Question......

427 S/O · #1 (**permalink**) 01-14-2009, 10:31 AM

What's the term/name of transmissions like the ones on snowmobiles, where you have a belt and two pulleys. One pulley opens and the other closes for torque purposes.

Thanks in advance.

392cobra · #2 (**permalink**) 01-14-2009, 10:35 AM

CVT..... continuously-variable transmissions .

427 S/O · #3 (**permalink**) 01-14-2009, 10:37 AM

Thanks, I remember Ford working on one, guess it's so simple there's no money in it?.

Speedysnake · #4 (**permalink**) 01-14-2009, 11:09 AM

Ford still has a constant speed drive in their Freestyle and at least on of their hybrids. I don't know how it works, but it feels wierd!

Continuously Variable Transmission (CVT)What it is: A continuously variable transmission is an automatic that can select any desired drive ratio within its operating range. Unlike a traditional three, four, or five-speed automatic transmission, the CVT is an "infinite speed" transmission. It continually selects an optimum overall drive ratio between engine and drive wheels for all operating conditions, whether accelerating or cruising. Unlike conventional automatics, there are no perceptible shifts. During maximum acceleration, the drive ratio is adjusted to maintain peak engine horsepower. At a constant vehicle speed, the ratio is set to maintain an optimum balance of fuel economy and driveability. A CVT provides smooth, fast acceleration and high cruising efficiency with the convenience of an automatic transmission. How it works: The most common CVT design uses a segmented metal V-belt running between two pulleys. Each pulley consists of a pair of cones that can be moved close together or further apart to adjust the diameter at which the belt operates. The pulley ratios are electronically controlled to select the best overall drive ratio based on throttle position, vehicle speed and engine speed. Customer benefit: Performance, fuel economy improvement and smoother operation.

tcrist · #5 (**permalink**) 01-14-2009, 12:36 PM

We use to call that a centrifical (sp?) clutch.
Terry

strictlypersonl · #6 (**permalink**) 01-14-2009, 12:50 PM

A CVT uses two variable-diameter pulleys connected by a rubber or steel belt. As one pulley diameter gets smaller, the other gets larger so that the length of the belt stays the same but the gearing ratio changes.

A centrifugal clutch is not a CVT, it's just an automatic clutch that uses something like brake shoes that are thrown outward against a drum (that drives the wheels indirectly) as rpm increase so that they are disengaged at low speeds and lock up at high speeds.

bomelia · #7 (**permalink**) 01-14-2009, 12:54 PM

CVT is not a Centrifugal Clutch.

I have a CVT in my drill press. Cool as heck.

Mike

427 S/O · #8 (**permalink**) 01-14-2009, 04:00 PM

Like this.........

http://www.youtube.com/watch?v=LlWYTnaDnK0

Silverback51 · #9 (**permalink**) 01-14-2009, 04:23 PM

Both the Nissan Morano and Dodge Calibre have these transmissions. I have driven both, and it would take some getting used to.

Wayne Maybury · #10 (**permalink**) 01-14-2009, 04:58 PM

I used to race snow mobiles many years ago and the reliability of these "transmissions" wasn't very good. Actually the clutch and drive discs were OK but the belts would wear out quite quickly. These were racing sleds so I used to beat them up really hard so it may not be a fair example.

Does anyone know how the automotive CVT's hold up as the mileage increases?

Wayne

tcrist · #11 (**permalink**) 01-14-2009, 05:10 PM

Guess I should have read the post closer but it was my lunch time at work. I guess that it works on somewhat the same principal though. CVT's have 2 pullys and a centrifical clutch has only 1?

Terry

Speedysnake · #12 (**permalink**) 01-14-2009, 05:31 PM

My son has a Ford Freestyle with the CVT. I believe he has over 30K miles on it, no problem so far

It's wierd, no feel of any shifting, and the tach just sort of drifts up and down.

427 S/O · #13 (**permalink**) 01-15-2009, 11:15 AM

Curious..I'm heddn' up to Alan Vigil (if their still in business) and drive one. I know that poor salesman is gonna' try his damnest to sell it.

PDUB · #14 (**permalink**) 01-18-2009, 11:28 PM

Have had very little experience with snow machines, but when was younger, I remember the neighbor calling the system a torque converter rather than CVT... though he could have been using some generic term for it.

427 S/O · #15 (**permalink**) 01-19-2009, 07:39 AM

Just a thought...a heavy duty CVT would be awesome in a cobra, holding that fine line between torque and horsepower for continuous blowout acceleration. And possibly work in reverse with assisted breaking........like I said..just a thought....

Silverback51 · #16 (**permalink**) 01-19-2009, 02:59 PM

Quote:

Originally Posted by 427 S/O

Just a thought...a heavy duty CVT would be awesome in a cobra, holding that fine line between torque and horsepower for continuous blowout acceleration. And possibly work in reverse with assisted breaking........like I said..just a thought....

Sorry, not for me.

I like down shifting for the twisty bits.

SP01715 · #17 (**permalink**) 01-19-2009, 04:16 PM

I have an offroad vehicle (Yamaha Rhino) with this system. It works well, but the belts do fail. I just watched a guy replace a belt on his vehicle yesterday, and he had a hell of a time getting the fragments of the old belt out. He told me they last about 100 hours or so, and should then be replaced. I would take a regular tranny if I had the choice.