Lift capacity of 3-pt hitch question (plz keep it simple)

[CDN Farm Boy]

Specifications beyond the eyes are only meaningful if the geometry is specified with the spec. and it usually isn't. You can modify this geometry and achieve a perfect parallelogram. If you do this the lift at the eyes will equal the lift at any point beyond the eyes until the front lifts or something breaks. I suggest you add more control for geometry in your request above. For example, the weight a given tractor can lift will change depending on which 3pt fork is used due to differing distances between the bottom pins and the top link.

Ya, we got that. 14 pages debating the merits of a PERFECT parallelogram. None of our tractors are perfect and pretty sure none of us are going to cut them up to make it one so what's the point of suggesting it?

I'm pretty sure Sodo's request was a very basic "can your tractor lift what it is claimed to be able to lift?" And I'm pretty sure he was asking in a practical sense, not a theoretically perfect paralellogram. Yes, there are some variables that can made as complicated as you like but if you don't care about absolute precision in the calculations, only the basic of application, can some of the variables be ignored and still have 'reasonably' accurate information? Most of you are trying to take the manufacture's spec and work out from that. Try working the other way around from the maximum weight able to be lifted to see if the manufacture's spec is accurate. Since we are talking max capacity, I'd suggest setting up the links in the holes providing greatest lift capacity and at the fork end, use vertical spacing according to the SAE spec.

 

[LD1]

The tractor is only part of what determines how true the parallelogram is.

Toplink length. Many different lengths sold. Some really short, some really long.

Implement pin spacing between toplink and lower link. All of my stuff is old equipment. Nothing conforms to "standard" or is QH compatible. If the TL is spaced really high above the lower links on teh implement it wont lift as much, spacer closing is closer to parallel, and will lift more. I have about a dozen homemade implements, Root ripper, single shank ripper, multiple trailer movers, carry-alls, etc. Things like the 6' ripper, that sticks back pretty far like a rear blade (cause it rotates 180*), I make the toplink higher on the implement, so it lifts and rotates and gets it higher off the ground for clearance when crossing swales or uneven terrain.

When doing things like the trailer movers, I make the toplink much closer to the lower links. To Actually make it a PERFECT parallelogram. That way through out the entire lift range, the ball hitch remains at the same angle, and dont rotate around and mess up the trailer couplers.

 

[gladehound]

I wrote

Specifications beyond the eyes are only meaningful if the geometry is specified with the spec. and it usually isn't. You can modify this geometry and achieve a perfect parallelogram. If you do this the lift at the eyes will equal the lift at any point beyond the eyes until the front lifts or something breaks. I suggest you add more control for geometry in your request above. For example, the weight a given tractor can lift will change depending on which 3pt fork is used due to differing distances between the bottom pins and the top link.

Then Farm Boy wrote

Ya, we got that. 14 pages debating the merits of a PERFECT parallelogram. None of our tractors are perfect and pretty sure none of us are going to cut them up to make it one so what's the point of suggesting it?

I'm pretty sure Sodo's request was a very basic "can your tractor lift what it is claimed to be able to lift?" And I'm pretty sure he was asking in a practical sense, not a theoretically perfect paralellogram. Yes, there are some variables that can made as complicated as you like but if you don't care about absolute precision in the calculations, only the basic of application, can some of the variables be ignored and still have 'reasonably' accurate information? Most of you are trying to take the manufacture's spec and work out from that. Try working the other way around from the maximum weight able to be lifted to see if the manufacture's spec is accurate. Since we are talking max capacity, I'd suggest setting up the links in the holes providing greatest lift capacity and at the fork end, use vertical spacing according to the SAE spec.

Then LD1 writes...

The tractor is only part of what determines how true the parallelogram is.

Toplink length. Many different lengths sold. Some really short, some really long.

Implement pin spacing between toplink and lower link. All of my stuff is old equipment. Nothing conforms to "standard" or is QH compatible. If the TL is spaced really high above the lower links on teh implement it wont lift as much, spacer closing is closer to parallel, and will lift more. I have about a dozen homemade implements, Root ripper, single shank ripper, multiple trailer movers, carry-alls, etc. Things like the 6' ripper, that sticks back pretty far like a rear blade (cause it rotates 180*), I make the toplink higher on the implement, so it lifts and rotates and gets it higher off the ground for clearance when crossing swales or uneven terrain.

