HST - How Does It Work?

[frank_f15]

BIRD : I LIKE YOUR DESCRIPTION BEST/w3tcompact/icons/smile.gif i don't really know how it works, just know that it works just fine. and if anything really goes wrong with it i will let the REAL MECHANICS(A.KA KUBMECH) deal with it.

 

[ewoss3]

actually, from experience $2000 is really not that high when it comes to fixing transmissions. We took our ford 601 workhorse in with a busted 2nd gear and the price was $1700. Two years before that we had the clutch unit replaced for $750. So from my viewpoint, it appears to be a moot point on wether either is more expensive.

 

[hwp]

I have read this thread through from one end to the other, including the various references, and I am still confused. Does anyone know of a site with a simple animation that shows how the system works?

 

[MossRoad]

There were some links in the third of fourth reply that had some animations. Did you see those?

 

[Harv]

Interesting that y'all are revisiting this thread exactly one year after it began, give or take a few hours.

Kinda spooky, now that I think of it.

 

[MossRoad]

Oh my gosh! That is weird!!!

 

[DFB]

What a strange coincidence! /w3tcompact/icons/shocked.gif

DFB

 

[DFB]

Howard,

I don't know of any other sites off hand. I'd like to see the inner workings of the TC hydro's myself.

Best I can do here is to try to better describe how the drive system works on my Deere. I've attached a scan of the internal components. In application there is a housing that covers over the piston motor and of course all the gear clusters behind the the valve block locate inside of either the center case and/or rear transxale cases which also contain all the hydraulic oil.(sump)

The engine input shaft turns both the charge pump and piston pump. Oil from the charge pump passes thru the valve block to the piston pump. The variable postion of the swash plate, linked externally to the foot control pedal(s) and controlled by the operator, determines the amount of oil the piston pump displaces by changing the length of the piston stroke. Pumped oil is then routed back thru the valve block to the piston motor. Piston motor turns by the same type of piston pumping action. The motor's output shaft then drives the toothed gear clusters.

On this tractor hydraulic flow is also used move the clutch and brake plates used to control the PTO.

Maybe this can help.

DFB

 

[hwp]

Thanks DFB:

I am starting to get the picture. One of the aspects I found confusing related to how the volume of the pump varied. What I had missed was that there are several pistons and that the angle of variable swashplate determines the length of stroke of the pistons as cylinder block of the pump rotates. This changes the volume of flow from the pump to the hydraulic motor. The swashplate in the motor is fixed so the speed of rotation of the motor varies with the volume of fluid coming from the pump. But how does changing the angle of the variable swashplate from one direction to the other change direction of the motor? Is the direction of the flow of oil reversed? Are there valves linked to the variable swashplate that open and close to make the oil flow one way or the other?

I found the attached diagram in the Service Manual for my tractor quite helpful.

 

[hwp]

This is another diagram from my service manual with my annotation about hte valving.