Well long break i would say before i wrote something on my this blog....the other one still gets my attention at times. However, the reason for that was lack of time and also lack of interest i could garner from my readers. However, looks like i want to try again and give it one more shot to make this blog useful enough to folks in order to get some interest from them.
The topic for today is "Transmissions"
Why do we need a transmission...or do we need one?
Frankly we would not need one, we could simply control the speed of a motor the same way we control the speed in our ceiling fan. However, unfortunately our automobiles use motors which are not electricity powered. They are IC's or Internal combustion engines which run most efficiently in a fixed narrow range of RPM. They are not able to produce the same amount of torque at all the RPM's and of course are not efficient at all RPM ranges. At very low RPM the engines suffer from lower dynamic torque and hence we need to somehow use the same RPM to get the needed torque demands. At cruising speeds we require lesser torque as compared to when we are climbing a hill. All these means that the IC engine has to meet various requirements of torque, speed and efficient operation. This can be achieved very easily using a Transmission. A transmission ensure that the Engine can be run in a narrow band of RPM where it runs most efficiently and uses gears to meet the driver request of torque or speed.
How does it do it?
A simple transmission "conceptually" is a set of gears with different gear ratio's. If the engine is running at x RPM using a gear ration you can get y RPM at you transmission shaft based on the following formula:
X * GR = Y
GR = Gear Ratio
X = Engine RPM
Y = Transmission Shaft RPM
However, this is an ideal case....losses will come into picture like in any system.
if GR>1 then Y is greater than X. This is rarely done since this means that Transmission shaft RPM is higher than engine RPM. This basically means that your car is completely free. This condition is called Overdrive and mostly seen in higher end car with ECU's and TCU's which keep monitoring if everything is still under control.
What are gears and gear ratio's?
A picture speaks more than words...so here is the picture
Ever wondered why the car or bike will not climb a steep incline when we are on a higher gear as compared to a lower gear? At a higher gear the transmission transfers most of the engine speed to the tires as compared to the torque. If we consider power delivered by engine constant then either we can have higher torque or angular velocity. Hence at the higher gear ( more angular velocity) we need to really rev the engine hard to make the vehicle climb ( more revs more power output) in order to meet the higher torque requirement.
In coming blogs it will try to explain what different transmission can do and how they do it. But basics are these...
1. For a constant power by the engine i.e. constant RPM on engine shaft we should be able to get different torques and output speeds.
2. Gears are one of the mechanism's for doing what we need in point (1). There are other methods like use of pulleys, belts and electro mechanical couplings.
The topic for today is "Transmissions"
Why do we need a transmission...or do we need one?
Frankly we would not need one, we could simply control the speed of a motor the same way we control the speed in our ceiling fan. However, unfortunately our automobiles use motors which are not electricity powered. They are IC's or Internal combustion engines which run most efficiently in a fixed narrow range of RPM. They are not able to produce the same amount of torque at all the RPM's and of course are not efficient at all RPM ranges. At very low RPM the engines suffer from lower dynamic torque and hence we need to somehow use the same RPM to get the needed torque demands. At cruising speeds we require lesser torque as compared to when we are climbing a hill. All these means that the IC engine has to meet various requirements of torque, speed and efficient operation. This can be achieved very easily using a Transmission. A transmission ensure that the Engine can be run in a narrow band of RPM where it runs most efficiently and uses gears to meet the driver request of torque or speed.
How does it do it?
A simple transmission "conceptually" is a set of gears with different gear ratio's. If the engine is running at x RPM using a gear ration you can get y RPM at you transmission shaft based on the following formula:
X * GR = Y
GR = Gear Ratio
X = Engine RPM
Y = Transmission Shaft RPM
However, this is an ideal case....losses will come into picture like in any system.
if GR>1 then Y is greater than X. This is rarely done since this means that Transmission shaft RPM is higher than engine RPM. This basically means that your car is completely free. This condition is called Overdrive and mostly seen in higher end car with ECU's and TCU's which keep monitoring if everything is still under control.
What are gears and gear ratio's?
A picture speaks more than words...so here is the picture
Ever wondered why the car or bike will not climb a steep incline when we are on a higher gear as compared to a lower gear? At a higher gear the transmission transfers most of the engine speed to the tires as compared to the torque. If we consider power delivered by engine constant then either we can have higher torque or angular velocity. Hence at the higher gear ( more angular velocity) we need to really rev the engine hard to make the vehicle climb ( more revs more power output) in order to meet the higher torque requirement.
In coming blogs it will try to explain what different transmission can do and how they do it. But basics are these...
1. For a constant power by the engine i.e. constant RPM on engine shaft we should be able to get different torques and output speeds.
2. Gears are one of the mechanism's for doing what we need in point (1). There are other methods like use of pulleys, belts and electro mechanical couplings.
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