About: I am passionate about anything and everything engineering and physics. I am interested in much of chemistry and biology and I enjoy most art and craft + cooking and baking. I have completed my bachelor's in ...
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
"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

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 

Step 2: Flywheel Assembly

Here you would want the output shaft to be stationary while the shaft connected to the plate and wheel assembly to be able to slide in and out. The flywheel uses 3 axis on each side to make it able to "contract" when centripetal forces move the middle axis out.
Remember to add a rubber-band or two or the flywheel might not return to its default configuration, selecting the rubber band requires some trial and error as there are many variables.

Step 3: Powering the Unit

Since 99% of this project is made of Lego, i would use Lego to power it.
here i used two 5000rpm lego motors with very very low torque, so i geared it down a little (1:3 i think)
but feel free to use anything you like 

Step 4: Some Extra Photos

a few photos of the project

Step 5: A VIDEO of It Working!!

here is a video of my CVT-IVT in action



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    24 Discussions


    2 years ago

    Does anyone have any idea of how to make a gear that would work like the disc in this case?

    1 reply

    Reply 2 years ago

    I did consider that possibility but for such a system, you would need either one or both gears to be able to change pitch.

    Here is something i came up with that might interest you


    6 years ago on Introduction

    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.

    1 reply

    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.

    1 reply

    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


    6 years ago on Introduction

    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?! :)


    Reply 6 years ago on Introduction

    Just do demonstrate how it works. They use transmissions like this in cars.


    7 years ago on Introduction

    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.

    3 replies

    7 years ago on Introduction

    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.

    1 reply

    Reply 7 years ago on Introduction

    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


    7 years ago on Introduction

    I'm sorry to ask this, but I'm juts not that smart. What does this do again?