Model of the Kenworth T900 truck in the Australian road train variant. Features proportional steering using the NXT unit, remotely locked fifth wheel, working turn signals, three trailers, lights and custom stickers.  

Datasheet:

Completion date: 14/05/2012
Power: electric (Power Functions / NXT)
Dimensions: truck: length 67 studs / width 20 studs / height 31 studs, trailer #1: length 103 studs / width: 18 studs / height: 28 studs, trailer #2: length 122 studs / width 18 studs / height 9 studs, trailer #3: length 97 studs / width 18 studs / height 24 studs
Weight: truck: 2.891 kg, trailer #1: 2.378 kg, trailer #2: 1.440 kg, trailer #3: 2.194 kg
Suspension: none
Propulsion: 1 x NXT motor geared 3:1
Motors: 3 x NXT motor

This model was based on the Kenworth T900 truck converted to an Australian road train version. At the same time, it was an experiment on merging NXT functionality with a Model Team look.

I have started by modeling a pure T900 truck, adding some modifications typical for road trains along the way. The result is neither a stock Kenworth T900 nor a classic road train, but it still fits within the wide array of customizations popular among Australian drivers (and sheep).

The heart of the model was a NXT unit located at the back of the sleeper module. Since the chassis was entirely taken by two NXT motors (yes, they are this big), the sleeper was actually where almost all mechanical and electric elements were housed. Among them was a third NXT motor used to lock and unlock the fifth wheel, the 8878 rechargeable Power Functions battery for powering lights and turn signals, a Power Functions IR receiver for controlling the turn signals and HiTechnic IR Link sensor for allowing the NXT unit to send commands to the IR receiver.

It may come as a surprise that the model had an IR receiver housed inside next to the IR link sensor, but it resulted from sensor’s poor IR range. I was initially hoping to be able to install the sensor on an external NXT controller, thus having a chance to add IR receivers and turn signals in the trailers too, but with a model of that size the sensor simply wouldn’t reach the truck and all trailers at the same time. Also, with all the effort put into steering the model over a Bluetooth link, it would be a waste to be limited by the poor IR range.

The model had just a few functions. Both rear axles were driven by a single NXT motor geared 3:1, and the front axle was steered by another NXT motor without a clutch. There was no suspension, as it would affect the look of the model and it was hardly needed since it was never supposed to leave my apartment’s floor.  The fifth wheel was locked and unlocked using a horizontal 40-tooth gear with a short beam on its side, driven by the third NXT motor located in the sleeper. By rotating the wheel, the beam would block and unblock the fifth wheel’s only “exit”.

The front turn signals were controlled remotely and operated by the software, that is by the NXT unit turning them on and off repeatedly using the IR Link sensor. I did not install rear or any other turn signals for the fear of compromising the truck’s look with too many exposed wires and LEDs, but I have added working turn signals indicators on driver’s dashboard. I have also used the speaker of the truck’s NXT unit to honk (or rather beep) on command, and to beep while on reverse. It was a very simple thing and I have omitted it when trying to shorten the video.

The sleeper module was literally bursting at seams with electric elements and wires. There were three access hatches in it: top one for the 8878 battery, rear one for the NXT unit’s front panel, and a side one for taking the entire NXT unit out for battery replacement. The wires, especially the stiff NXT wires, proved problematic because they had to be arranged so as to allow moving the NXT unit out and back in. Eventually, the whole space at the back of the cabin was taken by wires and the side access hatch tended to stick out a little.

The entire set-up, that is the truck and three trailers, was controlled by a very simple external controller using another NXT unit. I have initially attempted to use the Hailfire Droid’s wheel as a steering wheel, but it proved unusable because using it to drive any regular gear wheel created very high gear acceleration which generated plenty of resistance. Gearing down in the latter stage was not an option, as a very considerable backlash in gear wheels was created. I was also tempted to build a pedal-like device to control the throttle, but with the NXT wires being quite short and impossible to connect in series, it proved pointless – I would have to keep such a pedal right next to the NXT unit.

The controller  was a variation of my NXT brick-to-brick remote, allowing proportional steering and drive with a speed control, as well as controlling all the remaining functions with touch sensors and NXT unit’s buttons. It was running the RobotC software, resulting in delay in the other NXT unit’s reactions over Bluetooth link. A secondary, more comfortable way of controlling the model was to use a computer with a gaming pad. Using a Bluetooth link and the RobotC software, it allowed to control the model with minimum delays and the gaming pad provided plenty of buttons and two analog joysticks which were used for speed-control for both drive and steering.

I was not fully happy with the model. Its functionality was troublesome, with a lot of effort required to start and connect the two NXT units, with delays in steering, and most importantly with the enormous amount of space taken by the NXT elements. Its look was somewhat compromised, with some simplifications in the bonnet and cabin’s roof area, and with the side air filters shortened to allow to open the bonnet up – the only alternative here was to cut the front bumper to move the bonnet’s hinge lower, which I didn’t want to do. I was afraid it was the kind of model that makes a good first impression, and goes downhill from there. Still, it was an interesting experience in using the NXT elements and in merging them with the PF ones.

