SSQA multi use base

[Stomper]

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.

 

[wuntun]

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.

 

[wuntun]

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.

 

[Stomper]

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.

 

[wuntun]

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.

 

[Stomper]

Heres where I'm at now. I made up all the cylinder mounts and just have them tacked in place for now. I will pick up the rest of the hydraulic parts tomorrow and cycle everything to make sure it works before I weld it solid. After that all it should need is some paint.

 

[goeduck]

Looking good !

 

[LouNY]

The only thing I see and it may be to late to do anything about is the grapple doesn't reach to the end or past the tips.
That is how my grapple is built and at times to grap something I have to go to almost full curl to get the grapple close enough to the ground, example a 6" log flat on the ground and you can't or don't want to drive into the ground and get the bottom under the log and then clamp it, I have to curl way under to get the grapple points close to the ground to try and clamp the log.
View attachment IMG_20171013_105931483.jpg
if the grapples where longer I think it would be easier to get ahold of some things.
But your build is impressive, looks good.

 

[Stomper]

Thanks and good point about the grapple length. That actually crossed my mind as I was measuring up for the cylinder length but it was too late. I designed the grapple length without the removable teeth installed on the bucket and thats where I went wrong. The teeth add an extra 3 to 4 inches. If I find it too much of an issue I guess I could add some length to the grapple arms just past the cylinder mount. I didnt think it would be an issue but thats where my lack of experience with using a grapple come in I guess.

 

[Stomper]

Well I took the advice of some of you and extended the length of the grapple as well as the stroke to have it open more. It was s bit of work but I think it was for the best. I still have to build a cover to protect the cylinder and finish the pivot shaft.