Just Curious

Ford 2000; 3 cyl. gasser; 4/1 trans....I just bought a 2011 Nissan Rogue from a friend and the car has a 'constantly variable transmission' (CVT). Step on the gas and it goes but with no apparent shifts to different gears. Is that type of transmission anything like a shuttle shift or hydrostatic transmission in tractors? I have no experience with shuttle shift or HST tractors but see mention of them in this forum and others all the time. Just curious to see if my Rogue CVT transmission is a first cousin or distant cousin to the tractor transmission. Thanks.
 

I don't know the particulars of the Nissan CVT, but other automotive designs are chain driven where the "sprockets" (shaped more like pulleys) vary in pitch diameter by expanding or contracting.

Totally different from hydrostatic drives where a variable displacement hydraulic pump pressurizes fluid and moves a driving motor.

Which is also totally different from a shuttle shift which is a forward/reverse gearbox in combination with a regular gear transmission.
 
In operation, similar to the HST. Step on a pedal to go forward.
The harder you push the faster you go. No shifting with an HST.

With an HST you would step on a different pedal, or the rear of
the same to go backward. Again, the harder you push, faster you
go. Mine also has a Hi and Lo range for both forward and reverse.
Some where hand operated like my old Cub Cadet lawn tractor.
No pedal on that one.

Mechanically, they are not the same things though.
 
My new tractor has a cvt transmission. Still getting use to it but I like it. Handy for loader work and works great with my 3 point tiller.
 
HST (hydrostatic) transmissions have no mechanical coupling between the engine and the rear axle. Simplified, the engine drives a variable displacement hydraulic pump. A variable displacement, reversible hydraulic motor drives the rear axle. The hydraulic oil flow provides the connection between power source and axle. The variable speed and reversibility inherent in such systems results in a very convenient and easy to control transmission, albeit at the expense of reduced efficiency.

A shuttle shift transmission is usually a conventional gear type transmission with a reversing unit in front. The reverser can be mechanical (usually synchronized) or hydraulic. Such systems are less versatile (not CVT) than HST systems but more efficient and less expensive. Clutching is required to reverse direction with a syncro-shuttle and to change gears in the (usually (always?) synchronized) main transmission. Clutching is not required to change direction in a modern hydraulic (power shuttle) transmission, though I usually do because I usually want to change gears in the main transmission at the same time.

Some CUT tractors, e.g., CNH Boomer 8N, have mechanical CVT transmissions that are not HSTs, but such units are not common in these markets.

Dean
 
(quoted from post at 10:40:50 11/30/17) HST (hydrostatic) transmissions have no mechanical coupling between the engine and the rear axle. Simplified, the engine drives a variable displacement hydraulic pump. A variable displacement, reversible hydraulic motor drives the rear axle. The hydraulic oil flow provides the connection between power source and axle. The variable speed and reversibility inherent in such systems results in a very convenient and easy to control transmission, albeit at the expense of reduced efficiency.

A shuttle shift transmission is usually a conventional gear type transmission with a reversing unit in front. The reverser can be mechanical (usually synchronized) or hydraulic. Such systems are less versatile (not CVT) than HST systems but more efficient and less expensive. Clutching is required to reverse direction with a syncro-shuttle and to change gears in the (usually (always?) synchronized) main transmission. Clutching is not required to change direction in a modern hydraulic (power shuttle) transmission, though I usually do because I usually want to change gears in the main transmission at the same time.

Some CUT tractors, e.g., CNH Boomer 8N, have mechanical CVT transmissions that are not HSTs, but such units are not common in these markets.

Dean

Lot's of innovation going on in the CVT arena. Here's a brief video describing one of Caterpillar's latest CVT transmissions that is a dual path mechanical/hydrostatic hybrid that attempts to leverage the best of both worlds while eliminating the inefficiencies of a pure hydrostatic drive. They claim it delivers a 25% increase in fuel economy over their previous generation transmissions ;-)

[u:0d61899e64]Caterpillar CVT[/u:0d61899e64]

TOH
 
Similar systems have been around for some time in high HP AG machines, e.g., CNH, to provide "CVT" features while, at the same time, achieving acceptable efficiency.

Frankly, I believe diesel/electric technology is more suitable for (at least) high HP AG machines.

FWIW, European locomotive manufacturers (MAN?) attempted to market "HST" locomotives in the US in the late 1950s-early 1960s while failing miserably due to unacceptable efficiency.

It will surprise me if diesel/electric technology does not become available (initially) in the high HP AG market (as well as the OTR road tractor market) in the immediate future.

Stay tuned.

Dean
 
(quoted from post at 18:55:07 12/01/17) Similar systems have been around for some time in high HP AG machines, e.g., CNH, to provide "CVT" features while, at the same time, achieving acceptable efficiency.

Frankly, I believe diesel/electric technology is more suitable for (at least) high HP AG machines.

FWIW, European locomotive manufacturers (MAN?) attempted to market "HST" locomotives in the US in the late 1950s-early 1960s while failing miserably due to unacceptable efficiency.

It will surprise me if diesel/electric technology does not become available (initially) in the high HP AG market (as well as the OTR road tractor market) in the immediate future.

Stay tuned.

Dean

Diesel/electric is already here:

[u:50e6e97a7a]Caterpillar 988K XE Electric Wheel Loader[/u:50e6e97a7a]

TOH
 

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