3-Point Hitch Top link mount tore off back of differential case

[the old grind]

If I understand this post mortem (2 pins in top link hole(s) caused a fulcrum/rotational situation) correctly, the top link on a 3pt BH is not functional like on any other attachment. There's a "stiffleg" that go's from the lower lift pins to the top link. Without this you would be unable to put the tractors weight down to the outriggers and would be relying on the BH weight ONLY to do all the digging, or it's no longer a parallel arms movement (lift arms and top link) as in a normal 3ph. You can see it in the first picture.

Check the down-force on your 3PH. Oh wait there is none and the tractor's weight is somewhat moot other than for lateral stability in X and Y planes.

Also note that 'pull' on the top link is minimal when load is close to the pins but increases dramatically if several feet back. Ever have to add front weight or load the FEL to keep front wheels on the ground with a huge mower or when using a boom pole? Somebody has and that's why IMO we don't need to prove interference or pinch points as causal.

 

[Rustyiron]

I don't understand your point, is there one? Obviously there's no dp, but trying to put the bucket into even a pile of sand with a normally connected 3ph you'd pick up the BH. That stiff leg does transfer what weight is available from the tractor. There's no question that the leverage to "pull" is much greater in this situation, I just argue the "top link" (that's not a traditional top link in this arrangement) had a "pinching" condition against the lower (unused) pin at the tractor that would/could restrict the travel of this rigid top link causing a "prying" effect that assisted in this destruction. It's a hard thing to describe and maybe we just are not "getting" each other.:thumbsup:

 

[Rustyiron]

Perfect. I can understand very short descriptions.

 

[Jstpssng]

I feel for the OP. What a bad situation!

But I am wondering what the manual for the tractor states regarding attaching a backhoe to it. I know with my B2910, it requires a heavy duty top link bracket if a 3PH backhoe is attached. Been using my 3PH backhoe for 18 years without an issue, But that is just me.

No doubt that a sub frame mounted backhoe is a better setup.

Do the manuals for more recent tractors than mine, which was purchased in 2002, prohibit use of a 3PH backhoe?

Curious more than anything...

I just read through my manual quickly (covers the 3901 as well as my 3301) and didn't see a thing about backhoes. Perhaps they cover it in the book for that implement. Contrast that with the Massey warrantee; it specifically voids the warrantee if you use a 3 pth BH. The way that it's written, if I used my BH once and lost the engine a year later, they could refuse to pay if they wanted to be that way.
That was a deal breaker when I was tractor shopping 2 years ago.

I worry more about breaking it when transporting than when I am actually digging, as I run at idle and don't pull very hard with it. I have been intending to get a subframe but as I mentioned before my BH750 is too old to get a custom frame, so it will have to be modified to fit.
Reading this thread makes me think I need to move it farther up the list; as in, before I use the hoe next time.


I think the "crowd sharing" is more of a young people thing... you give me five dollars today, and tomorrow I give it back to you for something else.
Most TBN members put that five in the bank, along with many more over time, in case they ever need it.


As for digging; my first BH would indeed ride up and down on the 3 pth arms. I actually did a lot of work with it, digging stumps and planting trees. I even dug a 5 foot deep hole and set a utility pole for a friend of mine.
It was a CadPlan kit which I bought premade... a school teacher downstate at Windham High used to buy the kit, weld them up, and sell them for 3K. It had about 10% less pulling power than my woods 750, but would very easily pull itself apart if I wasn't careful. I learned to scratch with it, not push; otherwise it could have driven me right up into the roll bar.

 

[ptsg]

I don't understand your point, is there one? Obviously there's no dp, but trying to put the bucket into even a pile of sand with a normally connected 3ph you'd pick up the BH. That stiff leg does transfer what weight is available from the tractor. There's no question that the leverage to "pull" is much greater in this situation, I just argue the "top link" (that's not a traditional top link in this arrangement) had a "pinching" condition against the lower (unused) pin at the tractor that would/could restrict the travel of this rigid top link causing a "prying" effect that assisted in this destruction. It's a hard thing to describe and maybe we just are not "getting" each other.:thumbsup:

It's indeed hard to describe. The second pin on the top link mount, doesn't make any difference. That top link doesn't move up and down enough to hit that pin.

