Oil & Fuel purpose of throttle on column

[NuBota]

Arien,
Please bare with me. Separate from E hydro which I don"t have, your saying the tractor moves its wheels when the foot pedal is depressed by virtue of hydraulic power transmitted to the wheels. So you don't go faster by pressing on the gas and increasing engine output like a car or is this just auto throttle

You're on track there I think - these other guys have explained it better but somewhat technical - so, yea in my understanding it is hydraulic power to the wheels - the pedal changes the flow rate (and direction for reverse) which controls your ground speed. If you increase engine throttle - the flow rate will also be higher because the hydro pump now has more pressure. Your loader and 3ph will also move and respond faster - so it is a combination of the two (just like a car engine and trans - just different mechanics, i.e. no gears)

 

[tjt35]

Nubota,
Thanx. I am in the process of going to "how to" website to increase my knowledge of hydraulics.

 

[joshuabardwell]

I'll tell you how I think of it, in case a different person putting it a different way helps shed some light.

The throttle lever on the column sets engine RPM. This is analogous to the accelerator pedal on a car. The main difference is that, in a tractor, you typically set a fixed RPM on the throttle, whereas on a car, the RPM goes up and down as the car accelerates more and less (more RPM = more acceleration, and vice versa). You set a fixed RPM on a tractor at least in part because the throttle controls the PTO RPM, and PTO-driven implements are designed to be driven at a fixed RPM (typically, 540 RPM).

On older, gear-driven tractors, there was no hydro pedal. You simply set the rpm, pushed in the clutch, chose a gear, and let the clutch out. Away you go. Within a single gear, increasing or decreasing the tractor's throttle will cause the tractor to go faster or slower, like with a car, but that's now how a tractor is typically used. With a tractor, you typically set a fixed RPM on the throttle and then choose a travel speed by changing gears.

With a hydrostatic tractor, it can get confusing, because there is a pedal on the floor board, and we're all so used to a car that we tend to think of it as an accelerator, but it's not. The hydrostatic pedal is actually more like a gear shift than an accelerator. When the pedal is not pressed at all, the transmission is in "neutral" (sort of). As you depress the pedal just a little bit, it is like being in a very low gear: lots of torque, slow travel speed. The more you press the pedal, the higher the gear the transmission is effectively in, and you get less torque with more travel speed.

The difference between a hydrostat and a gas pedal in a car is illustrated by the way that you respond when there is not enough power. If you're going up a hill in a car and you want the car to go faster, you might press the accelerator more, or downshift. With a hydrostatic tractor, if you are going up a hill and the engine bogs down, pushing the hydrostatic pedal down more just "shifts" the tractor to an effectively higher gear. The engine just bogs some more. You actually have to let up off the pedal, "shifting" the tractor to an effectively lower gear, at which point the engine stops bogging down and you pick up speed again. You can also turn up the throttle if it isn't already maxed out, but with hydrostats, the throttle will typically be running close to max, because they perform best at higher RPMs.

 

[tjt35]

joshua,
Thanx. That part makes sense. So I guess the engine, other than its gear driven PTO function, simply provides hydraulic pressure to move the wheels, loader etc.; sort of like a log splitter.

 

[arlen4720]

eHydro is the hydrostatic transmission. eThottle is a feature. Please advise on which type of transmission you're getting. I believe there is another type of hydrostatic transmission available for the 4000 series tractor, it is called the auto HST, it behaves similar to an automotive system with just a big gas pedal and a reverser lever. Is that what you're talking about? If your proposed Tractor has two peddles on the right side one for forward, and one for reverse, then you have an eHydro.

 

[tjt35]

This 4320 is ehydro hydrostatic transmission

 

[joshuabardwell]

joshua,
Thanx. That part makes sense. So I guess the engine, other than its gear driven PTO function, simply provides hydraulic pressure to move the wheels, loader etc.; sort of like a log splitter.

On a hydrostatic transmission, I believe that's right. The engine drives a hydraulic pump, which drives all functions except the PTO.

 

[tjt35]

Joshua,
I believe that is correct. The engine crankshaft provides rotary energy which is converted to liquid pressure at the hydraulic pump which in turn drives a hydraulic motor (usually a piston) and then converted back to rotary energy (often but not always) to work the wheels, loader, etc.
Thank you for your help. I had no idea that a tractor uses such a simple but sophisticated system. This also explains the floor pedal being more of a gear shift than an accelerator.

 

[CalG]

Speaking from the "Non-hydrostatic" perspective, (12 speed shuttle shift) The hand trottle allows a fixed minimum engine rpm that allows predictable hydraulic and ground speed performance. The foot throttle can over ride , but the minimum is a given based on operator selection of throttle position.

This is VERY handy for loader work when your natural choice is to let off the foot throttle when you press in the clutch. but with a loader, lift and bucket speeds drop when you do.
On the flip side, it's only natural to put you foot into it when pushing a bucket into a pile. Taking advantage of fixed engine rpm allows the operator to optimise forward travel (pile penetration) and bucket filling for each load cycle.

Try it, you will see.

When I do loader work moving material, I set the engine rpms around 2000 and work ground speed from there. Oh! so much less operator load!

cheers

Cal