CVT

conventional transmissions have a number of fixed forward gear ratios, either geared or automatic transmission.

CVT vary the ratio as the vehicle speeds up to keep the engine at the most efficientn speed.

http://en.wikipedia.org/wiki/Continuously_variable_transmission\\google for more, spell it right. your spelling was wrong.

http://www.randolph-automotive.com/gearbox/gearboxindex.htm has a lot of useful links

Please stop giving free publicity to unrelated information here.

Continuously varieble transmissions , are belt driven (metalic or rubber) continuously expanding pulley with RPM increase , so you have veriable speed at drive axle they are one of automatic transmissions, at one end you have pulley mechanism that is expanding ie two concentric half pulleys closer at higher speed due to centrifugal weight expansion mechanism inside , at the other end you have same two half pulleys but in closed format activated by spring (contra spring) just opposite other end, so at stand still or low RPM you have lowest gear ratio like first gear in manual transmission , as you accelerate your engine side pulleys come closer to each other and belt expands across perefery tending to come accross circumference and at the other end contra springs compress proprtionate to weight increase in pulleys at engine end resulting in belt forced inside the drive end pulleys set ,so the RPM increase in drive axle , here most of the time engine runs constant with little veriation offcourse , in CVT you have infinite gear ratios continuously varing in between two finite set ratios suppose like first gear and 4th/5th gear inbetween it may be in decimals variations

It is use full compared to manual transmissions , here you have only throttle control and brakes at your control ,no hard work and judgement of gear selections , clutch depressions , when in high traffic conditions , climbing hill , fast start stop go situations , better fuel economy due to optimised driving condition forced my transmission mechanism compared to manual transmission were it is upto drivers ability to select gear ratio according to need.

That's not the only (or best) solution. Look up Torotrak.

i agree they are not best ,limited to load carrying capacity ,but quiet handy and functional and also not the only solution as not fuel efficient as they seem compared to manual transmissions just riding habits as such.Electronics controlled CVT `s are better to mechanical one and better of than auto transmission with torque converter and planetry gear system......

You'd have a job to do worse than the latter!

Unless of course you're one of the 'motor at each corner' fraternity, especially hydraulic.