My final 2010 Truck Trial vehicle, built in less than single week after the previous vehicle failed. Features full pendular suspension, 4×4 drive, lights and opening doors, bonnet and rear board.

Datasheet:

Completion date: 03/09/2010
Power: electric (Power Functions)
Dimensions: length 48 studs / width 26 studs / height 27 studs
Weight: 1.985 kg
Suspension: pendular, stabilized with shock absorbers
Propulsion: 1 x PF XL motor geared down 5:1
Top speed: uknown
Motors: 1 x PF XL, 1 x PF Medium

When I decided to abandon my Fiat SPA35 model, it was just a week before the Truck Trial race and my first decision was to pass on driving this time and to only take care of filming. Shortly after, I changed my mind and decided to try some simple 4×4 vehicle, just to drive something in the race. The vehicle was intended to combine the advantages of my two previous Truck Trial vehicles – Hummer H1 and Jeep Wrangler Rubicon, while also learning from Fiat’s failure. I wanted to try to model another famous 4×4 vehicle, so the classic Land Rover series 2 (dating all the way back to 1958) was pretty much an obvious choice.

While the complete model appears much like a Hummer/Wrangled hybrid on the outside, it was internally much closer to the Fiat model. The chassis was built completely with studless parts and used large Technic turntables to hold suspension modules in place – both solutions tested in the Fiat for the first time. The Land Rover shared engine location, gear ratio and wheels with the Wrangler and a studfull body with the Hummer. In fact, the Rover used studfull body around a studless chassis, whereas Wrangler used studless body around a studfull chassis.

The suspension has undergone some major changes in comparison to the version used in Fiat. The front axle was reverted to the version used in the Wrangler, and then a single turntable was attached behind it and the steering system was additionally reinforced. Both drive and steering were transferred through the turntable – steering by a solid driveshaft and steering by am empty differential sitting on it. The rear axle was built from a scratch between two turntables. There was no gearbox, and – just like in the Wrangler – the drive motor was located above the front axle, right under the bonnet. The racing rules we use state that every model has to be equipped with a piston engine of accurate configuration and placement, unless the actual drive motor is located where the original engine is. Thus, locating the motor under the bonnet meant that no piston engine was needed in the model, which saved space, weight and drive motor’s power. The steering was controlled by a single PF Medium motor geared down 15:1 and located low in the chassis, in front of the rear axle. The entire underside of the chassis was covered with studless parts, in order to create a single smooth surface that was unlikely to get  stuck on an obstacle, and in order to lower the centre of gravity as well.

Knowing that my Wrangler model had abundance of torque, I wanted the Rover to be much heavier.  Our racing rules take power-to-weight ratio of each individual model into account, therefore more weight at the same power means more points. Thus, I wanted the body to be massive, but at the same time it was my goal to keep the model’s centre of gravity low, despite its significant ground clearance (up to 7 studs under cabin’s floor). Therefore especially the lower portion of the body was built so densely that model came out almost undamaged from some crash tests I conducted later.

The body was equipped with a pair of opening doors, an opening bonnet with a spare wheel fixed on top of it (a common sight in early Land Rover versions), and opening rear board with the IR receiver attached to it. Most of the Land Rovers can be accessed from the back by a single door, and a board is a rarity. I chose the board over door because this way the IR receiver was more exposed, and could be pulled out from the cabin’s inside to some extend if needed. Moreover, the rear part of the cabin has been adapted to house a camera. Due to weak mounting points, this solution worked well only on flat, level surfaces, as proven during the race.

It should be noted that the model’s body was inaccurate: the front radiator grille should be put further back under the bonnet. I couldn’t model it because of the frame that braces the suspension module of the front axle. Moreover, inspired by the Inception movie featuring a tracked Hummer H1, I have created a simple set of four tracks for the Land Rover. The tracks and wheels could be easily swapped in the chassis, and while I did not intend to use the tracks outdoors (our racing rules don’t allow tracked vehicles of any kind), I have used these to drive around my apartment. The general performance was apparently inferior with tracks on, and in particular the traction was much worse than it was with wheels.

The completed model weighed a whopping 2.1 kg until I removed ballasted bricks that were mounted under the bonnet in order to shift the centre of gravity forward. It reduced model’s weight to just below 2 kg, and I decided to leave it like that because there was no time left for changes. The model performed well at this weight, it experienced no mechanical failures and displayed superb traction, but it was obvious that it will be struggling against its own weight.

Land Rover was warmly welcomed by other contestants because of its look and its very short building time. It performed well in the race, no mechanical failures occurred, but its weight turned out to be a real problem. The model ran out of power to climb on several occasions, and toppled over once. It ended up at the last place in the race, much to my disappointment. Yet still, other drivers and viewers were greatly impressed by its look, which led me to believe that it would be a waste to take it apart, and that the model should enter our last 2010 race on October, with open body design that should significantly reduce its weight.

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Large model of a Caterpillar front shovel excavator designed for a public display. Features a drivetrain with a subtractor, superstructure rotation mechanism, V12 piston engine, arm with 3 joints controlled remotely by motorized linear actuators, pneumatically opened bucket, remotely elevated operator’s cabin, lights and custom stickers.

Datasheet:

Completion date: 11/06/2010
Power: electric (Power Functions) / pneumatic (fed from internal compressor)
Dimensions (with the arm in ‘resting’ position): length 80 studs / width 28 studs / height 35 studs
Weight: 3.5 kg
Suspension: pendular bogies
Propulsion: PF XL motor geared down 9:1, through a subtractor
Motors: 2 x PF XL, 6 x PF Medium, 1 x 71427

I wanted to build a front shovel excavator controlled by linear actuators for some time already. It took me a while to find a machine with a distinctive silhouette (as many large front shovel excavators are shaped similarly) and my choice was the Caterpillar 90-tonne machine with an unusual cabin elevation system.

The model would be built at much later time if it wasn’t for the people from the Focus popular science magazine, who invited me over to a Picnic of Science held in Warsaw (the largest popular science event in whole Europe). It was a kind invitation, but it also meant a fixed term to build something spectacular and, so to say, public-proof. I had to hurry to make it on time, I even used my absence of leave to finish the model, but I felt it was still not tested sufficiently.

The look of the model is accurate to some degree. The size and all the dimensions are kept faithful, and the colour theme is an exact rendition of one of the two Caterpillar liveries I’ve seen this machine with. The details on the top of the model, however, were intended to look diverse rather than accurate, the V12 piston engine model is completely unrealistic (but it turned out to be a great crowd pleaser, as anticipated), and the arm lacks a single actuator. Additionally, the way the bucket opens up has been changed slightly to make the bucket look better and be more structurally sound.

