Model of a generic reach stacker. Features drive, steering, elevated and extended boom, elevated cabin, rotated head and motorized jaws.  

Datasheet:

Completion date: 01/04/2012
Power: electric (Power Functions)
Dimensions: length 38 studs (not including the arm) / width 22 studs (not including the arm) / height 22 studs
Weight: 1.565 kg
Suspension: none
Propulsion: 1 x PF XL motor geared 1.4:1
Motors: 2 x PF XL motor, 3 x PF Medium, 2 x micromotor

Reach stackers are highly specialized industrial machines that can be considered a distant variant of a telehandler. They are being used primarily in cargo terminals in ports around the world, where their task is to transport and arrange containers. I have been planning to build such a machine for a very long time, and I finally succeeded.

The model showed a generic, typical reach stacker rather than some particular model. The interesting thing about reach stackers is that they are absent from the offer of most of the European machinery manufacturers, except for the Liebherr company which produces reach stackers with arched booms, which would be extremely difficult to model with LEGO pieces.

The model was intended to be as simple, small and functional as possible. I have used no suspension system in it; I was unable to determine whether real reach stackers have any suspension systems, but it seems unlikely for machines that are designed to carry heavy loads around perfectly flat asphalt areas. For example, most front loaders have no suspension on their front axles to make them more stable with loads, and they are supposed to work in rough terrain.

Most of the model was built entirely studless, with exception for the sides of the hull, consisting of studfull bricks connected to the bearing frame. Thus, they were used to strengthen the chassis in its crucial section between the mounting points of the boom and of the linear actuators.

The model’s front axle was driven by PF XL motor through a single differential, and its four wheels were mounted on two small Technic turntables which acted as bearings, taking load off the axle. It seemed to work, as the model proved to be very agile, with and without the load. The rear axle was steered by a PF Medium motor with a very simple steering mechanism lacking a clutch or a return-to-center function. It had an extreme steering lock, merely thanks to removal of any parts of the body that could collide with wheels.

The boom, made of studless panels and self-container, was elevated by two large linear actuators driven by a single PF XL motor. A PF Medium motor installed at the back of the boom was used to extend it, through a system of a worm gear meshed with racks on the boom’s extendable section. The head at the tip of the boom included two micromotors, one for rotating it and another one for closing and opening its jaws. Since the head was intended to balance itself under own weight, just like in real machines, a weighted brick was attached to its side opposite the latter micromotor to counter-balance it. The head’s rotation range was full 360 degrees, and its jaws had a gripping range from 9 to 31 studs. Finally, a PF Medium motor and a small linear actuator were used to elevate the cabin and move it forward, but due to lack of space in the hull, the range of movement was minimal and the function was quite unimpressive.

One function that I toyed with and eventually abandoned was tilting the head forward and backward. Real reach stackers have such function, although it appears to be very rarely used. I did not expect to really need it, and it added plenty of technical difficulties, requiring another motor near the boom’s tip, or a pneumatic system routed to its tip, or perhaps an extending driveshaft inside the boom.

There were few interesting technical solutions that I’ve tried – other than using turntables as bearings, they included the construction of the boom which can be made much longer, and the jaws extension mechanism which was very simple, compact and yet reliable. In general, the model had a sturdy chassis and boom, but rather delicate head and jaws. Despite that, the jaws worked flawlessly with any kind of load, and the maximum load capacity of the model proved to be almost 0.5 kg, limited only by the torque of the PF XL motor elevating the boom and by the clutches in the linear actuators.

I have also used this opportunity to test my IR Link sensor which allows the NXT brick to control Power Functions devices. I have built a simple NXT controller with one joystick, using three motors and two touch sensors and working in two modes: drive mode and boom control mode. The controller worked rather well using my program written in ROBOTC which is included below, but the IR Link sensor was a disappointment: its range was shorter than that of PF remotes, and it caused delays in the reaction of PF motors. Still, controlling the model in such way, definitely more realistic than with regular Power Functions remotes, was an interesting experience.

Control program:

#pragma config(Sensor, S1, HTIRL, sensorI2CCustom)
#pragma config(Sensor,S3,touch1,sensorTouch)
#pragma config(Sensor,S4,touch2,sensorTouch)
#include "drivers/HTIRL-driver.h"
bool sending = false;
bool drivemode = true;
tPFmotor DriveMotor = pfmotor_S1_C1_A;
tPFmotor SteeringMotor = pfmotor_S1_C1_B;
tPFmotor BoomElevationMotor = pfmotor_S1_C2_A;
tPFmotor BoomExtensionMotor = pfmotor_S1_C2_B;
tPFmotor CabinMotor = pfmotor_S1_C3_A;
tPFmotor HeadCatchMotor = pfmotor_S1_C4_A;
tPFmotor HeadRotationMotor = pfmotor_S1_C4_B;