What I was trying to explain, is that, even though the top link is rigid and has that triangulation that prevents the 3 pt to simply lift, there is still the possibility of tilting the backhoe left/right (looking from the back of the tractor).

Since the provided top link doesn't have a ball joint (like a traditional top link) and it also fits tight in the top link mount, if the operator would accidentally push one stabilizer too far before the other one, it could twist that top link mount right off.

Or just by driving over a bump with one of the rear wheels, could possibly be hard enough to twist that top link mount too.

I hope it's somewhat understandable.

 

[WranglerX]

I feel for the OP. What a bad situation!

But I am wondering what the manual for the tractor states regarding attaching a backhoe to it. I know with my B2910, it requires a heavy duty top link bracket if a 3PH backhoe is attached. Been using my 3PH backhoe for 18 years without an issue, But that is just me.

No doubt that a sub frame mounted backhoe is a better setup.

Do the manuals for more recent tractors than mine, which was purchased in 2002, prohibit use of a 3PH backhoe?

Curious more than anything...

MY Massey Ferguson manual that covers the 1705 and 1710 (factory backhoe equipped) and the 1715 and the 1720 (factory backhoe equipped) states as graphic below...

 

[California]

re putting a 3-point BH in front of a skid-steer - Seems to me you would have to get out of the skid steer seat and climb up on the BH seat every time you moved. Same as I have to with the hoe on my tractor, because it wasn't designed for a tip-back seat or other dimensions to run the hoe without getting off the tractor seat and walking back there. My use digging out stumps doesn't need many dismount/move/remounts, but for trenching its a PIA. In summary, a tractor or skid-steer designed in the first place to mount a hoe and operate it from the driver's seat will be a lot more productive than a mismatched combination.

 

[the old grind]

Guys what I was getting at and in both digging and traveling positions is that the stabs are two points to lift the BH or the tractor once the 3PH is topped out bc it has no down force and will be. (points of stress from that? why not?)

That makes two points of contact with the ground. So if the FEL becomes the third point of support forces are on the 3PH in whatever direction they're exerted and between the three 'legs'. Otherwise we'd dig with front tires on the ground. I still contend that when traveling there's a lot of weight behind the pins and that puts uncommon tensile load on the top link while compressive on the draft arms.

IIRC that's why there are sub-frames and why they shouldn't connect to the top link. And any of us who dig much know forces come in all directions, intended or not. Doesn't have to be just one thing causing this, likely most all that have been suggested. Cracks could have begun from one thing or another and we tend to overthink the moment of disaster as being just one little detail that finally caused it.

btw, Kind of a shame we're not young enough to help a guy out by pitching in.

 

[California]

Looking at this modern gear I feel like Rip Van Winkle. My 1979 Kubota BH doesn't have that triangular stiffener. The BH's weight alone is all there is for digging. I raise the 3-point to drive around. For digging, lower the outriggers to let the hoe rest on the ground then drop the 3-point lever so it can't try to lift the hoe as the outriggers work down into the ground. Definitely Old School but this design is likely why I haven't broken anything in 15 years using a 3-point BH on a 24 hp tractor. Sure beats a shovel and wheelbarrow!

I think that comment that the custom (?) upper link doesn't allow any side to side slack, is important. Just swiveling the hoe to the side to dump the bucket loads side stress there. Doing this on a minor side slope would be worse. I wonder if that top link was original from Woods. It seems to me it should have a ball joint at the tractor end to prevent this stress.

 

[FTG-05]

FWIW, I just checked my Owner's Manual for my L4330 "Implement Limitations, page 12:

Backhoes:

Max digging depth, 90 inches.
Max weight: 990 lbs
Subframe: Necessary

This OM covers models L3130, L3430, L3830, L4330, L4630 and L5030.

By saying "subframe necessary", I'm guessing that that precludes the use of a 3ph backhoe.