CVT transmissions?

[Wile E]

I was looking at the New Holland website.........It is nice to look, even if you cant afford it.
So, What is a CVT transmission. I understand gear and hydrostatic. But what is a CVT, Continous Variable transmission. Is this like a snowmobile belt? I just cannot see a 90HP tractor using a system like this. If I was to buy a $75,000 tractor I would want a gear transmission, tried and true ya know.

 

[Bob]

Here's a link to a video of how the CIH version works. (A quick search didn't turn up the NH version.)


The steering systems on modern tracked tractors wors in a similar fashion.. a hydraulic motor geared to a planetary gearset varies the speed of each track for steering.

http://www.youtube.com/watch?v=A5_iNL9q18Y
CIH CVT

 

[D beatty]

A CVT ( continously variable transmission) is an automatic transmission that shifts gears but you don't hear or feel the transmission shift all you hear is the sound of the engine revving up or down on RPM's.

 

[JDemaris]

Yes, some DO use a variable belt sheave similar to a snowmobile drive. Subaru had one of the first ones in the USA ca. 1987 called an "EVCT." A trans that is "constantly varible" uses belts, hyrostatic, hydraulic, or a "Toric" drive. Most walk-behind snowblower and some older rider mowers have crude versions of Toric drives with rubber drive wheels.

 

[Mark-Mi]

I just watched several cvt videos from several manufactures. Now my head is spinning like a ring gear inside a cvt transmission. Ohhh, my head hurts.

 

[mkirsch]

Remember at one point, your "tried and true" gear drive, wasn't. It took many decades to perfect it.

I think CVT is the future, because you're always in the right gear, and that makes everything more efficient.

 

[Anonymous-0]

Here's chrysler's version, from the seventies, and yes, the government bought chrysler...
turbo encabulator

 

[farmer boy]

From what I understand, that's something like how a John Deere IVT works. Fendt(all AGCO) CVT has no gears. Based on the video I watched, it works on the same basis as a differential using a hydraulic pump and motor to help. Very efficent and little to no wear. Technically it's not even a shift into reverse.

 

[Dean]

Various technologies are used in so-called CVT transmissions.

Modern high HP AG units use an epicyclic (harmonic) drive powered by a variable speed hydraulic motor to achieve true variable speed across the operating range. These units are complex, expensive, not tolerant of inadequate maintenance and usually not serviceable by field personnel.

Automotive units use simpler, less expensive alternatives, e.g., connical sheeves surrounding a tapered metallic belt or series of balls.

The large scale introduction of electrical transmissions into both AG and over the road vehicles is inevitable.

Dean

 

[rrlund]

I believe the first ones patented by Oliver in the late 60s were primarily gear drive weren't they?

 

[Alan K]

White- Oliver/MM were working on just such a thing on what they called a corporate tractor back in the early 1970s. I guess it took too much money for research and it was dropped. I think the prototype or what is left of one of them is in the Floyd County Museum.

 

[Mike M]

Even the ones that got perfected got down graded (cheapened up) with time so they would fail more often.

 

[Bob]

An example of a segmented metal belt in the tractor world is the New Holland "Boomer 8N".

<img src = "http://i167.photobucket.com/albums/u125/27Grainfield/N%20Ford/cvt_zps37a10ab9.jpg">

 

[Wile E]

I still think that Gear drive is the best, most effective way to drive/shift/work a tractor.

Hydrostatic is nice of course, but somewhat complex and expensive.

 

[Pops1532]

(quoted from post at 16:44:45 01/31/14) I still think that Gear drive is the best, most effective way to drive/shift/work a tractor.

Hydrostatic is nice of course, but somewhat complex and expensive.

Even thought CVT has been around in some form for decades, many are still afraid of it. I think you'll find most that have experience with CVT tractors prefer them over gear tractors. I have a friend that's a powertrain engineer for a heavy equipment manufacturer. He speaks very highly of the CVT.

 

[Frank 41]

I thought Frendt had the first one and Deere and Case backengineered it.

 

[RodinNS]

I'm not really sure how the Steyr/CNH variable drive works... but the Fendt version is a hydro mechanical type of system that uses a type of hydro for the starting and light maneuvering type of stuff and then uses a variable drive system I think using a steel belt and sheaves or some similar idea. Regardless of how it's achieved, it is a very efficient, reliable system. Those tractors are pushing close to 400 hp today and I don't here about too many problems with them. Lots of guys are using them for hauling the large manure tanks because they're safer to work with then large 4WD tractors...
From what I understand, the Deere IVT system is good but not quite as reliable as the Fendt. Massey uses the same basic componentry as Fendt with a different user interface...
The big gain with the CVT transmission is that on lighter or varying loads it represents the opportunity to throttle back and still maintain appropriate ground AND PTO speeds so you can save a fairly substantial amount of fuel. On a dead pull such as heavy tillage.... no, it's probably not as effective or efficient as a power shift or gear drive.

Rod

 

[T in NE]

CVT is more efficient at just about anything but road travel. Then gear and powershift take over. Unless, of course, you've got time to back off and lose 1/4 of your road speed. Not around here.