Question

calculate if a Briggs and Stratton engine of 208cc is enough to make a 2 seater car (225 to 300 kgs). I don't know the torque of the engine.

Answer 1

For the very first estimate of required torque, we ignore all of other elements viz., aerodynamic drag, rolling resistance etc. and purely base our estimate on the traction required.

Let us assume that the:

mass of the vehicle is , m = 265 kg

top speed is 40 kmph, i.e., v = 11.11 m/s and that we want to achieve this speed in 20 seconds,

then the acceleration required will be , a = v/t = 11.11 / 20 = 0.56m/s²

Therefore the inertial force required to move a mass of 265 kg will be

F = ma = 265 * 0.56 = 148.4 N

Assume that we use tyres with radius, r = 0.25m

Now the torque required at the tyre base will be,

T = F x r = 148.4 x 0.25 = 37.1 Nm

T = 37.1 Nm

For obvious reasons, we need an Engine that produces more torque than this

Now, a 208cc,(950 series) engine from Briggs and Stratton, gives a torque output of only 12.88 Nm which is way below the desired value. Hence, it wouldn’t suffice.