Picture of Lego CVT-IVT
I have been looking at Continuously Variable Transmissions, CVT(s) and Infinitely Variable Transmission  IVT(s) for a few days and decided to make myself one.
i will walk you through the key parts so you can do it too
 (please give constructive comments about anything in this instructable...especially about the usage of terms)

 This is a plate and wheel model, basically the IVT part works by moving the wheel nearer or further from the center of the plate. The nearer a point is to the center of the plate, the slower it moves and thus turns the wheel slower but with more torque. The CVT part is the fly wheel which "contracts" along its axis when spun and thus, moving the wheel further from the center of the plate. 

due to some unknown problems, i am unable to add photo notes or embed my video, please bare with me while i try and fix this problem

oh, by the way, i am in the 13-18 category.

Alright, as pointed out by fellow user jj.inc:
"Actually, just for informational purpose, this is a CVT only, not an IVT. An IVT can output at such a low gear that there is no output at all. A ∞:0 ratio is not possible with this device, so it is a CVT which from ratio A:X to ratio B:X where X ≠ 0 can have infinite variance."

learn more about CVT and IVT by just google-ing it

Step 1: Plate and wheel assembly

Picture of plate and wheel assembly
Just attach a CD or any disc you are willing to sacrifice to the Lego parts ensuring that the lego axis is dead center.
i use wheels with tires to get a good grip on the CD, it might be better to make holes in the CD for the Legos to attach better

next you would want to get a wheel with its tire as the driven wheel, make sure you use one with good grip, the bigger the wheel you use(diameter) the slower it goes, but with more torque 
rsnyder81 year ago

Very nice

insmac2 years ago
Great job!
One note: When writing documentation you should never assume all readers will know what your acronyms mean. So, it is common, the first time it is used, to define all acronyms or jargon thus: CVT (constant velocity transmission).

In many cases you may even include a link to, for instance, a WIKI page where it is defined in more detail.
michaelgohjs (author)  insmac2 years ago
Hmm, good point. Thanks for the info.
I can't seem to find how you shift the drive axle left and right to vary the speed. Is there a hand not being shown in the video maybe?? :P And the balance wheel on top of the whole thing? How did that come into being?
Cool project.
michaelgohjs (author)  stringstretcher2 years ago
the driven axle moves left and right due to the variable geometry flywheel which shortens as it speeds up and lengthens as it slows down

the balancing wheel does not affect the function of device its there to...well balance it
kmcdowell43 years ago
i realize this is a bit old of a post.. but this is fantastic.. really enjoyed reading through this - watching the video.. the principle demonstrated here even as a 2nd year engineering student @ 31yrs old... I found this quite interesting/enlightening/entertaining etc.. and FROM LEGO?! lol how cool is that?! :)
RSV263 years ago
what dos it do ?
michaelgohjs (author)  RSV263 years ago
its a model of a transmission system, like in cars
for what?
CrashMGD RSV263 years ago
Just do demonstrate how it works. They use transmissions like this in cars.
RSV26 CrashMGD3 years ago
its still very cool.
jj.inc3 years ago
Actually, just for informational purpose, this is a CVT only, not an IVT. An IVT can output at such a low gear that there is no output at all. A ∞:0 ratio is not possible with this device, so it is a CVT which from ratio A:X to ratio B:X where X ≠ 0 can have infinite variance.
michaelgohjs (author)  jj.inc3 years ago
Oh... i really din't know that..
Thanks for the info (^.^)
BTW this thing is awesome
Dr_Stupid3 years ago
in simple terms, it's a model of a Constantly Variable Transmission, which could be used as a teaching aid, to explain the concept to people who don't know what one is or what it it does or how it works.
michaelgohjs (author)  Dr_Stupid3 years ago
Yup exactly! thanks

hmm.. never really thought of it as a teaching aid, but i think its kind of suitable since students would be able to see, hear and feel the system at work
isalas3 years ago
I'm sorry to ask this, but I'm juts not that smart. What does this do again?
michaelgohjs (author)  isalas3 years ago
dont look down on yourself mate, everyone is awesome in their own way,

anyway, its a transmission system to vary torque output based on the angular velocity of the output shaft

simply put its like a gearbox where when the wheel is near to the middle of the CD it spins slower but is more powerful, when it is towards the rim it spins faster but is less powerful, (powerful as in harder to stop or better ability to overcome resistance)
Samuelchoi3 years ago
不错!awsome,i like it!
I like anything made with Lego's! :)
michaelgohjs (author)  janesycamore4 years ago
THX!!.. same here.. i just love the fact you can make almost anything and if it does not work, non of the parts are gone..