Strong grapple (last question i promise!)

polemidis · Jan 26, 2018

I finished this grapple.

And did some FEM analysis, and revealed that I need to tweak it a little bit.

The only place that I am stuck and cannot analyse due to my software's limitation is the lid. Can anyone help me with his experience? What should be the thickness/size of a) the square tubing on the lid where the cylinder rod pushes? b) the thickness of the flat plates on the lids (the oily color)
I am pretty sure that the 2" x 2" x 1/8" sq. tube will be bent by the cylinder force. What you guys have? 1/4" or thicker? and the plates I have are 1/8". Should I make them 1/4"?? Obviously weight is our enemy on the FEL, I do not want to put anything more than I need. Like this the whole grapple is 432lbs (mostly made out of 3/8" steel). What do you guys have on your grapples plz?

I am one step before fabricating this monster. I think everything else is fine (well, in theory at least!

)

oosik · Jan 26, 2018

Well - I have in a grapple, what you are trying to stay away from - HEAVY. My Land Pride SGC 1560 weighs - 820#. The entire unit is 5/8" high carbon steel. Sooooo....... I would guess, 3/8" steel for the lid would be very adequate. My experience with this Land Pride grapple - it can be used for most anything short of a battering ram and suffer absolutely no damage. Its the type implement I can appreciate.

Your lid will only provide containment and very little, if any, support. However, you just might eventually use the lid for "breaking the soil" and back dragging to smooth/level an area. So consider those requirements when designing the lid - that's why I suggest 3/8" for the lid.

A suggestion - make the purple "arms" toothy on the top side, back to where they bend upwards and the yellow top arms toothy on the bottom side. Simple, small teeth will assist in holding any load more securely.

ovrszd · Jan 26, 2018

Anxious to see your production model in action!!

polemidis · Jan 27, 2018

ovrszd said:
Anxious to see your production model in action!!

I am too! I am logging all this winter and I have limbs everywhere. And I no longer try to pile the logs that I skid with the pallet fork, its so much pain. The grapple will make it 5x faster

But I still haven't figure out the square tube on the lid. Almost everything else is 3/8", the square tubing on the main body are 1/8", the lids most likely will be from 1/4". But the cylinder force will try to bent that square tube on the lid. I do not know if 1/4"will be enough there. Trying to get some input from you guys

polemidis · Jan 27, 2018

oosik said:
Well - I have in a grapple, what you are trying to stay away from - HEAVY. My Land Pride SGC 1560 weighs - 820#. The entire unit is 5/8" high carbon steel. Sooooo....... I would guess, 3/8" steel for the lid would be very adequate. My experience with this Land Pride grapple - it can be used for most anything short of a battering ram and suffer absolutely no damage. Its the type implement I can appreciate.

Your lid will only provide containment and very little, if any, support. However, you just might eventually use the lid for "breaking the soil" and back dragging to smooth/level an area. So consider those requirements when designing the lid - that's why I suggest 3/8" for the lid.

A suggestion - make the purple "arms" toothy on the top side, back to where they bend upwards and the yellow top arms toothy on the bottom side. Simple, small teeth will assist in holding any load more securely.

Sorry I have caused some confusion. Almost everything is 3/8" (the blues tines, gussets, hitches), the lids that are opening and closing (pink) are designed of 1/4", the oily plates from 1/8". My big question is the smaller brown square tubing on the lids (where the cylinder force is applied). 1/4" thickness? more? Excess weight is a big problem of course.

polemidis · Jan 29, 2018

So I sent this nesting to the supplier just to get an estimate (I forgot 2 pieces!). The cutting service is $300, and the charge for a whole sheet (4'6'' x 8'8'') of 3/8" steel is $388 for mild and $447 for A572 gr50. Small difference I think. $70 dollars for a lifetime tool is not much. I may ask him for the next grade to see if it also small difference. For some reason it looks cheap! for only 10c/lb i think it worth it to build it from the stronger steel.
SO the whole grapple will be a HUGEEEEe savings project!!! I mean really huge! I already hear whispers saying "backhoe, backhoe" in my ear!! hahahahahah

2458n · Feb 19, 2018

Get to cutting. Go with what you have figured. Performance should be great. If you tear it up so what you. you built it once. fix and move on.

rfc143 · Feb 20, 2018

I was going to suggest losing the holes (or making them smaller) at the stress riser where the lower jaws turn, but I see you've done that. Looks like a fine design. You do this in Solidworks? Want to send me a resume, lol? We're always looking.
One last thought: I've never really understood the dual lid thing. Why not a single lid powered by two actuators? I think the holding force would be much better.

polemidis · Feb 20, 2018

Not Solidworks, its expensive

I am using Freecad v0.17
About the dual lid, the only reason is to be able to grab uneven stuff. Like picking up firewood from a pile, or maybe brush

About resume lol!! Its funny that I was just looking to craiglist about maybe put an ad to offer CAD design!! My resume is just one year "playing" around with CAD. I mean one year ago I didn't know what CAD was!

But I love it. I mean I really love it!

I will sent you a PM

John_Mc · Feb 20, 2018

rfc143 said:
One last thought: I've never really understood the dual lid thing. Why not a single lid powered by two actuators? I think the holding force would be much better.

A single, wide lid can cause problems when grabbing a long log if it's not fairly straight & even: when the lid clamps down on one end of the log, it stops moving. The other end of the log may not be gripped at all, which allows that end to swing out of the grapple. This is why dedicated logging grapples tend to grab at three points (two on the bottom, and one from the narrow top). A wide single lid tends to pinch an uneven log at one point - the upper and lower grip one one end are right above one another