3-Point Standards

[timb]

Every chart I've been able to find listing the standard dimensions for 3-point hitches seems to only list the draft arm spacing (at the rear) and the various ball/pin sizes involved. Are there actually standard dimensions for the rest of the geometry of the hitch? Referring to the attached drawing, are there standards for...

1) the horizontal length of the draft arms (pin-to-pin) - dimension "A" in the drawing...

2) the vertical height of the front pivot for the center or top link above the draft arms - dimension "B" in the drawing...

3) the horizontal 'trailing' (or leading?) dimension of the front center or top link pivot from the front pivot of the draft arms - dimension "C" in the drawing...

Anyone have any scoop on the geometry?

 

[kensfarm]

I think it might be different for each type Class of tractor.. if you had a dealer close by.. they probably wouldn't mind you measuring a few tractors... or maybe contact an implement manufacturer.. they should know the dimensions for various 3 pt Classes.

 

[MadReferee]

Try looking at the link below. The picture at the bottom gives the 3pt width and height dimensions along with the pin sizes for all categories.

3pt Dimensions from TractorSmart

I have built several cat 1 3pt attachments and used these dimensions for every one.

I would guess that most tractors use different geometry on the tractor end of the 3pt. It would only seem logical due to different internal designs of the lifting mechanisms and the distances to clear tires, etc. However, the attachment end dimensions all should conform to the standard.

 

[beenthere]

Curious as to why you ask. Your large frame CUT (Deere 4710) is larger than my Deere 4300, so the tractor end of the 3pt arms (and legs) will be different, but the attachment end of both will work on Cat I equipment. The small frame CUT of Deere (4010, etc) and the 2010 are even tighter at the tractor end. Some even restricted to a limited Cat I.

Are you running into a problem, or designing a different attachment? Just curious here. /forums/images/graemlins/smile.gif

 

[timb]

The implement-connecting ball size and spacing of the draft arms are the primary elements of the hitch compatibility - at least with the implement 'static'. BUT - what I'm curious about - while you can vary the length of the top link to get the 'back' to where it needs to be - if there is no generally accepted standard as to the FRONT mount points / relationships - then one tractor may tend to rotate a given implement very differently through it's lift arc than another. It's also going to present a very different compression component to the tractor based on the resulting 'working' angle of the top link.

What got me wondering how much variation is acceptable is the optional draft control I had installed on my 4710 appears to move the front top link pivot point slightly back and down from the stock position without the draft control option. That means - for the same implement, compared to a stock 4710 - my top link has to be shortened, and the top link rests at a measurably steeper angle to the horizontal than it would otherwise have been.

Does that possible 'hitch front end' difference between tractors matter? Dunno. It might with certain implements - perhaps a box blade and just how it's 'approach angle' varies as you are lowering it and just starting to engage the ground. It could also effect how far a rotary cutter tilts or whether it remains roughly parallel to the ground as you lift it. And - how much a PHD changes angle as you drop it into the ground. That sort of thing.

 

[beenthere]

""Optional draft control""
Any pics? I'd be interested in what that is.

I have three different connecting pts at the tractor end of the top link, which makes a change in the up/down position of a 3pt attachment. Sounds like your added draft control may have a similar effect. I see a difference between the three settings when I have the carry-all platform on. On one position the platform stays parallel to the ground, up or down. At another, the carry-all platform is lower in front than in the back, when raised.

Standards? Seems like too many other variables - length of top link being one of them. But a good question.

 

[timb]

The draft control has the same setup - the original 1-pc casting is replaced by a littl more complex mechanism that pushes the pivot point back and down just a bit.

Here's the draft control - 4710 draft control

 

[JRP]

There are two standards.

Long before the quick hitch was invented the original 3pt standard was developed. Because the top link attachment and clearances below the pins did not matter and they were not even considered.

The quick hitch changed this. A quick hitch needs the three pins in exactly the same location, and also there needs to be clearance below the pins so the QH hooks can come up under the pins and pick up the attachment. The 3pt QH standard is much more involved. I think it costs about $60.

Get dimensions for and build to the QH standard. The QH is my best attachment. Very safe. The QH is like a computer. Until you understand what it does for you, you might think you don't need it. Once you have experienced it, you won't want to go back.

The Pat's QH is not what I'm talking about. Not the same animal. Of course, Pat likes it.

Go see the I-match hitch at a JD dealer or a Speeco at TSC. Get one, then build your attachment to fit.

A Cat I-II and II-III bushing slipped over a Cat I pin and tack welded is much less expensive than the Speeco pin adapter thing.

Hope this helps.