Have you seen the wheel(s) of a car spinning, but the car itself is not moving? Why does it happen?
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- #1441
- 02 Sep 2019
The reason is the existence of a differential in the car.
As you may already now the wheels of the car are moving with different speed in turns. The wheels on the outside go a larger distance, than the ones on the inside. However, both wheels are driven from the same motor. This is possible thanks to a gear mechanism called differential. It distributes the power from the motor to the wheels
The issue is that when one of the wheels has less traction than the other. For instance if the wheel is on ice or gets stuck in a whole. In such cases all of the power from the motor goes to the the wheel with less resistance - the one with less traction. This results in the wheel that has traction with the road not moving and hence the car is not moving.
Why should we put such a mechanism, when it causes troubles?
Actually engineers has thought of a lot of different solutions that prevent automobiles to get in such trouble situations. The most common is the locking mechanism. There are a lot of constructions that result in locking the differential. They does not allow the wheels to rotate with different speeds and this forces the motor to transfer power to both wheels.
Courses and lessons with this Tutorial
This Tutorial is used in the following courses and lessons
Level C1. "Transportation". Robotics with LEGO
This is the fifth level in the Robotics with LEGO curriculum for students in third or fourth grade.
For the first time robots with steering wheels are built in this level. Those robots use one or two drive motors. The work of the differential and its usage in vehicles is explored. Students learn in-depth the working of the light sensor to create better line-following programs. The first two-wheeled motorcycle-robot is built.
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Lesson 3 - Differential
Introduction
Today we build LEGO vehicle with differential! This will be the robot that would be closest to real automobile with rear wheel drive. We will learn why the differential is the solution to the different speed of the wheels during turns and what happens in case of lack of traction!
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Robotics with LEGO - Level 2.0 - Robots in Factories
The third level of the Robotics with LEGO curriculum for students from fifth to twelfth grades.
Robots in this level use two or three sensors at a time and students create more complex programs for them. The work of the differential and its usage in vehicles with one drive motor is explored. Robots interact with each other and transfer information or material between themselves. Students learn in depth how to create smoother line-following programs. In the end of the workday, robots leave the conveyor belt and relax with a recreational game of volleyball.
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