As you start your vehicle from rest you need varying torques (force).
At start you need maximum amount of torque available to produce high acceleration. As your speed goes higher your acceleration goes down and there less requirement for torque. This not the end of the story, As at higher speeds the vehicle has to cope with drag and air resistance which goes higher in square proportions. So you need a gearbox to meet the varying conditions.
The motor could be connected to the axle if these criteria were met
1. the motor was at maximum torque through a wide range of rpm
2. the axle as you said, was able in some way disengaged from the motor
3. the speed at idle for the motor was slow enough that the vehicle did not start moving at a rate to great for the situation. (lurching over grandma in the driveway)
All in all, the reason for the transmission is to utilize the range of maximum engine capacity for the speeds you wish to travel and to redirect the motion of the engine and also lets not forget here that we might need to back up ,,,this makes reverse gear real handy..
If we could overcome instantaneous momentum problems a constant RPM engine directly attached to the axle shaft would as you might have guessed be the most efficient way to operate .Unfortunatley we have a LAW of physics that describes objects at rest and how they really wish to remain at rest..This gets in the way of a lot of really good ideas sometimes..Well have a good one from the E...
Gasoline engines have zero torque at zero speed. Steam engines do have torque at zero speed and indeed are used without gearing. Electric motors come in a variety of designs some of which have torque speed curves that match the requirements of automobiles. Some of the new Hybrid cars take advantage of this type of design.
Answers & Comments
Verified answer
As you start your vehicle from rest you need varying torques (force).
At start you need maximum amount of torque available to produce high acceleration. As your speed goes higher your acceleration goes down and there less requirement for torque. This not the end of the story, As at higher speeds the vehicle has to cope with drag and air resistance which goes higher in square proportions. So you need a gearbox to meet the varying conditions.
Tina...
The motor could be connected to the axle if these criteria were met
1. the motor was at maximum torque through a wide range of rpm
2. the axle as you said, was able in some way disengaged from the motor
3. the speed at idle for the motor was slow enough that the vehicle did not start moving at a rate to great for the situation. (lurching over grandma in the driveway)
All in all, the reason for the transmission is to utilize the range of maximum engine capacity for the speeds you wish to travel and to redirect the motion of the engine and also lets not forget here that we might need to back up ,,,this makes reverse gear real handy..
If we could overcome instantaneous momentum problems a constant RPM engine directly attached to the axle shaft would as you might have guessed be the most efficient way to operate .Unfortunatley we have a LAW of physics that describes objects at rest and how they really wish to remain at rest..This gets in the way of a lot of really good ideas sometimes..Well have a good one from the E...
Gasoline engines have zero torque at zero speed. Steam engines do have torque at zero speed and indeed are used without gearing. Electric motors come in a variety of designs some of which have torque speed curves that match the requirements of automobiles. Some of the new Hybrid cars take advantage of this type of design.