Torque value needed to move a particular vehicle

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Discussion Overview

The discussion revolves around calculating the torque required to move a 200 kg vehicle to a speed of 30 km/h using a 24V, 250W DC motor. Participants explore various factors affecting torque, including acceleration, friction, and comparisons with other vehicles.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant requests the torque needed for a specific vehicle weight and speed, indicating a lack of initial information.
  • Another participant notes that the required torque depends on acceleration and friction, highlighting the need for more data.
  • Acceleration is specified as 1.3 m/s², with a coefficient of friction of 0.02 and a wheel radius of 8 inches.
  • A calculation is presented estimating the total force required to be 30.5 kgf, leading to a torque of 60 Newton meters, with a comment that the motor's torque supply is irrelevant.
  • Concerns are raised about the feasibility of a 250W motor providing sufficient power, with calculations suggesting that maintaining acceleration to peak speed would require significantly more power.
  • A comparison is made with the Tata Nano, which reportedly requires only 51 N-m of torque to reach 60 km/h, raising questions about the relevance of torque values across different vehicle types.
  • It is noted that torque specifications for internal combustion engines are typically given at the flywheel, which may not directly apply to electric motors due to differences in gearing and power output considerations.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of torque values and the power requirements of the motor, indicating that no consensus has been reached on the calculations or comparisons made.

Contextual Notes

Participants highlight limitations in the initial data provided, such as assumptions about air resistance and the impact of gearing on torque values. The discussion remains open to interpretation based on these factors.

naeem shaik
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can i know how much torque is required to move a 200kg weighed vehicle to 30kmph by using 24v, 250w dcmotor
 
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The answer depends on how much acceleration and how much friction. You did not supply enough information for us to answer.
 
acceleration: 1.3m/s2
coefficient of friction: 0.02
wheel radius:8inch
 
OK, I'm rusty but I'll take a crack.

Acceleration ##F = m*a = 1.3 m/s^2 * 200 kgm = 260 Newtons = 26.5 kgf##
Rolling resistance ##200 kgf * 0.02 = 4 kgf## (assume air resistance is zero)
Total force, ##30.5 kgf##

The wheel radius is 8" or 0.2 m.
Torque = ##30.5 kgf * 0.2 m = 6.1 kgf*m = 60 n*m##
60 Newton meters torque is my answer.

The fact that torque is supplied by a motor is irrelevant.
 
If the acceleration is maintained all the way up to the peak speed of 30 km/h (8.3 meters/sec) then that's 300 Newtons times 8.3 meters/sec ~= 2500 watts. That's an awful lot to expect from a 250 watt motor.

If we assume, instead, that we are just supplying the 40 Newtons required to match rolling resistance then that's 40 Newtons times 8.3 meters/sec = 333 watts. That's still going to be pretty tough on the motor even without factoring in air resistance.
 
i noticed for tata nano car (i c engine) weighing 680kg needs only 51 n-m torque to accelerate to 60kmph in 10 sec can we compare the both in the case of torque required
 
naeem shaik said:
i noticed for tata nano car (i c engine) weighing 680kg needs only 51 n-m torque to accelerate to 60kmph in 10 sec can we compare the both in the case of torque required
IC Motor specs are generally given at the flywheel so any gearing is ignored. The torque value at the engine means little as it can be easily changed with the gear box. What matters is power output as, ignoring drive train losses, power is constant for any gear/wheel size/final drive etc
 
thanks for your help
 

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