HST Owners: Are there things to avoid?

[SPYDERLK]

I am not familar with some terms that many may understand, please tell me what stall the hydo means and how you know when it is happening and if it happens all at once or something you build up to or what. Thanks.

Lets say you are hooked to a big tree with your drawbar, and you have some really good traction, and your running a lower rpm. You press the forward pedal, and nothing happens, the wheels dont spin, because you have excellent traction, and the RPM is low. The tree does not move, and like a dummy you just sit there with your foot on the pedal and nothing is happening. ( I know you would not do this) The engine is still spinning the hydro pump. and pumping energy into it, but the hydraulic motor is not moving and the fluid is just heating up. (this is what he warns against) This is similar to in an automatic transmission when you "power brake" by pressing the brakes, and the accelerator at the same time, the engine is spinning the torque converter and it is in a stall condition because the transmission cannot move due to the braking . For a short period of time this is not going to tear anything up. but it you just held the pedal, and hoped something is going to happen.... well...something will.

James K0UA

Yes. And when you encounter this situation James sketched you ease the situation by choosing a lower gear range. Power in a HST goes from engine to pump to hyd motor to wheels. The mechanical gearing is between hydraulic motor and wheels. When you are in a hi gear range it takes more hyd pressure to push a given amount. The pump displacement is variable by the pedal - so you ease the pedal to make it easier when you notice the engine lugging. The pressure doesnt drop - the pump is just easier to turn because it pumps less fluid per revolution. Going to a lower mechanical gear allows use of less hyd pressure to give the needed push because the hyd motor is spinning more revolutions per wheel turn and thereby less torque is required from it. You naturally give more pedal for the speed you want. The pump pumps more fluid at lower pressure to do the same work. This is easier on the pump and motor. The engine, unless you bog it appreciably, really doesnt care.
larry

 

[k0ua]

Yes. And when you encounter this situation James sketched you ease the situation by choosing a lower gear range. Power in a HST goes from engine to pump to hyd motor to wheels. The mechanical gearing is between hydraulic motor and wheels. When you are in a hi gear range it takes more hyd pressure to push a given amount. The pump displacement is variable by the pedal - so you ease the pedal to make it easier when you notice the engine lugging. The pressure doesnt drop - the pump is just easier to turn because it pumps less fluid per revolution. Going to a lower mechanical gear allows use of less hyd pressure to give the needed push because the hyd motor is spinning more revolutions per wheel turn and thereby less torque is required from it. You naturally give more pedal for the speed you want. The pump pumps more fluid at lower pressure to do the same work. This is easier on the pump and motor. The engine, unless you bog it appreciably, really doesnt care.
larry

Thanks for adding to that Larry, that explains it very well.:thumbsup: That might even be good enough for a "sticky" when people ask about which range to use.
The higher mechanical range you select, it will be much easier to stall the hydrostat when it is loaded. But it was good that you explained the "why"

James K0UA

 

[MHarryE]

If you have a Kubota with treadle pedal, don't pile too much loose junk on the platform. It can roll under the pedal when you are driving forward and when you try to stop, well, my garage door has a crease across the lower panel with 2 upright creases at the ends of the horizontal crease. Exactly matches the width of the bucket on my L3710. Fortunately I got by with 2 rollers and 4 hinges. I keep the door panel with crease as a reminder never to do that again.

 

[First one]

I'm not sure if someone has said this but,when getting on and off the tractor it's a good idea to use you parking brake . Your tractor will move if your on a hill or uneven ground, I don't always use mine when on flat ground but always when there is a chance of it rolling. Your HST will not hold you ! Also while trying to move rocks sometimes it's better to turn off your auto throttle advance, so you can increase your rpm's to get more out of your hyd. but not sit there and spin your tires .