As for the functional side, it was largely affected by the unexpectedly huge weight of the model. While the chassis was providently built around a really massive studless frame, the drivetrain had to be additionally geared down to handle it. Even with the 9:1 gear reduction, some gears in the subtractor are still being grinded to dust. Not a single gear in the drivetrain was broken, but there was a plastic dust coming out whenever I opened up the subtractor. But in fact, the painfully low speed of the model is accurate as the real machine moves at 4.4 kmph.

There is a studless Technic turntable between the chassis and the superstructure. The stability is provided by four double rollers, consisting of two wedge belt wheels with rubber tires each, and integrated into the superstructure’s bearing frame (located, as usual, in its ‘floor’). The rollers are supported by large tiles on the top of the chassis. I have assumed that use of large rollers will be a convenient way of filling the gap between the superstructure and the chassis, and that the rubber tires will provide a degree of elasticity should the superstructure tilt while operating. Whether these assumptions were accurate or not is difficult to prove eventually. But I was right to only use four sets of rollers (front/rear/left/right one) as they provided sufficient stability for as long as they were part of a sound, rigid structure.

The major drawback of this model is the use of an 8-teeth gear wheel as the final part of the superstructure rotation mechanism. The weight of the superstructure coupled with the friction generated by the rollers’ rubber tires caused this gear to be severely damaged during final tests. Since it was very difficult to replace (read: it required to take half of the model apart) and there was no guarantee that the new gear wheel wouldn’t share its fate, I left if the way it was. Which means that the superstructure rotation works only when aided by hand. The video clearly shows that superstructure rotates as long as the rear part of the hull is being gently pushed (at some point I even use a single finger for that to demonstrate that there is indeed a mechanism working there and that I’m not simply rotating the superstructure by a hand). The use of the 8-teeth gear wheel, which worked fine in lighter models, was a mistake here to begin with. I should have used a worm gear instead, preferably one that would be mounted to the chassis and driven from the chassis.

The rear part of the hull houses the 8878 rechargeable battery which powers the whole model and which can be accessed by a small sliding lid. On its left, there is a big V12 piston engine driven by a separate PF Medium motor coupled with the drive motor (which means that there is no mechanical connection between this engine and the drivetrain whatsoever). The whole V12 is fully enclosed inside the hull, and can be displayed by opening up a two-piece lid. I always wanted to include a piston engine into an excavator model, and with a model that large I finally did. On the right side of the battery, there are four IR receivers and beneath them, there is a pneumatic autovalve which controls the opening/closing of the bucket.

The front part of the hull houses a massive frame around the arm’s main joint. The arm is 6 studs wide at this point, and there is a driveshaft, two pneumatic hoses and three electric wires going through the joint. On the right side of the arm there is a PF XL motor which drives two linear actuators that lift arm’s first section. There is also a PF switch which controls the lights on the arm, and which can be accessed by the means of a small door in the right side of the hull. On the left side, there is a cabin sitting on a scissor lift mechanism, which is moved by a single linear actuator driven by a 71427 motor located under the piston engine. The elevation range of the cabin is impressive, especially when you realize that the whole scissor lift mechanism is just 3 studs tall. The mechanism has its drawback too – it puts a very high load on the motor, so it has to be additionally geared down (hence the low speed of cabin elevating) and the weight of the cabin has to be kept low (hence the number of details is lower than intended).

The arm consists of two sections. The first one is controlled by the aforementioned PF XL motor which drives two linear actuators integrated into the front part of the superstructure’s frame. The second section is controlled by a PF Medium motor located in the hull, between the arm and the 8878 battery, which drives a single linear actuator integrated directly into the arm’s first section. There is another PF Medium motor inside the first section, which drives another two linear actuators that tilt the bucket. The second section of the arm is pretty much empty. The arm was built in the same way as it was with my previous excavator: it consists of a studless frame with directly attached actuators, and a studfull outer skin which provides extra stiffness but is not necessary for the arm to work. I am not quite pleased with the somewhat weird look of the pneumatic hoses on the arm – I could have enclosed these inside the arm, but I felt that an excavator’s arm ought to have some hoses on it. But due to the complex construction of the arm’s first section, there was no way to arrange the hoses in a more realistic manner.

The arm has some excellent movement range. In fact, it is somewhat better than that of the original machine – to the point at which it is not necessary to open the bucket to unload it, as it can be simply tilted.

As for the bucket opening mechanism, it is very simple and consists of just two small pneumatic cylinders. Some minor part of the load is usually left inside the bucket when it opens, but this is caused by the bucket’s inner shape which results from its internal studless frame rather than by the mechanism itself.

This has doubtlessly seen more practical use than any of my other excavators, as it was operated for a couple of hours straight during a public event. It has also successfully faced the devastating curiosity of little children present at the event, but I won’t describe the details lest I sound like a contraception promoter In fact, the failing superstructure rotation mechanism is the only thing that prevents me from calling it my best working excavator model ever. The model has been also highly acclaimed by LUGPol members – so highly, in fact, that I was genuinely surprised.

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Media reference:

Hobby Media (Italian only)

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Re-edition of the model of the Swedish MBT, built two years after the initial version. Features full suspension, remotely tilted hull, remotely controlled dozer blade and lights.

Datasheet:

Completion date: 06/03/2010
Power: electric (Power Functions)
Dimensions: length 67 studs (including main gun’s barrel) / width 25 studs / height 19 studs
Weight: 2.15 kg
Suspension: pendular bogies
Motors: 2 x PF Medium, 2 x PF XL

After almost exactly 2 years, I decided to re-build my perhaps most renown tank model. The S Tank, created back in 2008, has been extremely well welcomed, and no matter how many bigger, more accurate and more complex tank models I’ve built later, there were always some people claiming that S Tank was the best. I, on the other hand, was aware of many shortcomings of this model, and it was my goal to overcome these shortcomings in the following models – a fact that has apparently escaped the attention of many S Tank’s enthusiasts. Eventually, I decided to build this model again using my current level of modeling skills, even though it was against my ‘never build the same thing twice’ rule.

