Imagine two conical gears arranged side by side like this: |AV|, with a
belt that moves up and down coupling them together. With the belt on the
top, it has a ratio greater that one, as you move the belt down the ratio
becomes less than one.
Substantially. It's actually simpler, and was invented by Leonardo da Vinci,
but it has a belt (or a follower gear) that provides a single weak point.
With a regular transmission, if you break the gear assembly on first gear,
you can still start the car out in second... if you break synchronizers
you can double-clutch it home. With a CVT there isn't as much to break,
but if it does break you're dead in the water.
Well, it's continuous, so you can always have the transmission at the
precise ratio that is optimal, you don't have to have it at the nearest
gear. You don't need to use the clutch except for stopping, so the clutch
wear is greatly reduced.
I believe there was a Dutch car manufacturer that used it in the 1950s.
Subaru made one in the eighties too, as I recall.
"C'est un Nagra. C'est suisse, et tres, tres precis."
On Aug 30, 1:30 pm, firstname.lastname@example.org (Scott Dorsey) wrote:
Ford has had it in their 500 car for several years. It was designed by
If you want to see a real simple design, hang out by the golf course
and look at some of the older golf
carts. Cushman also had this real simple design in a lot of their 3
and 4 wheel scooters that are used by a lot
Like already stated, the "V" in the drive pulley gets bigger and the
"V" in the driven pulley gets smaller as you increase the speed.
Continuously variable depending on the speed. Of course, the cars are
One disadvantage is that most applications do not allow you to do any
John Deere lawn and garden tractors from the mid to early 60s, too.
Actually they had a regular multi-speed gearbox COMBINED with a
variable-speed belt drive system that allowed a broad range of speeds in
each gear. Very cool, I wish modern L&G tractors were as well-designed
and easy to use.
Towing the vehicle it's in, or towing something using the vehicle it's
If you mean to say a vehicle with a CVT can't tow, I'll beg to differ:
We used to tow a 7-hole ice shanty out onto the lake using a snowmobile
equipped with the typical-for-a-snowmobile CVT. The shanty took 7-8
strong men to hump it on or off the pickup, and likely weighed 1200
pounds, maybe more. So long as the sled could get enough traction on the
ice to move itself, it towed the shanty without any noticeable
Don Bruder - email@example.com - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
I agree. I have a Murano and have towed a rental trailer many times.
It does not tow as much as a Suburban but it's also a lighter
One disadvantage I have heard is that it's very expensive if there is
something wrong with the transmission because nobody knows how to work
on it, and the only option is to replace the whole thing at a dealer
for $6-7k + labor. I'm seriously considering whether to buy extended
warranty before the standard power train coverage expires.
Right. DAF was the Dutch car. It featured a belt made with little metal
stampings (for failure to be able to describe it more accurately)
Nissan did their homework and apparently came up with a CVT which is tough
It features steel belts.
I never knew Ford used any CVTs by Volvo, but if the poster says they did,
it is fair enough
Wikipedia has an entry for CVT's...
As a side note, they've been using similar 'transmissions' on large jet
aircraft for eons.
They're called 'constant speed drives' (CSD), and are used to drive
engine driven alternators at a constant rpm regardless of engine speed.
They work a little differently than automotive CVT's though. CSD's
internally have an engine driven variable output hydraulic pump powering
a hydraulic motor that actually drives the alternator.
Large aircraft mostly use AC current, so their alternators are rectifier
free, and output frequency is controlled by rotation speed. They're also
synchronized to keep multiple alternators in phase with one another.
Aircraft constant speed drives cost mega bucks...
The use of the CVTs goes back, I believe to the 1920s. Many companies
have tried it through the years, none had a lot of success for very
long. But then, the price of gas was never high enough. One obstacle
in the past is that belt drive type CVT was limited in horsepower,
which restricted it to lower powered cars. Nowadays there are
supposed to be belts that can handle very high hp.
Regular transmissions have a fixed number of predetermined ratios
between the input and output shafts, so when the transmission shifts
gears the engine speed has to drop suddenly (or slowly, but that wastes
energy in slipping the transmission clutches.) A CVT gradually varies
the input/output ratio so that the engine speed can remain constant or
near-constant as the car speeds up.
Pros- the engine can spend more time at the RPM where it is most
efficient. Cons: complexity, until recently fragility and limited to
less powerful engines.
They're not the only ones. You can find CVTs in the Dodge Caliber, Jeep
Compass/Patriot, and others.
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