Gaming pad control program:

#pragma config(Sensor, S4, HTIRL, sensorI2CCustom)
#include "drivers/HTIRL-driver.h"
#include "JoystickDriver.c"
tPFmotor SignalLeft = pfmotor_S4_C1_A;
tPFmotor SignalRight = pfmotor_S4_C1_B;

task Signals()
{
  while(true)
  {
    if(joy1Btn(2) == 1)
    {
      PFMotor(SignalRight, 7);
      nxtDisplayCenteredTextLine(5, " < [>]");
    }
    else if(joy1Btn(4) == 1)
    {
      PFMotor(SignalLeft, 7);
      nxtDisplayCenteredTextLine(5, "[<] > ");
    }
    else
    {
      PFMotor(SignalRight, 0);
      PFMotor(SignalLeft, 0);
      nxtDisplayCenteredTextLine(5, " <  > ");
    }
    wait1Msec(250);
    PFMotor(SignalRight, 0);
    PFMotor(SignalLeft, 0);
  }
}

task main()
{
  bMotorReflected[motorB] = true;
  bMotorReflected[motorC] = true;
  StartTask(Signals);
  while(true)
  {
    getJoystickSettings(joystick);
    motor[motorB] = 0;
    motor[motorC] = 0;
    motor[motorC] = joystick.joy1_y1 / 1.28;
    motor[motorB] = joystick.joy1_x1 / 1.28;
    nxtDisplayCenteredTextLine(0, "BATTERY: %3.1fV", nImmediateBatteryLevel / (float) 1000);
    nxtDisplayTextLine(2, "B: %d", motor[motorB]);
    nxtDisplayTextLine(3, "C: %d", motor[motorC]);

    if(joy1Btn(1) == 1)
      motor[motorA] = -100;
    else if(joy1Btn(3) == 1)
      motor[motorA] = 100;
    else
      motor[motorA] = 0;
  }
}
									

NXT-to-NXT control sender program:

#pragma config(Sensor,S1,touch1,sensorTouch)
#pragma config(Sensor,S2,touch2,sensorTouch)

bool leftturn = false;
bool rightturn = false;
bool soundhorn = false;

task BatLev()
{
  ubyte valueReceived[1];
  valueReceived[0] = 0;
  while(true)
  {
    cCmdMessageRead(valueReceived, 1, 1);
    nxtDisplayCenteredTextLine(0, "BAT: L%3.1f / R%3.1f", nImmediateBatteryLevel / (float) 1000, valueReceived[0] / (float) 10);
    wait1Msec(50);
  }
  return;
}

task Buttons() //0 = Gray Rectangle  1 = Right Arrow  2 = Left Arrow  3 = Orange Square
{
  nNxtButtonTask  = -2;nNxtExitClicks = 2;
  nxtDisplayCenteredTextLine(2, " <  > ");
  while(true)
  {
    if(nNxtButtonPressed == 1)
    {
      if (rightturn == false)
      {
        nxtDisplayCenteredTextLine(2, " < [>]");
        rightturn = true;
        leftturn = false;
      }
      else
     {
        nxtDisplayCenteredTextLine(2, " <  > ");
        rightturn = false;
        leftturn = false;
     }
    }
    else if(nNxtButtonPressed == 2)
    {
      if (leftturn == false)
      {
        nxtDisplayCenteredTextLine(2, "[<] > ");
        rightturn = false;
        leftturn = true;
      }
      else
     {
        nxtDisplayCenteredTextLine(2, " <  > ");
        rightturn = false;
        leftturn = false;
     }
    }
    else if(nNxtButtonPressed == 3)
    {
      soundhorn = true;
    }
  wait1Msec(350);
  }
}

task main()
{
  StartTask(BatLev);
  StartTask(Buttons);
  bFloatDuringInactiveMotorPWM = true;
  btConnect(1, "NXT2");
  while(true)
  {
    ubyte valueToSend[7];
    valueToSend[0] = nMotorEncoder[motorA];
    valueToSend[1] = nMotorEncoder[motorB];
    valueToSend[2] = SensorValue(touch1);
    valueToSend[3] = SensorValue(touch2);
    valueToSend[4] = rightturn;
    valueToSend[5] = leftturn;
    valueToSend[6] = soundhorn;
    cCmdMessageWriteToBluetooth(valueToSend, 7, 1);
    nxtDisplayTextLine(3, "Drive: %d", valueToSend[0]);
    nxtDisplayTextLine(4, "Steering: %d", valueToSend[1]);
    nxtDisplayTextLine(5, "Touch BLUE: %d", valueToSend[2]);
    nxtDisplayTextLine(6, "Touch RED: %d", valueToSend[3]);
    wait1Msec(50);
  }
}
									

