Why does high speed need less torque to keep the motorcycle moving?
Tiger asked:
At high speed, we shift at higher gears which exert much less torque on to the wheel. Why does at high speed, we need less torque to keep the motorcycle moving?
At high speed, we shift at higher gears which exert much less torque on to the wheel. Why does at high speed, we need less torque to keep the motorcycle moving?
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Its the other way round.
If the gear ratio is high, a smaller engine (producing lower torque) will be able to drive your motor cycle, albeit at a slow speed.
As your engine can produce more torque, you put it in a high (lower ratio) gear rather than let it rev up too high to reach that speed and waste fuel.
In the beginning you keep the ratio high as engine can only produce surplus power if it is allowed to run sufficiently above its idle speed, Once it gets at speeds above,say, 2000 RPM, you change to a higher gear to take advantage of higher than required torque available from the engine. Knowall
The only reason for torque T = fr when up and running steady, no matter what the rpm, is to overcome the friction in the hubs that would stop the wheels if a net force f were not imposed on the wheel hubs with radius r.
The net force f = ma = P – F is applied to the hubs, where F is the friction force acting in the direction opposite to P which is the power force pushing the hub around. As you can see, when the cycle is at constant speed and a = 0, P = F, meaning the only torque Pr needed to keep going is whatever it takes to offset the friction torque Fr.
But as the cycle is accelerating and a > 0, we need P – F > 0 meaning Pr > Fr and the torque applied Pr must exceed the frictional torque Fr. So we need more torque to get up to speed, but once we’re there we can back off a bit to keep up whatever speed we’ve gotten to. oldprof
Torque is important for acceleration, not maintaining speed. Once you get up to speed, you need the engine to overcome wind resistance and friction only.
You’ll need the most torque when accelerating from the stop, when you are in low gear. Once you get up to speed, than any gear ratio will supply enough to overcome the resistance. So what becomes more important is the matching of engine speed to ground speed, which is what the gears are for. William C
You need the torque when you start moving or accelerating; more precisely while opposing a force.
Initially you are at rest so you use first gear which gives maximum torque. This action lets the system(motorcycle + you) gain momentum. At higher speed you are somewhere near or exactly at your saturated speed thus change in velocity to reach at the saturation will be low resulting in low momentum gain which means you will be requiring low torque. At that speed the force needed is more for overcoming the friction by wind or engine itself rather than acceleration, which can be obtained by higher gears which provide you better turn ratio making vehicle operation more economical. Lucky
see when we start we need more torque as the vehicle is at the resting position and it needs a high quantity of torque to be moved whereas when we are at a speed we are in a motion and as a result the wheel does not want high torque or power to move the wheel as the wheel is already moving. PUNEET