# Lego CVT-IVT

18,105

37

24

Published

## Introduction: 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

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."

http://en.wikipedia.org/wiki/Continuously_variable_transmission
http://auto.howstuffworks.com/cvt.htm

## 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

## Recommendations

• ### Minecraft Class

4,491 Enrolled

• ### Colors of the Rainbow Contest

We have a be nice policy.

## Questions

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

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
https://www.instructables.com/id/Continuous-mesh-Positively-engaging-CVT/

Very nice

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.

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.

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

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?! :)

what dos it do ?

4 replies

its a model of a transmission system, like in cars

for what?

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

its still very cool.

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

Oh... i really din't know that..
Thanks for the info (^.^)

BTW this thing is awesome

Np

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.