Relation between Torque, Speed, power etc. respect to a electric car

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SUMMARY

The discussion focuses on calculating torque and gearing ratios for an electric go-kart project using a BLDC motor with a maximum power of 350 Watts and a peak torque of 12 Nm. The go-kart aims to reach a speed of 15 km/h with a total weight of approximately 200 kg and 30 cm diameter tires. Key calculations involve estimating wheel RPM, determining acceleration, and understanding the relationship between torque and force at the wheels. The participant seeks guidance on performing these calculations effectively.

PREREQUISITES
  • Understanding of basic physics concepts such as torque and acceleration.
  • Familiarity with electric motor specifications, particularly BLDC motors.
  • Knowledge of gearing ratios and their impact on vehicle performance.
  • Ability to perform calculations involving speed, weight, and force.
NEXT STEPS
  • Calculate the wheel RPM required to achieve 15 km/h using the tire diameter.
  • Determine the necessary gearing ratio based on motor RPM and desired wheel RPM.
  • Analyze the relationship between torque, acceleration, and force at the wheels.
  • Explore the implications of constant acceleration on overall performance metrics.
USEFUL FOR

This discussion is beneficial for engineering students, hobbyists building electric vehicles, and anyone interested in the physics of electric motor performance and vehicle dynamics.

ankgupta4
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hey guys,

I am building an electric go kart for a final project, and I'm just trying to get my initial justifications correct, with respect to the classical physics involved.

SPECS: i was the car to be able to reach 15km/h,
The total weight of the car will be approx 200kgs.
the size of the tires of the car are 30 cm in diamator.

Motor Type: BLDC Motor
Maximum Power: 350 Watt
Max. Operating voltage: 48v

so i need to calculate the torque... at the wheels , and then decide on the gearing ratio! this decision is obviously indicative on the parametors of the motor i have! and the goals i want to achieve! The Motor i have has a max RPM of 4000, and a peak torque of 12NM.


can anyone show me best how to perform these calculations ? i understand that i need acceleration ! can i assume constant acceleration ? if that is the case can i just say i would like the car to accelerate to 15km/h in 10 seconds

... any help will be much appreciated !
Thank You
 
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If this is your final project these should be easy to figure out -

1 estimate speed of the go-cart to the rpm of the wheel, then compare to the motor max speed.

2 acceleration will depend on the torque and then force where the wheel meets the road...
 

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