task Buttons()
{
  nNxtButtonTask  = -2;
  nNxtExitClicks = 2;
  nxtDisplayCenteredTextLine(0, "Not sending...");
  while(true)
  {
    if(nNxtButtonPressed == 3)
    {
      PlaySound(soundBeepBeep);
      if(sending == false){
        sending = true;
        nxtDisplayCenteredTextLine(0, "Sending...");
      }
      else{
        sending = false;
        nxtDisplayCenteredTextLine(0, "Not sending...");
      }
    }

    if(nNxtButtonPressed == 1)
    {
        drivemode = false;
        nxtDisplayCenteredTextLine(2, " DRIVE [BOOM]");
    }

    if(nNxtButtonPressed == 2)
    {
        drivemode = true;
        nxtDisplayCenteredTextLine(2, "[DRIVE] BOOM ");
    }

    if(nNxtButtonPressed == 0)
    {
      sending = false;
      PlaySound(soundBeepBeep);
      wait1Msec(400);
      PFMotor(DriveMotor, 0);
      PFMotor(SteeringMotor, 0);
      PFMotor(BoomElevationMotor, 0);
      PFMotor(BoomExtensionMotor, 0);
      PFMotor(HeadCatchMotor, 0);
      PFMotor(HeadRotationMotor, 0);
      PFMotor(CabinMotor, 0);
      StopAllTasks();
    }

    wait1Msec(400);
  }
}

task main()
{
  StartTask(Buttons);
  nxtDisplayCenteredTextLine(2, "[DRIVE] BOOM ");
  int LeftMotor = 0;
  int RightMotor = 0;
  int UpperMotor = 0;
  int RightButtons = 0;

  while (true) {
    if(drivemode == true)
    {
      LeftMotor = (nMotorEncoder[motorA] / 7) * -1;
      if (LeftMotor > 7) LeftMotor = 7;
      else if (LeftMotor < -7) LeftMotor = -7;

      RightMotor = (nMotorEncoder[motorC] / 10) * -1;
      if (RightMotor > 2) RightMotor = 2;
      else if (RightMotor < -2) RightMotor = -2;

      if (SensorValue(touch1) == 1) RightButtons = 7;
      else if (SensorValue(touch2) == 1) RightButtons = -7;
      else RightButtons = 0;

      nxtDisplayTextLine(4, "Left motor: %d", LeftMotor);
      nxtDisplayTextLine(5, "Right motor: %d", RightMotor);
      nxtDisplayTextLine(6, "Buttons: %d", RightButtons);
      nxtDisplayClearTextLine(7);

      if (sending == true)
      {
        PFMotor(DriveMotor, LeftMotor);
        PFMotor(SteeringMotor, RightMotor);
        PFMotor(CabinMotor, RightButtons);
      }
    }
    else
    {
      LeftMotor = nMotorEncoder[motorA] / 20;
      if (LeftMotor > 0) LeftMotor = 7;
      else if (LeftMotor < 0) LeftMotor = -7;

      UpperMotor = nMotorEncoder[motorB] / 20;
      if (UpperMotor > 0) UpperMotor = 7;
      else if (UpperMotor < 0) UpperMotor = -7;

      RightMotor = (nMotorEncoder[motorC] / 20) * -1;
      if (RightMotor > 0) RightMotor = 7;
      else if (RightMotor < 0) RightMotor = -7;

      if (SensorValue(touch1) == 1) RightButtons = 7;
      else if (SensorValue(touch2) == 1) RightButtons = -7;
      else RightButtons = 0;

      nxtDisplayTextLine(4, "Left motor: %d", LeftMotor);
      nxtDisplayTextLine(5, "Right motor: %d", RightMotor);
      nxtDisplayTextLine(6, "Upper motor: %d", UpperMotor);
      nxtDisplayTextLine(7, "Buttons: %d", RightButtons);

      if (sending == true)
      {
        PFMotor(BoomExtensionMotor, LeftMotor);
        PFMotor(BoomElevationMotor, UpperMotor);
        PFMotor(HeadRotationMotor, RightMotor);
        PFMotor(HeadCatchMotor, RightButtons);
      }
    }
    wait1Msec(200);
  }
}
									

Work in progress photos:

Photos:

Video:

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Media reference:

8studs (Polish only)

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Model of a South African MRAP vehicle. Features pendular suspension, 4×4 drive, 2-speed gearbox and lights.  

Datasheet:

Completion date: 18/08/2011
Power: electric (Power Functions)
Dimensions: length 41 studs / width 24 studs / height 22 studs
Weight: 2.074 kg
Suspension: pendular
Propulsion: 1 x PF XL geared 4.2:1 (low gear) / 2.5:1 (high gear)
Motors: 1 x PF XL, 3 x PF Medium

RG-35 4×4 is a modern small MRAP (Mine Resistant Ambush Protected) vehicle developed by BAE Systems South Africa as a smaller variant of base RG-35 6×6. It belongs to the second generation of the MRAP vehicles, which means that it combines high level of crew protection with impressive off-road capabilities. It was introduced in the first half of 2011, which means that it’s just starting to enter service, with the Canadian Army considering a massive order.

