What's the difference between a vario drivetrain and a hydrostatic ?

[Boomerang]

Similar or huge difference?

 

[davidroberts30]

Similar but huge differences

A hydrostatic uses a pump to drive a motor,oil drive

A vario uses a pump to drive a motor that drives a sun and ring gear so technically the drive is all mechanical albeit controlled by hydraulic

 

[john432]

 

[dannewhouse]

There was one a lot clearer can't find it arm.
Basically it's variable displacement pumps and motors being varied individually to force the mechanical side.

You beat me to the link!

 

[Fendtbro]

Similar but huge differences

A hydrostatic uses a pump to drive a motor,oil drive

A vario uses a pump to drive a motor that drives a sun and ring gear so technically the drive is all mechanical albeit controlled by hydraulic

It is 100% or so mechanical drive at full forward speed, rising to to nearly all hydrostatic at lowest speeds. Therefore very efficient at full road speed, the problem is getting up to full road speed as the damn box is hoovering up so much hp trying to get there.. sort of self defeating. You can see why lorries don’t use vario. And why all the modern stuff is 250horse plus when 150 used to do. Of course works great in the field on low draught pto work.

 

[DanniAgro]

A hydrostatic drive loses even more power than a CVT, that's why they never took off.

 

[Frankzy]

Similar or huge difference?

It's a completely regular hydro with a planetary gearset where one output is directly linked to the wheels and the other to the hydro.
At standstill the hydro swashplate is at 0 so all the engine power that's going into the planetary is just spinning the hydro pump since that output has no resistance as opposed to the one directly connected to the wheels.
As soon as you want to go forward however the swashplate angles out which then starts to turn the hydro engine and it turns the wheels.
The neat part is that since the hydro is now taking some effort to turn a small amount of the power going into the planetary will go through the output straight to the wheels. (not much mind you since it is geared very highly).
The more the hydro increase its ratio the harder it'll be to turn and the more power will just opt for the direct mechanical route, until finally the swashplate is at max angle and stood still while all engine power going through the direct output.


The ZF/CNH box complicates things a bit with a 4 speed gearbox so rather than just having just one point of 100% mechanical drive, they end up with four..