Conversion Factor for 3PH load capacity

[Reg]

[Yes, these things can be ignored because their resultant at the eyes is given.]....However, ignoring the fundamentals of a //ogram linkage by modeling it as a simple lever brings no understanding of the factors that cause its superior performance. Getting a "close" answer with your shortcut encourages you into thinking you are considering all the correct factors. You are not. The reason your answer comes close is that, in its normal lift and carry usage the linkage does not lend itself to a purely correct // setup so the manufacturer gives 24" numbers for the degraded setup that actually happens in normal use. These #s come out at about 80% of what is available at the eyes. [Not really all that close.]

In order to get 100% of what is available at the eyes all 4 arms must form a true //ogram. -- The top link must be the same length as the lift arms. Also, on the implement, the vert dimension from the pins to top link connection must be the same as that vertical dimension at the link connection points on the tractor body. Now all opposite arms will remain // as they move.

All that remains to test this straightforwardly is to get the vertical going segments of the //ogram truly vertical. [In many cases the tractor body lift link pins are well forward of the top link attach point. -- so the tractor rear would have to be elevated to acheive this.] Set up thusly an implement would rise straight and level and would rise exactly as far as the lift eyes. If you have 2K# lift at the eyes you would be able to lift 2k# minus the weight of the boompole at any point on your boompole.
larry

THIS question has nothing to do with the parallelogram that you are clinging to.
ONLY the length of the lift arms, the lift force available at their ends and the 24 inch distance (or whatever other distance) behind the eyes are relevant.
The rest of the parallelogram's structure is incidental, ONLY the bottom lever is relevant.

Absolutely could NOT lift 2,000 lbs 8ft out, a theoretically perfect parallelogram would have NO effect on this fact - though I wish it would, I could USE that (-:

 

[gpflepsen]

If spyder's contention were true, we could build cantilevered bridges to span any distance imaginable. And we all know that is not the case.

 

[SPYDERLK]

Spyder, I'd reconsider thinking along those lines. The lift capacity is determined by a function of the weight (force) and the distance from the lift assembly, or moment (torque). You are completely discounting the moment part.

THIS question has nothing to do with the parallelogram that you are clinging to.
ONLY the length of the lift arms, the lift force available at their ends and the 24 inch distance (or whatever other distance) behind the eyes are relevant.
The rest of the parallelogram's structure is incidental, ONLY the bottom lever is relevant.

Absolutely could NOT lift 2,000 lbs 8ft out, a theoretically perfect parallelogram would have NO effect on this fact - though I wish it would, I could USE that (-:

If spyder's contention were true, we could build cantilevered bridges to span any distance imaginable. And we all know that is not the case.

.......OK. Iv explained it pretty well. Yous are wrong. Im sorry that the mechanics of the situation confuses you. Fortunately there are people who understand it in the world so that it can be used on stuff where appropriate. Like scales, weight cancelation mechanisms, vehicle suspensions, tractor seats, tractor 3phs, robotics, camera stabilizing, etc. It is a shame not to have a glimmer of how this system works to control motion and force over distance. If yous did perhaps you could use it. How in the world could a // linkage allow cantilevering to any distance? [Unless you had weightless elements of infinite strength.] To answer a question not asked: The moment is borne by tension and compression of top and lift links and consolidated in the tractor body. There is no energy in this - only a torque, proportional to the distance out the weight is from the tractor body pivots, trying to tip the tractor backward.
larry

 

[piller]

There's theory and there's real world. Put up some numbers guys. My tractor manual specs 5510 lbs at lift point and 4630 lbs 24" behind lift point (at lower link end with links horizontal). So I get 84% (4630/5510) of lift 24" back.

 

[Reg]

There's theory and there's real world. Put up some numbers guys. My tractor manual specs 5510 lbs at lift point and 4630 lbs 24" behind lift point (at lower link end with links horizontal). So I get 84% (4630/5510) of lift 24" back.

Thanks, lets see if I can find published specs (CLAIMED capacities)... Nope, not in the user's manual, not in the glossy either.

Funny thing, the loader glossy says only 63% at 20" ahead of the pins; it should be the same arithmetic, different end of tractor and a MUCH longer arm to the pins.
Without the magic effect of an irrelevant para...nevermind.

Is that a Cat 2 tractor ?
Do you know your lower lift arm length ?