The model was built primarily to test the wheels and gear blocks from the 8110 Unimog set. It consisted of a short, fully studless chassis enclosed in a studfull body. Both axles had pendular suspension with 4 short shock absorbers on the rear, and 4 long shock absorbers on the front axle. The front axle had a Medium motor for steering integrated into it. The 8110′s set ball joints were used to attach axles to the chassis, as I expected them to support at least part of model’s weight thus reducing the friction on the driveshaft. Both axles also included differentials, as I expected them to be necessary for a vehicle with that short wheelbase. However, the presence of the differentials had a bad impact on model’s off-road capabilities.

The chassis, despite being very short and housing tall suspension modules, housed a remotely controlled 2-speed linear gearbox, a straight six piston engine with a separate Medium motor to drive it, and it even housed a motorized front winch unit until I decided to remove it to lower the model’s centre of gravity – and all of this with the right side of the hull recessed to accommodate for a spare wheel. The model had to weight at least 2 kg to be allowed to an outdoor Truck Trial race, and I achieved this weight by adding approximately 0.25 kg using weighed bricks. They were located at the very bottom of the body, thus lowering model’s centre of gravity.

The model turned out to have very soft suspension and additionally I have somehow mistaken the set-up of the gears in the drivetrain, resulting in an unusually low gear reduction. The latter rendered the model practically unable to drive outdoors, and it was eventually destroyed in an accident while I was driving it downhill. The short chassis was a disadvantage when climbing or descending, and the model tumbled forward over its front wheel and crashed.

I believe the model had a great potential, excellent ground clearance and one of the most effective chassis I’ve ever built. This potential was wasted due to my simple error in drivetrain’s construction and due to disadvantages of its short wheelbase.

Work in progress photos:

Photos:

Video:

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Model of a Spanish armoured personnel carrier. Features full independent suspension, 6×6 drive, 2-speed gearbox, remotely opener rear ramp, deployable tracked drone and lights.  

Datasheet:

Completion date: 14/08/2011
Power: electric (Power Functions)
Dimensions: length 56 studs / width 29 studs / height 24 studs
Weight: 2.306 kg
Suspension: full independent
Propulsion: 1 x PF XL geared 6.5:1 (low gear) / 2.3:1 (high gear)
Motors: 1 x PF XL, 3 x PF Medium, 2 x micromotor

BMR-2 is a modern Spanish armoured personnel carrier. It’s a fairly typical vehicle for its class and I have chosen it mainly for its short chassis with first and last axles steered. I was hoping it would work well in an outdoor Truck Trial race. Unfortunately, it turned out that this kind of a steering system won’t work for a vehicle of that size, weight and with these tires without differentials. I haven’t been able to build it on time and therefore I abandoned plans to try it in a race.

The model had a full independent suspension that used 8297′s set components. Axles #1 and #3 were steered through a common steering shaft, by a Medium motor geared down 9:1, with a safety clutch. All wheels were driven by a single PF XL motor through a remotely controlled 2-speed linear gearbox.

The chassis was entirely studless, with majority of internal components located above the middle axle. The body consisted mainly of plates supported by a frame of Technic bricks. This solution resulted  in an unusually low weight – something I was expecting and which prompted me to try using only one shock absorber per wheel. The suspension created this was was very soft, and even though it worked, the model displayed apparent tendency to ‘sit down’ on the third axle.

Close to the end of the building process I have realized that I can save up some internal space at the back of the model. It led me to realize an idea that followed me for a while (or was it planted?) – a small tracked drone deployed from inside. In a way, this was a MOC within a MOC, and thus: a MOCception The drone was extremely simple, built around two micromotors with chains instead tracks. The micromotors were powered and controlled by two long wires connected to a separate IR receiver inside the transporter.  The drone could be deployed once the rear ramp was opened and it could operate outside its carrier. It worked well, but due to its extremely low weight it was somewhat struggling against the wires. I have also integrated something like a simple passenger compartment into the upper hull’s surface, and it turned out to be perfectly fit for a single dwarf hamster.

Photos:

Video:

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Model of a pushback tug. Features a powerful propulsion system, elevated cabin and lights.  

Datasheet:

Completion date: 07/08/2011
Power: electric (Power Functions)
Dimensions: length 40 studs / width 16 studs / height 35 studs
Weight: 2.07 kg
Suspension: none
Propulsion: 2 x PF XL geared 24:1
Motors: 2 x PF XL, 1 x PF Medium

Pushback tugs, also called pushback tractors, are low-profile vehicles used to push and tow aircraft around the airport. They are in common use, as using a pushback tug is cheaper than having an aircraft move under its own power, and safer than having an aircraft move using jet engines. Pushback tugs come in two variants: the older one, with tractor connected to the nose gear by a tow bar, and the newer one which scoop up the nose wheel and lift it off the ground, effectively attaching themselves to it. I have chosen to model the newer variant, which is much more complex and more interesting. It was not modelled after any particular make of a pushback tug, just after the typical look of a vehicle of the newer variant, as I wanted to focus on performance rather than on accurate look.

