Kioti

[k0ua]

Lets see if I can clear up a couple of things. An ordinary Hydrostatic transmission consist of pump driven by the engine crankshaft, a swashplate with pistons and slippers that ride and rotate on that swashplate and a hydraulic motor. Your foot controls angle of that swashplate and hence the stroke of the pistons that control how much fluid flow passes to the hydraulic motor and the direction of that flow.

They hydraulic motor takes that flow of fluid and drives a standard unsynchronized old style 2 or 3 speed standard gear transmission. The human operator controls this old standard transmission with his hand. He selects which gear to be in based on his estimation of the torque and speed needed to do the job. The The hydro has nothing to do with gear selection in any way shape or form.

The old "let off of the hydro pedal to shift to a lower gear" is a misunderstanding. Here is what you are actually doing. You start up a hill and your speed slows. Why does the speed go down? Because the ENGINE is no longer in its torque sweet spot and is not making as much torque as you would like. The RPM's of the engine drop and the tractor slows down. So now you back off some on the hydro pedal and the tractor may actually speed up a bit or at the least does not continue to lose speed. Why?

Because by letting off of the hydro pedal you decrease the flow rate to the hydraulic motor as the piston's have a shorter stroke because you have decreased the angle of the swash plate. This would actually slow the tractor down some, but it also decreases the torque load on the engine. This has the effect of allowing the engine governor to actually increase the RPM of the engine because of the reduced load and get the engine back into its "sweet spot"

While is may seem that you have shifted to a lower "gear" you have only controlled the flow rate to the hydraulic motor

Remember a hydrostatic tractor transmission works NOTHING like an automatic transmission in your car or truck. NOTHING.

An engine always has to balance torque and speed and finding the right spot with your hydrostatic flow rate and the proper selection of the manual transmission gears after the hydraulic motor (which we call a "range" selector) is the key to making sure the engine stays in the spot that it makes maximum power.

 

[IndyJay]

Lets see if I can clear up a couple of things. An ordinary Hydrostatic transmission consist of pump driven by the engine crankshaft, a swashplate with pistons and slippers that ride and rotate on that swashplate and a hydraulic motor. Your foot controls angle of that swashplate and hence the stroke of the pistons that control how much fluid flow passes to the hydraulic motor and the direction of that flow.

They hydraulic motor takes that flow of fluid and drives a standard unsynchronized old style 2 or 3 speed standard gear transmission. The human operator controls this old standard transmission with his hand. He selects which gear to be in based on his estimation of the torque and speed needed to do the job. The The hydro has nothing to do with gear selection in any way shape or form.

The old "let off of the hydro pedal to shift to a lower gear" is a misunderstanding. Here is what you are actually doing. You start up a hill and your speed slows. Why does the speed go down? Because the ENGINE is no longer in its torque sweet spot and is not making as much torque as you would like. The RPM's of the engine drop and the tractor slows down. So now you back off some on the hydro pedal and the tractor may actually speed up a bit or at the least does not continue to lose speed. Why?

Because by letting off of the hydro pedal you decrease the flow rate to the hydraulic motor as the piston's have a shorter stroke because you have decreased the angle of the swash plate. This would actually slow the tractor down some, but it also decreases the torque load on the engine. This has the effect of allowing the engine governor to actually increase the RPM of the engine because of the reduced load and get the engine back into its "sweet spot"

While is may seem that you have shifted to a lower "gear" you have only controlled the flow rate to the hydraulic motor

Remember a hydrostatic tractor transmission works NOTHING like an automatic transmission in your car or truck. NOTHING.

An engine always has to balance torque and speed and finding the right spot with your hydrostatic flow rate and the proper selection of the manual transmission gears after the hydraulic motor (which we call a "range" selector) is the key to making sure the engine stays in the spot that it makes maximum power.

Best explanation I've seen yet!

 

[k0ua]

What gears? Does an HST have gears?

The ones in our tractors do. The ones on a lawn mower DO NOT. The reason for the manually operated gears (NOT under control of the transmission) to select lower ranges for more torque and less speed. 2 or 3 (better) are provided so that the operator can select as needed for the job, either more torque, less speed or more speed less torque or somewhere in the middle. Lawn mowers are in "HI" direct drive all the time, They are not very flexible, and it is not uncommon to have a load condition where the relief valve opens and the tractor does not move nor spin its tires. This doesn't happen all that often but it does happen. Simply because there is no torque multiplying mechanism (the gear ranges)

 

[k0ua]

And I have never seen a hydrostat that the pump acted as the motor or the motor as the pump. The directional changes are facilitated by the swash plate going to a negative angle and covering and uncovering ports feeding the hydraulic motor so that the flow goes one direction or the other. There is no reverse gearing at all just directional flow changes.

