How to calculate Torque on the rear wheels of an RC car?

In summary, the car has a weight of 1kg and the torque on each rear motor is needed to be measured. The car has a radius of wheels of 0.03m and the voltage input to the motors is 5V. The average velocity of the car is 0.33m/s. The car is assumed to have an acceleration time of 2s. The torque at takeoff and at constant velocity on a flat surface is unknown, but a force calculation for the car lifting off the ground can be done.
  • #1
Firedawn
2
0
Hi guys,

I'm working on a project where I need to find the torque produced by the rear wheels of an RC car so that I can convert it into power and then into the current required by the motor.
So T=ω×Pmech → Pmech → Pelec → Imotor
Here are the details for the car:
1kg weight
Torque on each rear motor (need to find torque of each)
Radius of wheels is r = 0.03m
Voltage input to motors is 5V
Average velocity of car is 0.33m/s
Assume acceleration time of 2s (not sure if needed)

What is the torque at takeoff and at constant velocity on a flat surface?
 
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  • #2
Have you thought of trying to measure the force by attaching various weights to the car and hang the weight to dangle off of a table while the car resting on the tabletop tries to pull it up?
 
  • #3
No because I need theoretical values since I do not currently have the motors.
 
  • #5
You could estimate the max possible torque by calculating the torque required to lift the front wheels off the ground...

Torque = (mass of car) * g * (distance from rear wheels to centre of mass)
 
  • #6
The torque at constant velocity is very hard to calculate because it depends on the rolling resistance and similar drag forces.

PS: That's the torque at the wheel. You need the gear ratio to calculate the torque at the motor.
 
Last edited:
  • #7
Firedawn said:
So T=ω×Pmech
Torque = power/rotational speed
Current = torque/torque constant
 
  • #8
The maximum force that can be handled by your car depends on the friction coefficient of your driven wheels. It doesn't matter if you use that force to accelerate, fight drag or rolling resistance or anything else.

This simulator should help define the power you need according to the performance you want.
 

1. How do I calculate the torque on the rear wheels of an RC car?

To calculate the torque on the rear wheels of an RC car, you will need to know the weight of the car, the radius of the wheels, and the gear ratio of the motor. The formula for torque is torque = force x distance. In this case, the force is the weight of the car and the distance is the radius of the wheels. Multiply the weight of the car in pounds by the radius of the wheels in inches and you will have the torque in inch-pounds. Then, divide this number by the gear ratio to get the torque on the rear wheels.

2. Why is torque important in an RC car?

Torque is important in an RC car because it is the force that rotates the rear wheels and propels the car forward. Without enough torque, the car will struggle to move or may not move at all. Torque also affects the acceleration and top speed of the car. A higher torque will result in faster acceleration and a higher top speed.

3. How can I increase the torque on the rear wheels of my RC car?

There are a few ways to increase the torque on the rear wheels of an RC car. One way is to upgrade the motor to a higher torque motor. Another way is to adjust the gear ratio to provide more torque to the wheels. You can also try using larger wheels with a larger radius, as this will increase the distance in the torque formula and result in a higher torque output.

4. Can torque be too high on an RC car?

Yes, torque can be too high on an RC car. If the torque is too high, it can put strain on the motor and other components, potentially causing them to overheat or break. It can also make the car difficult to control, especially at high speeds. It is important to find a balance between torque and speed for optimal performance.

5. How does the terrain affect the torque on an RC car's rear wheels?

The terrain can have a significant impact on the torque required to move an RC car. For example, if the car is driving on a flat surface, it will require less torque to move compared to driving on a rough or uphill terrain. This is because the wheels have to work harder to overcome the resistance of the terrain. It is important to consider the terrain when calculating and adjusting the torque on an RC car.

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