My goal was to make a model capable of towing 20 kg of load on a wheeled trailer. The trailer was essential to reduce the friction – according to my tests, the model was able to tow roughly 6 kg without a trailer, with the load being simply moved on the floor. As I was unable to determine whether the real tugs have suspension systems of any kind, I decided not to use any suspension in the model. There are two reasons for it: first, the suspension of any kind would make the drivetrain more likely to fail under tension, and second, a suspension system seems needless in a vehicle designed to drive solely on the perfectly flat areas of the airports.

The front axle of the model was steered and the rear axle was driven. The model steered poorly, as its center of gravity was close to the rear axle and as the rear axle had no differential. The propulsion system consisted of two PF XL motors geared down 24:1 each, generating a total torque of 696 N.cm, that is 48 times the torque of a single non-geared PF XL motor. The rear axle was reinforced to handle this kind of torque: it consisted of a number of short axles rather than a single long one to limit twisting, and the gear wheels on it were doubled and connected together with four pins each in order to lower the risk of physical damage.

Tests ran on the model have shown that its construction can handle the required tension (it was built around a massive frame, and the area around the rear axle was heavily reinforced) and that it has plenty of torque (I was thinking of adding another two PF XL motors if needed). Thus the limit of its towing capacity depended only on the traction of the rear axle’s four wheels. I’ve equipped the model with massive body and installed six weighted bricks around the rear axle to make the model heavier and thus improve the traction. The weighted bricks added extra 0.33 kg while taking relatively little space.

The body of the model was simple and had little functions (I decided to make the nose gear attachment mechanism non-functional, and one of several reasons was that it was very difficult to observe how it works in real vehicle). The cabin was elevated, just like in many real tugs, using a motorized scissor lift mechanism and a single small linear actuator.

The model was very simple, but turned out able to achieve its goal: it towed the trailer with 20 kg of load on it. At this point the model was already having problems with traction, depending on the area of the floor, and the trailer was so heavily burdened that its wheels kept slipping off axles every couple of minutes. I was afraid to physically damage the trailer, even though it was built around two layers of massive 16x8x1 bricks, and hence I did not test heavier loads. It would be interesting to see how much such a vehicle could handle if it was carrying the load directly on it, as this would ensure sufficient traction, but such a solution involves plenty of problems resulting from a huge load being placed on the model’s structure. I suppose it is possible to make a Lego vehicle that can carry 20 kg of load on it, but it should be probably significantly different, e.g. with tracks or with wheels with no tires on them.

Photos:

Video:

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Model of a Liebherr excavator with tunneling arm. Features a blend of electric and pneumatic functions, custom stickers and lights.  

Datasheet:

Completion date: 17/06/2011
Power: electric (Power Functions) / pneumatic (external manual pump)
Dimensions (with arm in driving position): length 40 studs / width 16 studs / height 35 studs
Weight: 1.497 kg
Suspension: none
Propulsion: 2 x PF Medium geared 1:1
Motors: 4 x PF Medium, 1 x 71427

Model of a regular Liebherr excavator with an uncommon tunneling arm. Model of the very same machine created in larger scale was released in 2010 by my fellow LUGPol member M_longer and is available here. M_longer introduced me to this excavator before he started to build it, and I liked it so much that I intended to build it first. Eventually my timing kind of failed, because my model was finished 10 months after his

My version of the excavator was intended to be much smaller than M_longer’s: his was scaled to the new tread system, and I decided to use the old one for mine. The resulting difference in scale means that my model is roughly 40% smaller. Seeing that the model would be quite small for its number of functions, I have been planning to use pneumatics wherever possible and to have an external pneumatic controller permanently attached to the model. This solution is sometimes called a ‘pneumatic leash’ and it was used in many of the models created by my idol builder, Jennifer Clark. I have never really used it before and I thought of this as of opportunity to feel like Jennifer

While I was in the process of cramming the mechanics inside the hull, it occurred to me that I will be able to integrate all four pneumatic valves into the hull at the cost of making its upper surface uglier. I decided it was worth it, and eventually the model’s only external element was a single manual pump, which allowed for more accurate control of the pneumatic system than a motorized compressor would.

As for the aesthetic side, I didn’t want the hull to look like a box, which was pointed out with my earlier Caterpillar excavator, so I decided to build the sides and the back of the hull using body panels and SNOT (studs not on top) technique. I think the model looked generally worse than M_longer’s version, which is disadvantage of the smaller scale, but it did include a number of details that were omitted by M_longer in his model – such as e.g. the side and rear view mirrors.

The model had 5 motorized and 4 pneumatic functions. The propulsion system was obviously motorized and consisted of two PF Medium motors geared 1:1 and located in the chassis. The chassis also housed a third PF Medium motor, which rotated the superstructure. The fourth PF Medium motor was located inside the superstructure and drove two large linear actuators that controlled the elevation of the arm’s first section. As the actuators were effectively handling the weight of the entire massive arm, I have assumed that pneumatic cylinders would be too weak or too inaccurate for this task. Finally, there was a  71427 motor located at the back of the hull, and it was chosen because it’s shorter than a PF Medium motor. Its function was driving the milling head, which was done by a single long driveshaft that went all the way from the back of the hull to the tip of the arm and which was articulated in five places.