The original S Tank, or Stridsvagn 103, is a fascinating machine all by itself. Designed in 50s, it was the main tank of the Swedish army for the next 40 years, until arrival of the Leopard 2. What was the key of its success and its long-term service? The fact that it was designed with Sweden in mind. Moreover, it was designed specifically for defensive roles. This is why the typical turret was removed completely, because the tank was intended to stay hidden waiting for the enemy to come. To operate in difficult Swedish terrain, the tank was fitted with then-advanced hydropneumatic suspension and a turbine engine (in addition to a traditional diesel engine), making it the world’s first MBT to use turbine engine. Aiming was done by moving the entire tank, using the suspension to tilt the hull as needed. In order to fire its main gun, the tank had to be stopped and its suspension locked – it was clearly a drawback, but it was acceptable given the tank’s defensive role. It should be also noted that in 50s and 60s the fire control systems were relatively primitive, and tanks rarely fired while moving. Finally, the S Tank was equipped with a front dozer blade, which could be used to entrench it quickly and without the need for crew to leave the vehicle.

Thanks to removal of the turret, the tank’s front could be protected by a single armored plate, set at an angle that made it very difficult to penetrate. Actually, at the time it was designed, the S Tank’s front armor was virtually impenetrable for any other tank’s armament. To make a full use of this advantage, the crew included two drivers – the second driver was facing backwards and had his own set of steering instruments. Thus the S Tank was able to drive backwards quickly, while being protected from the enemy by its front armor, as well as being able to return fire at any time.

The S Tank was clearly an unorthodox design, so specific that Sweden remained its only operator, but it could be pretty lethal to any advancing force. Why? Because it had to be spotted before it could be engaged. Now, take a good look at a fully entrenched S Tank:

The new model of the S Tank was supposed to be: accurate, performing well and dark gray. I believe it meets all these conditions. The hull, which was tilted pneumatically in the previous version, is now controlled by linear actuators. It takes much more hull’s internal space, but the stability provided by such solution is peerless. Since my first S Tank was driven by a single XL motor, and the motor was apparently working pretty hard, and now the PF speed control is available, I used two XL motors, each one driving a single track. The tracks’ suspension system consists of 4 large, realistic road wheels (6595 wheels without tires work very well with tracks) suspended on pendular bogies, two wheels per a single bogie. I wanted to use a torsion bars suspension for the first time, but it was impossible to make it work together with the tilted hull. The front dozer blade is operated by a single PF Medium motor instead of pneumatics, and it works better than I expected (this is an application where pneumatics usually performs better than motors do). It should be noted that front part of teh hull houses a traditional battery box rather than the rechargeable battery, and there are two reasons for that. Firstly, a battery box can provide more power for two PF XLs used simultaneously, and secondly I needed something heavy in model’s front part to acquire the proper weight distribution.

As for the visual details of the model, my goal was to model the most distinctive ones. Like many tanks with long service period, the S Tank has undergone several modifications and there are 4 variants of this tank, which differ mainly in details. Few details are fictional, just to fill some empty spaces. Please note that this model uses custom chrome sprocket wheels, rather than original ones that come only in yellow or orange at the moment. These wheels have been purchased at this Bricklink store.

The model took a lot of work and a lot of extra shopping for parts, but I think it was worth it. For me, it is clearly my best-looking tank up to date. It seems that models in dark gray look particularly well on photographs, which is why I attempted to make a couple of macro-like shots, even though I only had a general purpose lenses (macro lenses are expensive beyond human reason). The model performed very well too – it was my fastest tank up to date, and its large road wheels made the suspension’s work spectacular to watch. I have enjoyed driving it over a wrinkled blanket more than I enjoyed driving any other tank under any other conditions. However, there’s a good chance that it would perform better with a torsion bars suspension.

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Model of a JCB skid steer loader. Features drive, steering, remotely raised arm, tilted bucked and working roof lights.

Datasheet:

Completion date: 14/02/2010
Power: electric (Power Functions)
Dimensions:  length 31 studs / width 18 studs / height 20 studs
Weight: 0.73 kg
Suspension: none
Motors: 3 x PF Medium, 1 x micromotor

No a long ago, I have come into posession of the LEGO micromotor, something I wanted to have for years. Micromotors are unique, hard to get at a reasonable price, and impossible to replace in certain cases. When I finally got mine, I wanted to use it to control the horizontal angle of the main gun’s barrel in my T28 model, but the model was almost complete by the time I got the motor. Then it occurred to me that the smallest project on my list could definitely use the micromotor.

JCB 180 is a simple tracked skid steer loader. There are plenty of skid steer loaders and I was never interested in building one, viewing them as simple and technically boring. The JCB 180, however, is one of few loaders with a single arm instead of two, and that makes it challenging.

My goal was to  achieve maximum functionality while showing as little mechanics as possible. I’ve spent quite a while trying to fit a small transverse subtractor into the chassis, but I had to admit that it’s too large at this scale eventually. Therefore the drivetrain is very simple: it consists of two PF Medium motors, each driving a single track. Third PF Medium motor drives the linear actuator that controls the loader’s arm. Having one arm instead of two turned out to be a blessing in disguise, as there was no space inside the hull to drive two linear actuators or to transfer the movement from one arm to another. The roof lights are a good example of how compact this model is: they are coupled with the micromotor, because there was no space to connect them elsewhere.

The micromotor was located at the end of the arm, and it proved quite easy to integrate into a liftarms-based structure. It uses 3:1 gear reduction to change the bucket’s angle. I did some capacity tests with Lucius the hamster (roughly 60 grams heavy), and he was able to stay on the bucket without causing any sort of mechanical malfunction. The capacity, however, is severely limited by the fragile bucket’s construction – the first bucket I made was so heavy that it tilted to the side in a very ugly way. The final bucket was optimized for minimum weight.

The model was built in less than a single day, and it could certainly be somewhat upgraded. But I was satisfied with its functionality and look anyway, and considered it a relaxing build, without the need to make it better & better. It was also Lucius’ first time to appear in the AFOLs’ world.

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Model of the American WW2 super heavy tank prototype. Features full suspension, drivetrain with a subtractor, lights and advanced main gun control system.

Datasheet:

Completion date: 13/02/2010
Power: electric (Power Functions)
Dimensions:  length 73 studs (including main gun’s barrel) / width 30 studs / height 16 studs (not including aerials)
Weight: 2.2 kg
Suspension: pendular bogies
Motors: 2 x PF Medium, 2 x PF XL

T28 was an unusual project. Started in Spring 1945, it was designed to break through German defenses and to counter German super heavy tanks such as Maus or E100 (none completed, fortunately). The designers focused on the armament and armour of the tank at the cost of its mobility, and they decided not to use a typical turret as it would not be needed against fortifications. T28 had one of the thickest tank armours in history, but it was driven by an V8 engine providing merely 500 HP – a very little power for a tank of such weight. It was also one of few tanks to move around on 4 tracks. The outer set of tracks could be removed for transportation by train. The tank could drive on a road on inner tracks, towing the outer ones behind.

