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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Video:

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Media reference:

Hobby Media (Italian only)

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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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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.

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Video:

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Media reference:

TechnicBRICKs

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Model of the world’s largest wheeled front loader. Features 4×4 drive, realistic suspension, lights and arm & bucket controlled remotely with linear actuators.

Datasheet:

Completion date: 30/08/2009
Power: electric (Power Functions)
Dimensions:  length 58 studs / width 22 studs / height 23 studs
Weight: 1.57 kg
Suspension:  front – none / rear – pendular stabilized with shock absorbers
Motors: 1x 71427, 2x PF Medium, 1x PF XL

Articulated 4×4 vehicles seem to be my soft spot. So far I’ve built three front loaders and an articulated bulldozer, only to find out that I still have a reason to build another front loader – that is, I’ve never used linear actuators with a front loader until now.

The machine I’ve picked this time is the world’s largest wheeled front loader. Le Tourneau L-2350 (sounds French, but it’s actually USA-produced) was designed to co-operate with the largest mining dump trucks (such as e.g. Liebherr T282B whose model I’ve built some time earlier), and at a gross weight over 250 tonnes it is able to move 75 tonnes of load at a time. I was initially attracted by its immense size, hoping that it would allow me to build a large model with plenty of room for internal mechanics. It did not.

As usual, the model’s size was limited by the wheels. The original L-2350 is a huge machine, but unfortunately its wheels are huge too. With Lego 94mm wheels being the largest wheels available for this model I was forced to build it just 22 studs wide. 22 studs may seem like a lot, but only until you look closely at how a regular front loader is usually built: the bucket is 22 studs wide, while the vehicle with wheels is 20 studs wide. The hull without wheels is only 14 studs wide. It still sounds like a lot of place, but almost half of it is made with various small side bulges. The central part of the hull is merely 8 studs wide, and this is where the entire mechanics has to be placed.

The model is really compact – to the point where it would be impossible to build it without the 8878 battery – the standard PF battery box is way too large. It’s driven by a PF XL motor housed in the lower rear part of the hull. The rear axle consists of my usual 3-studs wide differential bracing, which serves as a pendular suspension stabilized by 4 shock absorbers (2 at each side). At the same time it transfers the drive further, through an universal joint, to the front axle which consists of the same, but fixed, bracing. The drive motor is also connected to a large fan that can be seen through a grill plate at the back of the vehicle. Front loaders usually have large radiators in the back, and I liked the idea of placing there a big fan that rotates as the vehicle drives.

The steering mechanism in such a model is always tricky because of the size limitations and a substantial gear reduction necessary. It’s impossible to use turntables in a model that small, and I found even the liftarms to be too large for the central joint structure. The structure was compacted as much as possible and is held together almost exclusively by a single vertical axle. The steering is achieved by a horizontal 40-teeth gear placed on this axle, which is driven by a PF Medium motor through a worm gear. The central joint is traversed by two universal joints – one driving the front axle, the other driving the arm elevation mechanism – and three wires, two of which power the front lights while the third one powers a 71427 motor located above the front axle.

Since it was literally impossible to house all the four motors inside the rear half of the vehicle (I was barely able to fit two IR receivers in there), I was forced to place one motor inside its front half. The motor had to be as short as possible, so the 71427 motor was an obvious choice – it’s two studs shorter that a PF Medium motor while providing similar speed (and much lower torque, but it was not needed for its function). Thus, the bucket is tilted by the 71427 motor via a safety clutch, and the arm is raised by a PF Medium motor housed in the rear part of the model.

The use of linear actuators was the very reason this model was built for, and it proved a significant advantage. Not only the linear actuators are far more accurate and stronger than pneumatic cylinders, but they also make the central joint free of any troublesome pneumatic hoses. There are three actuators used, only one operating the bucket – the real machine uses two hydraulic cylinders for that purpose, but the available space was simply too narrow for two actuators.

As for the look of the model, it suffers from a number of compromises for the sake of functionality – the most apparent of which is the battery box protruding upwards from the rear part of the hull. On the other hand I find the wheels quite neat. I couldn’t find any Lego wheels that would look like the real ones, so with a bit of inspiration from a fellow LUGPol builder M_longer, I’ve used black 94mm wheels with black tires and yellow sprocket wheels placed inside.

I consider it to be an average model. I must admit it performed somewhat better that I expected, but I still had the feeling that it could be much better if only I could make it a little bigger. It was also my first model with a high quality video – I made an effort of filming and rendering it in a quality that would comply with the YouTube HQ standard just to see what it would look like. I was pleased with the effect and decided to make all my future videos in that standard.

