Hi All(adsbygoogle = window.adsbygoogle || []).push({});

I have a typical automotive problem here i am being confused by;

I have a three wheeled vehicle with two driven wheels and i am trying to spec a motor/power supply for it. To do this i want to calculate the torque and therefore power required by the motor.

The process i have followed is;

Fc=Force at tyre contact patch

Fr=Sum of resistive forces

Fi=sum of inertial forces

Fg=gravititational forces =0 (car on a level road)

Fc = Fr+Fi

and then to find torque;

T=Torque (max torque negating transmission losses etc)

r=tyre radius

T=F.r

and for power;

P=power

[tex]\omega[/tex]=rotational velocity

P=[tex]\omega[/tex].T

Now the problem im having is that the inertial forces required to accelerate the vehicle are quite large and the torque im getting is much too large.

The vehicle stats are as follows;

Mass=410kg

Wheel radius = 0.33m (13inch)

Final velocity=26.6m/s (60mph)

Initial Velocity=0

0-60mph Time = 10s

Aero

Cd=0.15 (drag coef x)

Frontal area=1.74m^2

Density of air=1.225kg/m^3

For simplicity ive moddeled this as one wheel so dont need to worry about how many wheels are driven and the distribution of masses on those wheels.

My answer is telling me that i need around 430 Nm of torque (which is ridiculously high for a car like this) and conversley the power required is only 35 Kw. (around 50bhp)???

I may be making an incorrect assumption somewhere here, but if anyone can help that would be great.

(I also modeled in some transmission lossess into mine and rolling resitance of the tyres, as well as inertial forces of spinning tyres but these values were very small compared to the Aerodynamic drag and force required to accelerate the vehicle).

Cheers

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# Torque and Power required to accelerate a car from 0-60MPH

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