Out of 25 planned T28s, only two were built. The war ended before they were operational, and in 1947 they were subjected to evaluation. It went bad – one prototype was completely destroyed by engine fire, and the other one proved that a 500 HP engine can barely move it. Both were supposed to be scrapped, but the undamaged one was found in 1974 in a back field at Fort Belvoir, Virginia. It is unknown where it was earlier, and it is unknown how a tank of this size can remain unnoticed inside a military base

The model is relatively simple on the technical side. It uses only 4 motors, two to drive and the other two to control the main gun. Just like in the real tank, the main gun has limited traverse and elevation. The drivetrain consists of a subtractor and two PF XL motors, one for drive and one for steering, on assumption that it takes quite a torque to steer a tank that wide and with 4 tracks. The model is not entirely accurate – one of departures include a V6 piston engine in the back, instead of fuel tanks. The real machine was driven by V8 engine, but only 6 pistons can be seen through a 8×8 grill, so I used a V6 engine. It has internal lighting, with lights pointed at each piston, and all the lights are coupled with the drive engine, so the faster tank goes, the brighter the engine is.

Another departure is the shape of the front of the hull. It was changed mainly to house the main gun control mechanism. The real tank had its gun mantlet attached to the hull, while the model’s mantlet is attached to the barrel and moves together with it, hence it needs a certain margin of free space around it.

The most challenging element of the model was its suspension system – not because it’s advanced, but because it’s so expanded. Each of the four tracks uses four pendular bogies, each with two road wheels. It sums up to the total of 16 bogies with 32 road wheels. Each track’s suspension is separate and independent, and each track consists of 123 tread links. Together with the spare track section on the armour, it sums up to over 500 tread links used for the model.

The model looked really well, and it definitely paid off to build it in dark grey instead black. It performed well, although the main gun’s barrel was a bit wobbly. It also seemed to experience problems with the drive motor – it could drive backwards and turn very well, but it seemed that driving forwards put more and more tension on the motor. The problem seemed to be getting worse over time, and it is possible that the PF XL motor used for drive was defective. Because of that, the model appeared very slow on the video, whereas given a properly functioning motor it should have been faster. Still, it was my first tank in dark grey, and came highly acclaimed for its look.

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Pneumatic excavator with a full remote control. Features internal compressor, 3-position motorized pneumatic valves, integrated manometer, infinite freedom of superstructure rotation, lights, flashing warning lights, custom stickers and simple suspension.

Datasheet:

Completion date: 09/01/2010
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor)
Dimensions (with arm in the transport position):  length 72 studs / width 27 studs / height 56 studs
Weight: 2.77 kg
Suspension:  pendular bogies
Motors: 7 x PF Medium, 1 x 71427
Pneumatics: three circuits with motorized 3-position valves fed from internal 4-pump compressor; integrated manometer

The idea behind this model was simple: to build a fully pneumatically operated excavator with a full remote control. Such a mixture is unique – there are many pneumatic models of excavators, but nearly all of them are connected to an external controller, which houses all pneumatic valves and usually also the compressor. I thought it would be quite a challenge to make a similar model fully remote-controlled, and I was sure that a pneumatically operated arm would look more realistic that one operated by linear actuators (as demonstrated by my earlier Liebherr R996 excavator model).

I was looking for a classic tracked excavator, and – somewhat tired of Caterpillars and Liebherrs – I turned my interest to the Volvo machines. The EC290C excavator scaled down accordingly to the width of the tracks seemed a most proper vehicle to model.

When you think of a pneumatically operated excavator, it quickly becomes obvious that it needs a possibility to return the valves to the neutral position, or – more simply – to close them. With such a possibility all sections of the arms could be controlled independently (well, almost – they would still affect each other by changing the air pressure in the pneumatic system); without it every section would have to reach its extreme position to let another one operate. Therefore I was looking for a small, simple way of controlling the valves, and what I found was an invention of my fellow LUGPol member, Dmac. It’s a very simple solution, but a tricky one – it depends on the elasticity of specific liftarms in relation to the internal gearing of a PF Medium motor.

I have assumed that with all valves controlled in that manner and fed from an internal compressor whose speed I can control remotely, I will have a full control over the excavator’s movement with a satisfactory degree of accuracy.

The model uses an uncommon chassis. It is held together by a single transverse beam which houses two PF medium motors inside it, along with a reinforcing frame made of liftarms. Thus the beam appears small and almost completely smooth, with the motors completely enclosed. It puts quite an extreme load on the beam’s components, but it results in a realistic look, as the real machine also has a single transverse beam in the chassis, and its drive motors are not visible, housed in the superstructure.

Another important thing is that the original Volvo excavator has its drivetrain fully enclosed within the tracks , with no parts protruding out at all. To model it, I have used two long sections of LEGO Technic chain, each connecting one drive wheel to the motor and remaining within the tracks at all times. The colour of the chains matches the colour of the chassis bearing structure, which makes them almost impossible to spot. Together with the enclosed motors, it has lead some viewers to ask how exactly is the whole model driven.

The construction of the hull may seem simple, but it was challenging. First of all the hull is flat but large, and it sits asymmetrically on the turntable. To keep it structurally solid, a supporting frame was needed – it was built around the turntable and integrated into the hull’s floor, taking 1 stud of its height. To make things more complicated, I have decided to use the newer turntable variant because it matched my needs better, but its width was odd while the hull’s width according to the scale was even. To compensate for this difference, a half-stud wide liftarms were used in the frame to give it an even width. There is an additional structure integrated into the frame right above the turntable, which holds together the base of the arm and the base of the pneumatic cylinders that raise its first section, as well as the motor used to rotate the superstructure. Additionally, the compressor was attached to the frame – firstly to minimize its vibrations and secondly to compensate for its height.

The construction of the rest of the hull is pretty traditional – there is a rechargeable battery at the back, serving as a counterweight, and motorized valves on the sides. The right front part of the hull houses the flashing lights mechanism activated by a lever inside the operator’s cabin, which controls four warning lights: two at the rear end of the hull, one on cabin’s top and one on the arm’s side. The cabin has a full interior, despite the fact that it’s slightly smaller (mainly in length) that its real counterpart.