When doing things like the trailer movers, I make the toplink much closer to the lower links. To Actually make it a PERFECT parallelogram. That way through out the entire lift range, the ball hitch remains at the same angle, and dont rotate around and mess up the trailer couplers. .

If feel like someone owes me an apology But seriously, there is no reason why the theoretical and the practical cannot be one in the same. And if you understand that, you can take an implement that may be just a little to heavy to lift and modify your geometry so that you can lift it - and that my friend is practical.

 

[Sodo]

The test conditions now have 5 data points and 5 "notes".
Trying to "Keep it simple", to not scare anyone away from posting data, and ten details is pushin' it.

I kinda think if we complicate it further, we will get nowhere.

You know at some point you just have to kick all the engineers out, and stop allowing changes, or nothing happens at all. Not pointing fingers at anyone. Any engineer knows this is how it works, they all want perfection but you just can't have it. Technology changes before you've perfected it, and when technology changes you have to start over. Maybe NASA can do this, but TBN doesn't need it. It's just a 3-pt, and accuracy +/- 100 lbs is close enough.

Incidentally I can't remember what I needed this information for.

 

[LD1]

It seems you are wanting the perfection in the form of a simple formula. It ain't gonna happen.

Technology changing....I think not for a 3ph.

And accuracy +/- 100# may be the difference of lifting something or not.

I am all for testing a 3ph and posting results. But simply hooking a scale up about 24" back and maxing it out is incomplete data and does no one any good.

Do the test in ALL three toplink locations. And do each twice, once with toplink shortest, once with longest. Take the two readings and you will have a near linear graph of lift vs toplink lenght for each hole.

Now you can repeat all that for some distance further back. From THAT data you could calculate lift capacity at any other distance back for any of the toplink length or location configurations.

If someone were to do all of this and graph it out, then maybe everyone would understand just how dynamic the 3ph can be.

I have not tested mine, don't have the equipment or scales, don't have the need to, and do t want to waste half a day rigging stuff up. But a wild educated guess would tell me that I could make my 3ph (rated at 1998# at ball ends) lift pretty close to that at the tip of 4' forks. Probably in the 1600# range by the time you account for fork weight.

I also believe by simply shortening the toplink and putting it in the lowest hole, I could make it fail to lift 1000#.

 

[CDN Farm Boy]

I suggest you add more control for geometry in your request above.

Since we are talking max capacity, I'd suggest setting up the links in the holes providing greatest lift capacity and at the fork end, use vertical spacing according to the SAE spec.

The tractor is only part of what determines how true the parallelogram is.

Toplink length. Many different lengths sold. Some really short, some really long.

Implement pin spacing between toplink and lower link. All of my stuff is old equipment. Nothing conforms to "standard" or is QH compatible...

I wrote

Then Farm Boy wrote

Then LD1 writes...

If feel like someone owes me an apology But seriously, there is no reason why the theoretical and the practical cannot be one in the same. And if you understand that, you can take an implement that may be just a little to heavy to lift and modify your geometry so that you can lift it - and that my friend is practical.

I can apologize if it makes you feel better but I'd have no idea what for

I fail to see how LD1's post helps to clarify anything.

You asked for more control for the geometry.
I gave a suggestion as to how to give that control (and I suspect the same that the manufactures use) Sodo had also already given a suggestion
LD1s post states that there are a bunch of variables that can change how it performs (no arguing there) but that is adding unnecessary complication to the question and exactly what you asked to control.
You asked for control then ignored the suggestion how to do that with quoting some of the many possible variables and why a one-size-fits-all calculation won't work on only one size.


We all know there are a bunch of variables that can affect how the 3pt hitch performs, especially when you look at it from an engineering view. If we decide on fixed values for those variables, why does that not simplify the question?

