Martians 494 cvt pics

[ajlapp]

I was searching today for some pics of 494's cvt from 2004.......they pop up on google but the links to the website are busted.

Can anyone help me get the pics? I'd also be curious to discuss tuning and other cvt related things.

Thanks.

[Holtzman]

http://firstrobotics.uwaterloo.ca/gearboxesgallery.php

Scroll down about 2/3's of the way. Theres 4 or 5 good pics.

[sanddrag]

Originally Posted by ajlapp

I'd also be curious to discuss tuning and other cvt related things.

Thanks.

I just discovered today that my 1978 Peugeot 103 SP moped that I bought a little less than a week ago has a CVT type mechanism they call "the variator" The whole engine is mounted on a pivot and pushed with a spring to keep the belt tight. It is really quite mesmerizing to rev up the engine and watch the pulley slide over and essentially become larger and watch the engine shift backward to take up the slack in the belt. I have very little idea how it actually works, but it is quite fascinating.

Here is the owner's manual: http://www.mopedriders.org/html/manu...nersmanual.pdf
And here is the service manual: http://mopedriders.org/article_view....q=2&fldAuto=36

[JackN]

These are the pics of it that were on 1114's database for those who don't want to scroll.

http://firstrobotics.uwaterloo.ca/re...earboxes76.jpg
http://firstrobotics.uwaterloo.ca/re...earboxes78.jpg
http://firstrobotics.uwaterloo.ca/re...earboxes79.jpg
http://firstrobotics.uwaterloo.ca/re...earboxes80.jpg
http://firstrobotics.uwaterloo.ca/re...earboxes81.jpg
http://firstrobotics.uwaterloo.ca/re...earboxes82.jpg
http://firstrobotics.uwaterloo.ca/re...earboxes83.jpg

Our website is being rebuilt and the pictures haven't been moved yet.

Thanks for such a great program 1114.

[Lil' Lavery]

What are the points of the brass fin-thingies? I remember seeing it at IRI in 2004, and having the full system explained to me, but I can't recall what the brass fins do. No other CVT's I've seen has anything like them.

[Alex.Norton]

The brass fins are weights that are used to shift the cvt from a high ratio (high input to low output) to a low ratio. When the input spins fast they pull out causing the pulley they are on to close making the radius of the pulley higher this causing the ratio to get higher. When the input slows du to a larger amount of torque being need the weights are pulled in by a spring and opening the pulley making the ratio lower.

At least that is what I get from the pictures.

[Gabe]

So is this an automatic CVT or do the weights simply aid in shifting?

[Dan Richardson]

So is this an automatic CVT or do the weights simply aid in shifting?

CVT stands for Continuously Variable Transmission. This means that technically there is no "shifting" meaning no actual going from 1 gear to another. However the "shifting" in gear ratios happens in the variating size of the pulley.

To get an idea of what it does ( not how it works ) you can look at many off road dirt or dune buggy style cars. Also Nissan ( I believe ) has a new national advertisement of a CVT in one of their new cars. Motor revs up and no shift jerk, pretty neat.

Anyways, this is a sharp transmission I'm kinda bummed I didn't get to see this in person this year.

[ClintDog]

I am going to try to give you the best explanation i can. ok here we go, it is a continuously variable transmission and as the motor thats connected to it's rpm's raise the brass weight move inward towards the belt, when that happens the "gear ratio" changes making the power transfer much more efficient.

[AdamHeard]

centrifugal force makes the weights go in?

[=Martin=Taylor=]

Saw this in a Motor Trend article and decided to check it out.

Its quite a nifty idea and could definitely be implemented on a robot (they even mention robots as one of its applications).

Not only are they relatively small (bicycle hub) but they are also driven by chains!

[Lil' Lavery]

Originally Posted by cromat44

centrifugal force makes the weights go in?

INERTIA would make the weights change position, and help "shift" the gear ratio (although I've seen other CVT's, rather they use motors or other actuators to control the positioning of the pulleys).
http://auto.howstuffworks.com/cvt.html

[Andrew Blair]

Actually, to be completely accurate, it's a centripetal acceleration that causes the weights to exert a force outward, which operates the shift. Higher RPM means higher centripital acceleration, a higher force pushing outwards, and a different ratio.

More importantly, I had been ogling the available pictures of this transmission over about the past year, and when I glanced at it walking through the pits in Atlanta, myself and Cody from our team immediately ambushed the only kid in their pits. I actually apologize for that, I think I scared him a bit. "Can you demonstrate your CVT to us? Please?! We really want to see it! Please!"

Anyways, the thing is really, really cool, if it is a bit noisy. It shifts really smoothly, but it does seem to offer a lot of internal resistance to movement. But really, really slick!

[Lil' Lavery]

Originally Posted by Andrew Blair

Actually, to be completely accurate, it's a centripetal acceleration that causes the weights to exert a force outward, which operates the shift. Higher RPM means higher centripital acceleration, a higher force pushing outwards, and a different ratio.

Well, I was just trying to say that centrifugal force doesn't really exist
Besides, centripetal acceleration wouldn't exist without inertia. (well, little of physics would exist without other fundamental physics principles...)

[Alex.Norton]

Thanks for the correction. However, centrifugal force does exist, it the force that keeps the citizens of a country in the country or some such like that. I learned this in my geography class 4 years ago so its a little fuzzy and I was afraid that last night a 11:30 I would get them mixed up and of course, I did.