The arm is relatively narrow – only 4 studs wide. It was built by blending two structures: bearing frame made of liftarms which holds it together, and the outer ‘skin’ made of bricks which makes it stiff and gives it a realistic look. All the mounting points for the pneumatic cylinders are attached to the frame: the cylinders were integrated with the frame right at the beginning, in order to work out their optimal positions. There are three sets of pneumatic cylinders on the arm, two consisting of two cylinders, and one consisting of four. All of them are connected to the pneumatic system inside the hull: a mixture of elastic & rigid hoses is used to connect the pneumatic system to the arm. It should be noted that the sets of two cylinders tend to rotate around their longitudinal axle; to prevent this, they are connected to the arm by two axles that slide through certain points of the arm’s structure as the cylinders extend or retract.

The model worked well, given its strongly experimental construction. It has a number of significant flaws, however, the most important being the compressor which worked too slow. It was discovered only at the end of the building process, when the arm gained more weight that it had when the compressor was initially configured. The use of the manometer has paid off – the tests have shown that the pneumatic system was prone to breach at certain pressure. The turntable was a bit unstable, but it didn’t break – despite the fact that it had no supporting rollers or structure of any kind, and that at least 80% of the model’s weight was located in the superstructure.  There is a point on the video when you can hear the turntable squeaking as the superstructure rotates. The final drawback was the use of the standard bucket – I was planning to have a detachable custom bucket and some add-on devices to replace it with, and I even placed an extra outlet of the Power Functions system in the arm to let some motorized devices be connected and controlled. It turned out, however, that both the bucket and one add-on device I have prepared (a demolition jackhammer) were too heavy for the arm (the custom bucket was almost 5 times heavier that the standard one).

I was satisfied with this model despite its flaws. I had little experience with large pneumatic remote-controlled models before, and this proved to be a good lesson – especially when it comes to configuring the compressor. Usually, pneumatic models of this size use large compressors driven by the RC motors, which can fill the whole airtank in a couple of seconds. I had just four pumps and a compressor running at roughly 100 RPM, and it had to fill a system including over 3.5 meter of elastic hose (not including the rigid sections) and 19 pneumatic T-pieces.  Still, I was glad to have an unique self-contained pneumatic model with a fully wireless control. I liked its look to – the decision to use dark grey where I could theoretically use black as well has definitely paid off.

Photos:

Video:

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Media reference:

TechnicBRICKs

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Model of a modern French main battle tank. Features advanced independent suspension with adjustable ground clearance, gearless drivetrain, remotely rotated turret and commander’s gun, remotely elevated main gun, and an onboard wireless live feed cam.

Datasheet:

Completion date: 17/08/2009
Power: electric (Power Functions)
Dimensions:  length 58 studs (including barrel) / width 26 studs / height 22 studs (plus aerials)
Weight: 2.48 kg
Suspension:  full independent with adjustable ground clearance
Motors: 4x PF Medium, 2x PF XL

I have a special liking for the tracked vehicles, and especially for modern tanks which happen to be the most advanced tracked vehicles ever built. This is why, having built my last tank nearly a year ago, I was looking for a modern machine that would make a nice model. I wanted something similar to the previous model, the Abrams M1A2 tank, but smaller, lighter and more mobile. Since the Leopard was out of the question (I wouldn’t feel comfortable building a German tank), and the Merkava has an unusually shaped turret that would be difficult to model, I decided to build the Leclerc – a very good and distinctive example of today’s high-tech tank.

If we lay aside the popular jokes on French tanks, the Leclerc is a fairly outstanding and impressive machine. It was build for a very interesting reason: because none of the world’s tank lived up to the expectations of the French Army. As one may anticipate from that, it is in many ways different than earlier main battle tanks such as e.g. Abrams, and very likely sets standards for the future constructions.  There are differences in almost every aspect of its construction: for example when it comes to the defence, Leclerc’s design focuses strongly on the active protection. The tank is protected passively by a modular armour similiar to the one used in Leopard 2, but there are two layers of active protection being currently developed and scheduled to be put into use around 2015: the ‘soft’ layer is capable of jamming computer systems of the incoming missiles, while the ‘hard’ layer shoots down any incoming large-caliber projectiles. Both layers are supposed to be fully automated, with the latter one being capable of shooting down projectiles coming from any direction in time intervals as short as 0.6 second. Even Leclerc’s armament is unusual: instead of Rheinmetall 120mm cannon present in vast majority of modern tanks, it uses longer French-built GIAT 120mm cannon along with a custom French-produced ammunition and an automatic compressed air fume extraction system instead of the usual bore evacuator. The tank’s turret is built around an autoloader system designed specifically for Leclerc, which provides an impressive performance and at the same time allows to avoid many problems usually present with the standard autoloader systems. The most impressive things are many high-tech upgrades scheduled for the Leclerc: those include the aforementioned two layers of the active protection, but also multipurpose armour upgrades, the anti-missile decoys deployment systems, thermal signature reducers, and – probably the most impressive of all – Stealth armour kit.

The construction of the model started with a new suspension concept. I was happy with the performance of the independent suspension used in my Abrams model, but I wanted to make it even more realistic. In order to achieve it I have removed the most unrealistic element, the central tread wheels , and I fitted all the road wheels with thin full rubber tires. Thus the tracks have no solid point of contact with any road wheel whatsoever, and are kept in place only by the road wheels, without any use of the tread wheels which are commonly used in the official Lego sets. At first it seemed an unreliable solution, but it proved to be perfectly reliable – I had less slipped track cases with Leclerc than I have had with the Abrams, and they all happened only because the tread links came apart.

It was obvious from the beginning that the model will make use of the new 8878 rechargeable battery and of the PF speed control feature. It meant two things: that it will have plenty of internal hull space available, and a very simple drivetrain. I have eventually limited the drivetrain to just two short axles connecting motors directly to the respective drive wheels – with the speed control feature nothing more was needed to allow the tank to make turns at any angle, and it seemed to blend power with speed in a promising way. Moreover, such a drivetrain was extremely efficient and durable, since not a single gear was used.

With a lot of internal hull space at hand, I wanted to try an idea of using the independent suspension to adjust the ground clearance. It was achieved by mounting upper tips of all the shock absorbers on lengthwise liftarms, which were moved higher or lower by two coupled pairs of very short levers. That solution worked very well in the early construction stage, easily providing two studs of difference in ground clearance, at which rate the tank was actually able to sit on the ground. It was also possible to change ground clearance at any position, at any moment, even while driving, and the tank’s suspension remained fully functional all the time. The efficiency of this system, which took almost half of the internal hull’s space (there were 4 sets of worm gears all coupled together), was eventually severely crippled by two factors: firstly, the length of the tracks which was limited. The tracks weren’t, obviously, elastic, so their length remained the same as the suspension was raised or lowered. It left a small margin for differences, as the tracks couldn’t be too lose or too tight, and so the range of ground clearance adjustment was limited to approximately single stud. The latter factor was simply the model’s weight, which proved larger than expected and heavily loaded the mechanics of the ground clearance adjustment system. Even though the Leclerc was still much lighter than Abrams, its suspension was loaded a bit heavier because it consisted of just 12 sets of road wheels compared to Abrams’ 14 sets.

