keep breaking pins in my grapple

[TomSeller]

If in doubt I would keep feeding them grade 8 bolts so something else does not break. Curious what the mfr will say. Is it the top or bottom pin that is breaking, or both? Nice grapple you have.

http://www.sidneyattachments.com/10tinewidegrapple.php

 

[grapple man]

wow, thank you for all the replies. I have been buying attactments from this company for 7 years now and I have talked with them several times about this and other issues. As what I have found to be the norm for me when I have an issue the response is always wow you are the first time we have had the problem. BLAH BLAH. Anyway yes the bolts are breaking typically right where the threads meet the shoulder. I have very little gap between clevis and knuckle on grapple. I will check with the company and also going to try the blanks as soon as i can get them

thanks again

 

[grapple man]

If in doubt I would keep feeding them grade 8 bolts so something else does not break. Curious what the mfr will say. Is it the top or bottom pin that is breaking, or both? Nice grapple you have.

10 Tine Wide Gorilla Grapple - attachments for skid steer loaders, small compact construction equipment - Sidney Manufacturing Co. LLC

ha i was just looking thru my thousands of photos to post a good pic of the grapple and couldn't hardly find one. Yes they are really nice grapples we have two of the ten tine wide and one 6 tine one. the top pin is the one that breaks most often which this pin would be subject to much more flex and torque. Anyone have any suggestions for the best way to take up some of the slop i have in my holes. i will post one of my you tube videos. one minute.

 

[TomSeller]

ha i was just looking thru my thousands of photos to post a good pic of the grapple and couldn't hardly find one. Yes they are really nice grapples we have two of the ten tine wide and one 6 tine one. the top pin is the one that breaks most often which this pin would be subject to much more flex and torque. Anyone have any suggestions for the best way to take up some of the slop i have in my holes. i will post one of my you tube videos. one minute.Video Link: http://youtu.be/WtniM8BXCxA

The forces have to be equal and opposite on the cylinder so as long as you have a grade 8 in the bottom you should protect the equipment. I wonder if a stronger and maybe smaller diameter pin would work in a test try, in case it is the twist or flex at that end that starts the break in the pin.

 

[Guesseral]

To get rid of slop like that I have welded the hole shut and re-drilled it, just how large is the pin I don't remember seeing a size. You can get 3pt hitch pins for cat 1, 2, 3 they get pretty large. Or you could always go to a machine shop have them mic it and make a pin for it, I am sure they can get something stronger than grade 8.

 

[MechE1]

Wow. Very interesting. I would never design a cylinder/clevis joint like this using a bolt, and I have designed hundreds up to and over 50 tons of force. You should change this out with a properly fitting pin. Although grade 8 bolts are strong, they are also brittle and are designed to have strength when torqued, but not with side loading. There should be pleanty of pins available via hydraulic suppliers that would work for your situation. You'll have to check clearances along with diameter. If you have trouble finding one let me know.

 

[jmc]

That slop shown in the video could add impact loading on top of everything else.

 

[TomSeller]

That slop shown in the video could add impact loading on top of everything else.

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

 

[SPYDERLK]

no worries on the having problems. I have been in business several years now its all part of it. There is no doubt I use my equipment to its fullest potential and then some. I buy heavy stuff for that reason. We have had smaller grapples from this company and did have near the issue. These new ones are considreably wider and picking up 5000 lbs of material and squeezing it hundreds of times a day is hard on stuff. I think the issue is cause when the grapple teeth do not contact the material all at the same time allowing the teeth to torque different angles such as on a curved log or logs. And yes I understand your logic of having the cheaper pin break rather than the cylinder.

I am thinking of trying grade 8 bolt blanks since i am sure the threading process does weaken the bolt.

Breaking pins often cause secondary damage that is difficult to fix. The absence of stress risers is what you need. You are not actually breaking the bolt or pin, but fatiguing a specific weaker area on it. Your breakage is undoubtedly originating at a stress riser. A bolt whose shank extends all the way thru the stress area would work. That might be cheaper than the bolt blanks which will undoubtedly work.
larry

 

[TomSeller]

What are the operators doing when the pins break? Holding loads on the bottom of the grapple does not take much force. Are they crunching concrete? Dragging with the lid?