Finny Migs Blog

The Duowheel is a MOC inspired by the JK Brickworks Monowheel.  The original Monowheel uses a motor driven counterweight to steer, whereas the Duowheel uses tank style steering which is more sensitive.

The wheels are driven by two L motors with torque limited by two 76244 clutch gears on each axle to prevent the mechanism flipping over (most of the time, anyway).  The battery box is mounted low and also helps minimise flipping.

I originally tried to alter the original Monowheel outer wheel design by splitting it in half, but had issues with the edges falling off. The current design came to me when I was playing around with some tank treads and turned them inside-out. The reversed tread is held on by two axles that are joined in the middle by a 36 tooth gear for support, which then connects to the driving axles.

While it can be a bit tricky to get started (you need to give it a bit of a nudge, then you can get going), the Duowheel is very fun to drive and quite sturdy (apart from occasionally tipping over).

Instructions on how you can build your own Duowheel are available from our Duowheel page.

The folks over at Plos have released a research paper on the complexity of Lego® sets over the years.  It turns out that over the years, the average set size, number of different parts used and colours included in each set has gradually increased.

Though given the Flynn effect, this shouldn’t really be too much of an issue.  Despite all this, there is still always the option of buying “classic” bricks and building from there.

A few months ago I asked my daughter Alisz what Lego creation I should build next and she suggested that I build a ladybird, so over the past few months that’s what I’ve been working on.  It uses a crawler mechanism to move, has a shell that opens and wings that pop out.  The shell and head are made of around 1800 plates (and a few bricks for good measure), and around 1000* Technic pieces to drive each of the mechanisms.

The crawler mechanism is inspired by the Motorized Micro AT-TE created by JK Brickworks, which has been highly modified and strengthened to handle the 3kg of Lego it needs to support, and is powered by two XL motors.

The shell and head are inspired by the Ladybird created by Arjen Vuurzoon, and have been scaled up and redesigned to predominantly use plates (especially in the head/eye area).

While I initially tried a hinge similar to the dual axis hinge used in the original design, they were unable to support the additional weight of the enlarged shell.  This eventually led to me using a dual “type 2” turntable hinge mechanism driven by worm gears.  Due to space constraints the forward/backwards tilt axis is only used as an adjustment, with the shell opening outwards from the body.

The wings fold over and out simultaneously, which made for some interesting challenges when developing the mechanism.  The first iteration of the wings was very complex as it involved two separate mechanisms driven by a single motor that had to be precisely aligned in order to function properly.  The second iteration of the wings are more compact and only rely on a single movement to drive the wings over and outwards simultaneously, resulting in less time spent aligning cogs.  More information on the wings can be found in my folding wings post.

The head is secured by two axles that slide in once the top of the head has been opened.  Inside the head are two SBricks that drive the motors using a custom profile optimised for tank style steering, given that steering is achieved in a similar manner to a tank (the only difference is that the ladybird doesn’t have tracks).  Also housed inside the head are the motor and reduction gears that control the shell in/out movement.

The battery is housed underneath the wings and requires the shell to be open in order to be replaced.  The head can be removed and a separate battery pack used to open the shell if the internal batteries are completely flat, or the shell can be removed from the body.  Once the shell has been opened, the wings can be removed to reveal the battery pack which can then be changed over as required.  A long lift arm is attached to the battery pack to make switching as easy as possible.

* – Very, very rough estimate

Anyone who is a subscriber of the Finny Migs mailing list would have seen the miniature Trojan horse I created. Last year, I decided to upscale the original MOC by a factor of 4. The end result after a few months work was 4kg of moving Trojan horse, consisting four XL motors, two M motors, two battery packs and three IR receivers.

Originally, the legs were driven by an M motor sitting on top of each leg with a reduction gear box in between, however​ reliability issues eventually resulted in direct driven XL motors being used. At the 2017 Bricks for Woden School I discovered some further shortcomings in the strength of the legs, but luckily I was able to buy some 2 x 4 bricks at the show that worked a treat in reinforcing the structure.

The head is made up of a large number of slope and inverted slope bricks. There is an archer minifig that pops out of the top of the head, and the head itself has a door/mane that opens. The head is secured by a plate at the top, 8 pins at the front of the body and a securing axle to stop the head from falling off while the horse is moving. As the head is removable and the archer motor is contained within the body of the horse, two cogs are used to transfer torque allowing the head to be easily removed.

The undercarriage ramp is used to release attacking minifigs from inside the horse. The ramp is driven by a large actuator connected directly to an M motor and comes to rest on a boardwalk that doubles as reinforcement for the legs.  Additionally, the top and side of the horse open to reveal some more minifigs preparing for battle.

At the rear of the horse is a removable tail (with a minifig clinging on for dear life) that reveals two battery packs.  The first battery pack drives two IR receivers, the first connected to the archer and ramp, and the second connected to two XL motors.  The second battery pack drives the remaining IR receiver and two XL motors.