calculate bucket pryout force.

[Rara Avis]

I still like my answer. "Call and ask"

jb

I agree, but he seemed to reject it...so I provide him with the math...

 

[MJPetersen]

Paul,

That is indeed an interesting site and shows how you also have to take into account the dipper movement. Thanks for finding that for us.

Mike

 

[dfkrug]

Untitled Document

Search for this on the page...Calculation of Breakout Force and Digging Force on Backhoe Attachment

Interesting site. Seems the standard (DIN) method of quoting dipper
stick digging force is not the maximum. The max occurs when the
bkt is curled all the way. The bkt curl point at which breakout force is
max is NOT the position at which the dipper stick force is max.

 

[wedge40]

Interesting site. Seems the standard (DIN) method of quoting dipper
stick digging force is not the maximum. The max occurs when the
bkt is curled all the way. The bkt curl point at which breakout force is
max is NOT the position at which the dipper stick force is max.

I found this on a site that sells backhoes. These are made in the US.
Please tell me if these numbers are close or are they bending the truth.
I'm interested in the forces.


Maximum digging depth....................................................................8?
Digging depth (two foot flat bottom) .................................................7?
Reach from swing pivot ...............................................................10?1
Transport height ..........................................................................7?0
Bucket clearance............................................................................6?
Bucket Rotation.............................................................................165ｰ
Swing arc.....................................................................................180ｰ
Stabilize spread down (Operating).....................................................7?
Stabilize spread up (Transporting) .....................................................5?
Bucket pry-out power - in excess of ...........................................6900 lbs.
Bucket curl power at cutting lip .................................................3200 lbs.
Crowd power at end of dipping stick ...........................................1692 lbs.
Lift at end of boom....................................................................760 lbs.
Lift at end of stick w/boom & dipper stick extended.........................455 lbs
Hydraulic system relief valve setting.. ......................................2000 P.S.I.
Hydraulic flow requirements ..............................................4.5 to 6 G.P.M.
Shipping weight (less bucket)......................................................860 lbs.
Recommended tractor size ....................................................40 to 45 HP
Boom cylinder..........................................................Bore 2.5?Stroke 20
Dipper stick cylinder .................................................Bore 2.5?Stroke 14
Bucket cylinder ........................................................Bore 2.5?Stoke 14
Swing cylinder (two).................................................Bore 2.5?Stroke 10
Stabilizer cylinder (two).............................................Bore 2.5?Stroke 10納/SIZE]

With a 2.5" bore and 2000 psi the force at the cylinder end is 9812.

 

[dfkrug]

WEDGE, the dipper stick force seems low, and I don't know what that
"bucket pry out power" is.

"Bucket pry-out power - in excess of ...........................................6900 lbs.
Bucket curl power at cutting lip .................................................3 200 lb"

The largest force quoted should be the bucket breakout force, which
seems to be the latter #, 3200.

What hoe is that you quoted?

 

[dfkrug]

With a 2.5" bore and 2000 psi the force at the cylinder end is 9812.

Yeah that is the force applied by the cylinder. Now you need to look
at the moment arms to determine what net force will be applied to the
end of the dipper, and to the teeth of the bkt.

 

[rbargeron]

The biggest "pryout" force happens when the back/bottom of the bucket is pressing against the ground and becomes the pivot point - like when you push with the boom while curling the bucket to break roots around a stump. The discussion above will give the force available from the bucket's curl linkage - then boom force can be added to the mix to get the max total force available at the teeth. The exact answer is usually not as important as whether or not it is enough

 

[dfkrug]

RBARGERON,
It is true that you can gain leverage when prying with the bkt
by pivoting on the bottom of the bkt. This transfers the curl
cylinder force to a shorter moment arm. This is how we can
tip up the edges of multi-thousand pound rocks. You can go
further than that, too. If you stick your bucket's teeth into
a fairly narrow gap, as between 2 rocks, you can apply many
more thousands of lbs of force, as now the moment arm pivot
is just a few inches.

 

[wedge40]

WEDGE, the dipper stick force seems low, and I don't know what that
"bucket pry out power" is.

"Bucket pry-out power - in excess of ...........................................6900 lbs.
Bucket curl power at cutting lip .................................................3 200 lb"

The largest force quoted should be the bucket breakout force, which
seems to be the latter #, 3200.

What hoe is that you quoted?

Its a Koyker KB75. They use to sell three different models but now they are down to just one.

 

[dfkrug]

Koyker. OK, that company has been around a while and is known
for its aftermkt loaders. They acquired the Kelly line of b/hs a
few years ago and both products were sold for a while.