Here are the ACTUAL Lift Capacities of the RK24 L75 FEL @ Varoius Heights (w/ Graph!)

[snymat68]

Nice looking chart and data presentation! As an engineer, I have great appreciation for data presented in such a way that is easy to consume and postulate relationships/conclusions.

I don't think it was mentioned, but did you stop when the rear tires began to lift, or did the bucket just stop moving?

I had the backhoe installed. The loader wasn't gonna lift that.

 

[s219]

As someone who works with load cells and calibration a lot, a couple things about the results concern me from a data perspective. First is the kink/shift between 50" and 56", any guesses on that? Second are the constant loads from 38" to 50" and 56" to 62". Both of those suggest that either something fouled or the scale was sticking or has very coarse sensitivity. Finally, the shape is not consistent with the way a loader curve should look (most tractors have a loader curve in the owner's manual you can lookup for an example). Because the loader arms are a simple linkage, you should see a smooth parabolic shape to the lift curve. There should not be kinks or flat spots.

Was the chain always vertical? Did you adjust the position of the tractor so that the loader was directly above the pull point at each measurement? That could possibly affect the results but I still suspect some sort of fouling or sensitivity issue at play.

BTW, I think this is a great idea, just saying the curves don't look the way they are supposed to, so something isn't right.

 

[atsah]

Try lifting something 1550lbs, that scale is nowhere near accurate.

 

[snymat68]

As someone who works with load cells and calibration a lot, a couple things about the results concern me from a data perspective. First is the kink/shift between 50" and 56", any guesses on that? Second are the constant loads from 38" to 50" and 56" to 62". Both of those suggest that either something fouled or the scale was sticking or has very coarse sensitivity. Finally, the shape is not consistent with the way a loader curve should look (most tractors have a loader curve in the owner's manual you can lookup for an example). Because the loader arms are a simple linkage, you should see a smooth parabolic shape to the lift curve. There should not be kinks or flat spots.

Was the chain always vertical? Did you adjust the position of the tractor so that the loader was directly above the pull point at each measurement? That could possibly affect the results but I still suspect some sort of fouling or sensitivity issue at play.

BTW, I think this is a great idea, just saying the curves don't look the way they are supposed to, so something isn't right.

I tried to keep the chain vertical for all tests, but there was probably a little variation.

Try lifting something 1550lbs, that scale is nowhere near accurate.

The scale is accurate. I lifted several known weights with it and it was right on.

 

[LD1]

I agree that something seems off. Lifting 1600# with a loader that only weighs 480# that INCLUDES the bucket. And being THAT much over the MFG's rated numbers.....something isnt right.

The MFG's numbers are calculated based on geometry, cylinder size, and hydraulic pressure. Nothing more, nothing less. Everyone often "claims" under rated numbers, or reduced numbers for "safety" reasons or stability, or front axle, or whatever. None of that is true. Its simply a calculation, and is close to real world numbers. The problem is most people dont know how to interpret the MFGs specs. And when their loader is "rated" for XXXX pounds to max height....and they can lift several hundred more than that at a modest height......people start throwing around the word "underrated". And too many people try to justify it with the safety, stability, etc excuses. When in fact it is nothing more than a failure to understand the "rating".

That said.....I'd be curious to know the bore x stroke that they are using for the lift cylinders. And further....if you want an actual calculation and some understanding....I need THREE simple measurements (to start) to go along with cylinder specs. If you look at the side of the loader.....the lift cylinder has two pins. And the boom where it attaches to the upright post is a third pin. With cylinder completely collapsed.....(might raise the front of the tractor) these three pins form a triangle. I need the lengths.

 

[snymat68]

I agree that something seems off. Lifting 1600# with a loader that only weighs 480# that INCLUDES the bucket. And being THAT much over the MFG's rated numbers.....something isnt right.

The MFG's numbers are calculated based on geometry, cylinder size, and hydraulic pressure. Nothing more, nothing less. Everyone often "claims" under rated numbers, or reduced numbers for "safety" reasons or stability, or front axle, or whatever. None of that is true. Its simply a calculation, and is close to real world numbers. The problem is most people dont know how to interpret the MFGs specs. And when their loader is "rated" for XXXX pounds to max height....and they can lift several hundred more than that at a modest height......people start throwing around the word "underrated". And too many people try to justify it with the safety, stability, etc excuses. When in fact it is nothing more than a failure to understand the "rating".

That said.....I'd be curious to know the bore x stroke that they are using for the lift cylinders. And further....if you want an actual calculation and some understanding....I need THREE simple measurements (to start) to go along with cylinder specs. If you look at the side of the loader.....the lift cylinder has two pins. And the boom where it attaches to the upright post is a third pin. With cylinder completely collapsed.....(might raise the front of the tractor) these three pins form a triangle. I need the lengths.

I'll get you the specs and measurements tonight, but only if you promise to show your work. I'm interested in the equations/math used.

 

[LD1]

I'll get you the specs and measurements tonight, but only if you promise to show your work. I'm interested in the equations/math used.

No problem.

But the critical key is cylinder bore diameter. Cause without the MFG spec, its difficult to measure without guessing.

I am betting 40mm bore

 

[snymat68]

No problem.

But the critical key is cylinder bore diameter. Cause without the MFG spec, its difficult to measure without guessing.

I am betting 40mm bore

I have bore gauges and a saw! LOL It's still under warranty. "No sir. I don't know how that cylinder failed. One minute it was fine, the next it was in two pieces!" :laughing:

 

[LD1]

I have bore gauges and a saw! LOL It's still under warranty. "No sir. I don't know how that cylinder failed. One minute it was fine, the next it was in two pieces!" :laughing:

At least you have a good sense of humor.

The math (if you like math) is the easy part. Its actually understanding the concepts and how to apply the math that give most people fits.

 

[4570Man]

Wouldn’t it be a lot easier to figure out the ratio between the distance the loader pins move and the cylinder stroke? That method would fail to account for it being stronger at the bottom and would instead give an average. And you’ll need to know the psi the tractor is putting out.