The remaining hull space was used to house the battery (in front of the hull, with a small access hatch in the armour under the front part of the turret), three IR receivers (located next to drive motors, partially below rear part of the turret) and a PF Medium motor controlling the turret’s rotation. The last solution was unusual for my tank models, as the previous ones had this mechanism housed inside the turret itself. It made the turret’s internal structure a lot simplier, which was important to me because I wanted very much to model its distinctively flattened silhouette. Thus, the turret ended up housing two PF Medium motors, first of which was used to elevate the main gun. The elevation system used a single linear actuator, much like in the Abrams model, except this time it was located in a central position to make the main gun’s barrel more stable. As for the latter PF Medium motor, I initially intended to use it for a main gun recoil system, an improved version of the one used in the Abrams, but I have eventually decided not to make these two models more similar to each other than they already were. It left me with just a few possible options to use the extra motor, so the motor was eventually used to make a ‘turret in a turret’, that is to rotate commander’s gun, which is a nod towards the realism as the real Leclerc has this gun controlled remotely from inside the tank. Thanks to that, there was a lot of space left inside the other side of the turret, which I have used for something I wanted to use already in Abrams – an onboard live feed camera showing forward view from the turret. I have used a simple micro industrial surveillance wireless camera, exactly the one used much earlier in my Moon Rover. It fit inside the turret very well, and I was particularly pleased with the sound recorded from inside the model – the sound of moving tracks seemed more realistic than I could have ever imagined.

The model enjoyed a fairly good reception. I didn’t really like its aesthetic side which seemed too much like that of the Abrams model, but I loved the performance provided by the powerful drivetrain and the sophisticated suspension system. It seemed to have all the impressive power of Abram’s drivetrain, but moved much more swiftly and fluently. It was my fastest tank model at this weight and the first one to use Power Functions speed control feature.

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Model of a Caterpillar tracked dozer. Features remotely controlled drive, steering, blade and ripper.

Datasheet:

Completion date: 09/05/2009
Power: electric (Power Functions)
Dimensions:  length 50 studs / width 26 studs / height 25 studs
Weight: 1.56 kg
Suspension:  none
Motors: 5 x PF Medium

I was interested in the unusual Caterpillar tracked dozers for some time, but I couldn’t build such a dozer earlier because the triangular shape of tracks required 6 sprocket wheels and I only had 4. Having finally acquired the missing 2 wheels, I proceeded with the construction right away.

Nowadays, when one builds a yellow tracked dozer it will be obviously compared to the famous Lego 8275 set.  Since it was clear from the beginning that my model would be significantly smaller, it was my goal to include in it more functions than the 8275 had, and thus surpass it in terms of functionality.

The basic difficulty is that the Caterpillar tracked dozers are unusually narrow – the width of the hull is only slightly greater that the width of a single track. When I calculated dimensions of model with the new tracks system which are 5 studs wide, it turned out that the hull will be just 6 studs wide.  It happened to be just the minimal possible size to house a battery box and several motors inside. Since with the coming of the new 8879 speed control enabled handset the subtractors have become obsolete, the model was supposed to be driven by two identical motors located side-to-side. With the hull just 6 studs wide the only possible choice were the PF Medium motors, and they turned out to be a fortunate one. However, to make them fit in the hull it was necessary to make openings in its sides, so that the motors actually traverse through it.

Another difficulty is the layout of the tracks: they have contact with the ground at a relatively long area, yet they are just 6 studs apart from each other. It makes the model’s weight distribution crucial for its handling. Hence the entire model is built in a perfectly symmetrical way, both externally and internally, with the only exception of bevel gears at the linear actuators and the on/off switch. Placement of the battery box low between the front part of the tracks was a second factor that contributed to the proper weight distribution.

With the drive motors successfully located in the hull it was relatively easy to make the rest of the motors fit in.  Several tricks were needed to handle the problem of model’s limited size; for instance the axle that controls elevation of the ripper is driven not by gears but by a system of very short levers. The gears would simply take too much space, and since the axle’s rotation is very limited, the levers can do the job. Moreover, the fifth motor that changes the ripper’s tilt is controlled by a switch inside the cabin, because a switch is much smaller than another IR receiver.

The ripper’s geometry makes it maintain its tilt as the elevation changes. The ripper is strong enough to lift the back of the dozer off the ground, but not strong enough to endure when the dozer drives in such position. The blade, on the other hand, is robust enough to lift the front of the dozer and endure any kind of manoeuvres. I tried to make the dozer lift itself entirely on the blade and the ripper, but in this case the ripper couldn’t take the load.

Other than that, the model’s performance was satisfactory and it was quite a pleasure to drive it, especially with the new handset (the difference in driving with the old and the new handset is presented in the video below). I was happy with its aesthetic side too, although I was aware of several compromises between model’s look and functionality. For instance the driver’s cabin was made longer by 1 stud to house the IR receivers, and it resulted in the changed shape of the dozer’s rear side. Additionally, the bonnet protrudes forward a little more than it should, because of the battery box located right behind it. On the other hand the model has no suspension whatsoever, since it was the only way to fit it with the proper number of properly sized bogies. And I have used metallic silver cheese slopes as the tips of ripper’s blades because it looked more realistic than any usual colour. A minimal amount of custom stickers was used to make the model appear more realistic. I chose not to use the lights, partially because of the limited internal space available and partially to avoid the wires hanging from the headlights, as was the case of my 854G wheeled dozer model.

The model was well welcomed as a good example of my building abilities. It was not better than was expected of me, but it did not disappoint anybody either. Personally, I have considered it to be a relaxing project noteworthy only for its compactness and the first example of the use of the 8879 handset.

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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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Klocki, The Brothers Brick

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Model of one of the largest Liebherr excavators. Features 6 motors with full remote control, chassis driven from the superstructure and infinite freedom of superstructure rotation.

