Grapple project OPEN SOURCE

[Rustyiron]

I just joined in late, you math guy's make me wish I had paid more attention in school. polemidis, if you would like to see a 7' grapple that I bought over 15 years ago (Lofflin mfg) that has spent it's life on a 115 hp skid steer w/tracks to observe how a hillbilly can abuse one and the results after all those years, I'm a few hours "down the road" from you.
In all seriousness, I have abused it (done things it was not intended for) and I only have "tweeked" one of the lid's a few inches from closing "square". That was pulling logs out from the end and turning. Very good post here and welcome to tbn!

 

[jmc]

In all seriousness, I have abused it (done things it was not intended for) and I only have "tweeked" one of the lid's a few inches from closing "square". That was pulling logs out from the end and turning.

If that's not one of the warnings in every grapple owner's manual, it should be!

 

[texasranger556]

Yes, I forgot it, thank you! But vertical or horizontal? Maybe laminate them to make them thicker too?


Thank you. Is something common usually on the tractor side?

It doesn't really matter because you would be attaching to your tractor hydraulics with quick couplers (which have a range of options there too). You can buy hoses with ORB/SAE on one end and JIC on the other if you want. I stick with JIC on both ends where I can then use adapters so I can interchange hoses in a pinch.

For reference my John Deere uses metric ORB for some connections, ORFS for others, square thread pipe for a lot of the backhoe connections.

 

[ovrszd]

Need to gusset the lower tines

Also needs more bracing in the claws unless heavy high tensile steel is used. Might incorporate a cylinder protector into that part cause it can't be used without one.

 

[Zebrafive]

Got you. I am wondering if it makes the lid more stiff, and if that worths the extra weight. Anyway, I just used the simple approach with bolts/ nuts instead of a tube with a greasable pin. If that fails soon or needs too much greasing I will upgrade it with the enclosed pin.

I think the design is almost complete. I just need some bracing on the lid, some expanded metal at the back and some protection below the cylinder. But I am tired, I need a break from CADing. I will start working on the BoM. What I am missing is a easy way to do the nesting for the CNC. Freecad's nesting tool is in development and does not work well yet.

Here is the step file.
Here are the original Freecad files if someone wants to edit them (needs Freecad v0.17)

With these 2.5" cylinders I get 2130lbs at the closed position
or 1360lbs with the 2" cylinders
And thats the geometry. The cylinder at the closed position is not 100% extended, it has a little travel yet thats why the lids look like they are overlaping the tines.
View attachment 527741

I love the colors! hahaha
View attachment 527742

I have no opinion on SAE vs NPTF ports. Other than the SAE uses a o-ring that seals easier, but the NPT has more fittings available??? What are the fittings on the 3rd function of a tractor does anyone know plz?, I found similar cylinders with SAE ports I can replace them

I would skip the expanded metal for the back. Use sheet metal for under the cylinders. And NOT use NPTF threads/fittings!

IMO go with SAE/ORB fittings. They seal better and are much nicer to work with especially if you have to take then apart in the future. Generally I like ORB male to JIC male 90 (or 45) degree fittings on cylinders then get female JIC hoses which come with swivels.

There is also ORFS (o-ring face seal) which is about the best for sealing and serviceability, but they aren't as common and more expensive.

Also JIC and ORB use the same thread pitch so in a pinch you can add an o-ring to a JIC male fitting and thread it into an ORB port.

Agree!!!

It doesn't really matter because you would be attaching to your tractor hydraulics with quick couplers (which have a range of options there too). You can buy hoses with ORB/SAE on one end and JIC on the other if you want. I stick with JIC on both ends where I can then use adapters so I can interchange hoses in a pinch.

For reference my John Deere uses metric ORB for some connections, ORFS for others, square thread pipe for a lot of the backhoe connections.

Agree! I like hoses with Female JIC swivels, reusable, do not leak, replacement hoses easy to find.

 

[skills4lou]

I would skip the expanded metal for the back. Use sheet metal for under the cylinders. And NOT use NPTF threads/fittings!

Agree!!!



Agree! I like hoses with Female JIC swivels, reusable, do not leak, replacement hoses easy to find.

Just to throw a monkey wrench in...
Did you consider placing the cylinder(s) behind the bucket? Your clamp would pivot at the top of the bucket, with some extra length sticking out the back for a lever that the rod actuates. It solves the angle problem by pushing nearly perpendicular to the lever arm at full clamped position.

 

[LD1]

Just to throw a monkey wrench in...
Did you consider placing the cylinder(s) behind the bucket? Your clamp would pivot at the top of the bucket, with some extra length sticking out the back for a lever that the rod actuates. It solves the angle problem by pushing nearly perpendicular to the lever arm at full clamped position.

But you'd have a heck of a lever disadvantage. So unlikely you would gain much in the long run if anything

 

[skills4lou]

But you'd have a heck of a lever disadvantage. So unlikely you would gain much in the long run if anything

Not really. Maybe I explained it poorly. Google "clamshell loader bucket" for pictures. Compact design, cylinders are protected, and plenty of clamping force. It also avoids the large lever arm going up above the back portion, which is usually the part that gets torn off on large farm equipment that is working round bales.

