3-Point Hitch How much can the 3pt link hold?

[Bob_Skurka]

Larry, the huge factor you are not taking into account is hydraulic system that is connected to the 3pt. It is only capable of applying a specific amount of maximum pressure. Once the leverage on the 3pt generates enough pressure to exert more pressure than the maximum amount the hydraulics can hold, then the lifting stops. The parallelogram linkage is for stability not for lifting since the toplink does nothing to add/decrease capacity of the lift. The entire lift is based on hydraulic pressure and leverage.

Perhaps I am not good at explaining myself so you and I may have to agree to disagree, but the manufacturers spec sheets confirm my calculations in every case that I looked at and I have run calculations on several tractors from every major tractor company (Deere, Kubota, NH, Case, Mahindra, Montana, Kioti, Massy, etc).

 

[MrChris]

Thanks for the discussion guys. I'm suprised at the two different points being made, but I understand both. I'm new to tractors but I figured tractors have been around for a while and the basic mechanics fo lifting things has not changed, and that my question would have been a somewhat simple one. To be more specific...I'm looking at a no till drill. I can hear the laughter already......what with a 32hp tractor...are you nuts... but a company called Kasco (kascomfg.com) makes some smaller models. I'm interested in their 3 pt5' vari-slice model kos-604 (4" spacing). I thought about a version you could just tow, but they say you can control a 3pt version better. I'm told it weighs in at 1080# and my tractor should be able to handle it. The center of gravity of the unit appears to me that it would not be farther than 24" back from the ball joint looking at the online picture of the 6' model. I have some grades to deal with as you can see in my tractor pic (few weeds yes, but little grass also..too many horses on too little acres!!) so I'm concerned about that.

 

[SPYDERLK]

Quote: "The parallelogram linkage is for stability not for lifting since the toplink does nothing to add/decrease capacity of the lift. The entire lift is based on hydraulic pressure and leverage."

The toplink completes the approximate //gram linkage and is the reason that the force upward at the eyes can be transmitted back without lessening significantly. The force available at the end of an attached boompole is much greater than that which would be available at the end of a liftarm extended to reach as far back. Indeed, when the //gram is in the part of the lift where it is working sweetly, the force at its end is roughly identical to that at the lift eyes. With experimentation you can actually better the lift eye force within a very limited range of lift.

Your calculations are agreeing with published specs meant to give guidance for max lift as governed by safety. These just take into account the added leverage on the tractor by the weight being further back. They arent going to tell you you can lift more than is safe.

Please take another look at whats happening. Try some experiments.
larry

 

[Bob_Skurka]

The toplink completes the approximate //gram linkage and is the reason that the force upward at the eyes can be transmitted back without lessening significantly. The force available at the end of an attached boompole is much greater than that which would be available at the end of a liftarm extended to reach as far back. Indeed, when the //gram is in the part of the lift where it is working sweetly, the force at its end is roughly identical to that at the lift eyes. With experimentation you can actually better the lift eye force within a very limited range of lift.

If you bolt, weld or clamp something to the lower lift arms, the tractor will lift the same total weight as if you have something attached to the lower arms + the toplink. The toplink simply provides control, stabiltiy. But the lower arms do all the lifting. A static weight will prove this. Moving the weight farther back from the rear of the tractor creates leverage. Every action has an equal an opposite reaction. In this case that means that the farther the weight is moved back, the more mechanical leverage you have pressing against the hydraulic system. Connect up a set of pallet forks on your 3pt hitch, try to pick up 1000# wtih the tips of the forks and a tractor that has a 1000# capacity. I bet you can't do it. The hydraulic system has a pressure release setting, it is you limit and it works against you when the load moves back and leverage comes into play.

Your calculations are agreeing with published specs meant to give guidance for max lift as governed by safety. These just take into account the added leverage on the tractor by the weight being further back. They arent going to tell you you can lift more than is safe.

Again, agree to disagree, but my calculations have nothing to do with safe lifting at all, they have to do with actual capacity that can be lifted. Nothing more.

