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I know that lower gears have higher acceleration & low top speeds and higher gears have low acceleration & higher top speeds. But I would like to know why this gear system was designed first of all? What happens internally?
My second question is that nowadays there are scooty peps'(gearless) that have 125 cc. So does a 125 cc bike with gear have any advantage?

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2 Answers 2

up vote 8 down vote accepted

Your questions don't appear to match the headline, but to try and help:

Why are gears used when there is automatic gear technology?

  • Because automatic gears have more losses- so you don't get as much efficiency from your drive train.
  • Because automatic gears can't read your mind and may not choose the best gear for what you want to do.
  • Because the greater complexity leads to more maintenance or more breakdowns.

Why was this gear technology developed

That is just how power works. If you turn the drive cog more times for a number of output turns, you get more torque but less top speed. It's basic physics. Have a look at this howstuffworks page for a detailed explanation.

Does a bike with gears have any advantage

Absolutely! It is lighter, requires less maintenance, is potentially safer in an emergency situation, and in fact the only good thing about the automatic scooters is that they are very easy for beginners to learn on as they don't need to worry about gears, clutch etc.

An animation to explain Continuous Variable Gears (from Wikipedia):

enter image description here

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Thanks You. I have accepted your answer. Can you give me some links that explain how gear works in detail WITH animations? I have tried googleing it. But it is too scientific. So gearless scooties also have gears(automatic)? Why have gears - manual or automatic? If you want I will post a separate question. –  Ashwin Oct 8 '12 at 15:07
    
@Ashwin, Ever ridden a bicycle with gears? How about a bicycle without gears? The bike with gears allows you to go both up steeper hills than you could without gears, and down hills faster than you could without gears. You can't turn the pedals infinitely fast, and you can't push them infinitely hard. The gears help you get the most out of the bicycle while working within your physical limitations. In this case, "you" are just like the motorcycle engine. It has a limited torque output and a limited maximum RPM. The gears expand the range of speeds that the motorcycle can operate in. –  mac Oct 10 '12 at 16:32
    
@mac : ok. I got it. –  Ashwin Oct 10 '12 at 16:44

Scooters have only a single gear or pulley. So the acceleration and speed will remain the same and sometimes the engine has to apply more power to move the vehicle(If the load is heavy) this makes the engine less efficient. In bikes the 1st gear give better acceleration which helps in pulling heavy loads also.So the bike applies less energy to pull than compared to a scooter.So more efficiency. In the last gear the engines speed is multiplied by the gears.Since we change the gears from 1st to last the acceleration in last gear does not matter as it will be low only if we try to move the bike from rest when in the last gear.

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