Grapple Design

[dtd24]

I stayed with the 2x6x1.125 from surplus center

Surplus Center Item Detail

the other was too small. I have two revised designs not sure which is best. Rev 1 has less "mouth", Rev 3 is shaped more like 3RRL.

Need some professional opinions once again. Please ring in on both.

 

[Farmerford]

Number one is best. I roughly scaled your drawing and it appears that the effective length of the moment arm for the cylinder is 4" (perpendicular distance from centerline of cylinder to upper arm pivot) and that the distance from the arm pivot to the tip is 24". That means the force at the tips of the claws will be 4/24, or 1/6 of the cylinder force. A 2" cylinder produces about 6,000# of force at 2000psi. So the force at the tips will be about 1,000#. That is more than enough to hold brush, but if you are using the grapple and bucket as a claw to lift a rock or other object where it must be gripped tightly, then 1,000# of pressure from the grapple tips may be needed.

 

[jinman]

Your design is improving by leaps and bounds. The only thing I would point out is that the grapple tip may still be in the way of some FEL jobs. For example, if you need to scoop dirt that is next to a building foundation, you need to have your bucket flat on the ground, approach the foundation until the the bucket lightly touches, and then curl to scoop the dirt into the bucket. With your grapple, a wall above the foundation would be penetrated by the grapple jaw points before the lip of the bucket touched the foundation. You could curl the bucket back, but then you would miss a lot of material.

I'm just brainstorming and you will always have some tradeoffs. This one might be very minor because you may never use your bucket like I described in close proximity to a structure. If you make the grapple pinned and easily removable like mine, you could remove it and the negative effects would be nullified.

Is a plywood or cardboard mockup the next step?

 

[dtd24]

I think 1 is the best as well. I think 3 may have a problem with retracting as stated about my first design.

jinman, I do get what you are saying, but the grapple will be removable if needed. I would much rather build one with it's own bucket, but trying to keep the cost down. Maybe I will build this one ,play with it awhile, and sell it when I get ready to build the next.

Yes a plywood mock is in order !!!!!!! Just gotta make sure I'm sold on the design.

DaveD

 

[Farmerford]

dtd24:

Note that the hydraulic cylinder base pivot should be located above the pivot for the grapples by about the same distance as the travel of the cylinder. For a 6" travel cylinder, if you mount the cylinder base 6" above the grapple pivot, the cylinder will retract fully when it is approximately vertical. That will give you the maximum pressure on the grapple tips and at the same time allow the grapple to swing back to approximately vertical. Then move the cylinder pivot back an inch or so so that the grapples will pivot back far enough to clear the bucket.

 

[3RRL]

dtd24,
Both your revisions are a great improvement and you have not sacrificed that "cool" look to it.
I'm impressed with your ability to quickly change your design like that. Couple things to consider and you already stated that yours would be removable so it will not interfere with anything you don't need it for.
So concentrate on your most usage now, and what attributes each revision provides best.
-How wide do you want the jaw opening for major grabbing of stuff?
-How small/large do you want the jaw opening when it is shut?
-Will you ever need to buck tree trunks grabbed by the grapple?
-Any other function you want to accomplish with your grapple that your design choice allow/disallows?

It's looking really good now so you should be cutting steel soon.
It would be great to see that thing come to life. Be sure to post a lot of pictures for us.

One thing that IslandTractor stated about the single, wider jaw. I agree with him that a single jaw bucket grapple would have worked for me. After using my dual grapple set-up for numerous tasks, there has only been one incident where the dual grapples, or a wider grapple was needed. That was when I had to grab a boulder with only the corner of my bucket and one grapple. I could not get to it any other way. Other than that, a single grapple would have done me fine....but the duallys look pretty cool.

 

[moeh1]

DTD,
I like the feedback you're getting and your mod design #1 also. I am adding more hydraulics this year, plant to add one of these later myself. One extra tip that I read months ago was in regard to grapple layout so the grapple misses any teeth on a toothbar. If you are ever going to add one of those, now might be the time.
Cheers,

 

[dtd24]

Good point on the tooth bar I have made another quicky design change that I am rolling with. I think I will build the tooth bar too, so I can build around grapple.

 

[dtd24]

Did it again!!!!

 

[moeh1]

I can't believe you marked one as final already, with only 3 pages on this thread. I think once you add the toothbar, it will come out about as far as the grapple, at least then you'd have holes in the wall at the top and the bottom when your try to sneak up on something tight. LOL Have you got a front view to go along with this yet?