NXT-to-NXT control receiver program:

#pragma config(Sensor, S4, HTIRL, sensorI2CCustom)
#include "drivers/HTIRL-driver.h"
tPFmotor SignalLeft = pfmotor_S4_C1_A;
tPFmotor SignalRight = pfmotor_S4_C1_B;
// config start
//bMotorReflected[motorA] = true;
//bMotorReflected[motorB] = true;
//bMotorReflected[motorC] = true;
bool buzzOnRev = true; // buzzing while on reverse
int steerAcc = 10; // steering accuracy margin (degrees)
// config end

int turnSignals = 0;

task Signals()
{
  while(true)
  {
    if(turnSignals == 1)
    {
      PFMotor(SignalRight, 7);
    }
    else if(turnSignals == 2)
    {
      PFMotor(SignalLeft, 7);
    }
    else
    {
      PFMotor(SignalRight, 0);
      PFMotor(SignalLeft, 0);
    }
    wait1Msec(250);
    PFMotor(SignalRight, 0);
    PFMotor(SignalLeft, 0);
  }
  wait1Msec(50);
}

task BatLev()
{
  while(true)
  {
    nxtDisplayCenteredTextLine(0, "BAT: L %3.1fV", nImmediateBatteryLevel / (float) 1000);
    ubyte valueToSend[1];
    valueToSend[0] = nImmediateBatteryLevel / (float) 100;
    cCmdMessageWriteToBluetooth(valueToSend, 1, 1);
    wait1Msec(50);
  }
  return;
}

task main()
{
  StartTask(BatLev);
  StartTask(Signals);
  nVolume = 3; // starting volume
  ubyte valueReceived[7];
  valueReceived[0] = 0;
  valueReceived[1] = 0;
  valueReceived[2] = 0;
  valueReceived[3] = 0;
  valueReceived[4] = 0;
  valueReceived[5] = 0;
  valueReceived[6] = 0;

  while(true)
  {
    cCmdMessageRead(valueReceived, 7, 1);
    nxtDisplayTextLine(2, "Drive: %d", valueReceived[0]);
    nxtDisplayTextLine(3, "Steering: %d", valueReceived[1]);
    nxtDisplayTextLine(4, "Touch BLUE: %d", valueReceived[2]);
    nxtDisplayTextLine(5, "Touch RED: %d", valueReceived[3]);

    // motorC (drive)
    motor[motorC] = 0;
    int afactor = valueReceived[0] / 5;
    if (afactor > 1 && afactor < 25)
    {
      afactor = afactor * 10;
      if (afactor > 100) afactor = 100;
      motor[motorC] = afactor;
      if (buzzOnRev == true) PlaySound(soundException);
    }
    else if (afactor > 1 && afactor > 25)
    {
      afactor = (51 - afactor) * -10;
      if (afactor < -100) afactor = -100;
      motor[motorC] = afactor;
      if (buzzOnRev == true) ClearSounds();
    }

    // motorB (steering)
    motor[motorB] = 0;
    int bfactor = valueReceived[1];
    if (bfactor > 1 && bfactor < 75) bfactor = bfactor;
    else if (bfactor > 1 && bfactor > 75) bfactor = (256 - bfactor) * -1;
    nxtDisplayTextLine(7,"Mtr B: %d/%d",nMotorEncoder[motorB], bfactor);
    bfactor = bfactor * 4;

    if (nMotorEncoder[motorB] < (bfactor + steerAcc)) while(nMotorEncoder[motorB] < bfactor) motor[motorB] = 10;
    else if (nMotorEncoder[motorB] > (bfactor - steerAcc)) while(nMotorEncoder[motorB] > bfactor) motor[motorB] = -10;
    else motor[motorB] = 0;

    // motorA
    motor[motorA] = 0;
    if (valueReceived[2] == 1) motor[motorA] = 100;
    else if (valueReceived[3] == 1)motor[motorA] = -100;

    // turn signals
    if (valueReceived[4] == 1) turnSignals = 1;
    else if (valueReceived[5] == 1) turnSignals = 2;
    else turnSignals = 0;

    // horn
    if (valueReceived[6] == 1) PlayTone(784, 50);
    else ClearSounds();

    wait1Msec(50);
  }
}

									

Work in progress photos:

Photos:

Video:

Click here to view the embedded video.

Media reference:

8 studs, The Brothers Brick, The LEGO Car Blog

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Model of the legendary 60′s racing car. Features full suspension, remote-controlled drive, steering and turn signals, lights and custom stickers.  