The 71427 motor was not controlled remotely, like the other four motors, but was instead connected to a switch located in the front right part of the hull. The same switch controlled two lights on the arm, as there was simply not enough space inside the hull to connect them together with hull’s front and rear lights. As a result, the lights on the arm lit up as the milling head works.

The whole electric system was powered from a single 8878 rechargeable battery located in the rear left part of the hull. The battery was accessible through a hatch in the left side of the hull, and was lying on its side in order to stay aligned with the side body panel.

The pneumatic system consisted of a single large cylinder that controlled elevation of the dozer blade in front of the chassis, two small cylinders that tilted the arm’s second section left and right, two large cylinders that controlled elevation of the arm’s third section and a single large cylinder that controlled the angle of the arm’s head. The arm itself was a fully studless structure partially covered by a studfull shell. Its range of movement was reasonably close to that of the original machine, and it was robust enough to support the model on one side. The milling head could be easily removed and replaced by e.g. a bucket or… something else.

It should be noted that the model’s driving speed and superstructure’s rotation speed were both inflated. I have done this on purpose, because I wanted to use the full potential of the model’s motors, knowing that I can reduce the abundant speed at any moment using the speed dial remote.

I was fairly satisfied with this model. It was compact yet full of various functions, it blended motors, linear actuators and pneumatics using the advantages of  each, and it looked quite good and accurate. Despite having no gear reduction at all, it was perfectly able to push and tow the 8110 Unimog set which weights over 2 kg. I consider it a noticeable step forward from my previous excavators in terms of blending aesthetics and functionality, and – unlike my previous excavators – it appeared free from severe disadvantages to me.

Photos:

Video:

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Media reference:

TechnicBRICKs

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My second marine vessel, another multi-hulled boat. Features rotary propulsion system and makes use of the Lego RC unit. Also included: the Grim Reaper.

Datasheet:

Completion date: 29/06/2011
Power: electric (RC unit)
Dimensions: length 96 studs / width 32 studs / height 32 studs (including propellers, not including antenna)
Weight: 1.756 kg
Displacement: 1.9 kg
Suspension: none
Propulsion: 2 x RC motor
Motors: 2 x RC, 1 x PF Medium

My second boat was intended to be larger, faster and radio-controlled, unlike the previous one which depended on easily lost IR link. I have finally managed to buy a Lego RC unit and RC handset – something I was looking for for years – and the new boat was a perfect opportunity to use it.

I was looking for larger displacement, so I have taken the four 50821 hulls from my previous boat, combined them back-to-back creating two very long and thin hulls, and added the 54100 hull in the center, where it increased the total displacement significantly. Eventually the boat was surprisingly heavy but it used less than half of its total displacement. You can notice on the video that the draught of the hulls is noticeably smaller than it was with my first boat.

The goal of the propulsion system was to provide high speed regardless of the direction – my first boat used two independent motors, which run work at full power only when going straight ahead.  This time I decided to use two RC motors, as they seemed better suited for the job, and the use of the RC unit guaranteed unleashing their full power. The two motors were combined into a single block, without being mechanically coupled. The block also included driveshafts and propellers, and was mounted at the back of the central hull and rotated left or right by a PF Medium motor and a single small linear actuator in order to make a turn. The propellers were the same as in my first boat: four 9-studs long propellers combined into two four-bladed units. Another difference was that the propellers were not protruding in the back this time, but they were fully enclosed within the block, with liftarms in front and behind them. I was hoping this would help against algae and that it would be generally robust. Luckily, there were no algae in the part of the lake where the boat was tested. As for the robustness, the Trimaran ran aground at least once, to the point where propellers hit the bottom, and it was able to reverse and get back to deep water without any help from the outside.

The propellers were driven from the RC motors’ slower outputs with 1:1 gear ratio.

I was toying with the idea of using the RC unit’s steering output to control some spring cannons, which would make the boat able to fire at targets. However, I decided that it’s crucial to secure the RC units against humidity and I wrapped it in a freezer bag along with part of the wires, which made using its steering input difficult. There was also no real place for cannons left once the crew was installed on the deck.

As for the aesthetics, I thought: why build another dull, plain boat when I can build the Terror of the Ducks and the Vessel of Pure Evil? So, I have prepared a large and diverse crew, including undead ninja, zombie sailor and the Grim Reaper himself, and added some decorative elements such as skulls, bones, wings and the unique Lego globe from the 4191 set.  It made people passing by give me weirdest looks (and that’s without them looking closely at the boat), but it clearly impressed the ducks.

The boat turned out slower than I expected, which could have resulted partially from its huge weight. Other than that, the propulsion system worked flawlessly, and the steering was very accurate. The RC unit proved to be a very good purchase as well, as I was able to make the boat go several meters away from the shore and roughly up to 10 meters away from me. I did not test the actual maximum range, but it was far greater than the range of the IR-based Power Functions system.

