What factors make loader specs so close - yet so different?

[jim_wilson]

I've been comparing a Kubota B3300 and L3800 on their specs (trying to make a purchase decision) - and their is something that is bugging me - because it sort of doesn't make any sense.

When I look at the loader specs for the two tractors I see:



Lift capacity (pivot pin) :

B3300SU (LA504) = 1065
L3800 (LA524) = 1131 (max ht.)

Lift Capacity: (forward) :

B3300SU (LA504) = (19.7in) 730
L3800 (LA524) = (500mm) 855 (max ht.)

Breakout Force (pivot pin):

B3300SU (LA504) = 2474
L3800 (LA524) = 2462

Breakout Force (forward):

B3300SU (LA504) = (19.7 in) 1737
L3800 (LA524) = 1874



The breakout force at the pivot pin on the two loaders is very close. Yet - the forward numbers on breakout force are a lot different. The lift capacity at the pivot pin on both are close - but they are farther apart on the forward number.

Is this a leverage thing? Or is the cylinder diameter affecting some numbers more drastically than others?

 

[oldnslo]

My guess would be leverage or mounting location of the curl cylinders in relation to the bucket pivot point.

Hydraulic cylinders provide a constant force at a constant pressure.

 

[Zebrafive]

I am think it all relates to the geometry of the boom cylinders. The relation ship to their mount position on the mast and boom and the distance from the boom pivot pin to the bucket pivot pin.

My definition of breakout force is the bucket lift force at the ground level using the boom lift cylinders.

Bucket rollback force would be using the curl cylinders.

 

[J_J]

Excerpt:

Here's what Cat says the SAE (Society of Automotive Engineers) definition is for wheel loaders:


Breakout force is the maximum sustained vertical upward force exterted 100mm (4" behind the tip of the bucket cutting edge and achieved through the ability to lift and/or rollback about the specified pivot point under the following conditions:


Here is what Case says about the 1845C

The maximum rated operating load of the Case 1845C is 1,750 lbs., and the tipping load is 3,545 lbs. The breakout force of the bucket and lift arm is the maximum force that the machine is able to exert. The breakout force of the lift cylinder is 3,450 lbs., and the breakout force of the bucket cylinder is 4,690 lbs. With the bucket loaded it takes 4.3 seconds to raise the lift, 2.9 seconds to lower it, 2 seconds to dump the bucket and 1.4 seconds to roll back the bucket.

More breakway/breakout force is achieved with the combined power of the loader lift and bucket (crowd-dump-fill) cylinders. The combination of a tractor/loader's weight, hydraulic lift capacity, loader design, traction all are important ingredients to determine how much "breakout" force the equipment may develop.