3-Point Hitch Top Link Bracket Positioning

[sd455dan]

If your tractor's three point hitch has Draft ability, the hole options will usually affect the draft operation.
Your tractor's manual should tell you which hole to use for each type of work you're doing.

this agrees with my Ford tractors manual, in draft control mode

as an example my 3000 suggests using the top link hole for lighter implements, the lower hole for heavier units,

the 3000, 5000 mounts the top link to the rockshaft differently and IIRC the holes placements achieve the same effect - top hole lightest implement, bottom heaviest as stated above this is for draft reaction and sensitivity.

my 3000 isn't supposed to have reaction in the position control mode , but it does effect operation of the post hole digger, if the top link is placed in the top hole... it is hard to get smooth control of the up and down motion of the 3 point. if placed in the lower hole it is much smoother in operation and easier to control.... hope this makes a little sense

 

[Baby Grand]

Trying to make generalizations about which top link hole works for what task across all tractor makes is not a winning proposition. You've got to either go with what the owners manual for a particular model suggests, or examine the geometry (measure & analyze) on a case by case basis. Small changes in the ratio of linkage lengths can have significant effects on implement motion.

 

[DaveOmak]

The three holes change the leverage applied to the draft control "actuator".... Top hole, less pressure needed to raise the implement... Bottom hole, most pressure needed to raise the implement... That is assuming you have "Draft Control" capabilities on your tractor, and the lever is switched to the "Draft Control" position.....

 

[Treesanddust]

I agree this is a great discussion.

During my research I've also noticed that John Deere and Kubota manuals are diametrically opposed to each other in their recommendations! In theory, they should be the same (for the principles of physics do not change). The angle between the tractor and the implement is the driver of force. The different approaches between John Deere and Kubota make no sense!

Does anyone have else have a manual for a different brand that they can reference?

Jack

The bracket on the tractor that has the three holes is usually hinged on either the top or the bottom, allowing for a lever effect with the toplink acting as the lever. The closer you pin the toplink to the hinge, the more pressure it takes to activate the draft function and the more stress the bracket can handle. Because there is no set standard on which end to hinge the connection, you will have differences as to which hole to use.

 

[Jack3489]

Treesanddust, in my case (Kubota L3800) and the John Deere example cited above the three hole top link brackets are fixed to the tractor differential, thus no movement or "draft control" mechanism as you've properly described. I've actually looked at both tractors and the brackets are essentially mounted in the same location and the hole spacing is the same. The confusing factor is the totally different guidance from the two manufactures.

More importantly, I'm still unable (even with everyone's help) to find any reference documents that outline the theory aspects of this issue.

It certainly appears there is ample confusion regarding the general guidance. I again, appreciate this discussion and the many views and ideas brought forth.

Jack

 

[Baby Grand]

Treesanddust, in my case (Kubota L3800) and the John Deere example cited above the three hole top link brackets are fixed to the tractor differential, thus no movement or "draft control" mechanism as you've properly described. I've actually looked at both tractors and the brackets are essentially mounted in the same location and the hole spacing is the same. The confusing factor is the totally different guidance from the two manufactures.

More importantly, I'm still unable (even with everyone's help) to find any reference documents that outline the theory aspects of this issue.
It certainly appears there is ample confusion regarding the general guidance. I again, appreciate this discussion and the many views and ideas brought forth.

Jack

Four-bar linkage - Wikipedia, the free encyclopedia

Trying to make generalizations about which top link hole works for what task across all tractor makes is not a winning proposition. You've got to either go with what the owners manual for a particular model suggests, or examine the geometry (measure & analyze) on a case by case basis. Small changes in the ratio of linkage lengths can have significant effects on implement motion and reaction forces. The physics don't lie.

 

[LD1]

Without draft control, the 3 holes are just to give you flexibility in how you want the implement to react when raising.

The uppermost hole will give the most lifting power, but less lift height at the tail of the implement. This hole also keeps the implement the most level through out the lift cycle (handy for a trailer-mover-hitch-thingy). It also puts the least about of stress on the top link and top link mount.

The bottom hole will give less lift force, but much more range of travel at the tail of the implement. It also puts the most stress on the TL. This hole is handy for things like a boom pole that you need alot of height but not much power, or for very un-even terrain with a longer implement like a blade or brush cutter, as it lifts the tailwheel higher. Also handy for loading those implements on a trailer with a steep ramp.

The middle hole is just that....middle of the road.

So whatever hole you use dont really matter to much, its just options to give you a choice in how you want things to react.

 

[jimmysisson]

Google the Ferguson System for the theory. If your tractor has Draft, that top link mounting bracket ( with the holes ) pivots on one end or the other and in its middle pushes or pulls on the actuator for the internal hydraulic draft control.

I think my Ford 2120 has the option to pin that bracket solid (to avoid over-using the actuator?). Can't recall the details just now; away from tractor.

Different holes, per manuals for different models are, as has been said, for differing designs of that bracket.

Jim

 

[firemanpat2910]

our new 50hp mf only has one hole, way up high. i cant get my hole digger to raise high enough for transport.