Loader bending metal on loader

[George2615]

This is how I could see the dogleg getting bent. See arrows in pic as to direction of force.
Please correct me if I'm wrong. It wouldn't be the first time.

1) Bucket is in dump position.
2) Tractor is moved up to a solid structure like a tree with bucket cutting edge touching tree.
3) Operator tries to curl the bucket up, bucket or tree do not move, resulting hydraulic pressure pulling piston in will bend dogleg as shown in previously posted pics.

The loader relief valve should have prevented further damage. With 1/2" thick steel its pretty tough to bend one piece let alone bending two pieces.
Is it possible the owners of the bent doglegs have boosted or turned up their loader relief pressure setting?

 

[SPYDERLK]

This is how I could see the dogleg getting bent. See arrows in pic as to direction of force.
Please correct me if I'm wrong. It wouldn't be the first time.

1) Bucket is in dump position.
2) Tractor is moved up to a solid structure like a tree with bucket cutting edge touching tree.
3) Operator tries to curl the bucket up, bucket or tree do not move, resulting hydraulic pressure pulling piston in will bend dogleg as shown in previously posted pics.

The loader relief valve should have prevented further damage. 1/2" thick steel is pretty tough to bend.
Is it possible the owners of the bent doglegs have boosted or turned up their loader relief pressure setting?

Yes that arrow on the dog has to be in compression with the apex of the triangle being pulled by the cyl. ... And, yes that will tend to buckle the dog.

The situation is opposite when backdragging, resulting in the dog being in tension.

Are those a full 1/2" thick?
larry

 

[George2615]

That arrow on the dog has to be in compression with the apex of the triangle being pulled by the cyl. ... And, yes that will tend to buckle the dog.

I agree. the cylinder is pulling on the flat bar trying to curl the bucket up, if nothing is preventing the bucket from moving the the dogleg just acts as a pivot point but if the flat bar pulling the bucket up cannot move the force is then transferred to downward force (compression) on the dogleg. This asks the question why the relief valve didn't open to prevent damage to the dogleg.

 

[SPYDERLK]

Are they really 1/2" thick? Relief is not acting when the valve is centered. The tractor force or loader arm force is acting against the closed curl valve. No pressure limit.

 

[Tbolt76]

George,
Great diagram and dialogue! I love this forum! Sounds like the lesson is don't try to move an immovable object, even if you own an LS!
Tom

 

[George2615]

Here's another pic of a loader set to back drag. If the cylinder piston is set to this position and doesn't move while back dragging wouldn't the force be transferred to compression on the dogleg?

 

[George2615]

Are they really 1/2" thick? Relief is not acting when the valve is centered. The tractor force or loader arm force is acting against the closed curl valve. No pressure limit.

My mistake. I just went out and measured mine and they are 3/8" thick, not 1/2" which they probably should be. Relief valve would be in play if they were trying to curl the bucket against an immovable object.

 

[SPYDERLK]

No. Putting the arrow on the cyl ram would help clarify. It would be a force applied outward [to resist being pushed in]. So the dog would be in tension.

 

[SPYDERLK]

My mistake. I just went out and measured mine and they are 3/8" thick, not 1/2" which they probably should be. Relief valve would be in play if they were trying to curl the bucket against an immovable object.

Yes, in play if trying to curl. But if the curl spool is centered the curl cyls are deadheaded - and what you do with the tractor or lift arms can try to change the curl. And it cant change w/o failure of some sort.

Those 3/8" doglegs and the close pin spacings on the carrier add up to an overstressed curl system. Very little performance margin.
larry

 

[altamaha]

Thanks for the illustrations.. I can see from the pics that the cylinder pulling (uncurl) would apply most pressure (for bending) on the dogs, while the cylinder pushing would put more pressure on the link from the top of bucket to the cylinder connection point.. thanks for the lesson on applied physics.