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