Grapple build question

[fasttruck860]

I'm just about to get started building a grapple after going back and forth over design and lead times. I have a friend that owes me a favor and is providing the cnc cut AR400 steel for free which will be all the tines. I'm going to fabricate the mounts, brackets and braces. The one issue I'm unsure of is the clearance for the hinge tubing and hinge rod. I'll be using DOM tubing and most likely a solid steel rod for the pin unless I should be using something else. I was thinking at least a 1" rod. What should I leave for clearance for grease, 1/16" or 1/8" or should it be tighter? I don't have a lathe so shaving it down will be difficult but I'm sure I can figure something out if I need to.

 

[texasranger556]

I just modified a bucket to fit my small backhoe by building new ears, ended up with about 0.030" clearance between the 1.25" pins and holes on the bucket ears.

 

[oosik]

I have no idea what the clearance is on my keeper pins on the "lid" of my grapple. It must be pretty tight. With the hydraulics disconnected on their connection to the upper lid - I can lift/shake the upper lid and it just moves smoothly up/down. No apparent looseness or rattle.

I have a Land Pride - SGC1560 grapple. 60" wide, 820#. The pins that hold the hydraulics to the upper lid, pins that hold the hydraulics to the bottom of the grapple and the pins that hold the upper lid to the grapple - all are 1.25".

 

[fasttruck860]

Okay. So it looks like I'm aiming for a tight fit or about 1/32" clearance. I'll have to look into increasing the pin size, although the thickness of steel around the mount would start to suffer.

 

[ptsg]

On my homemade loader, I left about 0.004" to 0.006" clearance between the pin and the bore on all of the pivot points. It's loose enough that you don't feel any play and grease can still go in just fine.

 

[mikester]

You need to decide on how sloppy you want your fit.

Start with google "greaseable pin hole tolerance chart"

also consider using bronze bushings and beef up your pin bosses.

Sloppy fit + high force loads = unhappy customer

 

[fasttruck860]

What type of steel should i use for the pin? This will be a single lid so only one pin.

 

[LD1]

You need a set of dial (or digital) calipers for measuring pin clearences. something that will measure in .001" of an inch. Not a tape measure reading fractions. 1/32 is WAY too sloppy for a pin in a greasable bore. .004-.005" is sufficient. Any sloppier and your hole will be oval in no time. Not due to wear, but hammering.

You mention ONE pin because its a single lid. Not sure your design....my single lid has TWO pins at each end.

IF you dont have a lathe....shoulder bolts are a pretty exact size and quite hard. ANd if you get the right length you can secure with a nut and not worry about squeezing too tight and binding....and no cotters to loose in the brush. You can also get nominal size bronze bushings for pretty cheap

 

[fasttruck860]

That all makes sense and gives me more to think about. I think the size DOM tubing I'm planning on using has a tolerance of -.005" ID so I'll just figure on a tight fit and look into the shoulder pins. I was thinking a single pin because this will be a single piston upper lid, although I can easily make two pins work. A single long pin is going to be much harder to get aligned correctly especially if anything warps from welding.

 

[fasttruck860]

You need to decide on how sloppy you want your fit.

Start with google "greaseable pin hole tolerance chart"

also consider using bronze bushings and beef up your pin bosses.

Sloppy fit + high force loads = unhappy customer

You need a set of dial (or digital) calipers for measuring pin clearences. something that will measure in .001" of an inch. Not a tape measure reading fractions. 1/32 is WAY too sloppy for a pin in a greasable bore. .004-.005" is sufficient. Any sloppier and your hole will be oval in no time. Not due to wear, but hammering.

You mention ONE pin because its a single lid. Not sure your design....my single lid has TWO pins at each end.

IF you dont have a lathe....shoulder bolts are a pretty exact size and quite hard. ANd if you get the right length you can secure with a nut and not worry about squeezing too tight and binding....and no cotters to loose in the brush. You can also get nominal size bronze bushings for pretty cheap

How would I use the bushings without a lathe? I'm struggling to visualize how this would work. I can think of one way but that would require using a larger ID tube on the ends and just inserting the bushing.

