Lift Float Dumb Question

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Willy
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Lift Float Dumb Question

Postby Willy » Tue Jan 02, 2018 9:54 am

Rather than jump into someone else's thread, I thought I'd ask my dumb question separately. Most of what I know about Farmalls came from my Grandpa who was illiterate but knew Farmalls like the back of his hand and tended to use his own terminology in teaching me. And most of it was with a Super C. So at times, I can get a little confused on what's actually being said with the finer details. And I can get a bit OCD with wanting to know how it all works and works together.

Just to make sure I've got this right, on a Cub with Touch Control Lift, the lift holds everything at a steady level in relation to the tractor with no float function. Float is provided by the pressure rods and springs (at least on the 144 cultivator set up that I have).

Thanks in advance

Willy
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tmays
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Re: Lift Float Dumb Question

Postby tmays » Tue Jan 02, 2018 9:59 am

Fast hitch or no fast hitch?
Thomas

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Willy
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Re: Lift Float Dumb Question

Postby Willy » Tue Jan 02, 2018 10:14 am

No fast hitch. Just regular bolt the pieces onto the Cub. I've only ever seen pictures of a fast hitch.
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Nah, it's not leaking oil. It's just marking it's territory.

staninlowerAL
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Re: Lift Float Dumb Question

Postby staninlowerAL » Tue Jan 02, 2018 10:18 am

To give a precise answer to your question and in addition to tmays' response, I believe the particular implement would have to be examined. Your comment about springs/rods, etc probably holds true for cultivators in general but other implements do have some float capability depending on how they are connected to the tractor and lift system. Examples: a lift type disc will typically have some float ability depending on how the drawbar is utilized as well as the lifting mechanism (chains or rods). The same goes for the moldboard type plows and disc type plows. Generally speaking the primary attachment point is somewhat rigid and the float/flexability is provided by the lifting link. Just my 2 cents worth.

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Re: Lift Float Dumb Question

Postby tmays » Tue Jan 02, 2018 10:46 am

With no fast hitch, then yes, you’re correct on cultivators. Stan touched on the other stuff. Also, depending on what shanks you have, there are trip mechanisms for them in case you hit something solid. Although I wouldn’t necessarily say the cults are floating. The rods are down pressure rods
Thomas

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Re: Lift Float Dumb Question

Postby Jim Becker » Tue Jan 02, 2018 11:25 am

I'm going to back up a little bit and comment on some basics and associated terminology, as I think that is where your question comes from. If you want to dig a little deeper into the terminology of hydraulics, here is a page reference. It gets deeper into some things beyond what you are asking.
http://www.precisionfluidpower.com/hydr ... -glossary/

This is a simplification.

First off, the cylinder built into the Touch-Control is a double acting cylinder, which means it applies force in both directions. It is coupled directly to the rockshaft, giving the rockshaft force both ways. A double acting cylinder has a fluid connection to each end, (usually hoses, drilled passages inside the Touch-Control).

A double acting cylinder is typically controlled by a 4-way valve (has 4 fluid connections or ports). One connection feeds pressurized fluid to the valve, a second returns fluid back to the reservoir, the remaining 2 go to each end of the cylinder. The valve has 3 positions that can be selected by the operator. Neutral allows fluid to pass from the inlet to the outlet while flow is blocked to both cylinder ports. The cylinder will be held in its current position. The valve's up (or raise, or lift) position connects the inlet to one cylinder port and the other cylinder port to the return. The cylinder extends as long as the valve is in this position. The valve's down (or lower) position does the same as up, except it reverses the 2 cylinder ports causing the cylinder to retract.

A float valve is a 4-way valve that has a fourth control position. In the fourth position, all 4 ports are open to each other. This allows fluid to pass freely from the inlet to the outlet but additionally allows the cylinder to extend or retract from external forces, preventing the hydraulic fluid from stopping the motion.

A snow plow blade is a good example of an implement that you want to float. It needs to stay in contact with the road but not try to dig through it, no matter how uneven the surface. Other implements (e.g. cultivator, planter) work better if some actual force in a downward direction is applied. This could be done by adding weight, although that is usually not the most practical way to do so. So the lift system is used to apply the force. This is usually referred to as down pressure (sometimes called down force, which would be a more correct term).

As already stated, on a Cub you have a double acting cylinder connected to the rockshaft, applying force in both directions. With the cultivator, you want to apply a controlled amount of down pressure. You control it with springs that are included in the mechanical linkage. You have a rear rockshaft that is solidly linked to the Touch-Control rockshaft. The rear rockshaft is thus capable of applying force in both directions but does not float. The pressure rods and springs can compress, with the required force determined by how the springs are adjusted, but do not stretch. Thus the Touch-Control will positively lift the cultivator, but the down force is mechanically controlled by the spring adjustment and how far the rockshaft is lowered. This is done without a float capability built into the Touch-Control. The front cultivators are controlled in a similar fashion with the pressure spring assemblies built into the linkage of the universal mounting frames.

On a Fast-Hitch Cub, the link from the Touch Control rockshaft back to the Fast-Hitch rockshaft has an adjustable collar that can be set to eliminate downward force at the hitch. This is often referred to as letting the hitch float, but is a slightly different use of the word float than is used in a hydraulic system. It accomplishes the same thing. The Fast-Hitch needs to be able to float for draft controlled implements like a moldboard plow. The same is accomplished for the non-Fast-Hitch plow by using a chain to lift it.

staninlowerAL
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Re: Lift Float Dumb Question

Postby staninlowerAL » Tue Jan 02, 2018 4:19 pm

Excellent explanation Jim. I was almost certain you would weigh in on this one and your description of how things work is the best I have ever read.

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Re: Lift Float Dumb Question

Postby Willy » Tue Jan 02, 2018 7:56 pm

Thanks for the responses! I've got a better idea now how it all works together.
Waking up the ol' Cub

Nah, it's not leaking oil. It's just marking it's territory.


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