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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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A typical truss tower crane. Features three types of truss, movable trolley and counterweight, and unusual rotation system.

Datasheet:

Completion date: 15/03/2009
Power: electric (Power Functions)
Dimensions:  length 184 studs / width 19 studs (not including the baseplate) / height 159 studs
Weight: 2.89 kg
Load capacity: accidentally collapsed at 438 grams
Suspension: none
Motors: 1 x PF Medium, 1 x PF XL, 2 x  71427

I’ve been fascinated by truss constructions for a long time, and it felt natural to eventually build a simple truss crane. Or, to be more specific – I thought a tower crane was simple until I actually started to build one.

I have used two important points of reference: a tower crane by Philo,  and a bigger one by Thomas Avery. The crane was meant to be realistic, and thus was built pretty closely after a typical scheme:

The most important part are obviously truss modules. Typically, a truss can be a subject to up to four factors: bending, twisting, compression and stretching. It is possible to build a truss resistant to all these factors, but such a truss is heavy and rarely has to actually bear all four factors. It is therefore a good solution to use the lightest truss possible, designed to bear only specific factors. This is the case of this crane – out of three truss types used none is capable of bearing all the mentioned four factors.

First, there is the tower mast. I have designed something I could call a perfect truss module for it, but it turned out to be too parts-consuming. Such a module can be built with bricks and beams, in a rectangular shape. It consists of vertical 9-studs long beams connected to a horizontal 10-studs long bricks, and reinforced slantways with 13-studs long beams. All these dimensions fit perfectly, and it’s very easy to stack such modules one upon another. I did not, however, possess enough parts to build a mast of desired height (I wanted the crane to be able to transport loads from the floor to my table) with such modules, so I used a simplier, less stiff version.

The tower mast is modular, with lower part reinforced by counterforts from four sides and by vertical beams on the edges. It would be perfect to reinforce the entire mast with the beams, but I did not have the sufficient number  of beams in a single colour, and I was unwilling to make the crane multi-coloured, nor to buy extra parts for it. The mast is resistant to compression, twisting and bending, but not to stretching because of its modular construction.

Secondly, the counterjib. It was meant to have empty space inside, so I used a rectangular truss with only two sides reinforced. It is resistant to everything except twisting.

Finally the jib. It was quite a challenge to make it triangular, just like in real cranes, but the triangular truss is much lighter than a rectangular one of this size would be, while being resistant to bending and compression. It is prone to twisting and to some extend to stretching, but is secured from the latter by a stay. It was very convenient to use as a crane runway.

The entire crane is obviously modular: it consists of the tower mast, the upper arm (jib and counterjib together) plus a turntable crown. The turntable is not a usual one. There is a regular Lego turntable used to connect the upper arm to the mast, reinforced by six rollers (in two sets, 3 in front, 3 in back) located above it. The rollers rest on a crown that encloses the turntable. Up to this point it is quite a usual solution, but it’s the first heavily reinforced turntable I’ve ever built, and it performed flawlessly (largely thanks to the rollers being located several studs above the turntable, I guess). Now, the unusual thing is how the crane rotates – it does not use the actual turntable. Instead, as I’ve learnt from Thomas Avery’s work that any rotation-transferring mechanism may be prone to twisting at this size, I have used a vertical 16-studs long axle from the Jumping Giant set, which is made of a more flexible material that the usual axles, and the entire crane rotates around that axle. It goes through the entire turntable, its lower end is fixed to the turntable’s lower part, and the upper end is set inside the upper arm structure so that it may rotate inside. Thus, the axle is deliberately twisted by rotation, and softens the jib’s movement when the rotation motor starts or stops. A motor speed control would come very handy here, but it was only possible with the WeDo system at the time. In fact, I have successfully tested the rotation mechanism with the WeDo set, controlling the rotation speed, but it was very inconvenient because the crane had to be placed near a computer, and connected to it by a wire.

The counterjib contains two counterweights – a fixed one at the end, and a movable one inside. Note that a movable counterweight is as far as I know a purely fictional idea, not used in the real cranes. I have used it on assumption that it would help to balance the jib’s load and thus improve the crane’s load capacity – which it did. Initially, I planned even to make the counterbalancing automated – by means of the stay connected to jib and counterjib, and to an axle in the middle of the crane. As jib would lower itself under load, it would pull the stay and move the mentioned axle, which would then turn a PF switch on, thus activating the counterbalance’s drive system.  I believe it was a theoretically correct idea, but in reality it turned out impossible to calibrate the PF switch’s sensivity and the movement range of a loaded jib relatively to the middle of the crane.