Finally, I have experimented a bit with both photos and the video. Photos of the crew were taken inside a light tent, on an acrylic sheet, hence the reflections below. The video was taken using telephoto lens with a polarizing filter on it. The filter did not work as expected, perhaps due to poor lighting conditions, and it made the image blurry when close to the maximum zoom. I decided not to use it any more.

Photos:

Video:

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

Datasheet:

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

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

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

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

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

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

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Model of the Humvee designed for Truck Trial races. Features full independent suspension, portal axles, 2-speed remote controlled gearbox, lights, opened bonnet, doors and rear hatch.  

Datasheet:

Completion date: 14/04/2011
Power: electric (Power Functions)
Dimensions: length 53 studs / width 26 studs / height 24 studs (not including antennas)
Weight: 2.319 kg
Suspension: full independent with portal axles
Propulsion: 1 x PF XL geared 8.3:1 (1st gear) / 3:1 (2nd gear)
Top speed: unknown
Motors: 2 x PF Medium, 1 x PF XL, 1 x micromotor

A little less than a year ago, I’ve built a simple Hummer H1 model designed specifically for the Truck Trial races. It turned out to perform better than expected, until the chain present in its drivetrain broke. I was relatively pleased with this model, until several months later I have come across a civilian H1 parked on a street. Having used this opportunity to inspect it as much as possible from the outside, I have come to the only proper conclusion: that my model was unsatisfactory.

While planning to build a new model – this time called Humvee to emphasize that it would be based on the military H1′s – I’ve decided to use the often-criticized black colour, because Humvees simply look excellent in plain black. I have also decided that I can’t simplify the suspension system like I did in my earlier model (which was suspended on simple pendular modules), but rather try and recreate the suspension system of the real vehicle. This is a tricky feature, as the Humvees have full independent suspension with portal axles. It’s fairly easy to build independent suspension or portal axles with Lego pieces, but it’s quite a different story to build independent suspension and portal axles. It means that Lego pieces that are designed for independent suspensions are pretty much out of the question. Instead, I had to create this kind of suspension using common pieces only.

Sophisticated suspension systems like this  are usually wide – building the new model in the same scale as the old one was impossible. When I’ve tried the old Technic wheels that have best diameter/width ratio, it turned out that I can make the suspension 23 studs wide, including the wheels (my earlier model was 20 studs wide). Since the model scaled to the size of the wheels would be 24 studs wide, that suited perfectly – except that it meant abandoning the 1/13 scale required by the Truck Trial rules, which means that the model would not be classified in the race. I decided to accept that rather than to build another small model with simplified suspension system. Additionally, the minimum weight limit for the race has been changed from 1kg to 2kg, starting this year, which meant that my earlier model would be far too small to participate.

Another decision was to use a gearbox this time (my previous model had none), and my recently developed 2-speed heavy duty linear gearbox was an obvious choice. The gearbox design was so good that I wasn’t the only one using it in the race – Maniek’s truck used a gearbox like this copied with my permission.

Mechanically, the model used a custom independent suspension system with portal axles, with a 3:1 gear reduction at the wheels, and was driven by a single XL motors using a 2-speed gearbox with ratios 8.3:1 at lower gear and 3:1 at higher gear. There were four motors total: one for drive, one for steering (housed under the bonnet), one for shifting the gearbox (housed under the gearbox) and one micromotor for rotating the steering wheel as if it was actually working (which can be considered a cheat, but is not forbidden in the Truck Trial rules). 4 IR channels were used to control the model, with the fourth one used to turn on/off the lights remotely.

Aesthetically, I have focused on improving the shortcomings of my previous model and on modelling the features which are exclusive for the military Humvees. These included intake and exhaust snorkels, which I’ve never seen used in civilian vehicles, as well as the design of the whole rear end of the model, which is quite different in civilian versions. Namely, the location of rear-lights is different, and there are recesses for two jerrycans on the sides. Inside the model, there were two well-detailed seats in front and a radio station between them. There were no rear seats, as the space was taken by the gearbox control system, and the rear seats are usually folded in military vehicles, and thus can’t be seen from the outside. The model obviously included plenty of parts that could be opened: the bonnet, all four doors and the rear hatch which was split in two pieces: one opening upwards, another opening downwards. Just like in the real Humvee, the intake snorkel stayed in place when the bonnet was opened – this was one of the features I’ve missed in my earlier model.

The model performed well at the beginning of the Truck Trial race. It drove through the first section flawlessly, with lower gear used to climb uphill and higher gear used to descend downhill. The problems started at the beginning of the second section, where it simply stopped moving. As there was no easy way to locate the damage at all, I had to give up the race. It eventually turned out that I did a big mistake by meshing three 8-tooth gears in a row (which I did to split the main driveshafts in two, as required by the suspension system). Even though the gears were protected by 3:1 gear reduction at the wheels, they have shifted on their axles (as 8-tooth gears are slightly narrower than a single stud) and started to grind each other, severely damaging their teeth. Thus a careless drivetrain design resulted in six damaged gears and in the model utterly unable to move. Additionally, the front wheels had a strong tendency to bend, for no apparent reason. I would suspect some flaw in the suspension design, but the rear axle used almost identical design and the rear wheels did not bend at all.