Datasheet:

Completion date: 17/01/2012
Power: electric (RC unit)
Dimensions: length 67 studs / width 31 studs / height 17 studs (not including antenna)
Weight: 2.35 kg
Suspension: full independent
Propulsion: 2 x RC motor geared 5:1
Motors: 2 x RC motor, 1 x PF Medium, 1 x micromotor
Top speed: 2.2 kmph

Ford GT40 is a classic racing car with a beautiful history. It was built for one purpose only: to defeat the Ferrari team in the Le Mans race – a goal set by Ford after failure to buy out the entire Ferrari company (Enzo Ferrari changed his mind in the last second). To understand the gravity of this challenge you should know that the Ferrari team won Le Mans six times in row starting from 1960.

The basic design of the car was purchased by the Ford from Lola Cars company owned by Erica Broadley and located in Huntingdon, UK. It can be therefore considered originally a British car. However, Ford spent several months working on car’s aerodynamic properties, under supervision of former CEO of the Aston Martin company, before it was considered race-ready. The finished car was the fastest car of its time, and it won Le Mans race four times in a row between 1966 and 1969 year. When it debuted in 1966, three GT40s have won three first places in the race. Keep in mind that we are talking about race that involved brands such as Ferrari or Porsche – it’s difficult to think of any modern Ford car completing such a task.

The original GT40s were built in a limited number, and the number of “civil” versions was even smaller, making it one of the world’s most often copied cars in the years to follow. It can be roughly estimated that the number of replicas today is several times greater than that of the original cars. Around 2002 the Ford company decided finally to create a new edition of the car, which was supposed to be as close to the first GT40 as possible. In reality, it was largely different, including being taller than 40 inches – a number the GT40′s name originated from – and it was therefore named Ford GT. Due to many differences some Gt40 enthusiast consider the new edition “softened” or completely ignore its existence. You can see the differences between new version (in front) and the old one (in back) below:

If you are looking to learn more about this legendary car, you can see a dedicated Top Gear episode here, and you can listen to how it sounds here.

Ford Gt40 is called the most beautiful car ever made by some – which is arguable, given the fact that its look does not stand out so much from the look of other cars of its era. In fact, it’s strikingly similar to some cars built around the same time (e.g. Lamborghini Miura P400 version S) or even slightly earlier (e.g. Porsche 904 GTS). As large models of supercars give little room for functions (no space) or for performance (weight), my goal was to make the model look real and authentic. Out of many versions of the GT40, with many details looking much differently, I have chosen the Mark II version – one that had a history of engine failures, but that also included many interesting and unique details, including air intakes on top of the rear bonnet. Some other details, such as the absence of side mirrors, show that it’s a racing version of the car. My decision to build the body of the model fully studless was strengthened by seeing a Ford GT40 model by Arvo brothers. I consider them to be among the world’s top studfull builders but their studfull model does not appeal to me – and I don’t think I could possibly top it.
Most of all I wanted to model the shapes of the car properly, looking for a balance between using beams, panels and flexible axles. I was looking for something between the approach of the LEGO 8448 set (body made of just general contours with gaping holes) and that of some older cars by Crowkillers (fully enclosed bodies made primarily of beams).  Some compromises proved necessary – the roof was a single part, without parts of it being attached to doors, because I was unable to find a good-looking solution to that. The front bonnet did not open and the rear bonnet was inaccurate – it should open with all side air intakes attached to it, but it only opened with the top two.

Most difficult part of modelling the body was the front of it, particularly the front mudguards and headlights. If you look at front of the Gt40, its mudguards follow a complex curve which slightly rises towards the sides of the car. I wanted to model this feature, which I consider crucial in making the model look accurate, and I think I achieved that using large panels set at complex angles, with flexible axles drawing the outer body contours. The headlights, on another hand, are nearly rectangle-shaped and come with vertical ribbing, typical for headlights of all cars of that time. I eventually used blocks of 1×2 trans-clear plates, which I think look accurate, but they absorb much of the light of the Lego LEDs behind them.

The model had only driver’s seat in the cabin, and it was moved to the side because of the RC unit occupying the center. The dashboard was completely inaccurate – it rested on top of the bearing frame, so there was no space to experiment with shaping it. The exhaust pipes were tilted downward a little more than they should, allowing the rear bonnet to open up further. Behind the cabin, there was a simple, static mock-up of the engine with some details, but less than I intended to include – I didn’t want to make the model heavier than it already was.

The construction of the model was 95% studless, with only rear axle using studded bearing structure around the differential. The bearing frame was built around the RC unit which was moved forward into the cabin, practically right next up to the front axle. The frame was rigid, but not completely – therefore the rear bonnet could be locked to the back of the cabin, thus providing extra stiffness to the top-rear part of the body.

While the model was not technically complex, it was challenging to integrate all the functions I wanted it to have with the RC unit and with the way it works.

