lift capacity vs. breakout force

[carpenter383]

This may seem like a dumb question, but while researching tractors I've noticed some loaders have a breakout force that is basically double the lift capacity. While other loaders' rated lift capacity is only say 400 lbs shy of the breakout force. So is the rated lift capacity simply what the manufacturer feels is safe, based on a given tractor? Am I missing something?

 

[Eagleview]

The breakout force is the amount the bucket can exert in it's crowd back function ie. tearing out a tree root while rolling the bucket back , as opposed to trying to lift it with the loaders lift arms (lift capacity).

 

[carpenter383]

I thought that was "roll back" force

 

[CHDinCT]

I believe that break out force to some degree is dependent on how far out the front edge of the bucket is from the bucket cylinders; therefore, two buckets of the same capacity but with different dimensions would have different breakout numbers. The farther out the front edge is, the less breakout force it will have. This is one factor, but I believe there are others such as the size of the bucket cylinders.

 

[J_J]

This may seem like a dumb question, but while researching tractors I've noticed some loaders have a breakout force that is basically double the lift capacity. While other loaders' rated lift capacity is only say 400 lbs shy of the breakout force. So is the rated lift capacity simply what the manufacturer feels is safe, based on a given tractor? Am I missing something?

I believe that they build or order a certain bucket, and then figure the cylinder size that will give a reasonable breakout before the bucket is destroyed. You can over power a bucket real easy by using the wrong cylinder. You will probably rip out your mounting brackets, or warp your bucket. Other things to consider is the front to back length. A shorter bucket on the same frame, will have a greater break out force, due to mechanical advantage. The same thing applies to the lift cylinders also. You could go to a larger cylinder, but you might place your front axles at risk, by overload. Just enough is what they settle on.

If you built a super strong bucket, and your front pins can take it, you could go to a larger cylinder. I am sure that someone put some kind of measuring device on the bucket and curled the bucket back to see what break out force they can give the bucket.

 

[carpenter383]

Well It makes more sense now, I thought breakout force was at max psi when the pressure relief valve opens thanks for the info guys

 

[john_bud]

Lift is obviously how heavy of an object you can lift "at a particular location" with respect to the loader. Some (unscrupulous) companies will give that rated at the lower pivot point. That's beyond the back of the bucket (closer to the tractor) and the number is worthless. A better one is "bucket center" as that is where you will have a load. An even better one is to have it at 500mm forward of the bucket edge. That is where a chained on load like a large log is often located. Heck, I'd be happy if they would just certify how many pounds of heaped dirt can be picked up to full height!

Break out is the upward force generated at the bucket lip. It is larger than the lift as the bucket can be on the ground and there is some "pry" action occurring with some down force transferred to the back of the bucket. Some will refer to it as the "roll back" force and that's a good description. JJ is correct that you can over power the bucket and bend it if you go too big on the cylinder. That's fairly rare as they match the cylinders to the bucket nowadays pretty well.

 

[schmism]

i physcally can not get a larger cylinder on my roll back function on the bucket due to geometry. The fat end of the cylinder (when fully extended) only sits about 1/4" above the loader arm. Course I have the older loader design that pins the cylinder directly to the bucket and not to a 2nd linkage.

 

[john_bud]

i physcally can not get a larger cylinder on my roll back function on the bucket due to geometry. The fat end of the cylinder (when fully extended) only sits about 1/4" above the loader arm. Course I have the older loader design that pins the cylinder directly to the bucket and not to a 2nd linkage.

Can not???? Always took that to be a challenge...

Sure you can. Cut off the old ears, weld on new ones that give a larger cylinder some room to breath.

 

[Eagleview]

Large loaders use a "Z" linkage on the bucket . The ram is then able to push out on the "Z" linkage which reverses the direction of thrust so the bucket rolls back which gives a greater breakout force . A ram has more push power than pulling power because of the piston area that the oil can work against is less on the ram side than the other side . As a rough example , there may be 5 square inches on the piston face . Say 2,000psi working pressure , 5X2,000psi=10,000lbs pushing force . On the other side that has the ram bar attached you may only have 3 square inches of piston surface area because the ram bar takes up the extra room . So you have 3X2,000psi=6,000lbs pushing force .