Despite its obvious flaws, I consider this model a step forward from the previous one. It has proven my gearbox design reliable in the racing conditions, and it used a complex suspension system, to a moderate success.  However, as I’m unable to identify the reason for the bending of the front wheels, it seems I should abandon this suspension design.

Work in progress photos:

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Simple vehicle built for fun. Features 4 driven rubber tracks, chassis elevation system and remote-controlled Zamor cannon.  

Datasheet:

Completion date: 24/02/2011
Power: electric (Power Functions)
Dimensions: length 36 studs / width 23 studs / height 50 studs
Weight: 1.14 kg
Suspension: none
Propulsion: 2 x PF Medium motor geared 1:1
Top speed: 1.60 kmph
Motors: 4 x PF Medium, 2 x PF XL

The idea for this vehicle has evolved quite a bit. Initially meant to be a successor of my Moon Rover, since I am deeply fascinated by all the robotic contraptions NASA sends into space, it has gradually became something built rather for fun than for pretending my room’s floor is another planet. It was also important to me to build it without having to take apart my previous construction, which meant that I could use 3 IR receivers and 6 motors at best.

The Prowler has become an opportunity to experiment with a HD video. Having finally a full-HD-capable camera at hand, I was eager to try producing some high quality panoramic video. I have chosen to use Ulead Video Studio to do so, a decision which I severely regretted later, and I started by trying to produce a full HD video, which turned out to require a machine much more powerful than my PC. Having decided on regular HD instead, I proceeded to work on the video, which became increasingly frustrating, as the Ulead software turned out to work really slow.

It seems that the frustration over the video, which I felt compelled to finish against all odds, has affected the work on the model itself. For instance, the two Medium motors geared 1:1 proved incapable of driving over any serious obstacle, and I didn’t want to modify the drivetrain, because it would mean reworking the whole chassis. The live feed camera, which worked flawlessly the day before I started filming, proved unwilling to co-operate with my PC when I needed it to. I’ve tried for a couple of times, but I was unable to get a signal from it, which is why there is no single image from this camera in this video – I just didn’t manage to film it when it worked. Finally, the Zamor launchers proved quite difficult to control remotely. I wanted to have two of them, launched one after another continuously by a single motor with an eccentric mechanism. For some reason – perhaps because my Zamor launchers were brand new – it turned out to require an enormous amount of torque, rendering the eccentric mechanism completely useless, as it would yield to the launcher’s resistance regardless of how much reinforced it was. I have tried a couple of solutions, and eventually settled down on a single launcher with a primitive control system consisting of a single motorized linear actuator. It meant that the launcher control system could not work continuously, but required switching back and forth. In the end, the Zamor launcher proved largely inaccurate anyway. Since the spheres would not always sit in the launcher in exactly the same position, there was a significant spread when firing them. It was acceptable for just having fun and shooting large targets, but it still took me over an hour to get the short at the beginning of the video right.

I would say that it’s a clearly unimportant construction, perhaps something I needed to relax after a long and tedious work on the previous one.  Still, I have learned something from building it, which means that it was worth building anyway.

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

Datasheet:

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

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

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

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

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

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

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

Thus, the list of motors is as follows:

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

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

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

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

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

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

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

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

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

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

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

Work in progress photos:

Photos (caution: some large ones included):

Videos:

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Media reference:

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

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My first supercar-class model. Features full suspension, remote drive & steering, remotely elevated rear axle, remotely opened doors, lights and custom stickers.  

Datasheet:

Completion date: 27/12/2010
Power: electric (Power Functions)
Dimensions: length 75 studs / width 26 studs / height 20 studs
Weight: 3.507 kg
Suspension: front – double wishbone / rear – live axle
Propulsion: 2 x PF XL motor geared 2.33:1
Top speed: 0.91 kmph
Motors: 3 x PF Medium, 2 x PF XL, 1 x 71427, 1 x micromotor

I have been making attempts at my first supercar for quite a while now. First I started with Lamborghini Reventon model, then I’ve ran into some problems building a supercar that large and complex, so I decided to put it on hold and build something simplier, just to gain experience. ‘Something simplier’, however, turned out to be a strenuous piece of work, largely due to my decision to use studfull body. I have chosen to model a car with relatively simple silhouette – the classic 1969 Dodge Charger R/T, a fine example of the muscle cars era.

I should start by saying that I’m not fully happy with how the model turned out. The original Charger’s silhouette is shaped by subtle curves, which I have simplified to the point of building a box on wheels. The model is very heavy and slow, and it was a great lesson of the tricky things about the supercar models.

It turns out that motorized supercars are quite a challenge. Unlike trucks or military vehicles, they have little internal space to use for mechanics and even less space for a bearing structure. The problem is that the cabin’s interior is usually taken and so is the engine bay, which leaves only the car’s floor to fit the frame in. The Charger is built around a studless frame, which, reinforced as it is, can’t possibly hold it together alone. Extra stiffness is provided by the body of the model, which is massive and prevents it from bending. It takes a special way of holding to carry the model without damaging it.