Datasheet:

Completion date: 12/02/2009
Power: electric (Power Functions)
Dimensions:  length 47 studs / width 18 studs / height 27 studs (with arm in transport position)
Weight: 1.52 kg
Suspension: none
Motors: 4 x PF Medium, 2 x  71427

My goal here was to create a fully remote controlled, pneumaticless model of an existing excavator, while keeping it reasonably small. My long-time affection made me to turn to Liebherr excavators, and I have chosen the R996 Litronic model with the undershot arm, due to its hull’s shape and arm’s construction. It was scaled to the size of the 3-studs wide tracks, which also suited the size of the linear actuators quite well.

The priority was to reconcile a realistic drivetrain with an enclosed hull construction. In real excavators the chassis is basically driven by one or many motors located inside the superstructure, thus ensuring the infinite freedom of superstructure rotation. This is possible thanks to a hydraulic system, which can’t be modeled with currently available Lego parts. Therefore, it can be only solved by pneumatic or mechanical means, the latter solution being much more compact and reliable. An iconic example of the mechanical solution is the model of a JCB JS220 excavator by Jennifer Clark. The essential trick is to transmit the drive through the turntable by a vertical axle with a free rotating driving ring on it. The driving ring can be assisted by an extension driving ring to transfer the drive further vertically, and eventually is meshed with the t16 gears used in the gearboxes. Thus we have the vertical axle transmitting drive to one track and the driving ring transmitting drive to the other track independently.

The functioning of this solution is slightly affected by the superstructure’s rotation, as the position of motors in relation to the tracks changes. Usually it results in the tracks being slowly driven by the supestructure’s movement, but this effect can be greatly reduced by the gear reduction below the superstructure. Here, however, the use of 71427 motors plus the gear reduction and the model’s weight resulted in motors being driven by the rotation rather than the tracks. Still, the drivetrain worked flawlessly, which can be clearly seen on the video when the superstructure is rotated clockwise while the chassis turns in place counterclockwise.

The hull’s construction was challenging from the very beginning. About half of its internal space is occupied by a battery box, and additional space is required by the IR receivers along with the wires. This leaves just about 40% or less of the internal space to be taken by the motors. I initially hoped to contain 4 motors inside the hull, but eventually only three fit in. The other three were incorporated directly into the arm, which helped to counterbalance the weight of the battery box and simplified the transmission system inside the arm.

I’ve spent a lot of time working on the geometry of the arm, and in the end it’s range of movement is as close to the real one as possible, while the number and the location of the linear actuators is almost identical to the number and location of the real machine’s hydraulic cylinders. The model turned out to work quite efficiently, it had a good weight distribution (although it could use a little more weight in the rear part), passed all practical tests, and was able to easily support itself on the arm in order to e.g. lift the front part of tracks above the ground. I was satisfied with its performance and considered it one of my most compact constructions ever.

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DoubleBrick

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Inspired by PistenBully snowgroomers. Features full independent suspension, dual longitudinal subtractor drive, pneumatic system with motorized valves and automated internal electric compressor, 3-section crane with infinite freedom of rotation, and lights.

Datasheet:

Completion date: 01/02/2009
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor)
Dimensions:  length 84 studs / width 30 studs / height 39 studs (with crane in transport position)
Weight: 3.9 kg
Suspension: full independent with shock absorbers
Motors: 9 x PF Medium, 2 x PF XL
Pneumatics: two circuits with motorized valves, fed from internal electric compressor with a pressure switch and an airank

Somewhat spontanical construction, inspired by some PistenBully snowgroomers I’ve seen over winter. I wanted to model the entire functionality of such a snowgroomer, and this eventually turned out to require 11 motors. Here’s a full list of motors and the functions they control:

1. PF XL – drive (left tread)
2. PF XL – drive (right tread)
3. PF Medium – steering
4. PF Medium – pneumatic valve #1
5. PF Medium – pneumatic valve #2
6. PF Medium – crane rotation
7. PF Medium – lower crane section
8. PF Medium – upper crane section
9. PF Medium – compressor
10. PF Medium – flashing lights
11. PF Medium – front blade tilt

As can be easily seen, we have 3 motors more than the number of channels available with the PF system. To deal with it, we need to control these 3 motors by some other means. Namely:

1. both drive motors are controlled by a single channel
2. the flashing lights motor is permanently on, so it needs no channel
3. the compressor motor is controlled automatically by a pressure switch

The vehicle is suspended on 8 road wheels, each with an indepent suspension module with a shock absorber. There are shock absorbers of two different hardnesses used (first and last modules use harder shock absorbers than the middle ones). The front retracting wheels, and rear drive wheels are not suspended. The drivetrain consists of a dual longitudinal subtractor, where two PF XL motors drive the vehicle (one motor per one track), and the PF Medium motor controls steering by slowing down one PF XL and speeding up the other. It is, of course, possible to turn in place too.

A very unusual feature of the model is its pneumatic system. It consists of just two circuits, one with 3, the other one with 4 large pneumatic cylinders. Both circuits use regular pneumatic valves, which are motorized by PF Medium motors via safety clutches. The entire system is powered by a large electric compressor, that uses 4 small pumps divided into two units; when one unit is retracted, the other one is extended. It enables the compressor to operate more smoothly, reduces the vibrations it transfers to the hull, and makes the flow of air more fluent. The compressor is connected to an airtank, due to the high pressure needed straight off to operate the circuits quickly. The motor driving the compressor is controlled by a pressure switch, and thus the entire compressor module works in an entirely automated mode.  The construction of a pressure switch is strictly based on a concept created much earlier for the old pole reversers. Here I have just used the new PF switch instead. It is switched by two small pneumatic cylinders wrapped by a rubber band. Only the lower inlet of both cylinders is connected to the pneumatic system, therefore given a high enough pressure they overcome the rubber band and extend, turing the switch off. When the pressure drops, the rubber band forces the cylinders back, thus turning the switch on. I have used two cylinders due to a higher resistance of the PF switch compared to the one of the old pole reverser. The functioning of the pressure switch is shown in detail in both videos.

The front blade has one additional feature – it can be tilted left or right. The tilt is controlled by a PF Medium motor, via a safety clutch and a shaft that uses a number of universal joints to reach the blade’s head, where through a worm screw it rotates a vertical axle. Both front blade and rear smoothing plate are mounted on parallel levers, so they maintain their angle regardless of the elevation. I’ve tried to make the rear plate work more realistically by suspending it on two shock absorbers that press it against the ground. Thus the plate remains raised towards its front regardless of the ground’s shape. It does not, however, have the option to tilt left/right which is present in some snowgroomers.

