because of the bracings keeping the knobs inside the suspension’s rocking levers. While they performed quite well before, now they tended to bend under the truck’s full weight. As a consequence the knob wheels became slightly displaced, and came into contact with other parts of the suspension. It has crippled the truck so severely that I decided to abandon this chassis design entirely, seeing no space for improvements. My first idea was to rebuild the truck from a scratch, but after a careful consideration I have canceled the Unimog project and started to build a 4×4 truck with longer chassis and two differentials. So after all,  this model has never been driven outdoors.

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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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