Built a quick and dirty thumb.

[npalen]

I'm wondering what actually caused the rod to bend other than simple column overload. Were the pins lubed so they could turn freely? I see that you have good provision for greasing but I sometimes forget to lube prior to prototype testing.

 

[aarolar]

OK here's V2, dad and I talked and he felt the rod failed because the mount failed and vice versa so I welded it up proper this time. Besides the repad I also changed the open width to 36" instead of 42" and that alone made a world of difference in the smoothness of operation. The gussets are a good idea and I may add that at a later date.



Thanks for all the input guys I hope it works out better this time.

 

[aarolar]

I'm wondering what actually caused the rod to bend other than simple column overload. Were the pins lubed so they could turn freely? I see that you have good provision for greasing but I sometimes forget to lube prior to prototype testing.

Yes it was greased I'm a nut about greasing stuff it's actually a job I enjoy.

 

[ovrszd]

I'm wondering what actually caused the rod to bend other than simple column overload. Were the pins lubed so they could turn freely? I see that you have good provision for greasing but I sometimes forget to lube prior to prototype testing.

The rod bent because more load was placed on it than the hydraulics had the ability to produce. Hafta think about that for a bit.

 

[ovrszd]

The mount failure happened second.

 

[npalen]

The rod bent because more load was placed on it than the hydraulics had the ability to produce. Hafta think about that for a bit.

So you're saying that the rod would not have bent if there was more psi available?

 

[ovrszd]

So you're saying that the rod would not have bent if there was more psi available?

Nope.

I'm saying the host tractor cannot produce enough hydraulic pressure to bend the rod under normal use situations. It bent because forces in excess of the hydraulic capability were applied to the rod.

 

[ovrszd]

Getting ready to check out for the evening. Don't want to leave with an open question.

If the tractor had the hydraulic capability to bend the rod, it could be accomplished by activating the valve to close the claw and holding it. The tractor does not have that hydraulic capability. So to bend the rod there had to be forces outside the hydraulic capability of the tractor. Pretty simple if you think about it.

I've bent three cylinder rods. Never once was it because of the hydraulic strength of the tractor......

 

[spursjingles]

Fix or toss? Ovrszd

View attachment 499802

Wow! That must have been some stress to bend like that. New cylinder should not be too much. I pay 75 canadian for those.

 

[aczlan]

So you're saying that the rod would not have bent if there was more psi available?

When you have the grapple in fully closed position, how much clearance was there between the bottom of the clevis on the rod end of the cylinder and the bracket on the grapple? Looking at your picture, it appears that there isn't much clearance there and if they touch that could have been what bent your rod.

Aaron Z

 

[ovrszd]

Aaron, that's possible. Might also explain tearing the tab loose from the claw frame. I had it in my head that he exerted external forces on the claw beyond what the hydraulics could apply.

 

[npalen]

I doubt that's the case as the rod appears to have bent with the cylinder rod in the near retracted position. The rod would have bent further back toward the piston is it was nearly extended and the base casting hit the cylinder anchor. I'm pretending to be Sherlock Holmes here.

 

[ovrszd]

I doubt that's the case as the rod appears to have bent with the cylinder rod in the near retracted position. The rod would have bent further back toward the piston is it was nearly extended and the base casting hit the cylinder anchor. I'm pretending to be Sherlock Holmes here.

Me too. Your theory is sound though.

 

[nybirdman]

I would guess he had the cylinder(grapple thumb) partially close and rolled the bucket down on a solid object.So the force of the FEL was on the cylinder.I say this because I have done something similar;I have a shorter stroke and the cylinder was closed but was pushed beyond the stoke of the cylinder.Hard to explain but it's all in the geometry of the design.Mine is a Green's Machine.

 

[ovrszd]

I would guess he had the cylinder(grapple thumb) partially close and rolled the bucket down on a solid object.So the force of the FEL was on the cylinder.I say this because I have done something similar;I have a shorter stroke and the cylinder was closed but was pushed beyond the stoke of the cylinder.Hard to explain but it's all in the geometry of the design.Mine is a Green's Machine.

Something similar is my contention as well.

 

[aarolar]

Well thanks for all the compliments but I'm afraid I have some bad news, I've already broken it. I was trying to grab a pile of brush and had the thumb half open and pinned it against a tree and rolled the bucket down at the same time and bent the rod and tore the mount off. I was a little worried about the welds on the mount tearing out being I used AR plate and I know how to fix that issue but there ain't no fixing a bent rod. Now I gotta decide if I'll cut my losses and buy a dedicated grapple or invest in a new cylinder to fix this.

View attachment 499782

I don't know what all the speculation is I said exactly what killed it in my earlier post...

 

[ovrszd]

No worries. We're just visiting. We can stop if you like?

 

[aarolar]

No worries. We're just visiting. We can stop if you like?

No problem I'm just curious at all the confusion, the big question is how to keep it from happening again?

 

[ovrszd]

No problem I'm just curious at all the confusion, the big question is how to keep it from happening again?

Very simple, don't do what you did again.

 

[aarolar]

Very simple, don't do what you did again.

Easier said than done working blindly.