Quick Hitches Does Quick Hitches Compromise Lift Capacity?

[eastexan]

The reason I ask is that Quick Hitches extend the implement out an extra 4", and have been wondering if there would be a loss in a tractor's lift capacity? Or would it just effect the center of gravity? Or neither?

I've noticed that a tractor's lift capacity rating is usually measured at 24". Using a QH would extend it out to 28". It sounds reasonable to me that the farther out you go, the heavier it becomes. And, if the front end of the tractor was already light with a heavy implement, then adding a QH might cause you to have to add some front weights.

What are your thoughts?

 

[kennyd]

You are correct, absolutely they do affect lift capacity since they move the load further away. But how often are you/we lifting at near capacity on the 3PH? Most users have rear blades or box blades that weigh less than half of what a typical 3PH can lift.

 

[LD1]

It really doesnt effect the capacity that much. But you are correct that it does change the center of gravity and make more weight required up front.

A 3PH is a modified parallelogram linkage. That means that what it "can" lift doesnt diminish much at all the farther back you go. The real limiting factor is keeping the front end down.

And if you are talking about the case 385 you have in your profile, according to t-data, it can lift 2150lbs @ 24" back. I cant imagine you are trying to lift anything even close to that:confused2: So just add some more weight up front if required and all is good.

 

[RoyJackson]

3PH capacities are frequently given at 24" aft (as ws written). Some are also give at the "eyeball" of the link.
Figure a QH weighs 60 lbs...that weight would have to be factored in on the lifting capacity.
However, I can't see this having too much effect for most users. That 3PH capacity is a lot more then any of my implements weigh and I don't think I'm alone in that situation.

 

[JB4310]

3PH capacities are frequently given at 24" aft (as ws written). Some are also give at the "eyeball" of the link.
Figure a QH weighs 60 lbs...that weight would have to be factored in on the lifting capacity.
However, I can't see this having too much effect for most users. That 3PH capacity is a lot more then any of my implements weigh and I don't think I'm alone in that situation.

It would be barely measurable if that capacity was from 24" rearward of the lift arms. it would be a little more a factor if the spec was right at the lift arms.
It's about leverage ratio, so yes it would reduce the capacity but not by a noticeable amount.

Anyway, this usually happens before the 3pt fails to lift, at least from my experiance :laughing:

 

[RoyJackson]

It would be barely measurable if that capacity was from 24" rearward of the lift arms. it would be a little more a factor if the spec was right at the lift arms.
It's about leverage ratio, so yes it would reduce the capacity but not by a noticeable amount.

Anyway, this usually happens before the 3pt fails to lift, at least from my experiance :laughing:

That happened to me once.
I always installed the loader, then the ballast box...but one time I hooked up the ballast box first (on my old 790...not too long after I got that ballast box).
Needless to say, the 3PH didn't lift, but the front end of the tractor sure did!!
No damage and I lowered the tractor as soon as I felt the front end come up (front tires probably never got more then 8-10 inches off the ground).
Kind of surprised me...I'd frequently lifted a 60" Befco RFM (450 lbs, per the Befco site) with no front ballast. I guess that extra 200-300 lbs in the ballast box was enough to do the job though...

 

[kco]

I think the reduction can be calculated using moments taken about the connection point of the horizontal lift arm at the tractor. I used rough measurements from my Kioti and the following assumptions:
- lift capacity = 2,000 lbs
- vertical lift arm distance from pivot = 1.0'
- 3 point end hole distance from pivot = 1.25'
- implement weight 2' behind 3 point arm end = 2.0' (= 4.25' from pivot point)
- quick hitch adds 4" (0.33') to distance from the pivot point (= total distance of 4.58')

Ignoring the quick hitch weight, the lift capacity would be reduced to 1,855.9 lbs from 2,000 lbs. To account for the quick hitch weight one just has to calculate its moment 2.25' from the pivot point and add it to the moment due to the implement.

To calculate the additional front weight required to move a 2,000 lb load 4" farther back from the hitch one would calculate moments using the rear axle as the pivot point. On my Kioti that would be about 4.5' back to the centre of the implement and 8' forward to the grill guard. The calculation suggests 82.5 lbs would be required to keep the tractor front/back balance the same as before.

The attached .pdf shows the calculations.

 

[JB4310]

The attached .pdf shows the calculations.

I like the way you did your homework, I figured there would be a formula to use.
I'm not bright enough to check your calculations, but assuming you're right that's about 7% loss. Not bad, but more than I would of guessed, especially for using the 24" rearward position for the capacity.

