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Breakout Capacity

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Rob
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2000-05-10          16144


Newbie question:Most loader and backhoe specs include both lift capacity AND breakout capacity. Lift is obvious enough but what does breakout mean?Thanks ahead of time, Rob.



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Bird Senter
Join Date: Jun 1999
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2000-05-10          16148


Rob, I think you'll find that the "lift capacity" is the maximum weight the loader will lift to its maximum height (all the way up), and the "breakout" is the weight the bucket will lift by curling it back at ground level. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2000-05-11          16165


That's my impression as well. I think there are two breakout ratings, one for bucket curl and another for the dipper stick (dragging the bucket back). I guess lift capacity means the point at which the hydraulics stall.

When I thought about it, there's a bunch of geometry in a backhoe. I realized this probably is another 'how ratings are measured' thing. I haven't thought through the geometry of a backhoe, but there seem to be some variables, and there should be a standard way of measuring capacity.

For example, the boom lifts in an arc. For a given weight in the bucket, I suspect that the force exerted on the lift cylinder changes through the lift arc. The maximum force may be when the boom is at 90 degrees. The position of the stick also should affect force on the lift cylinder. The least force required probably is with the stick is back.

Of course, the lift ratings are complicated by their relationship to reach ratings. A manufacturer may choose to engineer a hoe for a bit more reach. The extra reach probably comes at the expense of lift, unless larger bore hydraulic cylinders are used.

Anyway, I suspect that unless manufacturers are all using standard rating measurements, it's a bit difficult to make comparisons from manufacturer stats.

Another way of judging the strength of a backhoe may be the recommended minimum hydraulics pump capacity. One way of getting more lift capacity is to use larger bore cylinders. However, larger cylinders require bigger pumps, unless engineers figure the operator is happy just sitting around waiting for the cylinders to cycle.

I know that lifting the boom causes the engine to work harder and longer than other operations. It does take awhile for my hoe to lift a bucket of dirt out of the hole. One of the things I'd want to know when evaluating a hoe is how long it takes the boom to cycle with a pump at the recommended GPM. ....


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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2000-05-11          16179


lift capacity is tied to safe operation, breakout is where the relief valve says no more and puts the oil back into the system via bypass. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2000-05-12          16203


Yeah, I'd buy that. Breakout means stalling the hydraulics and lift capacity means safe operation. I know that lifting the bucket out of a narrow trench, dragging the sides, and stalling the lift is one thing. Having a full bucket and the boom and stick extended is another thing. I'm just as happy I didn't get the wide bucket. More weight, more worry about safe operation.

Even so, the idea that a safe operation spec can be related only to the hoe seems difficult to understand. Surely differences among all the tractors a 3ph hoe could be put on would affect safe operation. I guess that's my point, I don't know how to evaluate these specs, and I don't know if they actually can be compared. ....


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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2000-05-13          16230


Tom, I don't know who's brand you are looking at for the b'hoe to give you two spec's. I looked at the lines I carry and they give break outs on the hoe. The break out capacity on the hoe is what is most critical for output of the hoe. If you never hit the breakouts on the hoe of coarse it will have less stress and last longer between major maintinace. ....


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TomG
Join Date: Feb 2002
Posts: 5406 Upper Ottawa Valley
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2000-05-14          16264


Art: I've had a Kelley B600 for about a year. I looked for the brochure before making my first post. I find the instructions and warranty stuff, but not the specifications. So, I'm working from memory. I'm almost certain I recall a rating for the dipper, but can't remember if it was described as breakout, maximum force or something else.

Anyway, whether it's speced on a hoe or not, I think the capacity of the dipper is important. I'm as likely to stall the dipper as the bucket curl, especially when I'm trying to keep a level trench floor.
....


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