The propulsion system consisted of two hard-coupled RC motors connected to the rear axle’s differential with 5:1 gear reduction (that is larger reduction than shown on photos – I had to increase it after taking photos). The transmission system also included a Lego speedometer, with the display integrated into passenger’s side of the dashboard. The model is rather slow – I was hoping to keep its weight under 2 kg, and with the final weight being much larger the motors were so strained that the batteries in the RC unit lasted about 5 minutes.

The suspension used typical Lego double wishbone independent suspension, with two short yellow shock absorbers per each wheel. It was soft, particularly the rear axle which carried most of the model’s weight. Just like in the original car, the front suspension is slightly narrower and the rear wheels wear bigger tires – in this case, tires were enlarged by putting two rubber treads over each of them. It should be noted that the model drove better without the treads that with them.

The steering system used steering output of the RC unit. The RC steering module could not be used because it was much too narrow. The steering wheel was attached to the RC unit’s output too through a series of gears. The steering lock was small – the RC steering unit rotates by small angle, and I couldn’t gear it up because there was no space for large gear wheels under the low bonnet.

The front and rear lights, using three pairs of Lego LEDs, were connected to the same output as the propulsion motors. They only shone when the model was driving, and they blinked when it started because of the RC motors taking all the power available.

The turn signals system, which took quite a lot of work to include, was based on my earlier mechanism. This time, however, it was remote-controlled rather than automated. I simply wanted to try remote-controlling it freely, and besides it would be nearly impossible to use it with the RC unit’s steering output. Instead, it was connected to the RC unit’s auxiliary output and it consisted of two parts connected only with wires – which was necessary to fit it in. First part was a micromotor driving an old 9V switch, located vertically at the back of the cabin, between the RC motors. The second part was a PF Medium motor rotating two PF switches, coupled with old toothed half-bushes so that turning one switch on turned the other one off. I wanted to control them with another micromotor, leaving enough space for passenger’s seat, but it proved too weak.  The turn signals could be made with just two pairs of Lego LEDs, except that their wires were too short. I had to use four pairs instead, and since the GT40 has single turn signals, I ended up with two spare LEDs in front and two in back. I have installed the front LEDs into the dashboard, creating turn signals indicator in front of the driver, and I have simply hidden the two rear ones.

The model had its imperfections and compromises, but in general it was fun, looked good and it was a great experience in studless building. I can say it was slower than I expected but looked better than I hoped. I think the photos of it are among the best I’ve ever made, and I also put a lot of work into the video, with a good effect. It was a good lesson for my future supercars, because it was example of a very typical supercar, with central engine, low ground clearance and rear axle drive.

Work in progress photos:

Photos:

Video:

Click here to view the embedded video.

Media reference:

8 studs (Polish only), TechnicBRICKs, Technic Delicatessen, The LEGO Car Blog

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Model of the famous WW2 German heavy tank. Features drive, steering, rotated turret, elevated main cannon and lights.  

Datasheet:

Completion date: 21/12/2011
Power: electric (Power Functions)
Dimensions: length 25 studs (36 studs including main cannon’s barrel) / width 14 studs / height 11 studs (not including antenna)
Weight: 0.694 kg
Suspension: none
Propulsion: 2 x PF Medium geared 1:1
Motors: 3 x PF Medium, 1 x micromotor

The Tiger tank is the probably most famous German WW2 tank, and one of the most famous tanks in history. It entered service as a heavy tank in 1942, and it was exceptionally advanced for the time, as well as deadly effective. The tank’s powerful gun and thick armour made it an unprecedented threat to both Soviet and Allied tanks. There is also another side to the Tiger, which states that the tank was over-engineered, extremely expensive and time-consuming to both produce and to maintain, and its fuel consumption was monstrous, especially for the crumbling economy of the after-1942 Nazi Germany. It was also designed in accordance with a doctrine of armoured warfare that was already obsolete – it was intended to win by superior firepower and thick armour, while the Soviet tanks, much cheaper and easy to produce in large numbers, were already winning by manoeuvrability, sloped armour and by working in groups. To make things worse, the Tiger was rushed into service without proper quality control and on-site technical support, resulting in many tanks disabled by technical malfunctions or being abandoned after getting stuck because there were no means to haul them out. Still, it was an impressive and fearsome tank, even if its significance has been exaggerated by the Nazi propaganda. One could say that it was a great tank itself, but it required maintenance and logistics on a level its creators were unable to provide.

As for the model, I was initially going to build it in large scale, with tracks of the newer type, but my primary goal was  to properly model its distinctive overlapping road wheels. This element is often ignored and simplified in the models of the Tiger, and I wanted to get it right. It turned out difficult to do at large scale, but I figured out that I could simply use Technic discs at a smaller one. Since there pieces don’t exist in dark bluish grey colour, I had to settle on next closest to it, that is pearl dark grey.

The model has undergone a rigorous technical control. 