Another important feature is the crane. It has the typical construction of small cranes (called HDS cranes in Polish technical terminology) used e.g. on cargo trucks and trailers: namely three sections, first vertical, two movable, with a hook at the tip. Two linear actuators are used here, both driven by PF Medium motors located inside the first, vertical section, without safety clutches. It provides precision and strength that pneumatics could not ensure. The crane’s first section is particularly complex and compact, due to space limitations imposed by the closely located battery box. One minor drawback of the crane’s design is the universal joint used to transfer drive from first to second section. It can’t operate when bent too much, so the third crane section becomes immobile whenever the second section is low. It is very inconvenient while connecting / disconnecting the load from the hook, but it provides load capacity far better than in a version with bevel gears instead of the universal joint (approx. 180 g compared to 50 g). On the video, the crane is carrying a 50-grams heavy truss module without even slightly bending under load. With loads heavier that 180 grams problems with the turntable’s stability begin to occur.

The infinite freedom of rotation is provided by a PF Medium motor located in the hull, and by the fact that there are only two wires going through the turntable. After a large number of revolutions these wires would eventually become entangled, but I assume that such situation is unlikely to happen during a regular utilization.

The last feature are the model’s lights, some of which are flashing. It is possible thanks to the solution used already earlier in my Tow Truck – a motor that drives the PF switch by an eccentric mechanism. The second video clearly shows details of this mechanism.

The model was well received, even though personally I did not consider it to be a project of a crucial importance. Perhaps the reason is that it was not my intention to try to use as much motors as possible, I simply wanted to model the functions of a particular vehicle. I liked, however, how well pneumatic system and linear actuators are compared in this single construction. The pros and cons of both these systems are clearly seen here – a pneumatically controlled crane would lack strength and precision, whereas LAs-controlled blade and plate would not adapt their elevation to the ground, not to mention how troublesome would it be to transfer the drive to LAs that would fold their wings. Thus, I have come to consider this model a good example of PF system’s potential not restricted by the 8 channels limit, as well as an excellent study of how pneumatics and linear actuators complete each other.

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Klocki, Particolarmente urgentissimo!, TechnicBRICKs, YFOLe (Polish only)

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Successor of the Challenger 2 model. Features advanced suspension system, dual 2-speed remote controlled gearbox, remotely rotated turret and elevated gun, main gun recoil mechanism, battery box sledge mounting system, custom stickers and lights.

Datasheet:

Completion date: 17/10/2008
Power: electric (Power Functions)
Dimensions:  length 74 studs / width 26 studs / height 18 studs
Weight: 2.83 kg
Suspension:  full independent with separate shock absorbers for each road wheel
Motors: 5 x PF Medium, 2 x PF XL

While building my Challenger 2 model, I got plenty of new ideas, some of which had to be dropped because of the limited size of the model. I don’t usually like to build two constructions of the same type in a row, but in this case the number of these ideas was so large that I’ve immediately started to build another, bigger model with newer treads system.

The suspension system was pretty much the same, except it used tread wheels of the newer tread system, seven road wheels on each side of the tank, and shock absorbers of three different, mixed hardnesses (compared to two hardnesses in the Challenger 2). This time the hull size was kept accurate, and was not deformed by the suspension system. The radius of the road wheels was slightly smaller than imposed by the scale (3 studs instead of 4).

The drivetrain, on the other hand, was completely different. It didn’t use any form of subtractor – instead, a single PF XL motor drove each track via a driving ring-based 2-speed gearbox. The gearbox could be actually called two gearboxes, as it consisted of two identical, independent modules. Each of these modules was controlled by a PF Medium motor, which resulted in the possibility to remotely change gears for left and right tank’s track independently. The gear ratios of both gears differed three times. If we include turning in place, it means that the gearboxes offered 10 possible combinations of the model’s turning radius. This was, however, somewhat inconvenient in practice, and the separate speed control of each XL motor would certainly be a better solution.

Gearbox was located at the back of the hull, inside a special chamber with internal lighting and 8×8 plate with grill on the top, so that it could be easily seen what gears are currently selected. The top grill plate was mounted in such a way, that it served as an easy access hatch in case if any problems with changing gears should occur (which never happened). Nearer to the middle of the hull were two XL motors, and then two Medium motors that controlled the gearbox (both with safety clutches). Front part of the hull housed a battery box with a special sledge mounting system. Thanks to that system, the box was firmly installed inside the hull, but could be removed from below in a matter of seconds. Moreover, the system was only slightly larger than the box itself, and didn’t require any extra parts to be attached to the box. Finally, the very front of the hull housed three of four model’s IR receivers.

The turret’s construction was based majorly on the turret of the Challenger 2. It housed three Medium motors, one IR receiver,  and a single linear actuator. It was powered from the hull via two wires, which granted large rotation freedom. One motor with a safety clutch was used to rotate the turret, and it could be rotated through 360 degrees, although not as smoothly as the Challenger’s turret because of the worse weight distribution (the rear of the turret was much heavier than the front). The other motor powered linear actuator that controlled the main gun’s elevation, exactly in the same way as in the Challenger. The third motor controlled the main gun recoil system. It consisted of a motorized eccentric mechanism with a string attached in such a manner that the string was continuously pulled back time by time. The other end of the string was attached to the main gun’s cradle, which provided 1 stud of longitudinal movement and contained a rubber band that worked against the string. Thus, with the recoil system engaged, the main gun was pulled back by the string, and then moved back forth by the rubber band. It happened in continous cycles, regardless of the gun’s elevation. One drawback of this solution was that the gun was somewhat unstable, and vibrated while driving. This effect could be, however, greatly reduced in case of a shorter and lighter gun.

I was very happy with the final look and performance of the model. While unstable main gun looked a bit ridiculous, the tank made up for it with the flawlessly working suspension and drivetrain. Using shock absorbers of different hardnesses was a good solution, although the last pair of road wheels was troublesome to suspend (it needed hard shock absorbers to not yield to the model’s weight while driving forwards, but such absorbers only worked a little bit on the obstacles). Driving the model with two XL motors was a good idea too, it is clearly seen on the video that such a drivetrain was quite powerful, despite the tank’s weight. It should be noted that it was difficult to make the model turn in place on any not-really-smooth surface, probably because of the tracks’ length. Still, it was quite an advanced and well-functioning model, and for some time I have even considered it an ultimate level of how far a tank model can be developed. Which was obviously not true Additionally, it was my first model photographed with professional lighting and against a professional background – especially the lighting greatly increased the quality of final pictures.

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Klocki

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