Fall 2015, Team of Three
The Task:
Create a remote controlled vehicle to navigate an obstacle course as quickly as possible. You are not allowed to use wheels.
Results: The “Lazy Flapjack”
Design:
For basic forward and backward movement, the vehicle has two legs that move in tandem to lift the body of the machine and set it back down again. A gearbox allows the drive motor to provide the appropriate power for this displacement.
The vehicle was optimized to complete the maze obstacle, which provided size limitations and set restrictions on the turning radius. To design for this, the vehicle is able to point-turn: while the legs are off the ground, servo motors rotate the top of the base to change the orientation of the legs. This allows the legs to step in any direction.
Challenges:
Power and Legs: The provided lithium battery
pack and the drive motor for the RC vehicle was heavy compared to the acrylic and wood used for the chassis. In order for “the Lazy Flapjack” to move, the drive motor needed to be geared down. We developed a gearbox to allow movement.
The thin legs had difficulty coping with the weight, particularly because “the Lazy Flapjack” swayed when it stepped down. I experimented with different leg materials, and selected wood for flexibility and fracture prevention.
CAD design of a leg
Chain Tension: The chains for the legs had a propensity to slip off of the sprockets. The issue was not resolved by the time of competition, though we experimented with adding chain tension by inserting sprockets midway up the chain.
Cable Control: The 360˚ turning mechanism meant that cables to the drive motor, attached to the battery, needed to be able to rotate and retract when the vehicle turned. We dealt with this issue by feeding the cables through a hole in the chassis and allowing extra wire length: given more time, a superior solution might be a method of cable contraction.
Wobble: “The Lazy Flapjack” wobbled back and forth relative to its current direction of movement–this limited its maximum speed.
My Primary Contributions
- Idea for point turning mechanism
- Solidworks design iterations
- Designed and fabricated the legs and their attachment
- Fabricated the shaft collars
- Laser-cut iterations of the chassis
- General assembly
76 Final Paper Download
Vehicle in the atrium
Drive Motor
Concept Sketch 2
Leg Assembly
