Materials

• Lego.  The entire physical structure of the robot was built out of Lego pieces.  This was the only option available to us.
• Infrared (IR) sensors.  We used IR sensors to detect and move towards the candle.  We found IR to be the more effective than heat or light sensors in detecting a candle.
• Handy Board.  We chose to use a Handy Board to program and control the robot because we had the most experience using it in the class.
• Shaving Cream.  Our decision to use shaving cream as a method of extinguishing is described in the Final Design page.

Description

Our first robot was a simple vehicle with four wheels that carried the can of shaving cream, the Handy Board, and the pushing mechanism. The frame of the vehicle was constructed from two axles, connected on each side by two long Lego bricks, braced together in the middle. We built a cage to hold the shaving cream can in place. The pushing mechanism was attached to the top of the cage. The cage rested upon the front half of the frame. The Handy Board rested on back part of the frame. Two motors, attached to the frame just behind the Handy Board, powered the rear wheels.

The pushing mechanism was a gear train with a 27:1 reduction. A gear rack inserted into the back of the gear train pushed down onto the can, dispensing the shaving cream. On each side, the axles of the gear train extend into a wall, two Legos bricks in thickness. The motor is built into one of the walls. These walls serve as bracing, holding the gear train together and in place, and anchoring the motor. Due to the amount of torque required to dispense the shaving cream, it was necessary to anchor both the gear train and the motor very securely.

Visit our Robotics Design Studio web page to see pictures of this design.

Results and Analysis

Locomotion
In building this robot, we focused on extinguishing the candle, and not on navigating the maze. The robot was able to move forward and zigzag towards the candle. However, with the locomotion system that it had, it would not have been able to effectively navigate through a maze. The driving wheels are located at the rear of the robot, with two unpowered wheels at the front. the front wheels make it difficult to turn corners, adding a great deal of friction.

Extinguishing
The pushing mechanism that we created for this robot was very effective and small in size. We found no serious faults with our design.

Size
This robot did not exceed the size requirements for the competition.

Space
The cage which we built up around the can of shaving cream was a very inefficient use of space and weight. Additionally, we did a poor job of planning the distribution of weight. The can, cage, and pushing mechanism comprised the majority of the weight that the vehicle carried; these components were situated on top of the front wheels, but it was the rear wheels that powered and directed the motion.

Stability
Two thin axles were supporting the weight of the entire vehicle, and the connecting sides were not sufficiently secure. 

We put very little planning into the design of this structure before we began to build it, and thus the structure we came up with was very flawed.  We put a great deal more planning into the next design we built, which can be seen on our Final Design page.

• Lisa Marie Hazel (lhazel@wellesley.edu)
• Meredith Shotwell (mshotwel@wellesley.edu)
• Created: January 22, 2000
• Last Modified: May 7, 2000