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Bucket Break Out Force

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kthompson
Join Date: Oct 2005
Posts: 5223 South Carolina
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2007-10-23          147240


Have a rep to tell me "single pin placement" for bucket breakout force is different some how than other company's way of giving their bucket breakout force. Does that make sense? Looking at pictures of the Volvo machine who's owner who is telling me this looks the same to me as other brands of buckets. Thanks guys. kt

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Bucket Break Out Force

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candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
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2007-10-23          147245


KThompson,

Bucket break-out force is figured based on several factors.

1. The size of the cylinder.

2. The hydraulic system's set pressures.

3. The leverage offered by the amount of offset from the bucket pivot pin.

4. The engineered strength of the various pins, bucket, and arm.

Bigger cylinders provide greater forces. Higher Hyd. pressures offer greater break-out forces. More offset provides more leverage.....but reduces bucket rotation. And none of these factors make much difference if the arm, pin supports, or bucket are made out of scrap beer cans.

Me thinks the salesman needs a lesson in basic physics.

Joel ....

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Bucket Break Out Force

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Murf
Join Date: Dec 1999
Posts: 7155 Toronto Area, Ontario, Canada
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2007-10-23          147246


Kenneth, I suspect what you (and the salesman) are talking about is the 'new' style of cylinder placement on some loaders.

A lot of industry people refer to it as a 'Z' boom because of the geometry involved.

All they have really done is changed the standard 4 cylinders, 2 cylinders, one on each arm, to lift the loader, and 2 cylinders, one on each arm, to roll the bucket, loader configuration. The Z boom style uses only two cylinders instead of 4, they are each centered on the loader frame, one lifts the boom, the other rolls the bucket.

However, despite Joel's comments to the contrary, they are indeed stronger with bucket breakout or rollback, because of basic physics.

Aside from the fact the cylinder that rolls the bucket is larger (1 bigger cylinder instead of 2 smaller ones) they have reversed the cylinder actuation through the use of different geometry. In this arrangement the cylinder PUSHES to curl the bucket up (breakout) instead of pulling.

Even on a relatively small cylinder this simple change makes a HUGE difference. For example, a 4" cylinder, with a 2" rod being fed 2,500 psi will generate 23,562 pounds of pull and 31,416 pounds of push, that's an increase of 7,854 pounds or 33% of force from the same cylinder, merely because of pushing instead of pulling!

As you get bigger the difference can be even more substantial as the ratio between cylinder diameter and piston rod size moves away from 2:1 as in the example above.

Now in order to make a statement like the salesman did, I'd like to see the spec.'s in order to see exactly what he's talking about, but it certainly is possible.

Best of luck. ....

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Bucket Break Out Force

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kthompson
Join Date: Oct 2005
Posts: 5223 South Carolina
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2007-10-23          147247


I understand the geometry fine. Talked with him further since posting this and he said some companies play games in the bucket they use for test purposes to be able to report the bucket breakout force. It is a Volvo machine. He went on to say sort of what Murf hit at, without knowing the bucket used it means little. kt ....

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Bucket Break Out Force

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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
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2007-10-23          147250


Murf I know you know this but for the benefit of others primarily Kenny ;) geometry aside, the only reason any double-acting cylinder has more push than pull is simple surface area of the piston--the push side has the most available area; the rod side has the rod which can take up like you mentioned 30% of the area. Some cylinders on CUT FELs have almost no pull due to the rod nearly occupying all the space in the cylinder.

Also, the Z configuration is stronger torsionally as it uses essentially one frame on a common pivot versus two frames separated by a tubular torsion-resisting member on two pivots. Even with that member, they are apt to wrack side to side also.

And if memory serves, Caterpillar has gone or making more available the Z as it works better for/as a tool carrier. The reason escapes me though (possibly because it is more rigid)---and it's probably cheaper to produce too! ....

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Bucket Break Out Force

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earthwrks
Join Date: Dec 2003
Posts: 3853 Home Office in Flat Rock, Michigan
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2007-10-23          147252


By definition--- it's got nothing to with geometry, or power, or size of cylinders or the shape of the boom.

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:
a. through g. are specs as to how to set up the machine for testing---level ground, no parking brake on, rear end not secured down, etc.

h. If the (hydraulic) circuit used causes the rear of the vehicle to leave the ground, then the vertical force value required to raise the vehicle is the BREAKOUT FORCE. ....

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