Now what did I do?

[Alpha Dog]

OK folks, I finally got the 3rd function and my grapple installed. Reinforced bucket, necked it down from 3/8" to 1/4" hoses to the grapple cylinder like was suggested here on my last post.
I went out to the farm yesterday to move brush, and as I picked up the second bucket full of brush (biggest stuff maybe 2 to 3 inches in diameter, nothing heavy), I noticed the grapple wasn't "grappling". I raised the bucket where I could see it, and noticed that the ram part of the hydraulic cylinder was "a little bent" (OK, a little bit of an understatement, it was bent at around 30 degrees, at about 9/10ths fully extended).
(see picture).
My question is: What did I do wrong?
The cylinder is 1.5" x 10" x .75" and had 3/8" ports, which I necked down to 1/4" to fit the hoses. I had picked up one bucketfull of brush and dumped it, so this most likely happened as the grapple closed around a second load of brush and I started to back up with it. (As far as I could tell, there was nothing on top of the grapple or between it and the cylinder as I started to back up.)
Since at about $100 per cylinder, I can't afford to do this too many times, I'd appreciate any input you folks could give, before I go buy another cylinder.

 

[J_J]

Did you make this grapple?

It looks like you have a straight on push. Geometry is not correct.

One of the ends of the cyl should be higher that the other. Otherwise, the cyl should start pushing at an angle not straight.

Can you show a picture of the whole cyl?

 

[wdchyd]

the bent cyl was probably caused by an induced load (backing up and snagging on the ground).....the "over-pressure" has no way to relieve itself when the control valve is in neutral.....if it had a work port relief in the control valve then the cyl would just retract when it hit that condition...

Another thing for you is to check that hose crimp in the pics.....it looks like a Gates hose end that was not properly crimped, it shouldn't have a bulge on the neck

 

[wdchyd]

Did you make this grapple?

It looks like you have a straight on push. Geometry is not correct.

One of the ends of the cyl should be higher that the other. Otherwise, the cyl should start pushing at an angle not straight.

Can you show a picture of the whole cyl?

Yes, the geometry is a contributing factor, leverage can either with you or against you

 

[J_J]

I was also thinking the cyl rod might be to long. Otherwise when grapple is closed all the way, you have maybe, 3 more in of cyl rod to push out. If the relief does not go off, you will push out a weld or bend the shaft.

Remove the rod end connection with the grapple down extend the rod al the way and see if the cyl pin hole is way past the tabs on the grapple.

You will not be able to do it with that cyl, but you can measure the distance .

Did you do a test run with you off the tractor to see if things were working correctly, such as binding or hoses rubbing, etc.

 

[Alpha Dog]

OK, looking at what you guys mentioned,
1. It's not homemade, the tabs on rear of the bracket are higher than the front mount.
2. I had the hoses made by a local shop, putting 3/8" fittings on the 1/4" hose at that end, rather than bushings, to reduce the number of fittings I'd have to deal with, and there are no bulges in them I can find.
3. As you said, I can't check for length with that cylinder, but I am now suspicious.
(FYI, I took the grapple off when it bent, I had other work to do, so the pictures show it after I set it back in place today, hence the pins not secured, the hoses "draped" rather than covered with a protector, etc.)
4. I did buy a commercially made 3rd function "kit" but I don't know how/where any "relief" works on it, so I'll have to check that.

However, the "geometry" comments made me think of a possible cause. I put the whole thing together after reinforcing the bucket, and tested it for fit and function. At the time, I heard contact, and it appeared that the tines contacted the bucket on the inside, at the "ripple" behind the cutting edge of the bucket. (picture of grapple "down" after it bent).
When I just went out to my "re-mocked up" tractor and "stepped on the grapple" (can't hurt that cylinder anymore), it "popped" and went into the bucket almost to the back before being stopped by the cylinder. I noticed that the bottom of the cylinder itself was now "in contact" with the back of the "web" on the grapple.
So my guess is (without another cylinder, I can't check this yet) that the "clank" I heard when I lowered the grapple when testing was NOT the tines hitting the bucket, but the cylinder hitting the back of the web, and that the cylinder extended just long enough beyond the "proper length" that when it pushed on into the bucket (as the brush broke and compressed), that there was pressure on the bottom of the cylinder, which is the direction it would have to be for that particular "bend." (picture of grapple after I just "pushed it past where it stopped before).
Even though I measured and confirmed with the grapple maker that this one would fit, I took my measurements BEFORE I reinforced the top of the bucket, which made the mounting point at least 1/4" higher than the original top of the bucket (probably more than that, as the top wasn't as "sharp" as angle iron, and not exactly 90 degrees). That would have changed my measurements just enough to let the grapple go too far into the bucket. (Hindsight being what it is, but I should have thought of this).
If this seems logical, let me know, because the easiest "fixes" I can think of for that is to weld some "spurs" on the grapple's tines, to prevent it from going far enough into the bucket to allow the cylinder contact the web (and probably "relieving" the back of the web a little larger than the diameter of the cylinder for an inch or two as "insurance," and re-measure to see if I can use a cylinder that extends a little less than the one I destroyed.)
That should prevent the grapple from "over-extending" and putting it in a bind, (which is what I HOPE happened, as it seems easy enough to fix).

 

[wdchyd]

yep, I see it now....the doggone thing was trying to bend the cyl around the corner..:confused2:

 

[wdchyd]

When you get the new cyl, best to move the cyl manually through the motions with the hyd lines off to watch for clearance issues and/or binding

 

[gengine]

I think wdchyd said it.:laughing: If you can deal with your grapple only closing as far as it is in the first picture of post #6, then it looks like you can just get a cylinder with two inches less stroke. If you need it to close all the way, then I think your going to need to do some sort of fabricating. I don't know how much webbing is in there or how much you really want to remove. When you pick up a new cylinder, pin it on there before any hoses and move the grapple through it's full movement and make sure you have the clearance you need. If the cylinder hits the webbing again, pull a pin and see how much more rod is still in the cylinder. You'll know which way to go from there. Good luck!

 

[J_J]

Use some PVC pipe with in a pipe to see just what size cyl rod you need and or raise the tabs on the grapple or both.