Torque required to move a bicycle

[ravi.nifty]

Hi,

1)I need to find the torque required to move a bicycle from rest, i.e. What is the amount of torque required to be applied at the axis of the wheel of a bicycle, in order to move a 100 kg weight present on it? (Please note that the vechile is at halt and we need to set it into motion, (In short what is the static or starting torque required))

2) What is the amount of torque required to be applied at the axis of the wheel of a bicycle, in order to move a 100 kg weight present on it, When it is needs to move on an uphill of 45 degree ? (Please note that the vechile is at halt and we need to set it into motion), Also answer questions a,b,c of the above question.

3) What is the minimum amount of torque that needs to be applied at the axis of the wheel, to keep it in motion (to avoid coming to halt) when the vechile is already in motion?

4) The vehicle is in motion, and we are trying to accelerate it further, the engine on acceleration will deliver lower torque at higher speeds, Now what is the minimum value to which the torque can be decreased? (what is the minimum amount of torque required to accelerate a vehicle from 20Kmph to 30Kmph. )

 

[jloram]

In an ideal system, any amount of torque will accellerate any amount of weight. The amount of accelleration will depend on the amount of torque and the amount of weight.

In a real world system you'll have to know the static friction (sometimes called stick-friction) which will determine the startup torque.

And, the rolling losses (tires deflection, bearing and gear losses, etc.) and aerodynamic losses, which will determine the amount of force that counters the torque while the object is in motion. Rolling losses are fairly constant, Aerodynamic losses are square-law.

 

[dreit]

Can anyone briefly describe the physics of torque to me? I haven't learned about it yet and was just curious.

 

[ctech4285]

torque is mesured in Nm (i hope at least, if not google tourque unit converstion). that means that if you push with a force of 1N on a lever of 1m you have a tourque of 1Nm

if you want to push your bike with a force of 1N and you tire radius is 1m you need a tourque of 1Nm on the tire. if you have a pedel that's conected throw a gear of 1/10 you would need 10Nm on the pedal.

easy way to keep track of this is to use the conservation of energy law.
forece * distance = work, not really conservation of engergy but a consquense of it.

 

[blimpyway]

to accelerate from 20 to 30 km/h you need to apply at least the torqueneeded to maintain constant speed at 30km/h.

a vehicle movement there are these forces in equilibrium:
- propulsion and braking forces from by engine/cyclist/propeller and brakes
- aerodynamic drag, given by forward speed plus front wind, if any, squared together. And Cx and air density.
- rolling resistance that normally is a fraction of weight. Reasonable rolling resistance is lower than 1%, good is closer to 0,1%.
- gravity/inertia - when the road is not horizontal, inclination will oppose (ascending) or sustain (descending) forward movement. Or acceleration when vehicle changes speed. Horizontal, constant speed means inertial/gravity forces are nil.

Starting on a horizontal road requires overcoming at least rolling resistance. I'm not sure if this is always enough

Wheel torque is given by forward force (or backward braking) multiplied with propulsion/braking wheel radius.