After deciding on a small scale, the main challenge was to make the model fully remote controlled despite its very small size; the finished model’s hull was only 20 cm long and it could fit on the palm of my hand. My secondary goal, besides that, was to properly model the shape of the air filters on the rear of the tank, which are half-round but Lego builders often make them all-round or even rectangular. I achieved this by using four 6191 bricks, which was also a challenge as they only appear in dark bluish grey in a single Lego set, one brick per set.

Eventually, the model had to house four motors, two IR receivers, a battery and approximately 2 meters of wire, plus the large Technic turntable which would provide a stable base for the turret while allowing to install a motor in it. I won’t be dwelling on how hard it was, let’s just say that there were times when the functionality of the model depended on whether I can move some element half stud further or not.

The model was quite simple technically. It was driven by two PF Medium motors located in the middle of the hull, which drove rear sprockets with 1:1 gearing (the only ratio possible as there was no space for any large gear wheels). There was a battery in front of the hull, and a third Medium motor next to it, which drove the turret’s turntable through a worm gear. There was a single wire that entered the turret and powered a micromotor installed inside it, which drove another worm gear and thus controlled the elevation of the main gun’s barrel. There was no suspension whatsoever, and the two headlights on top of the hull had Lego LEDs inside them and shutters made of the bases of Lego levers.

The look of the model was not meant to be consistent with one particular of many versions of the Tiger, I just wanted it to be characteristic, which means that it’s close to the tanks from the early production batches. Its side number – 131 – was not random; the 131 Tiger tank can be found in the Bovington Museum in UK, and it’s probably the world’s only Tiger tank in driving condition today.

The model did not look perfectly; the hull was too tall by roughly 3/4 of a stud, and the turret had a gap beneath it to allow the worm gear to mesh with its turntable. This could be avoided if there was enough space in the hull to ‘sink’ the turntable inside it, but there wasn’t. The turret was 9 studs wide, built around a micromotor and held together by its roof rather than by its bottom. Its look was affected by mechanical parts inside it – its front was too tall and its rear end is a little too far to the back. Finally, the main gun’s barrel’s dimensions had to be heavily approximated at this scale – for example, the longest section of it should be 0.75 stud thick while the thickest section should be 1.5 stud thick. There are simply no Lego pieces with such dimensions that would have the required look.

The model was fun to play with, but clearly suffered from small size and low weight. It’s almost my lightest tank model ever, one third lighter than my T-72M tank and almost as light as my very simple Mark I tank – and it has more road wheels than any of those; 24 to be exact, with only 16 visible from the sides. Therefore its traction was poor and it was difficult to drive over my floor, where any unevenness (and there are many) affected its direction. I believe it would perform much better with more weight, stronger chassis and a simple suspension system, as proved by my earlier T-72 tank model, which had exactly the same tracks and propulsion system. This means that this model is probably example of the level of “miniaturization” that is already bad for its functionality.

Work in progress photos:

Photos:

Video:

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

Datasheet:

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

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

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

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

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

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

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

Thus, the list of motors is as follows:

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

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

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

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

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

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

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

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

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

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

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

Work in progress photos:

Photos (caution: some large ones included):

Videos:

Click here to view the embedded video.

Click here to view the embedded video.

Media reference:

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

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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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Datasheet:

Completion date: 28/10/2010
Power: electric (Power Functions)
Dimensions: length 70 studs (including main gun’s barrel) / width 26 studs / height 23 studs (not including antennas)
Weight: 3.42 kg
Suspension: torsion bars
Propulsion: 4 x PF XL motor geared 1:1
Top speed: 1.5 kmph
Motors: 4 x PF XL, 2 x PF Medium, 1 x Micromotor

My first dark grey tank with a conventional construction (i.e. with a turret). I broke my ‘no German tanks’ rule, but at least the 2A4 version serves also with Polish army. It’s also the last version of Leopard with it’s original turret, whose distinctive shape (resulting from limitations of then-early modular armour technology) reminds me somewhat of German WW2 tanks. Leopard 2 is the world’s first 3rd generation tank (a brief explanation on tanks generations is available here), resulting from a failed joint German-US Main Battle Tank project (one that gave birth to Abrams M1 too) and introduced in late seventies. It’s a very universal construction with strong focus on mobility, and it has become quite popular, especially within EU. Widely considered as European Abrams’ counterpart, it has seen action e.g. in Kosovo and Afghanistan. The newest version currently in service is 2A6, while a 2A7+ version is under development.