Inside the jib, there are two sets of ropes. Both are connected to individual hoists; one of them lowers/rises the hook, while the other one moves the trolley along the jib. Because the space in the counterjib was taken, I could not use a very convenient and realistic solution present in the Philo’s crane – that is hoists  located in the rear part of the crane. Instead, hoists are located on the top of its middle part, and there is a complex system of pulleys that connects the hoists’ drums to the ropes inside the jib.

First set of ropes controls the height of the hook. It consists of a single rope, which through a system of pulleys makes it possible for the hook to maintain constant height while the trolley moves. It is obviously possible to operate the hook and the trolley at the same time, and the entire arrangment is shown below.

I have decided to use two drums in the hoisting block in order to have the hook suspended on 4 sections of rope, thus limiting the hook’s side sway while the crane rotates.

The other set of ropes, controlling the trolley’s position, doesn’t work so well. Philo has used a brilliant solution in his crane, where a single rope is kept tight by a shock absorber, and it goes through a single hoist drum that moves it. I tried to reproduce this mechanism, but in my case the rope tended to slip on the drum. Expecting heavy loads to be moved, I have dropped this idea and used two separate sections of rope on two separate drums (driven by a single motor). It is much more complex and much worse solution, because the drums work unevenly and the ropes get loose or strained all the time, depending on the trolley’s position. It was not possible to make their tensions even with a shock absorber, because the difference is simply far too great. So, the system I have created works, but not as smoothly as Philo’s one, and it needs manual corrections of ropes from time to time.

The crane was impressive due to its size and the regular truss modules. It was the first time that I was able to  sit under my construction, or that I was forced to get out of the way as it rotated. It went through a lot of testing, but collapsed before I managed to have some actual fun with it. It was really tiresome to build, but I consider it a precious experience that will be useful for my future constructions.

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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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Model of a Caterpillar articulated wheeled dozer. Features 4×4 drive, suspension, remote steering, remotely raised and tilted blade, lights and custom stickers.

Datasheet:

Completion date: 17/12/2008
Power: electric (Power Functions)
Dimensions:  length 57 studs / width 30 studs / height 22 studs
Weight:  1.73 kg
Suspension:  front – none / rear – pendular with shock absorbers
Motors: 4 x PF Medium

Another articulated Caterpillar vehicle. Partially similar to my earlier 990H front loader, but slightly larger and with different functionality. I wanted to use linear actuators instead of pneumatics, and that required more internal space that available inside a front loader. Therefore I decided to build a wheeled dozer, which offers more space inside the front hull’s part.

The drivetrain was simplier and more compact thanks to the use of new, 3-studs wide differentials. Only two motors were needed in the rear part of the hull, which could be therefore less massive and more realistic in size. The battery box was located in the same place, that is low behind the rear axle. It caused some problems with the weight distribution in case of the front loader, which did not have any heavy parts inside its front part. Here, another two motors were located above the front axle, so the weight distribution was much better.

The steering system was changed too. Earlier it was based on the horizontal 36-teeth gear braced in liftarms traversing the vehicle’s frame. This time, I wanted to try to save some space, and used a 12-teeth gear instead, with much weaker, yet more compact bracing. I was not satisified with the final result – the steering system worked, and supported model’s weight even when carried in hands, but the precision of steering was poor, and the central joint lacked stiffness.

As for the blade, I have attentively studied the construction and functionality of its real counterpart and decided to make it simplier and less functional. In the real 854G, the blade has the ability to turn to sides to a limited angle. Only a single hydraulic cylinder is needed to control this mechanism, but it meant that blade’s every point of attachment had to have two degrees of freedom. Thus the entire structure supporting the blade would become much more complex, and probably less rigid. Eventually, the blade was controlled by four actuators and turned out to be strong enough to lift the dozer’s front axle off the ground. The dozer performed reasonably well, except for the forementioned poor precision of steering. It could use a PF XL motor for drive to be able to push heavier loads, yet still the Medium motor provided a satisfactory torque.

The model was received much better than I expected. For me, it was merely a development of my earlier Caterpillar models, built partially for relaxation after the arduous work on the Colonial Marines APC model. Still, a considerable number of viewers expressed their accolade for the dozer.

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A mastless forklift. Features full independent suspension with normal & crab steering mode, remotely elevated boom, remotely tilted fork, remotely switched steering mode and lights.

