Lego Racers!
Team 1: Di Yu, Grant Halleran, Heng Li, Julia Petrich, and Uxue Zurutuza Dorronsoro
For this lab, we worked in teams using Legos to design a vehicle that, meeting certain constraints, would roll as far as possible on a track when released at the top of a testing ramp. We used experiment-driven exploration, hypothesizing ways that we could improve our vehicle’s performance and then completing simple experiments to validate or disprove our hypotheses.
Objectives
The purpose of this lab was to design a Lego vehicle under some given constraints and to test how far it was able to roll on a track when released at the top of the testing ramp. In this experiment, we observed how far our vehicle could travel on the ramp after changing specific variables of the prototype such as weight, wheels, shape, and symmetry.
Experimental Process
First, we made a basic model to meet the primary requirements for the lab: that our vehicle was stable enough to carry at least one Lego dude and 16-dots worth of Lego block cargo. Then, we worked together to figure out what variables we could play with to change the results. We agreed on the idea that the stability of the Lego vehicle as well as its ability to travel straight were significant points we should concentrate on in the tests. After that, we made hypotheses about what might be the independent variables for the tests. We changed one variable at one time and did the same test for three trials. We then compared the test results to the modifications to decide on specific design recommendations for the car.
Sequence of Experiments
We started with a basic model of the Lego vehicle that simply met all constraints (one Lego dude and 16-dots worth of Lego block cargo) given in the instruction. In the second test, we changed the rough white wheels to smoother yellow wheels and added lubricant (graphite) to the axles. In the third test, we added weight in the front and on the back of the vehicle and performed individual tests based on the different weight distributions. In the fourth test, we successively raised the front and back wheels. In the fifth test, we increased the total weight of the vehicle while keeping it well balanced (and adding wings). Finding that the fifth run had remarkable improvement in the stability of the vehicle, in the sixth test, we elongated the fifth plane-like vehicle and added more features in order to increase the weight. In the final test, we did not make too many changes to the weight or symmetry of vehicle. We did, however, amplify the aesthetics of the design by adding a co-pilot helmet and other fun but small parts to the vehicle and made a final test run on the ramp.
Experimental Hypothesis Validation
For the second test, we wanted to see if replacing the white wheels that we were given with the yellow wheels would improve the distance traveled. We had noticed that the white wheels, after being turned, started wobbling which increased the friction on the axle and slowed them down. We found that installing the yellow wheels increased the distance traveled by over 15 feet. In the third test, we wanted to see how the weight distribution affected the distance. Drag race cars, in which weight is located in the rear, inspired our design so we expected that the rear heavy car would travel further. This was validated when the rear heavy car traveled five more feet than the front heavy car and was much more stable. In the fourth experiment, we tested how the angle of the wheels affected the travel distance. In drag cars, they are positioned with the front of the car at a lower level than the back. We did not have a prediction for how this would affect the distance. It had little effect, probably because the stance of drag cars are intended to reduce the risk of flipping due to the acceleration of the car, which is clearly not an issue in this experiment. In the fifth, sixth, and seventh experiments, we tested how increasing the weight affected the distance. We hypothesized that increasing the weight would increase the distance because of the increase in momentum the car would gain at the bottom of the ramp. Between the fifth and seventh experiments the distance traveled increased by over 10 feet, validating our hypothesis. With the end of the seventh experiment, time had expired, and it was time to race. In the race, the car traveled 35 feet in the first run then under 15 in the second run due to a structural compromise.
Results Assessment
We tested our variables, using the following experiments:
- Basic model test, just meeting constraints
- Change wheels (from white to yellow)+Lube
- Added weight in the front and on the back
- Raised wheels in the front and in the back
- More added weight and rebalance
- Added length and weight
- Add co-pilot helmet and some other fun aesthetic decoration
Video Documentation
We recorded video of our tests, as well, a few of which we will share here:
Conclusions About Recommended Design
Through the hypothesis making and experimentation process, we identified some of the characteristics and features we recommend a Lego racer to have. First of all, in order to meet the objectives of the lab, the speed and stability of the car were key factors to consider. After running the different experiments we concluded that the following are the main factors that contributed to the success of our car:
Importance of the Wheels
The wheels play an important part in the design of the car. Each should have a similar rolling frequency in order to ensure a higher speed and greater coordination. In addition, using the lube to increase rolling speed considerably improved our test results, especially the distance the car traveled.
Symmetry and Distribution
To maintain balance and ensure it moves in a straight line, the car needs to be symmetric. Having a higher and wider back also contributed to those ends.
Weight and Length of the Car
Putting more weight into the car also improved the balance of the vehicle and increased the speed, we also discovered that a longer car structure was better than a shorter one.
Observations and Reflections
Through this short lab, we noted a number of good rules to follow when prototyping or following any sort of experimental process.
Clarify Requirements
It is important to begin any project by clarifying what the requirements of your prototype are. What features must the design have? What are the measurements for success? In this lab, we first discussed our necessary features (what kinds of pieces our prototype had to include) and our measurements of success (how far and how straight our prototype traveled). Being clear on the requirements is not constraining; it is freeing. When you know what is required of a project, by the brief or other documents, you have the space to roam free wherever there are no specified requirements. We experienced this with our requirement for how few pieces we were allowed to include in our prototype. There was no upper limit. When we discovered that a longer and heavier car traveled farther and straighter, we aimed to make the heaviest and longest car that wouldn’t fall apart on the track.
Kill Your Darlings
Don’t overwork an idea or spend too much time on something that clearly isn’t working. It’s good to be aware enough to know when a concept needs to be tabled or set aside. This is one reason why it’s good to use quick methods and cheap materials, especially early in the design process. That way, investment of time and money is low and changes or pivots can be made with little loss. While none of our prototypes completely failed, we did hit a wall with the iterations on version 1.0 of our Lego car. No minor adjustments were going to make major improvements, so we took what we learned from version 1.0 to create a drastically new version 2.0.
Test One Question at a Time
Each prototype should have a specific underlying purpose or a question that it is testing. The purposes for this are two-fold. One, it’s useful to be systematic, to know what specifically you are testing at every step, and therefore be able to use what you learn to make recommendations. Two, being clear on what you are trying to learn at each step is vital for the progression of the prototype, especially as you become ready to move from lower to higher fidelities. This is the method we used in this Lego racer lab.
Balance Making, Testing, and Understanding
When working through a prototyping process, there are three modes that a team should balance: making and creating, testing and evaluation, and understanding and synthesis. The act of making itself is crucial, but it’s important not to take too much time before getting to testing. It’s also good to build in some time to reflect on the results and decide next steps in a prototyping process. When working on this project, we found times where we would get too wrapped up in making small changes when instead we should just get to testing and try things out. This is one area where we could definitely improve.
Go to Extremes; Don’t Be Timid
It can be said that our initial prototype was in some ways conservative, it was small, met all the required constraints and requisites and was doing a good job in terms of distance and stability. Although we had a pretty good candidate to put forward, we knew we still had a lot to experiment and try, and decided to completely change our approach and go for a opposing and extreme prototype: try to build the longest possible vehicle. This very much contributed to our success in this project.
Work as a Team
One factor that is always a challenge (but is always vital) is teamwork. It is always a balance to strike, making sure everyone has an equal part in decision-making yet defining some roles to make sure point people are paying attention to different parts of the process. While the stakes are definitely lower during a short one-day lab, teamwork skills are always useful to practice to become a better group member.
To conclude, in even a quick project like this, there is much to be learned and practiced related to the process of prototyping. We look forward to applying these principles to future prototyping activities.
