Tractor Sizing How Much Can A Sub Compact Tractor lift?

[LD1]

My loader is rated at 860# at bucket edge, 1000# bucket center and 1150# at the pins.

I have lifted 1100#+ on clamp on forks with the load centered 20"+/- in front of the edge.

Underrated...maybe. But published spec is max height too.

To my knowledge, deere is the only one that publishes a spec to a height of 59" as well as max height. The 59" number is always alot more.

My loader manual has a graph that has the curve of lift capacity vs height. IIRC the max at the pins near ground level is somewhere around 2k

 

[dragoneggs]

Dragoneggs I just got off the phone with my Kubota dealer, and he says the lift capacities on the Kubota website are just wrong. In particular, he says that you will never be able to lift the 745 lbs. "at the pivot pin" capacity that is published, and in fact he says he has tried and cannot lift more that 500 lbs., even with the bucket tilted back (which presumably centres the load over the pivot pin). If so, this is a major misrepresentation on the part of Kubota. So, let's all try out or BX25's and see what we come up with.

Interesting. Maybe the pivot pin ratings include the bucket weight?

Is the guy talking about just lifting off the ground or raising to full height? I loaded my bucket which was low but not resting on the ground and proceeded to move it to the retaining wall and raise them up about 4ft. I bought the BXpanded pressure test kit and shims but haven't played with it yet I am working with stock from the factory settings.

 

[TJP89]

Maybe you guys can help me understand something here. I know that something is harder to lift higher, but I'm unclear on why. It seems that the pump has to apply the same pressure to lift the same weight at all heights. Although more fluid is in the cylinder, that shouldn't matter, because the pump is moving the same amount of fluid all the time. And the added weight of the fluid in the cylinders at height shouldn't affect it either.

The only thing I can think of is the usual mass/weight problem. Although the mass stays the same, the weight increases as the distance from the center of the earth increases, thus increasing the force applied in a downward direction, thus increasing the force needed to overcome the downward force and move up. However, as the distance between the ground and the top lift height of even a really big tractor is insignificant when compared to the radius of the earth and the other factors used in calculating that kind of thing, so that shouldn't increase the weight enough to make a difference.

Now, either my rusty college physics are wrong, or my understanding of something hydraulic is wrong, or all of you guys are wrong on the observed effects. The last isn't a reasonable expectation, and the physics are actually pretty simple (now I'm interested though, I might just go do the math on that), so I'm left with the fact that I'm missing something in the hydraulics. An explanation would be appreciated. I know it happens, I just want to know why.

 

[k0ua]

My loader is rated at 860# at bucket edge, 1000# bucket center and 1150# at the pins.

I have lifted 1100#+ on clamp on forks with the load centered 20"+/- in front of the edge.

Underrated...maybe. But published spec is max height too.

To my knowledge, deere is the only one that publishes a spec to a height of 59" as well as max height. The 59" number is always alot more.

My loader manual has a graph that has the curve of lift capacity vs height. IIRC the max at the pins near ground level is somewhere around 2k

That can help to explain some the the rather Large "Hawaiian love stones" I lifted with the ole 'bota. I sure as heck did not lift them to full height though.

 

[TSO]

Don't forget... Hydraulic relief pressure will play a huge role in the lift performance. Your pressure may be at spec, lower, or higher... Won't know until you check it.

My 1648 had been set about 6% below factory spec (was about 2350psi, spec is 2500psi), and when I adjusted it to the proper number, I gained about about 18% of lift strength.

For reference, my forks weigh just a hair under 400lbs, original max lift was 2040lbs evenly packed on the pallet, new max lift at proper spec was 2390lbs evenly spaced. May have been able to do a few more lbs, but I was using 40 & 50 pounds bags and I ran out.

Note: there was no "cheating" on those lifts, no tilting back to start the lift, no front-loading of the pallet to keep the weight closer to the tractor.... And these lift attempts were to about 40" off the ground.

 

[CDennyRun]

OP, those numbers are pretty impressive. The NH TZ24DA that I had was rated @ 780lbs at full height I think. With me being the only counterweight (145lbs) I was lucky to get 450lbs in the bucket without the rear tires becoming totally worthless. If I wasn't on level ground, that thing got really tippy with a bucket full of moist dirt. Great little tractor, but I'm sure glad to have moved up to a compact utility.

 

[LD1]

TJP89:

The lift is not a straight lift. Rather things pivot and the lift is in an arc. The higher you lift, the geometry is working against you, and you can lift less.

Picture the cylinder in relationship to the loader arm. The lower it is, the more it is trying to lift, the higher you go, the closer the lift arm and cylinder get to parallel, basically trying to separate the loader arm from the frame. The closer to parallel the arm and cylinder become, the less the force to actually lift.

