Lego Technic Wheeled Excavator MOC

Every few years, I will plan a new project, the last one was the motorized CAT 963D Tracked Loader. You can click the link if interested: 

http://norman0812.blogspot.com/2018/04/motorized-cat-963d-track-loader.html.

This year, I like to build a wheeled excavator in 2-3 months' time. As I had the experience of building the Lego 8043, it should be not very difficult. There are a number of wheeled excavator MOCs in the internet for reference. 

Among of them, I feel that the one completed by Pipasseyoyo is the best but only with photos and power-train diagram for reference. 

https://brickshelf.com/cgi-bin/gallery.cgi?f=566380

The outlook of my wheeled excavator I intended to build will use CAT 314F as reference, as I have two boxes of technic parts, I will build it gradually at the same time to order the suitable parts or colour.

Undercarriage 

Similar to any wheeled models, the wheeled excavator is comprising of steering and driving axles. The steering is controlled by a servo-motor, the driving axle is a differential design and driving by a L-motor.   As the two wheels are travelling at different speed, the differential would make the travel smoothier.  After completing the undercarriage, the next steep is to consider on how to put the IR receivers and battery box.

Oridinary wheeled models required only two motors, for steering and travel.  Wheeled excavator required four motors for steering, travel, front blade and rear outriggers, and two IR receivers.  With 4 motors requiring higher motor power, a large battery box is needed to extend the battery changing interval.

The battery box and IR receivers are nicely placed between the front and rear wheels.

Front blade & Rear Outriggers

After a week of trial and error, I finally finished the building of the front blade and rear outriggers.  Wheeled excavator only have 4 wheels on ground and is unstable during digging.  The front blade is not only to push dirt but also act as stablizer during digging.  Similarly, the rear outriggers needed to be lowered when digging at rear end.

After completing the front balde and rear outriggers, it is time to conisder on how to connect them with motors.  The space between rear wheels can only install two motors, finally I find some space between the batttery box and receivers for the third motos.  By using gears and connecting rods, it is not very difficult to connect the front blade and rear outriggers with motors.  The next step is to connect them with power and receivers for testing.

After a week of testing and adjusting the gears, connecting cables, etc.  The undercarriage can be tested for running.  Two IR controllers are used, the left one for front blade and rear outriggers, and the right one for travel and steering.

Upper Structure

After a few weeks of trying, dimantling and installating, the upper structure is finally completed.

The original Lego 8043 is using a M-motor for he raise and lowering of he boom.  As it is very heavy, it resulted to break he gears.  Some improvement [rpjects is to use XL-motor instead.   The Lego M-motor is turing faster than the XL-motor, eventhough XL-motor solved the power issue, it is still slow and required complicated gear system to increase the speed.

I used two XL-motors for the stick curling and grapple bucket, one M-motor for the turret turning and one RC-motor for the boom.  The RC-motor is mainly used for remote control car for its spped, the torque is similar to a XL-motor.  So I don't need a complicated gear system to achieve the desired speed.

For the controllers and battery box, after considering I don't have enough space for the battery box and two IR receivers, I opted for an integrated battery/control box for 4 channels.  AS the battery capacity is only half of those standard battery box, in addition to the XL and RC motors, it will not last for long and require constant re-charging.

Boom, Stick & Grapple Bucket

As the body is comparatively complicated and required to order more parts, I decided to finish the boom, stick and bucket first.   After taking reference of the Lego 8043, I made the boom and stick much more stronger as I am using RC and XL-motor with higher power.  The grapple bucket was purchased some time ago and it is handy to use in the project.

Slip Ring

After completing the body, I planned to add a few lighting kits on the machine.  As the integrated power/control box don't have an extra power outlet and the body don't have enough space for a largers battery box, I need to get the power from the undercarriage.  If I used an ordinary connecting cable, it will be strangled after a few dozen turns.  

As I had experience of modifying an excavator using slip ring to provide power to the track motors without any disruption to the turning, I will use the same for his project.

