Modern Vespa

Could anyone please expain, in layman's terms, how a CVT operates? Is it belt driven? Thanks

Sadly, it is complex and many different types.

http://en.wikipedia.org/wiki/Continuously_variable_transmission

it is kinda a belt driven, to a bunch of rollars and somehow connected to the wheel. it is not hard to work on but kinda hard to explain.

i stole it from the wikki page


Toroidal or roller-based CVT

Toroidal CVTs are made up of discs and rollers that transmit power between the discs. The discs can be pictured as two almost conical parts, point to point, with the sides dished such that the two parts could fill the central hole of a torus. One disc is the input, and the other is the output (they do not quite touch). Power is transferred from one side to the other by rollers. When the roller's axis is perpendicular to the axis of the near-conical parts, it contacts the near-conical parts at same-diameter locations and thus gives a 1:1 gear ratio. The roller can be moved along the axis of the near-conical parts, changing angle as needed to maintain contact. This will cause the roller to contact the near-conical parts at varying and distinct diameters, giving a gear ratio of something other than 1:1. Systems may be partial or full toroidal. Full toroidal systems are the most efficient design while partial toroidals may still require a torque converter, and hence lose efficiency.

Thanks, you really made that clearer to someone who obviously is just starting the mechanical learning curve.

lol, i tried... it is kinda hard to explain, what am i forgetting.

I don't know. I think this explains it better:

http://www.youtube.com/watch?v=hU0QZQRTNr0

thats just mean

Seriously, though, this thread gives a pretty good explanation with drawings:

What is a Continuously varying Transmission?

Also, here's a good link I noticed in that thread that puts it in motion:

http://www.teamcalamari.com/zumasrus/zdox/ztip4.html

I wrote up a pretty good explanation a few months ago. Now I just have to find it!

Sorry, I couldn't resist.

good post +1

Is this the one you're looking for?

What are roller weights? (Post 620981)

These may help:
http://www.youtube.com/watch?v=2XDqgGFfCso&feature=related
http://www.youtube.com/watch?v=8VYPsrOyIdw

The idea being the transmission changes its gearing to keep the engine at it's optimal RPM as long as possible.

Harvey

Check out the below link, it explains what a CVT is, and gives a demo of how it works.

http://www.youtube.com/watch?v=4o7MaM6tk9M

this puts it best as far as video....cool, now i get it as well...

Please don't think I'm jumping on you (well only a bit) - but if you just now 'get it' - how come you were trying to 'helpfully' explain it earlier? If you know an answer, give it, if you don't, zip. Please.

Yep, that's it! Thanks, Danny.

I just found it on my own, and when I came back here, you'd beat me to it!

i was winking becouse i was half joking, sorry. i did understand but now a little better than i did, all i posted is what i know and some info i found. just putting it out there but if i did not post it would have fallen off the main page and people would not been able to explain it better. but i offer what i can, even if it is a little. I don't try to act like i know it all, and i give credit where credit is due.

think of it, before i posted there was not a post in about 16 hrs or so, since i posted in the last 40 mins people have posted i think 3 videos and 2 other talks on MV about it, so i think it helps in a way, but like i said in the other posts, i thanked someone for the wikki post, for a great video, and also a great written post.

Understood - I could always see all the 'helpful' posts were well intentioned - and that's good.

Some of them were missing the target by 180 degrees though. So perhaps a leetle more restraint? I don't want in any way to dampen your undoubted enthusiasm, and I bet within a year of doing all your own spannering you'll be very authoritative - just not quite there yet. OK?

Keep up the good work.

like i said if i don't see an answer on a post and i think i could put a little input, someone will usally help put in all that i have left out. so i kinda try to work it like a team, and sort of i help get the ball rolling and not always have the best answer. But thanks i love these scooters and learning a lot off of MV because of you guys.

No harm in bouncing ideas - just be very sure none are totally duff ideas!

Thanks for keeping chirpy.

Ok, here's a simplified explanation.

On a multi-speed bicycle, (old style, with several gears at the pedals, and several gears at the rear hub) the smaller the gear is at the front, and the larger the gear is in the back, the easier it is to pedal, but the more limited your speed is. As you gain speed, you can shift to a larger gear up front, and a smaller diameter one in the back. This allows you to continuously pedal about the same speed, while the bike increases its forward speed. This is basically what happens in the scooter, but instead of a set of gears lined up in a row, imagine a cone that turns a belt. (this isn't exactly the hardware used in a Vespa, but it helps to picture it this way) as the belt slides from one end of the cone to the other, the "gear" is changing, not in big steps, but smoothly and gradually. As the belt moves towards the wider end of the cone on the front end, the slack that is taken from the belt makes it travel down to the smaller end of the cone in the back. As this happens, the front cone stays the same speed, but the speed of the belt and the rear cone both go up. The thing that causes the belt to travel up the front cone are weights (called rollers in a scoot) that respond with centrifugal force as the front begins spinning.

Here are some quick paint drawings

Nice, Drew.

Wow, thanks for the drawing and the You Tube video (the good one . I think I'm almost getting it!!!