Technical education

"Cé hé sin" (michael-m-mouse) 05/24/2016 at 15:07 • Filed to: Fendt, Agco, CVT, Tractor

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You like CVTs don’t you?

You like tractors too don’t you?

You can get them with CVTs and here’s how one of the simpler ones works.

There are complex ones too just in case you understand this one.

BvdV - The Dutch Engineer > Cé hé sin 05/24/2016 at 15:26

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Hmm, being a Dutchman I like my CVTs with more belt, however this is also quite an interesting setup.

Andy Sheehan, StreetsideStig > Cé hé sin 05/24/2016 at 15:35

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My favorite thing about this post is that you didn’t use an apostrophe to pluralize CVT.

Cé hé sin > Andy Sheehan, StreetsideStig 05/24/2016 at 16:16

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Because went to school and was awake during grammar.

Cé hé sin > BvdV - The Dutch Engineer 05/24/2016 at 16:26

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I doubt if belts are up to the 1,000 Nm or more you’d get from a large diesel.

What the video doesn’t say ( I think) is that there are two gears downstream of the CVT so you have two ranges, one for work and one for travel. In each range you start in CVT mode and then gradually move to direct drive.

There’s a more complex one where the engine drives both the sun wheel and a hydrostatic drive. The hydrostatic drive then turns the ring gear in the opposite direction to the sun gear so if you adjust its gearing you get the planet carrier, which drives the wheels, held stationary to give a geared neutral which will hold your tractor on a hill for you. When you want to proceed you change the hydrostatic gearing, the ring gear turns slower and the planet carrier then starts to turn with the sun gear and off you go. Alternatively you can get the ring gear to turn faster but in the other direction to the sun gear and off you go backwards.

BvdV - The Dutch Engineer > Cé hé sin 05/24/2016 at 16:38

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Yeah, IIRC most belt CVTs can’t handle more than 200Nm. However, DAF/van Doorne Transmissies made a CVT for Williams in the 90s, which could handle the torque of an F1 engine. But ofcourse you need a more solid system for the torque of a tractor.

Wow, that one sounds complicated, but I can see why that would be useful in a tractor.

Pickup_man > Cé hé sin 05/24/2016 at 17:01

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Took a course in college that covered these pretty well. This basic setup is what is in the vast majority of Ag equipment and heavy machinery. Like you mentioned in another comment, it’s pretty common to have a traditional gearbox with a few speeds mounted at the tail end of these as well, that way you have road gear, working gear etc. There are also several different setups from cheap and simple, but inefficient, to highly efficient, but more expensive. I really like these types of CVTs and learning about them was probably my favorite course I took in college.