I believe the percentage would be higher if calculated using the lift arm eyes as the starting point ??? Or is it the other way around?

JB.

 

[SPYDERLK]

It really doesnt effect the capacity that much. But you are correct that it does change the center of gravity and make more weight required up front.

A 3PH is a modified parallelogram linkage. That means that what it "can" lift doesnt diminish much at all the farther back you go. The real limiting factor is keeping the front end down.

And if you are talking about the case 385 you have in your profile, according to t-data, it can lift 2150lbs @ 24" back. I cant imagine you are trying to lift anything even close to that:confused2: So just add some more weight up front if required and all is good.

:thumbsup:Yes./\

I think the reduction can be calculated using moments taken about the connection point of the horizontal lift arm at the tractor. I used rough measurements from my Kioti and the following assumptions:
- lift capacity = 2,000 lbs
- vertical lift arm distance from pivot = 1.0'
- 3 point end hole distance from pivot = 1.25'
- implement weight 2' behind 3 point arm end = 2.0' (= 4.25' from pivot point)
- quick hitch adds 4" (0.33') to distance from the pivot point (= total distance of 4.58')

Ignoring the quick hitch weight, the lift capacity would be reduced to 1,855.9 lbs from 2,000 lbs. To account for the quick hitch weight one just has to calculate its moment 2.25' from the pivot point and add it to the moment due to the implement.

To calculate the additional front weight required to move a 2,000 lb load 4" farther back from the hitch one would calculate moments using the rear axle as the pivot point. On my Kioti that would be about 4.5' back to the centre of the implement and 8' forward to the grill guard. The calculation suggests 82.5 lbs would be required to keep the tractor front/back balance the same as before.

The attached .pdf shows the calculations.

From your description the lift numbers will be wrong with a std 3pt type QH, but correct for Pats QH. The preservation of the articulation points of the //ogram linkage in the former is the reason it will give superior lift. The lift loss with a std QH would be around 10% more than the weight of the QH. [There are a couple threads that have dealt with this in the past year or two.] ... Your front/ back balance concept is sound however.
larry

 

[LD1]

I like the way you did your homework, I figured there would be a formula to use.
I'm not bright enough to check your calculations, but assuming you're right that's about 7% loss. Not bad, but more than I would of guessed, especially for using the 24" rearward position for the capacity.

I believe the percentage would be higher if calculated using the lift arm eyes as the starting point ??? Or is it the other way around?

JB.

I think the reduction can be calculated using moments taken about the connection point of the horizontal lift arm at the tractor. I used rough measurements from my Kioti and the following assumptions:
- lift capacity = 2,000 lbs
- vertical lift arm distance from pivot = 1.0'
- 3 point end hole distance from pivot = 1.25'
- implement weight 2' behind 3 point arm end = 2.0' (= 4.25' from pivot point)
- quick hitch adds 4" (0.33') to distance from the pivot point (= total distance of 4.58')

Ignoring the quick hitch weight, the lift capacity would be reduced to 1,855.9 lbs from 2,000 lbs. To account for the quick hitch weight one just has to calculate its moment 2.25' from the pivot point and add it to the moment due to the implement.

To calculate the additional front weight required to move a 2,000 lb load 4" farther back from the hitch one would calculate moments using the rear axle as the pivot point. On my Kioti that would be about 4.5' back to the centre of the implement and 8' forward to the grill guard. The calculation suggests 82.5 lbs would be required to keep the tractor front/back balance the same as before.

The attached .pdf shows the calculations.

Wrong, wrong, and more wrong.

The 3PH is not a simple lever. And thus the calculations and rotation about the moment cannot be used.

Disclaimer: the 3PH calculations do NOT account for front end weight. It is assumed that you will have enough weight up there and that the components are strong enough to take the load.

That said, the 3PH can be adjusted in many ways with the toplink. Either by its length or its mounting position.

But if your particular tractor lets you mount it to for a perfect parallelogram, there will be NO loss in lift capacity at ANY distance rerward. (again, not accounting for front ballast or strength of components).

All tractors are different though. So how far they deviate from a true //ogram will affect the outcome. The farther from // they are, the greater reduction in capacity. But still not as much reduction as just trying to use a simple lever formula.

Rest assured that what I am saying here is accurate. We have been down this road (myself and spyderlk) before here on TBN. There is a few other threads where this is discussed to death at length.