# Torque requirements for launching a soccer ball

• kmcmacki
In summary: This increase in heat will reduce the life of the motor.Yes, I was planning on using electric motors.
kmcmacki
I am designing a soccer ball launcher (like the one in the attached picture) for school and am having trouble figuring out how much torque I need the motors to have.

I am trying to follow an energy analysis approach to get these calculations done. Attached is a file of my calculations so far. The idea behind them is that the wheels are already spinning with a tangential velocity equal to that of the ball launch speed so that there is then a transfer of energy from rotational energy in the wheels to kinetic energy in the ball. Then, the torque the motors must be able to provide is dependent on the time desired for the wheels to get balk up to speed after launching the ball.

Just looking for advice from anyone who can tell me if this is the correct approach and if not what the calculations should look like for this part of my design. Thanks.

#### Attachments

• image1.jpg
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• Design Calcs.pdf
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Welcome to PF, and fun project!

Will you be wanting to incorporate different wheel speeds to allow you to launch curved paths?

berkeman said:
Welcome to PF, and fun project!

Will you be wanting to incorporate different wheel speeds to allow you to launch curved paths?
Yes but for the calculations I will be assuming that the wheels will be rotating at the same speed for simplicity sake. To accommodate for this I have set the launch speed to much higher than necessary.

berkeman
Welcome!

I would sugggest to estimate the necesary rpm's of your motors first.
If direct drive, your selection would be based on available rpm's ranges of available motors and diameter of wheels.

berkeman
kmcmacki said:
The idea behind them is that the wheels are already spinning with a tangential velocity equal to that of the ball launch speed so that there is then a transfer of energy from rotational energy in the wheels to kinetic energy in the ball. Then, the torque the motors must be able to provide is dependent on the time desired for the wheels to get balk up to speed after launching the ball.
I did not look at your attached file. We prefer that you use LaTeX to put your calculations in your post.

That said, the approach you listed makes sense. The wheels will slow down, so the ball velocity will be the velocity after momentum is transferred. There is an assumption that wheel spacing and wheel to ball friction will be sufficient to get the ball up to the wheel velocity. Note that momentum is conserved, while kinetic energy is lost in this system.

If the wheels are several times heavier than the ball, then the wheel RPM drop will be small. You can then simplify your calculations by calculating only the torque needed to get the wheels back up to speed after throwing a ball.

Were you planning on driving will electric motors? If so, be aware that most electric motors heat up rapidly if the RPM drops more than about 2 to 3% from the no load speed.

berkeman

## 1. What is torque and how does it relate to launching a soccer ball?

Torque is a measure of the force that causes an object to rotate around an axis. In the case of launching a soccer ball, torque is the force that is applied to the ball to make it spin and travel through the air.

## 2. How do you determine the torque requirements for launching a soccer ball?

The torque requirements for launching a soccer ball depend on several factors, including the weight and size of the ball, the distance it needs to travel, and the desired trajectory. To determine the torque required, you can use the equation T = I * α, where T is the torque, I is the moment of inertia of the ball, and α is the angular acceleration.

## 3. What role does the angle of the launch play in torque requirements for a soccer ball?

The angle of the launch can greatly affect the torque requirements for a soccer ball. Launching the ball at a higher angle will require more torque to overcome the force of gravity and maintain its trajectory. On the other hand, launching the ball at a lower angle will require less torque but may result in a shorter distance traveled.

## 4. How does air resistance impact the torque requirements for launching a soccer ball?

Air resistance, also known as drag, can greatly impact the torque requirements for launching a soccer ball. The higher the air resistance, the more torque will be needed to overcome it and maintain the ball's trajectory. This is why it is important to consider the air resistance when determining the torque requirements for launching a soccer ball.

## 5. Can the torque requirements for launching a soccer ball be affected by external factors?

Yes, the torque requirements for launching a soccer ball can be affected by external factors such as wind, temperature, and altitude. These factors can alter the air resistance and the ball's trajectory, therefore changing the torque needed for a successful launch. It is important to take these factors into consideration when determining the torque requirements for launching a soccer ball.

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