Course 6 / Lecture 10:

# Make the robot more powerful using gears

There are many situations when you want to move heavy objects with your robot and the power of the motor is not sufficient. In these situations gear boxes are introduced in robotics to increase the power of the motor. In this lecture you will learn what a gear box is and how it can be used to make your robot stronger.

Figure 1 - Gearbox with 3 cogwheels

## What is Torque?

Torque - it is a rotation force. In other words, the torque is a measure of how much a force acting on an object causes that object to rotate. The greater the torque of the engine, the greater the weight the robot can pull.

## How can you make your robot more powerful using gears?

The heavier the weight you want to pull with your robot, the more torque required. In the previous lecture you have learned how you can make the Speeder faster using gears. The disadvantage of this is that the robot will be weaker. If you try to pull an object with it, the Sniffer is more likely to pull it then the Speeder. If you would like to make the Speeder more powerful, you just need to swap the cogweels with each other. So the smaller-diameter cogwheels must be driven by the motor, and the larger-diameter cogwheels must be connected to the wheels. Due to this, the Speeder will be slower than the Sniffer but it will be more torque. So in this case, the Speeder can take more weight than the Sniffer. By solving the following tasks you will be know the reasons.

Figure 2 - Gears make your motor stronger

## Create a program to drive both robots forward at 30% power.

You have solved similar tasks in the previous lectures, so it will not be hard for you to create this program. But to make it more useful, create two entry point for starting and stopping the robot. In the first part of the program you need to start the motors of the robots at 30% power, while in the other part you just need to stop them. Look at Figure 3 for help.

Figure 3 - This program code moves the Speeder for 3 seconds

## Try to pull the same weight with both robots.

You certainly noticed that the Sniffer pulled the same weight more confidently than the Speeder. The Sniffer is stronger because the large motors rotate the same angle as the wheels because they are connected to the large motors directly. But in case of the Speeder, the motors rotate less degrees than the wheels due to the gears. The lower the angle the motors have to turn to drive the wheels, the weaker the robot.

Figure 4 -

## Swap the cogwheels of the Speeder with each other, and pull the weights again.

STEP 1: Using 2 cogwheels

In this case, you can see that the robot become slower than the Sniffer. Do you know why it got slower? Due to the cogwheel swapping, the large motors rotate more degrees than the connected wheels. And this is why the robot become stronger. To make it even more understandable, there is an example on Figure 5 below. It is similar to the gearbox in the Speeder. So the smaller-diameter cogwheels are driven by the motor, and the larger-diameter cogwheels are connected to the wheels. Build your own Gearbox for trying it out.

Figure 5 - Use 2 gear wheels. The smaller gear should move the bigger one

STEP 2: Watch the video

There is a video below for demonstrating how the gearbox works with 2 cogwheels. If you rotates the smaller cogwheel, you should see that the larger one moves slowly. But if you rotates the larger cogwheel, the smaller one rotates faster.

Video 1 - Using 2 cogwheels

## Try to pull your object with your robot by using three gear wheels! Write down your experience!

STEP 1: Using 3 cogwheels

After you saw how the Gearbox works with 2 cogwheels, let's see how it works with 3 cogwheels. On Figure 6, you can see that one other cogwheel is connected to the previously seen Gearbox. If the small cogwheel were driven by the motor and the left-hand cogwheel was connected to the wheels, then the robot would be even stronger than if it was used the 2-cogwheels Gearbox. Upgrade your own Gearbox and rotate the two extreme cogwheels.

Figure 6 - Create stronger motion with 3 cogwheels

STEP 2: Watch the video

The video below demonstrates how the 3-cogwheels Gearbox works.

Video 2 - Using 3 cogwheels

## Program code

Figure 7 - Program code to move the robot slowly