I have started to work on this model in an unprecedented way, that is by buying a 1/35 scale plastic model kit of the Leopard 2A4 (which alone took a couple of months, as models of this versions of this tank at this scale are exceptionally rare, I only found them in Hobby Boss’ catalogue and already out of production) and putting it together for reference. I have obviously used a blueprint for calculating the dimensions too, but the plastic model gave me incomparably better reference, such as details of the portion of the hull that is covered by the turret or the decals compliant with German army’s marking patterns. It also helped me to get the idea of various subtle angles and shapes that were difficult to notice on a blueprint, and provided a clear view of some details that appeared vague on it. I am generally happy with the model’s look which suffered few compromises, except for a single serious one: the two grills on top of the rear hull surface, which should be round. I was forced to place three IR receivers beneath this surface, which made it impossible to accurately model the round shape of these grills – I wish I could do that e.g. like here.

Technically, the model was primarily meant to test a new suspension concept, based on torsion bars – a solution taken straight from the real tanks. Torsion bars suspension uses road wheel mounted on end of short rods, whose other end is set on a flexible element which twists under load, thus allowing the road wheel travel up and down. The simplest application of this solution with Lego pieces was a bit unorthodox: it required regular axles, which have a degree of elasticity, to be twisted.

Just like  in my previous tank model, the 6595 wheels have been used as the road wheels. They were mounted on bent 2×4 liftarms, so that they could rotate and maintain good ground clearance. The other ends of the liftarms were set on 8 studs long axles inserted transversely into the hull’s floor. Both ends of the axles were supported, but the inner ends, in the middle of the hull, were locked so they couldn’t rotate. Thus the axles were firmly braced in the chassis, with one end still free to rotate – the end with the liftarm and road wheel on it. It resulted in axle twisting slightly under load and then twisting back when the load was gone. Contrary to what I was afraid of, no apparent damage to the axles occurred, and this kind of suspension turned out to work excellently and to be extremely space-efficient (all it took was basically a single stud of hull’s height). Moreover, the hardness of this suspension can be easily adjusted by using shorter axles or by changing the locking point on them. In this model, each road wheel was subject to an average load of almost 250 grams and the suspension worked perfectly well with an 8 studs long axle, given 4 studs of space between the liftarm and the axle’s locking point.

The model is driven by an unusual number of four motors, all XL. Each of its four sprocket wheels is driven by a separate motor, and the whole set is powered from two separate battery boxes through two separate IR receivers (set on the same channel), with each battery box powering one left and one right motor. I hoped that the massive torque provided by all these motors together would make the model fast despite its weight, and early version with almost 3:1 gear ratio proved to be very fast. Unfortunately, the performance degraded rapidly with the growing weight, and at 3 kg the motors were unable to move the model at all. I’ve spent almost 2 hours changing the gear ratio to 1:1, viewing it as the most efficient ratio possible and unwilling to experiment with something between 3:1 and 1:1 lest I spent another 2 hours changing it again. It appears that XL motors, despite all their power, become increasingly ineffective when used with accelerating gear ratio. It is also possible that it takes more torque to move heavy tracked vehicle than it does for a wheeled one of the same weight.

Except for the four XL motors and two battery boxes, the hull houses three IR receivers, a single PF Medium motor that rotates the turret and the entire turret rotation mechanism along with a turntable. Placing the turret’s turntable inside the hull had a number of advantages: most importantly, it made the rotation mechanism simpler and more robust, and made the construction of turret’s base much simpler while leaving plenty of free room inside the turret. There are two wires going through the turntable, so it can’t rotate infinitely, and there is a simple liftarm frame the turret is built around. The frame includes a single roller behind the turntable, which keeps the turret’s rear end from touching the hull.

Inside the turret, I wanted to have a self-levelling main gun with remote elevation control. To put these two features together, I have built a module suspended on a transverse axle, which connected the main gun with its counterweight and had a micromotor in between, so that the angle between the main gun and its counterweight could be changed remotely. It worked as expected, joining the two features: changing the angle between the main gun and the counterweight by e.g. 30 degrees would result in the main gun going up (or down) by 15 degrees and the counterweight doing exactly the same, while the whole module kept self-levelling all the time. Two problems prevented me from using this mechanism: firstly, raising and lowering the counterweight required more space inside the turret than was available, and secondly, the micromotor’s wire kept affecting the module’s position, no matter how I arranged the wire. Eventually, I decided to keep the self-levelling feature and to remove the elevation control at all. Tank model with no main gun’s elevation control is certainly at disadvantage, but I thought that since all my tank models had this feature, I can do something different just this once. So, I removed the micromotor from the module, positioned the counterweight as close to the main gun as possible, and added another counterweight below the pivot point to lower the module’s centre of gravity – as it was apparent that the accuracy of self-levelling increases with the centre of gravity being further from the pivot point.

The micromotor which was removed from the self-levelling module served as a propulsion for commander’s cupola. It proved perfectly suited for this purpose, because no gear reduction was needed and the cupola is mounted directly on the motor.

