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  1. #31
    Silver Member
    Join Date
    Jul 2017
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    114
    Location
    Denare Beach
    Tractor
    2017 Kubota L2501

    Default Re: SSQA multi use base

    Quote Originally Posted by wuntun View Post
    Stomper, there is a formula, and the result is a variable graph, but it won't be necessary to do that for approximate force calculations. What your designing is considered a third class lever, with a velocity ratio. For a somewhat accurate force applied after the mechanical disadvantage, use distance from *grapple pivot pin* to the *hyd. cyl. pin* that pushes on the grapple. (let's say 6" for this example) You state to expect 6908# push at that pin, so, at same distance (6") measured from grapple pivot pin toward end of grapple, that force would be the SAME (excluding frictional losses). Now, (assume grapple is 24"), measuring out 6" = 6908#, 12" out = 3454#, 18" out = 1727#, and lastly at 24" at the tip of grapple = 863#. Your definitely not going to be "pinching" stumps in two, or cracking rocks with 863#'s of force, lol, but sure enough will crush old limbs and branches in two if they are caught nearer the middle of grapple at 3454#'s. Think the best analogy (albeit reversed) to lever vs. force is picture torque wrench, one foot long, would take 100# pull on the handle to get 100# torque. Likewise, a TWO foot torque wrench would only need 50# pull on the handle to get the *same* 100# torque on bolt, and so on and on with 3' wrench etc. Torque wrench GAINS power with length, but grapple LOSES power the further away from pivot pin. I have designed and built several hydraulic excavator thumbs, bucket grapples, and dump gate latches over the years. It can be very disappointing to build something without a solid design, only to find your efforts wasted because it is not strong enough, or worst yet, TOO strong and breaks equipment. I commend your undertaking the task to research it fully, you won't regret it!
    Thanks, That is how I thought it was figured out but wasn't 100% positive. Where I was confused was, I wasn't sure if the angle of the cylinder push direction, in relation to the direction of the force I wanted, had anything to do with it. At one point in the cycle when the grapple is being closed (or opened)the cylinder push is 90 degrees to the direction of force I want applied. In other words, I want the force to be straight down but the force applied is horizontal. I hope that makes sense.

  2. #32
    Member
    Join Date
    Jan 2011
    Posts
    40
    Location
    Sandhill, Ga.
    Tractor
    JD 4310 JD 790

    Default Re: SSQA multi use base

    It makes sense what your saying, and I may have responded too soon, and apologize. I mis-spoke that it is 3rd class, but should have typed 1st class, (think scissors or see-saw). But I was without knowing *your* intention of cylinder mounting position. If your going with a bell crank type, with the cylinder *behind* the bucket, the forces I listed will apply. The second image (yellow) is what I thought you were wanting to do, (and it may be). If your going for more of the brush/debris type grapple like the first image (black), then the calculations will be different. I suppose you could make a mock-up of your design, similar to how you posted the plywood grapple 'tooth' in mock form, and post your dimensions we could make a calculation from that. I usually make my mock-ups with cardboard, and run it through the motions, and see if they perform the intended function.
    Attached Thumbnails Attached Thumbnails SSQA multi use base-rgb_loflin_brush_grap3-jpg   SSQA multi use base-bradco-84-root-rake-grapple  

  3. #33
    Member
    Join Date
    Jan 2011
    Posts
    40
    Location
    Sandhill, Ga.
    Tractor
    JD 4310 JD 790

    Default Re: SSQA multi use base

    Here is another (first class lever) setup, to give some ideas there is more than one way to do it. Just *remember* during mock-up, to curl the bucket all the way back, and cycle your 'cardboard grapple' to check for interference with loader crossbar/hose connections/hood and grill/headlights/etc. before committing to cutting steel.
    Attached Thumbnails Attached Thumbnails SSQA multi use base-maxresdefault-jpg  

  4. #34
    Silver Member
    Join Date
    Jul 2017
    Posts
    114
    Location
    Denare Beach
    Tractor
    2017 Kubota L2501

    Default Re: SSQA multi use base

    Sorry for the late reply, I have been out of town. The cylinder mounting design that I will be going with is the same as the black grapple style in your post #32. I have mocked up a cardboard cylinder and have cycled the grapple and it clears everything nicely. This is how I came up with the 8" stroke, 16" retracted and 24" extended, giving me a 36" grapple to bucket opening.
    I will however, also be building a grapple arm for my pallet forks very similar to the link below that is the same configuration as the yellow one in the same post.

    Grapple attachment for pallet fork with low frame.

  5. #35
    Member
    Join Date
    Jan 2011
    Posts
    40
    Location
    Sandhill, Ga.
    Tractor
    JD 4310 JD 790

    Default Re: SSQA multi use base

    Sounds like a solid plan. That is a interesting design on the pallet fork grapple. Let's see some pics when you get some more progress.

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