 

[bcp]

Pictures with cylinders behind.



Root Rake Grapple For Kubota BX

Bruce

 

[marchanna]

Any chance you can get some FEA on it? That will tell you exactly where you need to add gussets

 

[LD1]

Not really. Maybe I explained it poorly. Google "clamshell loader bucket" for pictures. Compact design, cylinders are protected, and plenty of clamping force. It also avoids the large lever arm going up above the back portion, which is usually the part that gets torn off on large farm equipment that is working round bales.

I know what a clamshell bucket is. And what you are describing doing for a grapple is like the root rake that bcp posted a picture of.

The top clamp is a long lever. With the center picot much closer to the cylinder than the tips of the tines. The result is a long lever. The tips of the tines have what looks like a solid 8:1 advantage over the cylinder.

So while there is no reduction due to angle of cylinder mounting.....a cylinder with 8000# force will only yield 1000# or so of bite force.

So like I said, different design with it's own pros and cons....but not really gaining anything in terms of clamp force

 

[Zebrafive]

I am guessing with cylinders in back you might gain in opening size. My Rakemaster grapple is more a root rake design. My only wish is it would open more for picking up larger loads of brush.

 

[marchanna]

I think you値l find there痴 a trade-off of clamping pressure for greater range of opening. I would think the priority for a root grapple is more closing pressure, whereas a brush grapple would more opening capacity.

 

[LD1]

I think you値l find there痴 a trade-off of clamping pressure for greater range of opening. I would think the priority for a root grapple is more closing pressure, whereas a brush grapple would more opening capacity.

Yep, there is no free lunch.

IF a 2x8 cylinder is chosen.....you have approx 7850# of force to work with over an 8" range. THATS IT.

If your grapple travels 80" open to close...thats 10:1 and you will have 10x's less force....IE 785#

If your grapple travels 40" open to close.....you have twice the force at half the distance of the previous example.

 

[Rustyiron]

So while there is no reduction due to angle of cylinder mounting.....a cylinder with 8000# force will only yield 1000# or so of bite force.

LD, back a few posts you gave Richard (ovrszd) his clamping force on his bucket clamp he built, it sounded relatively low but he mentioned clamping on to a large (8'x12'?) sheet of 1/4'' plate (I took that as clamping form an edge, vertically) and having no troubles picking it up. That's a pretty tough "pick", I'm not being argumentative, but I wonder how much is really needed as you can usually clamp with the grapple ''rolled out" vertically, them roll back to more level with the "floor" of the grapple doing most of the work? :confused3:

 

[LD1]

How much is needed I don't know. But hey, more is better right?

 

[Rustyiron]

10-4 :thumbsup:

 

[polemidis]

Just to throw a monkey wrench in...
Did you consider placing the cylinder(s) behind the bucket? Your clamp would pivot at the top of the bucket, with some extra length sticking out the back for a lever that the rod actuates. It solves the angle problem by pushing nearly perpendicular to the lever arm at full clamped position.

Yes I did considered it. But I am loosing LOTS of clamping force because of the lever. I thing that the cylinder end up nice there, and the protective sheet will also double as bracing.

Any chance you can get some FEA on it? That will tell you exactly where you need to add gussets

Freecad has a FEM workshop, that uses Calculix. BUT, its soo more advanced than me. And most tutorials are for building with fountations etc, so it will take me some time to learn it. I decided to take the CAD learnign approach step by step! I know now about the 20% of the functions/commands. And the FEM looks soo scary!!


So what I am doing now is to try to get a nice nesting software, so we can finally have a .dfx file that anyone can take to a CNC machine and get the cut steel. But It will take a while as the Nesting tool of Freecad is buggy, and the whole process is messy. Also trying to figure out a a convenient way to have a repository for future designs also, that will also allow for more immediate development convertations, easier to collaborate. There is so much information on that thread but its lost in the depth of the 16 pagess. I do not expect that anyone will ready all the posts. Maybe a wiki website? I would like to note down all the ideas, and the mistakes also, so the next guy will have some heads up. The BoM is very easy I will finalize it when I find out how much steel I need, and get a guote.

 

[ovrszd]

How much is needed I don't know. But hey, more is better right?

I took more accurate measurements and I actually have 6" of distance between my claw hinge pin and barrel end of the cylinder pin rather than 4". I've gave up trying to calculate my "bite". It's simply above me.

 

[LD1]

I took more accurate measurements and I actually have 6" of distance between my claw hinge pin and barrel end of the cylinder pin rather than 4". I've gave up trying to calculate my "bite". It's simply above me.

Yea, that makes a difference.

Previously your cylinder was on a 7.1* angle, giving 970# of force at the cylinder for being on such angle, resulting in ~776# clamp force at the tines.

With the new measurements, You are on a 12.4* angle. Giving 1688# of force at the cylinder for that angle, resulting in ~1350# of clamping force.

Amazing what just a few inches and few degrees can make.