Sometimes the tradesmen learn from the engineers. Sometimes the engineers learn from the tradesmen. It's all about the learnin' my friend :thumbsup:

One thing I've learned that will most certainly have use to me is the comment about mechanical self-leveling loaders having more lift capacity than a comparable 'standard' loader due to the parallel linkage (or did I read that in the other thread?) . I've got to look more into that as I've been considering building one to replace the LA504 loader that is on my 3300.

 

[gladehound]

I can apologize if it makes you feel better but I'd have no idea what for

I fail to see how LD1's post helps to clarify anything.

You asked for more control for the geometry.
I gave a suggestion as to how to give that control (and I suspect the same that the manufactures use) Sodo had also already given a suggestion
LD1s post states that there are a bunch of variables that can change how it performs (no arguing there) but that is adding unnecessary complication to the question and exactly what you asked to control.
You asked for control then ignored the suggestion how to do that with quoting some of the many possible variables and why a one-size-fits-all calculation won't work on only one size.


We all know there are a bunch of variables that can affect how the 3pt hitch performs, especially when you look at it from an engineering view. If we decide on fixed values for those variables, why does that not simplify the question?

Sometimes the tradesmen learn from the engineers. Sometimes the engineers learn from the tradesmen. It's all about the learnin' my friend :thumbsup:

One thing I've learned that will most certainly have use to me is the comment about mechanical self-leveling loaders having more lift capacity than a comparable 'standard' loader due to the parallel linkage (or did I read that in the other thread?) . I've got to look more into that as I've been considering building one to replace the LA504 loader that is on my 3300.

I would have an interest in actually testing my 3pt hitch if I had a decent way of doing it. But my 3pt lifts over 3000 pounds at the eyes and my 3pt forks are rated for 1,000 pounds and aren't what they used to be. I'm looking at implement failure before I hit the relief on the hydraulics. The heaviest thing I have to lift is a 1,200 pound snow blower with the center of mass an estimated 30" back. It lifts that easily.

 

[roadhunter]

Lift capacity on a CUT seems to be a "perfect scenario" number that is difficult to actually make happen while working. But I can't' say I've ever overloaded the 3 point. Does the tractor tip or the 3 point just stop moving up?

I know the little Bobcat that I had would easily tip the tractor with the FEL even with a pretty big counter weight. By the time I took the weight of the bucket and bobtach off the lift capacity it would not lift much. Especially if you were driving.

It's really difficult comparing tractor lift capacities to skid steer capacities. Seems like the tractor rated capacity is likely very close to tipping weight but not so for the skid steer. It's like there is a bigger safety factor for some equipment compared to tractors for the FEL. Curious if you guy feel the 3 point is the same way?

 

[LD1]

Weather it stalls or weather the tractor tips is all about load placement.

Due to the geometry of the hitch, and the seemingly taboo word "parallelogram" you can shif the load way back and not cause much loss in capacity, if any.

What I mean by that is, let's say you have 1000# hanging a few feet back. Now let's shift that load a few more feet back. The front end feels more effect than the hydraulics do. You might have a max capacity @24" of 1500#. Shifting it back to 48", you might only have a max of 1200#, but the 1200#@4' is gonna make the front end lighter than 1500#@24".

To answer the question, I have stalled my 3ph hydraulics many times. Never had the front lift though.

Some examples.
1. Pulling my 6' root ripper, snag something, and fry to raise to break it out of the ground.
2. My single shank ripper. Looks like a subsoiler but a knife edge on Bottom to slice roots. Big 4-5" roots require a few attempts of lifting and pulling til they sljce.
3. Using the rear blade (which normally gets the toplink kn the bottom hole on the tractor to gain height and loose lift capacity). And using it to chain a log, lift the butt end, and pull. Some logs are too big.
4. Using the rear blade in reverse moving snow or dirt. Pushing back into a pile too hard before lifting.
5. Using the trailer mover and a chain trying to yank out stubborn locust posts that the FEL won't budge.
6. Not paying attention and trying to raise the bushhog when the tailwheel is under a bachkoe it was parked next to had a stabilzer arm that bled down.

 

[Egon]

If'n you want to change the three point lift configuration to lift more you will not be able to lift as high.