keep breaking pins in my grapple

[terryknight]

After seeing the video, that much slop is very abnormal. It seems the hole may be sized for a larger pin.

I agree. get the right sized pin/bolt even if you need to enlarge the hole on the end of the cylinder. have you elongated (egg shaped) the hole in the top of the grapple?

 

[Coyote machine]

I'd use a properly sized pin and thread both ends outside the clamping force area so threads would not be a factor. Use lock washers and nuts to complete the job. And consider backing the SS relief valve to just under the pressure at which the current bolts are breaking. You need to grapple the material not crush or pulverize it. And breaking things is counterproductive to effective use of machine and manpower. Cost also factors in on downtime.

 

[SPYDERLK]

I'd use a properly sized pin and thread both ends outside the clamping force area so threads would not be a factor. Use lock washers and nuts to complete the job. And consider backing the SS relief valve to just under the pressure at which the current bolts are breaking. You need to grapple the material not crush or pulverize it. And breaking things is counterproductive to effective use of machine and manpower. Cost also factors in on downtime.

:thumbsup: Thats an effective mechanical plan eliminating stress risers from the shear area. The forces the cyl is capable of at supply/relief pressure is not significant to the pin failure however. It is the significantly higher force that occurs when work prys or pulls against the tines while the cyl is deadheaded by a closed valve. Double shear on the 1" Gr8 should be in the neighborhood of 100 Tons. Should be more than plenty if the pin is designed correctly.
larry

 

[jenkinsph]

I think I would remove the slop and use 1" cylinder pins. I would also make sure the hydraulic pressures conform to the manufacturers specs, some of the skidsteers have higher pressures than the ag tractors.

 

[grapple man]

i will answer the questions in no particular order. When we break the pins we are doing various things. I am usually the operator and I am also the owner. So with that said I have to pay for my repairs, but i also have to pay for my repairs. What I mean by that is I work my equipment ten times harder than I would expect anyone else to do. So I break pins at different times. Sometimes crushing a tree into submission so I can pick up one or two more and take to the burn pile. Other times when I have ten hedge posts in the grapple and squeezing them so i can take off from the pile to the trailer. Time is important to me and i buy the heaviest attachments I can find to handle the abuse. I know I am going to abuse them, and I buy from a company that assures me they build them to take the abuse. Yes I have the grapples mounted on T770s which are within spec for the grapples. The holes are not egged out, just a little over drilled I will mic them this weekend to see what size specifically i need to fill the void. I appreciate all the input and ideas. The reason it bothers me so much is that when i had the more narrow grapple which we still use 7 years later we rarely break pins, but getting almost twice as wide would add amazing amounts of flex and torque when hauling hudge loads which is my goal with every grab.

 

[Guesseral]

i will answer the questions in no particular order. When we break the pins we are doing various things. I am usually the operator and I am also the owner. So with that said I have to pay for my repairs, but i also have to pay for my repairs. What I mean by that is I work my equipment ten times harder than I would expect anyone else to do. So I break pins at different times. Sometimes crushing a tree into submission so I can pick up one or two more and take to the burn pile. Other times when I have ten hedge posts in the grapple and squeezing them so i can take off from the pile to the trailer. Time is important to me and i buy the heaviest attachments I can find to handle the abuse. I know I am going to abuse them, and I buy from a company that assures me they build them to take the abuse. Yes I have the grapples mounted on T770s which are within spec for the grapples. The holes are not egged out, just a little over drilled I will mic them this weekend to see what size specifically i need to fill the void. I appreciate all the input and ideas. The reason it bothers me so much is that when i had the more narrow grapple which we still use 7 years later we rarely break pins, but getting almost twice as wide would add amazing amounts of flex and torque when hauling hudge loads which is my goal with every grab.

Not to be a smart a&& or seem like I know the answer but it could just be a design flaw. To me it would make sense that at twice the width, more weight, and more weight capacity (I just say more because I don't know the spec's) that the stress on the pins would be much greater and that there should be twice the cylinder. What I mean because that sounds stupid is that there should be two cylinders to spread out the clamping force which should cut the force on the pins in half, 1/2 on one side and 1/2 on the other.
That might not make sense to others but it sure makes sense to me!

 

[Xfaxman]

Not to be a smart a&& or seem like I know the answer but it could just be a design flaw. To me it would make sense that at twice the width, more weight, and more weight capacity (I just say more because I don't know the spec's) that the stress on the pins would be much greater and that there should be twice the cylinder. What I mean because that sounds stupid is that there should be two cylinders to spread out the clamping force which should cut the force on the pins in half, 1/2 on one side and 1/2 on the other.
That might not make sense to others but it sure makes sense to me!

I think with two cylinders on the single lid, the force at the pins from the cylinders would be the same as if it had one cylinder. The cylinders are in parallel, so the pressure is the same in each one. Any force transferred back through the lid would still be the same in each cylinder.

I have had the Six Tine version since January 2011. It has pins with grease zerks, guess I need to check for slop.

It will break concrete! Squeezed too hard.


This is the other half, notice the fresh break.


Here is a lot of force on one upper tine.


It has never broken a pin.

 

[CJONE]

Install a cross over relief for the clamping cyls. Adjust it down to where it clamps with enough force. But it will allow the grapple to release when the operator gets it into a bind. My guess is this is what is happening with the wider grapples. Cheap fix and gives you insurance as to abuse. CJ

 

[grapple man]

View attachment 343688
I think with two cylinders on the single lid, the force at the pins from the cylinders would be the same as if it had one cylinder. The cylinders are in parallel, so the pressure is the same in each one. Any force transferred back through the lid would still be the same in each cylinder.

I have had the Six Tine version since January 2011. It has pins with grease zerks, guess I need to check for slop.

It will break concrete! Squeezed too hard.
View attachment 343700 View attachment 343701

This is the other half, notice the fresh break.
View attachment 343702 View attachment 343703

Here is a lot of force on one upper tine.
View attachment 343704

good pics,
i love the 6 tine version. we broke some welds on the middle pivot bar, but bridged them up and kept on using the crap out of it. i can just get so much more done with the wide grapples. keeps so much brush away from the machine and out from under the tracks. i can move more brush than a d4 could even dream of in a day. we only broke 6 pins in our 6 tine grapple in about 7 years of use

 

[Xfaxman]

good pics,
i love the 6 tine version. we broke some welds on the middle pivot bar, but bridged them up and kept on using the crap out of it. i can just get so much more done with the wide grapples. keeps so much brush away from the machine and out from under the tracks. i can move more brush than a d4 could even dream of in a day. we only broke 6 pins in our 6 tine grapple in about 7 years of use

Thanks, I have a lot of pictures of this fantastic machine.

Since you are breaking pins from the cylinder force while clamping, I would plug a gauge into the extend coupler and see what the pressure is. 3600 psi on my 6 tine 4" cylinder is 45,239 pounds of push.

Does the 10 tine wide use a 5" cylinder?