 

[LAWALLSTRACTOR]

I think it was TIM IN IA that proved this out. He couldn't lift a round bale with his bale spear on the back of his 00 series tractor. Come to find out his bale spear was a 2 point set up only attaching to his lift arms. When he switched to a 3 point system bale spear he lifted the bale no problem.

 

[Bob_Skurka]

I think it was TIM IN IA that proved this out. He couldn't lift a round bale with his bale spear on the back of his 00 series tractor. Come to find out his bale spear was a 2 point set up only attaching to his lift arms. When he switched to a 3 point system bale spear he lifted the bale no problem.

Galen, go back and carefully re-read what Tim wrote. His relief valve was bad. After the dealer fixed it, the 2 point spear lifted the bales. However, about 2/3rds through the thread, and after the relief valve was fixed, he did also buy a new 3pt bale spear.

In the middle of that same thread about Tim's 3pt not lifting properly, this was posted:

Tim, sorry I somehow missed the last posts on this thread. YES, this arrangement - the one you posted pictures of - loses lift capacity as you move out from the balls. If you were to measure the length of your lift arms (A), and then measure the distance from where the lift arm pivots on the tractor to the "point" on the spears where the weight is being lifted (B), you could have a good idea of what to expect. The lift caacity will be A/B times the lift capacity at the balls. From the pictures Im guessing the fraction A/B is about 1/2. I just had to look back to the 1st to see how heavy those bales are - - I expected about 1Klb which wouldnt have explained it. But 1800 puts it very much into the iffy zone. I imagine your tractor is ok, but while youve got their attention get the mechanic to set your pump relief pressure to to high side of the spec. Springs lose a little bit of their tension during breakin for various reasons. This effect on hydraulic relief pressure is very small unless the seat actually wears. What isnt quite so small is the effect of heat. The spring is a little weaker while warm. The difference in relief pressure may go down 50psi (a percent or 2) in a hot system. This should be allowed for during adjustments made cold. If you can get them to show you where the adjustment is made please let us know.
Larry

Perhaps Larry and I are arguing very similar points but from different sides of the story and I am not understanding his points or I am not clearly writing my points?

 

[SPYDERLK]

Bob, my post to Tim that you quoted is meant to explain how his 2ph spear took away a lot of his lift force. I do not see anywhere in the post that his 2ph spear ever lifted those bales. He even had some indications of trouble with the 3ph spear. He may have had the top link pivot too low on the tractor. It should be high enuf that the three links run as close to parallel as possible. If the top link is aimed upward compared to the lift arms you wont get full lift force as you move back from the balls. Some tractors dont have a selection of top pivot holes appropriate to some implements.
larry

 

[texasjohn]

MrChris, as you can see, you get lots of good information on this site and sifting through it gives you the combined experience and opinions of numerous people.

Having clarified what you are trying to do, my opinions are as follows.

Yes, likely your tractor will handle the no till seeder. You will find out very quickly the first time you hook it up. Just get an agreement before you purchase it that if it doesn't fit your tractor you can return it.

Add about 200 or so pounds to allow for seed in the box and drive around with it lifted. Do this at the speed you would use to drive to and from your work area and hit a couple of bumps and gentle slopes. If the front end gets light or lifts off the ground, then more weight in front or slower going is dictated.

It WILL be easier to maneuver with a 3PH no till than a pull. Safety when drilling will be good because the drill will be in the ground, thus flipping backwards will be prevented in all except very extreme circumstances because the implement/top link will prevent that motion.

I have no personal experience about the implement weight needed to successfully no till. Perhaps the 1080 pound 3PH weight is sufficient. However, you may discover that better success is achieved for your ground with some added weight. It'll all depend on your ground conditions.

I suspect that the 3PH version is narrower and lighter than a pull version. This means that you will have more "gaps" in your seeding since you will need to make more passes to cover the ground. Likely, however, you may prefer the 3PT version because it will be easier to go back and hit the spots you miss.... and with your acreage and horses this will likely be a benefit.

Horses will ALWAYS have places where they leave the ground bare.