Boom Grapple Build

[Oasis]

Hi,
This is a boom/grapple combination. Besides the typical FEL hydraulic functions the boom can also be extended and swung left and right manually. The grapple runs off the tilt/curl function by way of a switching solenoid valve.

Why:
This tool is primarily for handling rock used in the constructing of ornamental ponds, streams, and waterfalls? I have access to a quarry where I run around collecting rocks that weigh a few hundred pounds each. I load them onto a trailer. I do a lot of work around homes and in established landscaped areas. The attachment is designed for use with my compact JD790. This attachment lets me grab a rock off my trailer and place it without having to dump rock or setup a backhoe working in tight places, with very little impact to yards....

Design:
Most of the designing was done in my head while working. I spent some time considering the pros/cons of other equipment and techniques that I've used, hit the drawing board and later shared a sketch for feedback. I wanted some extra reach for working off my trailer and for placing rock on slopes the swing would be handy for avoiding obstacles and for placing rock into awkward positions. A three-point grapple would offer a stable grip and minimal interference with adjacent rocks. After some consideration I decided to place the cylinder behind the grapple rather than on top of it. Again, less interference (and more protection).

I developed a small-scale plan on grid paper while calculating: geometry, cylinder specs, materials, weight... I used that to draw a slightly modified full-scale pattern using a compass, straight edge and a batten. I used the pattern (paper-doll style) to double check the geometry; cylinder movement, and jaw function The cylinder is larger than necessary here but it will also be used to power other attachments. Because of future plans I wanted to plumb my hydraulics with an adjustable relief valve anyway.

As you will see I strayed from the plan in a few places while building.

 

[magicheater]

That is a very neat concept. I am sure you have calculated the lifting ability which would be considerably less than the loader capacity. Does this use a Q/A plate for mounting? Personally I would not use the swing past the width of the loader arms. It would complicate the project too. Would it be hydraulically operated or have a finite amount of pin settings? What size stone are you using?

 

[Oasis]

Build:

The patterns were traced onto steel. Radius cuts and some large diameter holes were needed so I made a circle cutter for my torch. I used parts that I had on hand for this. The long threaded stainless rod was scrounged from a shipwreck that I found years ago. 的f what you want isn't washed up on the beach, you probably don't need it. Mosquito Coast (a classic DIY book/movie).

I used the circle cutter or a straight-line guide where I could. The rest was done free hand.

 

[Oasis]

Jaw Hinge:
The inner axel is a thick walled tube with a zerk recessed into one end. The other end is plugged. The tube has small holes drilled through it to allow grease to squirt between the inner and outer tubing.

 

[Oasis]

I made the typical FEL frame and then a triangle boom about 4 feet long with an extension. The arm pivots on pins and plates. The top plate has a series of index holes to lock the boom at a swing position.

 

[Oasis]

I used a solenoid selector valve for this. In case this is new to you; when the solenoid is activated, hydraulics are diverted from the FEL curl/tilt function to the grapple open/close. The switch for the solenoid is on the FEL joystick. I tried a push-on/release-off switch but decided to use a push-on/push-off switch. The sealed switch and housing are parts from my other profession.

 

[Oasis]

Use:
I've moved several tons of rock, a few brush piles and some firewood. The attachment works great. It seems to have a good strength to weight ratio and is a good match for the JD. Obviously it must be used within limits regarding load and balance especially at full extension and in the severe swing positions Naturally I use it in line and fully retracted, load near the ground...whenever possible. The maximum hydraulic lift is about 4-500 pounds, which also makes the JD pretty unstable. A good practical load is up to 300 pounds, which is what I was expecting.

 

[Oasis]

The 30" opening takes a pretty good bite from a brush pile. The easy reach with this light material is great for loading over the sides of my trailer...

 

[Oasis]

Costs:
I had some scrap and also hit the steel yard at $0.35 Lb x150, cylinder $46, selector valve $139, relief valve $90, pressure gauge $10, lines and fittings $200, teeth, pins, bolts $40, switch/housing/wire $40.

Thoughts:
The time spent planning, testing, making paper patterns was time well spent. Cutting and welding was actually the easy part. There are dozens of adapters, reducers, and elbows in use here. I drew a plumbing plan, which was a big help when buying parts and later installing them. I was glad to see all of the parts fit in the space I had planned for this. The worst part of this project was seeing some leaks after it was all put together. I had used Teflon paste on the NPT fitting (it worked in the past). I decided to take every thing apart (cleaning was a pain) and redo with high density Teflon tape, which I read about here_ good stuff.


Improvements:
I added a LED to indicate that the grapple function is on because knowing that can be critical at times. I extended the gussets on the grapple claw because I saw some flex there during awkward lift angles. I may add a flow control valve on the bucket tilt lines because it's pretty easy to move that function to fast.

 

[lhfarm]

I'm not sure what is more impressive - the design, construction or how well it works. You must get incredible satisfaction every time you place one of those rocks. Thanks for sharing. I'd love to see pictures of some of your projects accomplished with the grapple.