I first cut a 25cm connecting cable into half, put the slip ring in the middle, check the power connection before soldering and closing them with heat shrik tubing.  As the inner diameter of the turret turning table is 22mm and the outer diamater of the slip ring is the same, no modification is required.

Complete Machine

After almost 3 months, the wheeled excavator is already complted, eventhough there are a few small adjustments is needed.

Motorized CAT 963D Track Loader with Lego PF and SBrick Control

After installing or modifying a few models, it was the time to take up some challenges.  I chose CAT 963D not only it was related to my work but also there were a few models had been posted in the internet so I could make reference.  Among the several models, Makorol's model posted in 2012 was regarded as the best by many people, but he only posted with 20+ photos and a YouTube video.  Nonetheless, it was better than nothing and I could make reference by counting the number of bricks to measure the dimensions.

In the beginning, I had no clue on how to start but ordering a large number of bricks and plates with different lengths and shapes.  It took me a whole month and a few times to order and have the bricks and plates I needed.

Undercarriage

To make the undercarriage was not difficult as it was similar to those Lego Technic's.  I used two PF motors and one PF controller to control two tracks so that they could turn independently.

Upper Structure & Cab

It was not very difficult as they were not required to be a strong structure.  However making sure you used different shapes of bricks and plates to reinforce the structure and used nail polish if necessary.  

The structure to support the lifting arms' push rods and motors was another story.  Each push rod was driven by a PF motor through a universal joint.  As the push rods were supporting the weight of the lifting arms and bucket, it must be strong and solid, so I used glue to reinforce the structure.  

Lifting Arms & Bucket

It looked very simple but you needed to try different lengths to make a smooth lifting up and down motion.  

IR Remote Control

I used two PF remote controllers to control two tracks, lifting arm's up and down, and bucket curling.  To have enough space to house the battery case at the back, I put one PF controller at the front which was beneath the lifting arm structure.  The compact battery case was nicely installed at the back of the engine compartment.  The engine compartment room can be opened to take out the battery case for batteries replacement. 

SBrick Control
As I had a spare SBrick, I later modified the model with SBrick control.

Motorized Excavator with Independently Power Undercarriage & SBrick

The original tracks were powered by two motors in the upper parts of the excavator, through a series of gears.  With power losses through transmission, the tracks moved very slow and didn't want to move when the batteries were half drained.  

As I am using two SBricks, I place one SBrick in the carriage with two motors and battery case.  The tracks are now independently powered regardless, moving smoothly and a little bit faster than I expected.  By separating the upper part and undercarriage, I don't need to replace the batteries so often.

I also modified the SBrick control panel designed by Jurgen.  The original design was to use two sliders to control the forward and backward movement of the tracks.  Due to sensitivity of the control, it was difficult to synchronize the movement.   I replaced the sliders with a joystick in the middle, turning it by 45 degree.  By moving the spot up, both tracks are moving forward.  By moving the spot to left, the left track is moving backward while the right track moving forward making a left turn.  It is easier to control the travel of the excavator now and can have several movements at the same time.

Motorized Excavator with Infrared Remote Control & SBrick

An excavator has six actions: left and right tracks, slewing, boom, stick and bucket.   The original model has only two sets of IR remote control, controlling four motors.  Out of cost control or other reasons, the designer cleverly used the fourth motor as a switch.  The other three motors controlled the left, right track and slewing, by switching the fourth motor, the other three motors were then controlling the boom, stick and bucket.

Of course, some of the enthusiasts would definite not happy about this arrangement and started their own modifications.   Jurgens' modification, using three set of IR remote control and six motors were widely adopted by many people.   You would require to purchase an extra of 180 pirces of parts and power function components to complete the modifications.

Motorized Excavator 8043

This motorized excavator was originally modified by Jurgens. 

Three IR receivers, six motors and one battery case were tightly squeezed into the back of the excavator.

Left controller to control the slewing and stick, right controller to control the boom and bucket.

Middle controller, upside down to control the left and right tracks

Ultimate 8043s

Two SBricks replaced three IR receivers.

SBrick control panel designed by Jurgens.