Datasheet:

Completion date: 16/11/2008
Power: electric (Power Functions)
Dimensions:  length 62 studs / width 28 studs / height 18 studs
Weight:  1.48 kg
Suspension:  full independent with shock absorbers
Motors: 4 x PF Medium, 2 x PF XL

Upon acquiring the 8297 set, I felt compelled to utilize its suspension components along with the linear actuators, to refresh my earlier telehandler designs, and see what potential can they gain with the new parts. This resulted in a vehicle that is a mastless type of forklift, though it greatly resembles a telehandler. Well, that’s just the charm of the formal classification.

The basic feature of the model was the steering on both axles, which was possible in two modes: standard one and a crab steering. This time modes were switched by purely electric means: two separate motor controlled steering of front & rear axle, and the rear one was powered through a PF switch. The switch’s position could be changed remotely by another motor, and in result the rear axle would behave differently in the normal and in the crab steering mode. The system worked very well, mainly thanks to the use of clutches in both front & rear steering system. Thus, it was possible to switch modes at any moment, and adjust wheels’ position by simply turning them to the maximum. The amount of space needed, however, made me give up the idea of a 4 wheel drive, and eventually only the rear axle was driven. Additionally, it was the first use of the new, 3-studs wide differential in a suspension module that had both drive & steering. It worked, but performed below my expectations, and I have taken a completely different approach in my later use of this differential.

The second important feature was the construction of the boom. It consisted of two parallel levers – a system that normally offers the possibility of self-leveling one end accordingly to the other. Thus, the model’s fork maintains its tilt when the boom is raised and lowered. An uncommon solution was the use of another motor to change the position of one lever relatively to the other, which resulted in a simple and effective fork-tilting mechanism.

The model was given a raw, typically ‘Technic’ aesthetics, which met with a better response that I expected. Additionally, the fact that I restrained from using black colour this time, was much appreciated. This was also my first model whose photos’ colors were fixed by me the way the professional photos are fixed, and I was so pleased with the effect that it has become a standard for my later constructions.

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My second telehandler. Features 4×4 drive & steering, crab steering mode, full independent pneumatic suspension, pneumatically raised boom with a self-contained extension mechanism, pneumatically tilted fork, internal electric compressor and a high precision remote pneumatic valve.

Datasheet:

Completion date: 06/07/2008
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor)
Dimensions:  length 54 studs + boom / width 31 studs / height 21 studs
Weight: 2.1 kg
Suspension: full independent pneumatic
Motors: 4 x PF Medium, 2 x PF XL
Pneumatics: three circuits with manual valves and one with a remote high precision valve

My last complex project based on old parts – it used pneumatics for the lack of linear actuators, and the suspension components from the 8880 set. Built in a somewhat obsolete way, but with a number of new solutions.

The goal of the project was very simple: to take the subject of telehandlers and develop it further than I did when I approached it first at 2007. It has been fitted with a full independent suspension with 4×4 drive and steering – all based on the 8880 set’s suspension components. The suspension used pneumatic cylinders instead of shock absorbers, which not only allowed to control the ground clearance, but also to tilt the vehicle forward and backward, as the front and rear suspension used two independently operated pneumatic circuits. This feature prompted me to give up the outriggers system, which is present in some heavy telehandlers, because I could simply make the model rest on the ground. Furthermore, the steering system could operate in two modes: normal and crab steering. The modes have been selected mechanically, by a ratchet mechanism operated by a separate motor. It didn’t work quite well, because of some problems with engaging and disengaging gears. The steering wheel in the cab was not functional.

The boom has been raised by two pneumatic cylinders, controlled by a remote high precision valve. The valve consisted of a regular pneumatic valve switched by a 40-teeth gear, that was driven by a PF XL motor with a huge gear reduction (240:1). I have chosen this kind of solution, because my experience with pneumatics convinced me that Lego pneumatics can handle almost any load with a good precision, provided the valve is operated carefully enough. It’s purpose here was to lower the heavy boom carefully, and it worked well. The boom itself has been built in an entirely new way. There has been two sections, one enclosed completely in the other, and extended by racks. The novelty was the fact that the racks were operated not by a regular gear, but by a worm gear directly, so it was not the conventional rack and pinion mechanism. It was a bit tricky to get the worm gear in the proper position, but once there, it worked smoothly and saved a great deal of space, resulting in my first completely self-enclosed boom. The boom was extended by a PF Medium motor located at its base, because the size of that motor made it fit in there perfectly. The only disadvantage of this solution was the lack of a clutch between the motor and the worm gear, but that could be easily solved by the use of a linear clutch that I have developed later.

At the end of the boom, there was a simple fork tilted by a single pneumatic cylinder. Just like in my first telehandler, I found no solution to the problem of placing pneumatic hoses on an extendable boom, so there is some surplus of the hoses hanging free – an ugly and unrealistic solution. The load capacity of the boom was limited, because of the heavily loaded pneumatic system.