 

[AxleHub]

TJP89:

The lift is not a straight lift. Rather things pivot and the lift is in an arc. The higher you lift, the geometry is working against you, and you can lift less.

Picture the cylinder in relationship to the loader arm. The lower it is, the more it is trying to lift, the higher you go, the closer the lift arm and cylinder get to parallel, basically trying to separate the loader arm from the frame. The closer to parallel the arm and cylinder become, the less the force to actually lift.

Greetings LD1,

I'll have to admit that your explaination is bewildering to me.

If we're using your arc example physics would indicate that the high point of the arc (loader arms at their top most position) is the point of greatest assistance or self supporting by the arms. The arms themselves are carrying part of the downward pressure making the hydraulics less requiring constant pressure to maintain.

Meanwhile at a far lower point . . Maybe 3 feet off the ground (because of arms being curved) you have the hydraulics doing all the work and the arms themselces at their most horizontal position and their least arm support. Thats the point when the hydraulics are carring a bunch of the fel arm weight as well as thw payload weight.

But lets make it even a simpler example.

A. Your hands are holding a weight barbell with the rod 3 feet between the weights. Your hands are holding that rod next to your legs. Its easy holding it. Your muscles only have to hold the rod and weight because the arms are attached at the shoulders

B. Next you arc it up to being nearly over your head. At this point the same weight is harder to hold than at your legs . . But still manageable because your arms and bone structure are all helping to keep it in place as well as your muscles.

C. But if you arc your arms down so your arms are outstretched in front of you but at the same level as your shoulders . . You are sweating peanuts, bullets, or sweat like a fever because your support structure isn't able to help keep it at that level of the arc . . Only your muscles are keeping gravity at bay for the rod and weights AND your arms too.

The same is true with a fel with a bucket attached. the hydraulic system is doing everything to hold up over half the fel arms PLUS ALL the payload when the payload is 3 or so feet off the ground This is the payload stress peak because the hydraulics are holding up much of the fel arms gravity as well as the payload. . . something it doesn't have to do at the lowest level or at the highest level.

 

[sd455dan]

Check, I would be completely surprised if my Massey was that much stronger than a bx25 or bx2670. In my tests I used the hardest testing with forks and weight loads extended out on the pallet instead of tight to the pins. If your dealer us correct . . we're talking 350 lbs different. It just doesn't seem possible. However in all my years considering kubotas . . I never did really test thr fel with any level of weight in it.

The distance away from the pins does make a major difference in what any loader can lift-

My old ford 3000 is rated at 2000 lbs. in the bucket to full height (120") but one time I put a pair of chain on pallet forks on the bucket and tried to unload a full pallet of concrete.

Couldn't lift it off my old International dump bed until I got it down around 1300 lbs.

I also agree with LD1 about the difference in ability to lift dropping as the loader gets closer to full height- (could be wrong) but I think of it as an acute triangle when near full height.

The leverage the hydraulic cylinders can apply is greater at low lift heights due to the geometry,
the distance each inch of lift piston extension has to move the bucket attachment point increases with how close the loader gets to full lift .

It seems to (out weigh) the difference in static weight applied at different heights to the actual hydraulic cylinders.

I can not remember a time when lifting a border-line heavy weight in the bucket, where the loader actually sped up the higher the bucket got. some times the loader will only go so high,- yet at any place from the ground to chest high the loader will lift just fine...

Once again i could be wrong -but that has been my experience with my Ford ,Rhino and New Holland loaders

have some thoughts on this??..




Kudos on lifting the amount of weight you did with the GC1715 That is impressive for that size of machine

 

[Grandad4]

An engineer would be able to explain this better than me, but here's something to think about. What if the lift cylinders were not attached to the tractor at approximately the same location as the loader arms - between the front and rear tires - but instead were mounted somehow up front beneath the bucket, and were vertical so they pushed directly upward when lifting? Then your idea about the hydraulics doing the most work when the FEL arms are horizontal would be correct. And you'd be right that as the load got raised and weight shifted to the FEL arms, the hyd cylinder wouldn't have to push as hard to move the bucket.

But that would be an awkward setup for a loader, for sure, so instead we have the configuration we all know where the lift cylinder attaches to the FEL mount behind the front wheel. That makes the lifting forces more complex... something that won't necessarily be intuitively clear. In this setup, it's not just lifting the weight in the bucket, it's also making the FEL arm swing in an arc. As the arm climbs higher, the hyd cylinder progressively loses its leverage (its ability to make the FEL arm continue moving in its arc). At some point near vertical, the hyd cylinder will no longer be able to move the FEL arm any further, no matter how much or little weight is involved, because it is no longer applying any force along the arc. All of the hyd cylinder's force is pushing outward against the FEL arms, as if trying to separate it from the tractor.