Design A First Lego League
Robot Mission Model!

This mission is right up my alley. See, I have been a referee for the RI region competitions for the past several years. In that time, I have built hundreds of missions models and observed robots interacting with them. For a few years, I was also an FLL coach, so I also saw how the mission models can affect more than just the competition. Sometimes the mission models are team members first experience with Technic style of LEGO building. On our team, the team members built the mission models for the practice kit. In that case, it was helpful when the models were able to teach something to the team members. Hopefully, my entries to this competition meet that goal as well as being an interesting problem to solve.

Now to show you my Robot Mission Models Contest entries!


"Water" Pump

This is a "water" pump. This entry into the IDEAS contest is demonstrating a function that is often needed for robotics--transforming rotational motion into linear motion. The pump makes use of a piston which is constrained at the top. The rotation of the piston forces the bricks that are on top to move upwards. The topmost brick falls out of the pump when the piston reaches its apogee. When FLL team members analyze this mission, they will discover a technique that may give them inspiration for their robot.

In this mission model, the pump has been simplified. The mission is constrained to allowing the piston to only move partially. This is just enough to let the first "water" brick fall out. The handle which activates the pump should ideally be pushed slowly forward, moving the water up and ejecting the topmost "water" brick. However, if the robot is too aggressive in pushing, the handle can flip up, which would make the device more difficult to activate. Alternatively, the handle can be grasped by the robot and pulled forward until it stops, also ejecting the "water" brick.

I was inspired to make this model from my participation in Great Ball Contraption (GBC) demonstrations. In GBC, we use various methods to move LEGO soccer balls around from module to module. This is my take on a "ball pump." This model can actually be converted to a true ball pump pretty easily. That is why there are flags sticking out the ends. For a continuous flow of soccer balls, the model needs a method to prevent backflow. The flags are one way to do that. This model is missing the standard GBC input and output bins, however, since those wouldn't be necessary for an FLL mission model.

Completed condition of this mission is the blue "water" brick touching the mat. Points would be somewhere in the 10-30 range, depending on the other models, as this is a moderately easy task to solve.

Up close on the "pump" which is a fairly simple piston construction. The lever on the gear prevents the piston from making a complete rotation, but that is easily removed to watch it function.

Other GBC resources include:

Planet GBC

or really just searching for LEGO GBC on Youtube.


This entry into the contest is a balancing mission. Learning about how a model is balanced is critical in getting the best performance out of a robot. Additionally, this model demonstrates structural strength by incorporating several trusses. This is a more advanced robotics challenge and so would have more points for a perfect score. In this mission, the goal is to balance as many crates onto the truss as possible.

The model itself demonstrates a few techniques. The first is the strength gained in building with triangular shapes. There are several angled beams in various places in the model to add strength. Most obvious is the main balancing arm, which is designed as a truss structure. This is an important technique for budding roboticists to learn. The structural integrity of their robot will determine how consistently their robot performs. This is especially true with any outward appendages.

The second technique is a combination of up gearing along with dampening. From the perspective of the truss, the gears in the central column decrease power and increase the speed of the final gear. This adds just enough rotational inertia to prevent the main truss from swinging too wildly. Again, this allows the model to react more consistently.

Around the field mat, four crates would be positioned. Two of them are "metal" and are built using the fluted 1x2 "profile brick" alternating between vertical and horizontal to give a corrugated steel look. The other two are "wooden" crates and are built using brown, orange or tan bricks, or the palisade bricks. The key difference for the team to discover is that the wooden crates are lighter than the metal crates. (The wooden crates are hollow, while the metal crates contain additional bricks inside.) Therefore, to balance them on the truss structure requires thoughtful placement of each crate.

Mission scoring would be similar to the following:

- 10 points for each crate attached to the truss and NOT touching the mat

- 30 additional points if the truss is relatively parallel to the ground.

(It is actually quite obvious when the truss is balanced, but it can be slightly off of parallel due to small changes in crate position. If the crates are not balanced but are all attached, the truss arm should be stable at about 45 degrees with all crates of the mat.)

Want to have your robot try its hand against these missions? You can build them yourself. I have provided instructions!