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

[LD1]

I have no problems understanding how it works but please answer this: Just because the hitch CAN be dynamic, why does that mean that it HAS to be dynamic?

I am well aware that there is a whole pile of adjustment available and the height vs weight trade-off.....BUT if you don't adjust it, how is it still dynamic? Just pick a setting and leave it there.

I don't adjust mine for anything other than to get an implement to sit flat on the ground which isn't more than a turn or 2 of the top link (sure that makes a slight bit of a change but nothing compared to min length vs max length you guys are talking about). Lift arms stay in the same hole. Top link stays in the top hole. Everything I have runs on the QH so vertical separation at the attachment end stays consistent. For all intents and purposes, my hitch doesn't get adjusted. Is it still a dynamic hitch even though I NEVER make use of the adjustability of it?

Don't get me wrong, I'm not trying to pretend that there aren't reasons for using the available adjustability but I'm pretty sure I'm not the only one that isn't using it and has just set it and left it.

Your right, it doesnt HAVE to be dynamic if you never move it.

I move mine all the time. Have to lengthen it a good bit to get the rear blade to have the frame work level so that when angled, the cutting edge rotates around a level plane. I use the bottom hole for this (which is why I have to lengthen alot), so that when raised I get the blade a fair ways off the ground and not gouge things crossing uneven terrain. The trailer movers get the top hole and a more parallel lift. I adjust it alot with the bushhog too, cause with the front skids sitting on the ground, the front of the blades are too low. So when mowing, I have to lengthen, then when putting back on trailer I have to shorten.

My argument is simple. This thread and the many others that follow suit are wanting everyone to compare capacities, and come up with a simple formula. If I have my hitch set and never move it more than a turn or two, I could come up with a formula. But that would only be of benefit to someone with the exact same tractor, and having their hitch set the exact same way as me. And if I have mine set so the max it will lift at the tip of a boom pole is only 500lbs, That in no way implies that is the limits of the machine or hitch. Some simple adjustments of the top link might get me where I can lift 1000#. OR it might make it where my max is only 300# but can lift much higher.

You have a maximum given amount of force available at the ball ends. That dont change. Neither does its maximum range of motion. On my specific hitch, Ball ends from full up to full down move something close to 30" and can do that lifting 1998lbs. Everything else can be factored off that. If whatever point I am wanting to know my capacity moves 60" through out the hitches 30" range of travel, I will have 1/2 the capacity. If it moves 90" with the 30" of movement of the hitch, it will have 1/3 the capacity. Length behind the tractor is irrelevant as long as the front end stays down.

I guess what I am saying is figuring you hitch in one configuration and one configuration only, is only of benefit to you and no one else. If someone were to figure for all the settings and range of toplink lengths, then that would be of benefit to anyone who has the same tractor.

 

[CDN Farm Boy]

Your right, it doesnt HAVE to be dynamic if you never move it.


My argument is simple. This thread and the many others that follow suit are wanting everyone to compare capacities, and come up with a simple formula. If I have my hitch set and never move it more than a turn or two, I could come up with a formula. But that would only be of benefit to someone with the exact same tractor, and having their hitch set the exact same way as me. And if I have mine set so the max it will lift at the tip of a boom pole is only 500lbs, That in no way implies that is the limits of the machine or hitch.


.

Agreed.

This was the whole point of my argument. Not that you and the others with the same position were wrong, only that you were seemingly ignoring a (possibly small) percentage of users out there like me who could fairly accurately use a simple formula specific to the same static hitch configuration.

:drink:

 

[mike69440]

Strong hitch, snmall tractor Re: Lift capacity of 3-pt hitch question

http://www.tractorbynet.com/forums/...2-need-big-3pt-hitch-capacity.html?highlight=

An Honest 1600 lbs 24" beyond lift point compares with larger tractors.
Hovever the bucket curl force on the tractor leaves something to be desired.

 

[LeoC4]

Someone just answer the question

My JD 2720 3-point Cat 1 is rated at 1,433lbs at the link ends according to the owner's manual.

 

[searcyfarms]

there is no simple formula, there is no exact, many variables, the best way is to back up the tractor, see if it will lift what you need to lift and if it wont get a bigger tractor - you can come up with a maybe formula but real world results will tell the tale and there is always the reality that it might lift it but that doesnt mean the front wheels will be on the ground NOR that you can navigate what you are trying to lift to the place you want it to be - rear lift capacities DO NOT take into consideration movement, front wheels off ground, terrain, angles, liquid vs solids, etc......they are a general spec only to look at on paper and sometimes some manufacturers put in disclaimers that say with X amount of counterweight or front end weights etc.......good luck with this one - if you want to know before you buy, have them bring a tractor out and you try to do what you want to do with it then decide - or rent one and try it if they wont bring one out

 

[SmallChange]

I appreciate starting another thread on this subject. (Steel strength thread kinda got hijacked).

But kenny is right. This is not a simple thing to solve. Simple toplink adjustment will change how much it can lift.

Easiest solution if you want to get close (and all you need is a tape measure):

Hook up your forks and place them flat on the ground. Measure how high the lift pin is. (for this example, lets say 10")

Now raise the 3PH all the way. Measure the lift pin again. (lets say it is now 20")

Now measure the point at what you want to know the load capacity. IT can be whatever. Pallet center, fork tip, etc. Lets use the mid-point of a pallet. Lets say it raised up 15"

So........For 10" of movement at the ball ends, the pallet COG raised 15". Now its just a simple ratio. If you are rated to lift 1500# at the ball ends, you will be able to lift 1000# at the pallet COG. (less the weight of the forks and frame).

Playing with the toplink, for the same 10" of travel of the pins, you may be able to get MORE travel out of the forks which would be LESS lift capacity. You may also be able to get LESS travel from the forks, which would be MORE capacity.

Same methods can be applied to anything. Like a boom pole.

My bushhog tailwheel hangs about 8' behind my tractor. I can set my toplink so that when fully raised, the tailwheel only comes to about knee high. Or I can use the bottom hole and make the tailwheel raise to beyond waist high. (nice for loading onto trailer). Setting up like that with the TL in the bottom hole of the tractor gives the least capacity. Cause it will cause the tips of the forks, or tip of the boom pole to raise ALOT higher in relationship to the hitch.

Interesting thread.

This early post by LD1 is right -- I may not know much about tractors, but in my day job I am a physicist and have studied mechanics (which is the name of this subject). This post is fairly simple, and there is no simpler principle for predicting the lift capacity that is correct. And we are not talking about being fussy and insisting on perfect precision -- in fact if you have a TL hole high enough and an implement whose pin vertical separation is small enough and whose frame is long enough, you can actually create a NEGATIVE result; that is, you can hang weight on the end and find that your 3pt hitch goes up all by itself without the tractor lifting it. This isn't a precision issue, it's an issue of getting the wrong answer.

If you want things simpler, you can create a parallelogram by getting the TL geometry right, and use tractor specs for the ball ends. The point of parallelograms is that they make the ball end spec applicable everywhere else.

Or you can configure your whole setup and use a crane scale to see what force corresponds to going into relief. Which is great, if you already have the setup plus a crane scale. If you are trying to predict new equipment behavior, or if you don't happen to have a spare crane scale, this doesn't work.

It's hard for me to imagine a way of calculating the correct answer that is simpler than LD1's tape measure check while not requiring a parallelogram. And the whole point of asking whether something would work is to know without trying it. There are all kinds of possible reasons not to just try things -- it could require stuff that doesn't exist yet, you could be planning a job for which it's expensive to bring in other equipment if Plan A fails, it could even be dangerous.