It was an ambitious project, perhaps too ambitious for the availability of Lego parts at the time. Shortly after it was built, a range of new elements appeared, that could significantly improve the overall performance of the model. Additionally, the aesthetic side of the vehicle seemed half-baked at best. Still, it has been a very good test of some new ideas.

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My first excavator. Features chassis driven by the motors inside the superstructure, three pneumatic circuits with an internal electric compressor, and full freedom of the superstructure rotation.

Datasheet:

Completion date: 14/06/2008
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor)
Dimensions:  length 45 studs / width 19 studs / height 24 studs
Weight: 1.35 kg
Suspension: pendular bogies
Motors: 2 x PF Medium, 2 x PF XL
Pneumatics: three circuits with manual valves and internal electric compressor

From time to time I build something completely ignoring its aesthetical side, only to study some technical issue. Here is a very ugly case of that – an excavator built primarily to test the drivetrain system developed by Jennifer Clark and others, where the chassis is driven by the motors located inside a rotated superstructure. Since there are two motors needed, this is quite a challenge. A solution to that is the use of an ‘empty’ (without internal bevel gears) differential to transfer drive through the superstructure’s turntable. The differential is set on a vertical axle that transfers the drive of one motor, so that it can rotate on that axle freely and is not affected by its rotation. With such a setup, the differential is used to transfer the drive of the other motor, and it can be connected to a driving ring, if there is a need to transfer the drive further vertically. If used properly, this solution offers a full freedom of the superstructure rotation, at the cost of the rotation affecting the drivetrain – since the motors are stopped, the rotation movement drives one tread forwards and the other one backwards. This effect can be greatly limited by using gear reduction in the drivetrain below the turntable. Here, the worm gears were used for reduction, and the effect is barely observable.

This is exactly the type of the drivetrain used in this vehicle. There are two PF XL motors inside the superstructure, and each of them drives one tread. The superstructure is rotated by a PF Medium motor located inside it, and has full freedom of rotation, as there is only an axle and a differential traversing its turntable. Thanks to that, the chassis is very compact; there is axtually just a 7x7x7 studs liftarmic cube below the turntable, and the treads are connected to the sides of it.

The rest of the model is quite simple: there is an internal electric compressor driven by a PF Medium motor, that powers three pneumatic circuits, each with a manual valve. Two of them control the arm, and the third one controls the bucket. This construction has taught me a lot – among others that I can’t build from liftarms as easily and successfully as Nico71 does.

Note: some people ask if the bucket is the wrong way. No, it is not. There are two possible setups of excavator buckets: with the bucket facing backwards or forwards. The latter, which I have used here, is simply much less common, typical for mining excavators rather than for the ones at the construction sites.

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Model of a Caterpillar front loader. Features 4×4 drive, suspension, internal electric compressor and two pneumatic circuits, plus a 2-section arm with a progressive geometry.

Datasheet:

Completion date: 31/05/2008
Power: electric (Power Functions) / pneumatic (fed from internal electric compressor)
Dimensions:  length 60 studs / width 18 studs / height 27 studs
Weight: 1.56 kg
Suspension: rear – pendular with shock absorbers / front – none
Motors: 3 x PF Medium
Pneumatics: two circuits with manual valves and internal electric compressor

My third front loader, and second Caterpillar model. Although externally very different from my previous Cat R2900G, it is internally pretty close based on it, with a number of improvements. It features the same 4×4 drive, but the rear suspension is shorter, stronger, and fitted with a pair of half-floating shock absorbers that make it stable. Steering system is exactly the same, with the central joint rotated by the horizontal 36-tooth gear, a solution that blends compactness with robustness and precision very well. The compressor is the same too, but here it is driven by a separate motor. It powers two pneumatic circuits, that control two sections of the arm. The arm’s construction is very close to the original, and a particular effort was put to model the bucket-tilting mechanism, quite specific for Caterpillar machines. The arm has a progressive geometry, which means that the bucket slightly tilts forwards as the arm is lowered, and slightly tilts backwards as the arm is raised. The model uses an unique LEGO unitary bucket, whichI was able to buy at a bargain price.

The whole model is more accurate than the previous one, to the point where even the Caterpillar livery is modeled as well as possible without stickers. It has, however, a number of faults: the hull is too tall by 1 stud, the cabin is at least 2 studs too tall, and the rear part is too massive. Additionally, I was unable to model the banisters that cover top part of the original machine, because I had no appropriate parts at the time. Still, it was an extremely playable model.

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