 

[jthibodeau89]

How would I use the bushings without a lathe? I'm struggling to visualize how this would work. I can think of one way but that would require using a larger ID tube on the ends and just inserting the bushing.

You got it, larger ID tube sized for bushing. Here are a couple pics of the pins on my MTL grapple. Not sure if it has bushings. Pin is 1". If you plan on a single wide claw, you may want to consider 3 or 4 separate hinge pins, not just one on each end.
View attachment 695820

 

[fried1765]

You need to decide on how sloppy you want your fit.

Start with google "greaseable pin hole tolerance chart"

also consider using bronze bushings and beef up your pin bosses.

Sloppy fit + high force loads = unhappy customer

I modified my new (low end ) grapple to include both brass pins (greasable) and bronze bushings.
Any measurable wear will be easily correctable, by replacing the pins and/or bushings.
I was able to find 1" bronze bushings only .0625 thick.

 

[fasttruck860]

You guys have been a wealth of information. This is exactly what I needed. I'm going to modify my plan a bit and make sure I order the correct ID pipe for the brass bushings. One last question, can one end of the pin free float or is it better to bolt both ends?

 

[metalbender]

A little different take on home built. Mine was fabricated from old rod weeder parts. No bushings, just big bolts. Made this as a grapple/ rock digger. Bottom spikes are 3/4 inch thick. Tops are 5/8. Good quality steel in those old implements. Not perfect but the price was right.

 

[jthibodeau89]

You guys have been a wealth of information. This is exactly what I needed. I'm going to modify my plan a bit and make sure I order the correct ID pipe for the brass bushings. One last question, can one end of the pin free float or is it better to bolt both ends?

See my pics above for pin lock.

 

[fasttruck860]

See my pics above for pin lock.

I can't seem to view your attachments above.

 

[fried1765]

You guys have been a wealth of information. This is exactly what I needed. I'm going to modify my plan a bit and make sure I order the correct ID pipe for the brass bushings. One last question, can one end of the pin free float or is it better to bolt both ends?

You can order most any size bronze bushings online, or on E-Bay.

I put nuts on the ends of my two primary pins (had to thread the pins).
Others, I just drilled holes through, and used "hair pins" at each end.

 

[jmc]

Random thoughts...

Anecdotally, TBN member IslandTractor reported taking apart the jaw pivots on his inexpensive, but well used grapple and found that the axles were just regular bolts. So their wearing surface was the threads' crests. there were no grease zerks and the thread crests show some wear but not enough to replace, IIRC. I wouldn't build mine that way but it suggests that maybe those pivots are forgiving.

IIRC, a bolt's unthreaded section, if it has one, is usually smaller than its nominal diameter. (that might be because a rolled thread increases the major thread diameter so they undersize the blank) If that's the case, that undersize might be enough clearance with a tube ID that's precise. Still, with only a few thousandth of an inch clearance, a straightness problem with either component may require more slop or correction.

Maybe try a long bolt with a useful unthreaded length and cut off the excess thread.

I'd use the softest axle steel available since it's easier to replace an axle than the tubing.

 

[jthibodeau89]

How about now

 

[fried1765]

Random thoughts...

Anecdotally, TBN member IslandTractor reported taking apart the jaw pivots on his inexpensive, but well used grapple and found that the axles were just regular bolts. So their wearing surface was the threads' crests. there were no grease zerks and the thread crests show some wear but not enough to replace, IIRC. I wouldn't build mine that way but it suggests that maybe those pivots are forgiving.

IIRC, a bolt's unthreaded section, if it has one, is usually smaller than its nominal diameter. (that might be because a rolled thread increases the major thread diameter so they undersize the blank) If that's the case, that undersize might be enough clearance with a tube ID that's precise. Still, with only a few thousandth of an inch clearance, a straightness problem with either component may require more slop or correction.

Maybe try a long bolt with a useful unthreaded length and cut off the excess thread.

I'd use the softest axle steel available since it's easier to replace an axle than the tubing.

Mine came with the same sloppy steel pins, and bolts with threads.
Changed all that to brass/bronze pins and/or bushings at all wear points, and added zerks.