Aesthetically, the model has a number of drawbacks. As mentioned earlier, it lacks subtle curves which make the original car distinctive, and it also lacks the central ridge on the bonnet. The cavities in the doors are modelled very roughly and the front grille is recessed less than it should be. Additionally, the wheels are no less than three times wider than the wheels of the original Dodge Charger.

Technically, aside from its low speed, the model has a number of well working features. The most noticeable one is probably the headlights rotation mechanism, driven by a single micromotor, which tilts the headlights modules to make them open up or close, just like in the original car. When the headlights are fully opened, the micromotor stalls. Due to its silent operation and minuscule power demand, stalling it is less of a trouble than including some sort of a circuit breaker. The rear lights shine through a layer of 2×1 thin trans-red plates, which creates an interesting effect.

The doors are being opened by a motor located in the floor between the front seats (hence the lack of a gearbox). The motor uses two separate worm gears (without clutches, as they proved to yield too quickly) to open both doors simultaneously. Rather than integrating the doors into the studless frame, I decided to make them part of the studfull body, with standard hinges, and open them by means of small horizontal levers. Due to use of the worm gears, it is not possible to handle the doors by hand.

The rear suspension, which is based on a live axle with 4 links,  just like the one developed here, can be elevated. This is a feature present in some sport cars to provide a more favourable weight distribution when needed. The elevation is done by moving the base of the rear suspension’s shock absorbers by a single linear actuator driven by a PF Medium motor. The whole mechanism takes a lot of space, including the space where the trunk should be, and the single actuator is clearly struggling against model’s weight.

The building process, as mentioned before, turned out to be very strenuous and highly discouraging. If I’ve been hesitating between building studless and studfull supercars before, this experience has certainly convinced me to prefer studless. Therefore my next supercars will be most likely built in the way of modern Lego supercars, which includes a studless lightweight body built around a studfull frame – an exact opposite of how this model was built. I hope it will also make building them more enjoyable.

Work in progress photos:

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Simple arm with 4 motors, controllable and programmable with the LEGO Education WeDo software.

Datasheet:

Completion date: 19/06/2010
Power: electric (Power Functions) / pneumatic (fed from internal compressor)
Dimensions: height 58 studs / full length of the arm: 113 studs
Weight: 1.53 kg
Motors: 4 x PF Medium

I had access to the LEGO Education WeDo kit for some time, but it was only after I bought second USB hub that I was able to come up with some ideas on how to make use of it. The kit is in a way similar to the LEGO Mindstorms, except it employs the PF system’s components and it needs a computer to be run on. Therefore it is not as mobile as the LEGO Mindstorms with its separate CPU brick, but it’s much more flexible as it needs a computer and PF components that most of the builders already have.

One of the limitations of the WeDo system’s architecture is having just two independent outlets on each USB hub. While it is consistent with how the PF IR receivers work, it also means that you can only control 2 motors/sensors with the basic kit, and up to 6 motors/sensors maximum as the software can control up to 3 USB hubs at once. This is still, however, better than 3 motors that can be plugged to a single NXT brick.

The first version of the arm was built in a couple of hours to be displayed on the same public event as my Caterpillar excavator was. It was controlled by 4 PF switches, to allow viewers to control it manually. It was, however, built with the WeDo software in mind from the very beginning (hence just 4 motors) and after the event I fixed some minor shortcomings and plugged it to my notebook.

It was easy and convenient to control all the motors using a simple keyboard layout as presented below. Basically, there were two keys for each motor, for running it in one direction or another, and there was a single universal stop key. A separate key was responsible for executing complex programs, and I have prepared one such program for the video (it was a time-consuming task due to the need to manually pre-adjust range of each movement).

Another shortcoming of the WeDo software is that it controls motors using a timeout function and not a rotation counter like the Mindstorms do. The advantage of this solution is the ability to use any motor – the PF extension wires make it possible to plug any 9V motor into the PF system and thus to make it WeDo-controllable. The disadvantage is that motors are friction-sensitive, which means that a motor that is run forward and backward for exactly the same time rarely returns to the exact starting position because of the differences in friction it encounters. With the executable programs, I solved this issue by pre-adjusting every movement manually.

The arm itself consists of a simple grabber with 4 independent fingers, each with a rubber tip for improved grip. The fingers are controlled by an autovalve and thus are capable of adjusting to the shape of the grabbed object. The grabber has a wrist that can be rotated through 360 degrees and uses a safety clutch. The arm is elevated with two linear actuators, with the arm’s level being maintained throughout the elevation process. Two battery boxes are mounted on the rear side of the arm to act as a counterweight for the grabber and its load. Finally, the entire arm can be rotated through 360 degrees by a turntable at the top of the tower it sits on. It felt like something innovative to build, and had certainly a huge potential for various programs and arm’s modifications.

Photos:

Video:

Click here to view the embedded video.

Media reference:

Fascinating LEGO Model Of The Day, Robótica recreativa y educativa (Spanish only)

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