 

[SPYDERLK]

There's theory and there's real world. Put up some numbers guys. My tractor manual specs 5510 lbs at lift point and 4630 lbs 24" behind lift point (at lower link end with links horizontal). So I get 84% (4630/5510) of lift 24" back.

Yours does well. I note that my little Kubotas look like they approximate the //ogram better [just not quite enuf vert separation in the connection points to the tractor body] than the big Mahindra [which is good on that, but has more difference in length of lift and top links]. The Kubs are around 80%. Cant find the 24" lift rating on the MH. Would guess hi 60%s.
larry

 

[SPYDERLK]

[[[Funny thing, the loader glossy says only 63% at 20" ahead of the pins; it should be the same arithmetic, different end of tractor and a MUCH longer arm to the pins.
Without the magic effect of an irrelevant para...nevermind.]]]

Is that a Cat 2 tractor ?
Do you know your lower lift arm length ?

[Exactly! No //ogram linkage on the loader.] That is just simple leverage and you seem to be conveniently ignoring that the lift loss is much greater on FEL than 3ph. Im talking physics - not magic. It predates Merlin. Get a glimmer.
larry

 

[Reg]

[Exactly! No //ogram linkage on the loader.] That is just simple leverage and you seem to be conveniently ignoring that the lift loss is much greater on FEL than 3ph. Im talking physics - not magic. It predates Merlin. Get a glimmer.
larry

No need to be offensive about it, after all YOU are the one that has it all wrong here and you appear to be the ONLY one that doesn't get it (-:

It is clear that the info in my loader's glossy brochure has been SERIOUSLY down rated in the interests of stability.
No way does adding 20 inches to the distance from the main boom pivot to bucket pivot reduce the lift capacity by 37%, it is a suspiciously rounded to the nearest hundred (and too low) number.
I may do some measurements tomorrow.

Get out your lo skool fiziks text again, start at the very beginning.

Maybe this will help you to understand why the parallel O'Goohicky is irrelevant.
If you disconnected the top link and had REALLY TIGHT fitting lift arm pins - like SO TIGHT that you could lift the implement without it flopping backwards - you would in fact have the simple lever and lift capacity would be inversely proportional to distance.
Imagine WELDING the lift arms to the implement (on YOUR tractor, not MINE) grinz.
This is the function that the top link provides, holding the implement towards the tractor - plus making adjustments easier.
The top link does NO lifting, it merely holds the implement from flopping backwards.
Sure, there is tension in it, but that does NOT contribute anything to the lifting effort, it is "resultant" (look it up).
Coincidentally, it moves more or less parallel to the lift arms, not really it is only about 1/2 their length on a Cat 1 tractor.
OK, cut out those welds and reconnect the top link - no change, the lift arms are still levers, that really IS all.

 

[SPYDERLK]

No need to be offensive about it, after all YOU are the one that has it all wrong here and you appear to be the ONLY one that doesn't get it (-:
Get out your lo skool fiziks text again, start at the very beginning.

[[[Maybe this will help you to understand why the parallel O'Goohicky is irrelevant.
If you disconnected the top link and had REALLY TIGHT fitting lift arm pins - like SO TIGHT that you could lift the implement without it flopping backwards - you would in fact have the simple lever and lift capacity would be inversely proportional to distance.
Imagine WELDING the lift arms to the implement (on YOUR tractor, not MINE) grinz.
This is the function that the top link provides, holding the implement towards the tractor - plus making adjustments easier.
The top link does NO lifting, it merely holds the implement from flopping backwards.
[[Sure, there is tension in it, but that does NOT contribute anything to the lifting effort, it is "resultant" (look it up).]]
Coincidentally, it moves more or less parallel to the lift arms, not really it is only about 1/2 their length on a Cat 1 tractor.
OK, cut out those welds and reconnect the top link - no change, the lift arms are still levers, that really IS all.]]]

Sorry that I was offensive. I really wish that you could say something correct about this so that we could build a fuller understanding. Learning to spell physics may be a good 1st step to using it. Perhaps you should find something you have a question about. To answer one unasked: [[ The compression/tension on opposing elements actually balance one another, pushing down and up equally.]]

The weldup you suggest is totally unrealistic to what is actually happening.
larry

 

[E_Sanborn]

This is a relevant and useful thread which is providing illumination on the difficulty of reasonable persons coming to reasonable disagreement. I find myself in that rabbit hole on occasion; where the vigor of my argument may be more tied to my need to be right than the veracity of my assertions.