 

[Midniteoyl]

Understanding and Troubleshooting Hydrostatic Systems

Hydrostatic drives are used in a variety of applications throughout all types of industries. They are sometimes referred to as hydrostatic transmissions. Anytime one or more hydraulic motors…

www.machinerylubrication.com

An example of what @k0ua was talking about:

 

[Williy]

You guys are saying just because its
fluid drive it don't have gears????

My tractor transmission has:
Its 3 selections for shifting
2 front gears
2 front clutch gears
2 front drive gears
3 counter gears
3 reduction gears
2 idle gear shafts
there's more gear shafts
ALSO the PTO has many many gears

willy

 

[Midniteoyl]

You guys are saying just because its
fluid drive it don't have gears????

My tractor transmission has:
Its 3 selections for shifting
2 front gears
2 front clutch gears
2 front drive gears
3 counter gears
3 reduction gears
2 idle gear shafts
there's more gear shafts
ALSO the PTO has many many gears

willy

It has gears, just not in the hydraulics. The engine spins the pump, the pump spins the motor which in turn spins gears in the rear end, which you select as 'Low/Med/High'.

 

[k0ua]

Neil talked about changing gears when you press the pedal because he thinks you all are too simple to understand the explanation I gave you. I will assure you that pressing on the hydro pedal has NOTHING to do with any gears, because there are NO gears associated with the hydraulic pump and swash plate and cylinders/slippers and hydraulic motor and the only gears involved are the 3 speed range selector transmission that the operator controls with his hand.

Also in the second video he demonstrated stall guard on and off. Notice which range he demonstrated that feature in was HIGH range, because the tractor would not have stalled in either LO or Med. ranges. The tires would have spun. And in Lo or Med you can press that pedal to the floor if you want to when pushing into the pile and the result will be tire spin not engine dying.

Also be advised the all of those features he described are on the Grand L modes with their Hydrostat + transmission. This is not the standard old hydro that most brands have (like my Kioti for instance) Some of the newer Kioti's and other brands notably John Deere, now have some or nearly all of those features. But they were not common at all 10 years ago but were available on the Grand L machines from Kubota.

 

[Beeenvenue]

The big question is: What are you planning to do with it?

I have a 35HP HST CK series Kioti with an FEL. I've had it about 10 years and it's been really reliable without any problems. Comparing them side by side, it appears to be a much beefier design than an equivalent Kubota. The FEL has an easily detachable bucket via a quick-attach plate that allows me to connect to pallet forks- the Kubota did not have this. The roll bar folds down which makes it noce for mowing around trees.

The hydrostatic drive is great for moving snow and dirt as well as mowing with a 6' mower. I added a tooth bar to the bucket and excavated an 18 x 32' area 7' into the side of a hill and the tractor had no problem with that. The bucket is large enough to hold a fair amount but a couple full buckets of shale soil that floated the back end quickly showed the need for a 3 pt mounted counterweight on the back of the tractor to keep it safe.

On the negative side, the HST with 35HP isnt the best for field work unless you move up to a larger tractor to compensate for it. You lose a fair amount of HP due to the HST (35hp becomes 29 or so HP to the wheels) so the tractor bogs down quickly when pulling a 2 bottom plow. This isn't helped by the R4 tires that are useless for plowing. Further, with the HST foot pedal on the right side, there is no way to differential brake to control the tractor and help with turning even though the tractor is set up with differential brakes. A manual transmission and AG tires would be much better if you plan to do field work with this tractor. I'm glad I kept my NAA that pulls my 2 bottom with no problem.

Hope this helps and gives you some items to consider.

A bit misleading as the 35hp geared only has 31 hp at the pto. Any tractor is going to give up 10-15% of engine vs pto hp. Hst takes a bit more away (29.6 vs 31) but if 2 hp is that critical then buy a bigger tractor.

 

[ptsg]

A bit misleading as the 35hp geared only has 31 hp at the pto. Any tractor is going to give up 10-15% of engine vs pto hp. Hst takes a bit more away (29.6 vs 31) but if 2 hp is that critical then buy a bigger tractor.

That 2 HP difference is only if you're using a stationary implement like a wood chipper, generator. Once the tractor starts moving, that's were the losses will appear.