Question about steel strength??

Sodo · Mar 25, 2015

If you can find a commercially produced 3x4 pallet that has forklift slots on each side that might be a good basis for your two positions. Some 4x4 composite pallets will have both spacings on each side.

jodebg · Mar 25, 2015

Do forks ever get used close together for "special purposes"?

Wondering if I need to add closely spaced receivers for any good reason?

Sodo said:
If you can find a commercially produced 3x4 pallet that has forklift slots on each side that might be a good basis for your two positions. Some 4x4 composite pallets will have both spacings on each side.

bcp · Mar 25, 2015

Pallet jacks are closer than most forks, but their dimensions might be a good minimum for fork locations.

Pallet jack dimensions

Bruce

Mace Canute · Mar 25, 2015

LD1 said:
NO

NO again.

A parallelogram linkage does NOT need more force for a load farther out. It makes no difference where the load is, the force required to lift it is the same.

We have been down this road before.:mur:

Well then, you went down the wrong road.

bcp · Mar 25, 2015

The parallel linkage will not need more force to move a farther out load, but the result may be that the tractor front end lifts instead of the load. The lever, with the fulcrum at the rear tires, is now longer.

And 3pt hitches in normal configuration raise the rear of an implement more than the front, so they aren't really parallel linkages.

Bruce

Mace Canute · Mar 25, 2015

Sodo said:
.........

Thanks Mace thats helpful,,,,, IF it's how the 3-pt works inside a B7800. LD1 you seem to say this is NOT how a tractor 3-pt is actuated? I looked around on the net a little, could not find any useful mechanism diagrams.

If 3-pts are generally actuated as in the (Mercedes Benz / Unimog) pic above the lifting capacity is obviously position-dependent. Just at a glance I can see that there are positions where the lift force will be 50% of its max. LD1 note that the parallelogram linkage can vary this output further (plus & minus) because the top & bottom links are not same length. The output of a parallelogram is not given linear, it depends what you are measuring. For example if the input is a constant torque then output is sinusoidal (extremely non-linear) but some segments of the stroke can approximate linear.........

I have never seen a 3PH that is configured differently. The lower arm is attached to the tractor and this attachment point is the fulcrum. The arm that lifts the lower arm attaches between the fulcrum and the other end of the lower arm and it does not matter how that force is created, it could be from an internal cylinder and a rocker shaft and linkages similar to the diagram or from hydraulic cylinders that are attached on one end to the tractor while the other ends are attached to the lower arms. What matters is where that lifting force is applied in relationship to the load and fulcrum and if it is between the load and fulcrum, that makes it a Third Class lever. It doesn't matter if the length of the upper arm makes it a a true parallelogram or not, that only affects the attitude of the implement that is being lifted, not the force that is required to lift it. The force that is required to lift the load is dependent on how far the load is from the fulcrum. Period. What changes is the hydraulic pressure necessary to create that movement.

LD1 · Mar 25, 2015

Yes the 3PH lower arm itself is a 3rd class lever.

But anything attached to it doesnt follow simple lever rules. Since it is not rigidly attached to the lower arm and is free to rotate about the ball end of the lower arm.

most 3PH's arent perfect parallelograms by design. They want the tip od the implement to pitch up higher cause it is needed for long implements when crossing uneven terrain. That is why the lift capacity @ 24" is lower than the ball ends. But still significantly higher than it would be following a simple lever calculation.

If you want to know the lift, use a simple ratio. The force required to lift an object is directly proportional to how far it lifts it (in relation to the lifting mechanism.

IF you can set up the 3PH so that the forks lift perfectly level, and the tips raise the exact same amount as the heals, the lift capacity is the same at any point on the fork.

If the heal (right at the ball ends) lifts 12", and the tips raise 24", then you have 50% capacity at the tips.

But how high the tips lift is a variable that can be changed with different toplink length and placement. Thus the load capacity at the forktips can be altered with toplink adjustments.

Here Mace, read ALL of this thread and come back. http://www.tractorbynet.com/forums/...ph-load-capacity.html?highlight=parallelogram

Sodo · Mar 25, 2015

2x2x 1/8" tines 36" length are fine for a B7800.

Heres the calculator I used and my numbers. You can goof around a little with this if you need help ask. I would not use 1,000 lbs, on the tip of one tine that's too heavy for this application.

In usage you should secure your loads anyway and not let loads get to the tip or all on one tine. If it was 1,000 lbs rolling off a tine it might tip your tractor up and give you more to worry about than a bent tine. Your tines are removable, you can fix or replace them easily, probably better to have a reason not to overload them.

If you can't find a good source for the receiver socket material, you can buy these from Harbor Freight. 18" size will give you three 6-inch sockets, and 12" will provide two sockets. But you will need to be able to drill 5/8" holes (5/8" holesaw is pretty easy).

Sodo · Mar 25, 2015

LD1 said:
If the heal (right at the ball ends) lifts 12", and the tips raise 24", then you have 50% capacity at the tips.

This can be a factor, and it's not a constant either, it varies with the position due to parallelogram geometry and is affected by the length (or adjustment) of the top link. On my Kubota it goes almost perfect level up & down (1 to 1) if the hitch adapter pins are all in a vertical plane.

In addition there are variations of torque outputs at the lift arm axis that will affect capacity in a significant way. Good discussion and it interests me (and perhaps Joe too),,,,,but doesn't help Joe make a decision on weight and tubing sizes.