Oil & Fuel purpose of throttle on column

[tjt35]

Hi,
In process of buying jd 4320 ehydro, but dont understand the purpose of throttle on column as well as the floor. I think both can move the tractor forward, but how does the linkage to the rpm and the transmission work.
Thank you,
TJ

 

[wolfpack2]

The throttle on the column controls the engine RPM only. The foot pedals control the speed and direction of travel by changing the angle of the wash plate in the hydrostatic transmission. When using a PTO driven implement such as a mower, you set the throttle to the desired engine RPM for PTO operation and us the foot pedals to control the speed and direction of travel. Some eHydro tractor are equipped with an auto throttle switch. This links the engine RPM to the foot pedals and should not be used when operating a PTO implement, but is good for doing front end loader work or just transporting the tractor. The hand throttle will set the min engine RPM when using the auto throttle. The further you depress the pedals the higher the engine RPMs above this min setting.

 

[tjt35]

Wolf,
Thanx. I understood your explantation to the auto throttle explanation. I am assuming auto throttle is the same as cruise control and I thought that would be good for snowblowing a long driveway, but you say dont use it when operating a PTO implement. i am still a little confused.

 

[arlen4720]

Autothrottle is not the same as cruise control. Auto throttle increases the engine RPM as you press the foot pedal. The 4320 does not have the AutoThrottle option, only the 4520, and 4720. It is a great feature, and you should consider jumping up to a 4520 for that reason alone....If you plan on doing much loader work.
The reason that you don't use AutoThottle for PTO work is that you need to have the engine running nearly "wide open" to get the 540 RPM on PTO shaft.
You set the throttle lever to maintain the proper engine RPM (there is a mark on the tach), then control your ground speed with the foot pedal.
The cruise contol does not affect engine RPM, it just takes control over the ground speed (foot pedal). Cruise only works in forward though, so it won't be much use on a rear mounted snow blower.

 

[tjt35]

Arien,
Think I got it, but why wouldn't cruise work going forward

 

[wolfpack2]

The cruise control only controls the speed just like you car and woks independently of the auto throttle. The auto throttle turns the hydrostat pedals into accelerator pedals just like you car by changing engine RPM and speed without having to manually set the engine RPM with the hand throttle.

PTO implements like a snow thrower or mower are designed to run at a steady RPM. If you use the auto throttle, the engine RPM will change with speed which is not desirable. The normal operation for a hydrostatic equipped tractor is to set the engine RPM for the implement you are using and then use the pedals to adjust your speed while maintaining a steady engine/PTO RPM. If you are NOT using a PTO driven implement, the only need for the engine speed is for hydraulics and ground speed. Therefore you can use the hand throttle to set the minimum RPMs for the hydraulics to function at the level required and turn on the auto throttle to increase the engine RPM when needed for more ground speed. You can use the cruise control in either condition to maintain a constant speed when traveling long distances.

 

[arlen4720]

I screwed that up...I meant forward. I edited my post just now

 

[tjt35]

Thank you guys much. Even though the 4320 doesn't have auto throttle, I am trying to understand. Please forgive my ignorance. I get that the hand throttle controls continuous engine RPM for any given PTO task and the foot pedals control ground speed and the cruise control is the same as a car's. The purpose of the auto throttle "turns the hydrostatic pedals into accelerator pedals". What are the hydrostatic pedals and how would they differ from just using the foot throttle

 

[arlen4720]

What you are calling a "foot throttle" is not a throttle at all. It is the hydrostatic control. Like mentioned above, the foot pedals control the stroke of the hydrostat's piston pump. Auto Throttle is really called eThrottle (the John Deere name)
Just think of it like this: As you press the pedal down, the transmission shifts into higher and higher gears, so the ground speed keeps increasing whereas the engine RPM doesn't change, although the engine may "lug" a bit. Of course, there are no gears...It's a variable displacement piston pump feeding a fixed displacement hydraulic motor. So the pedals (via the computer), control the angle of the "swash plate" on the piston pump. The steeper the angle, the more fluid is moved (per pump revolution). The hydrostat pump is coupled directly to the engine...if the engine is spinning, so is the pump. The 3 range gearbox is connected to the output of the eHydro's hydraulic motor. This makes the tractor more useful, and keeps the hydrostatic transmission's system pressure within practicle limits (about 5500psi max).
With the eThrottle system, the computer just looks at the pedal postion, and increases the engine RPM accordingly. eThottle is really nice for loader work, especially when used in conjunction with LoadMatch.
The main "take away" is that the pedals control the amount of fluid that the pump is moving, thus the ground speed.

 

[tjt35]

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

 

[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