Finally, there is a PF Medium motor in the rear part of the turret. I had a lot of space available in the turret, but all the IR channels were already in use, so I was looking for some additional use of the channel controlling turret’s rotation. Eventually, I have built a copy of turret’s rotation mechanism inside the turret, driven by the aforementioned Medium motor and working in opposite direction. The motor was connected to a switch inside the hull, and the switch was connected to the same IR receiver’s output as the motor rotating the turret. It resulted in a possibility to turn on or off a mechanism that would rotate something on top of the turret against the turret itself, thus keeping it aligned with the hull. The obvious choice was to select gunner’s machinegun as the counter-rotated element. The mechanism worked well, but the difference in resistance met by the motor rotating the whole turret and the motor rotating the machinegun alone resulted in different speeds of rotation, with the machinegun rotating slightly faster than the turret. Thus the machinegun does not really stay aligned with the hull, but slowly rotates in opposite direction that the turret does. It should be noted that since two copies of turret’s rotation mechanism were built, there are actually two turntables in this model: one below the turret and another one inside it.

Despite its few shortcomings, the model met a very positive response, being occasionally called my best tank model yet. I was slightly disappointed by its speed, but delighted at its suspension which worked way beyond my expectations, providing excellent flotation without using a single shock absorber. Personally, I consider this model as a preliminary study for my next tank, the South Korean K2 Black Panther, which will develop some of Leopard’s solutions further and hopefully improve in general wherever possible.

Photos:

Work In Progress photos:

Video:

Click here to view the embedded video.

Media Reference:

Rock’n Tech (Portuguese only), The Brothers Brick

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

Datasheet:

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

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

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

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

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

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

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

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

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

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

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

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

Photos:

Work in progress photos:

Video:

Click here to view the embedded video.

Media reference:

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

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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.

Photos:

Work in progress photos:

Video:

Click here to view the embedded video.

Media reference:

Hobby Media (Italian only)

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

Datasheet:

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

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

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

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

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

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

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

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

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

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

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

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

Photos:

Video:

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Media reference:

TechnicBRICKs

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

Datasheet:

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

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

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

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

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

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

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

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

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

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

Photos:

Video:

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Media reference:

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

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Model of a classic hotrod. Features full independent suspension, rear axle drive, functional steering wheel, V8 piston engine, openable doors and custom stickers.

Datasheet:

Completion date: 26/07/2009
Power: electric (Power Functions)
Dimensions:  length 51 studs / width 30 studs / height 22 studs
Weight: 1.78 kg
Suspension:  full independent
Motors: 2 x PF Medium, 1 x PF XL

I have previously created a numer of variations on the ever-popular hotrod theme, until recently, having bought the Technic Racing wheels with the substantial help from donors, I have decided to finally build a classic hotrod. It was inspired by a number of hotrods built for the drag racing, and especially by the Wild Thing based on a Chevrolet Independence.

My important point of reference was my own model built eight months earlier, called the Flamboyant Hotrod. I wanted to explore the direction it set, that is a relatively small, short vehicle with curved sides, but this time I wanted it to look much more realistic. I was so pleased with the final effect that this is actually my first hotrod without the word “hotrod” as the part of its name – I felt that the type of the car is finally clearly apparent.

The front part of the vehicle was kept as simple as possible, and I think it served it well. The V8 piston engine was fitted with a large front fan and two side turbines – all of them moving together with the pistons. It should be, however, noted that I cared little for the realism of the engine design, so it has some features of a real engine, but is mostly made up. Since the engine was complex, and the drive motor was located far from it, I decided to do something very inappropriate and use an extra motor only to drive the engine. It is a blessing in disguise that both motors are coupled and hence both have their speeds controlled remotely, which looks particularly spectacular for the engine.

The cabin houses a drive motor, two IR receivers and the 8878 rechargeable battery, along with a simple interior. Both doors are openable, and the receivers are located at the rear windshield, under the roof, which causes some difficulties with the model’s remote control. Two notes about the cabin’s look: firstly, the rear part of it may look odd, because I intended it to appear as if the rear mudguards have been removed along with the adjacent body panels. It was actually the only way to fit the rear suspension and big rear wheels in. Secondly, the cabin is entirely black and only decorated by stickers. That is because I wanted the body to look sort of shabby, and the stickers seemed the only way to obtain that.

The suspension system is based closely on the solutions from the 8448 set, with rear axle driven through a differential of a new type, with a bracing I have developed some time before. The rear axle was also deliberately made wider. The steering system is quite typical, with a safety clutch and a functional steering wheel. The transmission system is trivial, and consists of a single PF XL motor, a single gear and a single differential. Since the motor already required much space inside the cabin, and I had the speed-control enabled handset at my disposal anyway, I didn’t feel it necessary to make it any more complex. Finally, the 8878 battery is located in the trunk, and it’s small dimensions are very useful here. There is a small flap on the side of the trunk that allows to turn the battery on or off.

The model, which took me only one week to build, enjoyed a good reception. Despite the technical simplicity, it was acclaimed for its classic look and for its impressive piston engine.

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