The "thumb"

[Sawyer Rob]

Just remember, when you have to grapple all the way open or closed, you want the cylinder ect. out of the way as much as possible, so the forks are useful for "other" operations too.

You don't want your cylinder ect. out there hogging up room on the forks.

SR

 

[WinterDeere]

Just remember, when you have to grapple all the way open or closed, you want the cylinder ect. out of the way as much as possible, so the forks are useful for "other" operations too.

You don't want your cylinder ect. out there hogging up room on the forks.

SR

Agreed, if possible. But that may be easier said than done, right? I may have to settle for "easily removable"!

Most of my usage for forks aside from moving logs, is moving wood sheds around, or packages of delivered lumber. Both are such that a thumb which still protrudes partly over the forks wouldn't be an issue.

So yes, I will try to get it to be completely out of the way / vertical when fully opened. But if that becomes impractical, it may not be a show-stopper for my case.

 

[WinterDeere]

I'll share some pictures of similar style of thumb and forks setup we have here for brainstorming purposes.

When I'm doing DIY projects, I usually look at lots of pictures and absorb as much as possible.

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Hey guys, do most of these thumb assemblies lift off of the frame, or are they welded on? They fall short of opening to 90 degrees, which is one of our goals, but if they easily lift off the frame for those occasions when you need to pick up a tall pallet, then that's no big deal.

I'm thinking that if they are indeed removable, it might make more sense to just sell what I have and buy one of those. I'd still want to weld 3-point lift tangs/pins onto it, so I'd be doing some fab either way (unless I find and buy one that's both 3-point and JDQA), but that might be less work than what I already have.

 

[ptsg]

Hey guys, do most of these thumb assemblies lift off of the frame, or are they welded on? They fall short of opening to 90 degrees, which is one of our goals, but if they easily lift off the frame for those occasions when you need to pick up a tall pallet, then that's no big deal.

I'm thinking that if they are indeed removable, it might make more sense to just sell what I have and buy one of those. I'd still want to weld 3-point lift tangs/pins onto it, so I'd be doing some fab either way (unless I find and buy one that's both 3-point and JDQA), but that might be less work than what I already have.

This one I shared in particular, it's solid with the forks frame and it's made specifically for logs. That's how smaller loggers haven't quite invested in a log crane yet load they trailers with.

You can remove it by pulling the pin for the thumb and the one for the cylinder, although, a little bit of work is needed compared to other solutions that may offer some sort of quick change feature.

The thumb design can vary a lot depending on your needs.

It shouldn't be too hard to create a quick change feature on the thumb that you could simply pull one or two pins and the assembly comes out. Like the concept of the receiver hitches, but a beefy one and mounted vertically so the assembly would slide up to come out.

 

[Xfaxman]

Hey guys, do most of these thumb assemblies lift off of the frame, or are they welded on? They fall short of opening to 90 degrees, which is one of our goals, but if they easily lift off the frame for those occasions when you need to pick up a tall pallet, then that's no big deal.

There is a slide on the forks style: https://www.4startools.com/336S27-Pallet-Fork-Mount-Grapple-336S27.htm

And: PALLET FORK – PRECISION MANUFACTURING

 

[WinterDeere]

It shouldn't be too hard to create a quick change feature on the thumb that you could simply pull one or two pins and the assembly comes out. Like the concept of the receiver hitches, but a beefy one and mounted vertically so the assembly would slide up to come out.

Definitely. In fact that is one of my design criteria, that I must be able to quickly remove it by pulling two pins, and maybe un-doing a Velcro tie for the hoses.

There is a slide on the forks style: https://www.4startools.com/336S27-Pallet-Fork-Mount-Grapple-336S27.htm

Very cool! But they sure do look heavy! I was hoping the more compact rigs that @ptsg had shared in post #38 would be removable, just like the forks.

I guess at this point, I'll probably continue looking at making my own, as I have some time stuck at a desk (doing my "day job") before I'll be able to get to the fab work. I did a quick mock-up last night with the cylinder located lower on the frame, which would require me to relocate my hitch receiver, but not a huge deal:



The cylinder rod actually rides perfectly between the tangs used for the 3-point top link, so this would only be used when the forks are on the loader, and would have to be removed on occasions when I want to put the forks on the 3-point.

Tonight or over the weekend, I'll try to mock up something more like what @ptsg showed us in post #38, with the cylinder mounted horizontally on top of the arm. That could work very nicely, although one of my new challenges has been trying to get something like 135°+ rotation of the arm, which is way beyond what any of the commercial solutions I've seen can do. That would permit the arm to go from full vertical, out of the way for lifting taller pallets, all the way to 45° down for clamping smaller logs back against the frame.

 

[DaBear3428]

@Sawyer Rob had posted this in another thread:



Serendipitous timing, I was both contemplating a grapple and setting up to modify my own 3-point forks for JDQA loader use. One of my primary loader uses is moving logs, all 15 foot lengths, and I do this using a pair of chain chokers arranged as a sling. It works great, but requires a lot of hopping off the seat, and it's not always the safest operation unhooking the chokers while piling logs.

Looking at @Sawyer Rob's rig, I started playing with the idea of using the top link pin on my 3-point fork frame for mounting of a cylinder to control a thumb. I won't need this top link pin when using the forks on the loader, so it's available. It appears all I need is an extra set of tangs welded to the top tube of the fork frame, to let the thumb pivot:

View attachment 777053
(click for full size)

The tube floating in air is the cross-member on the loader frame, need to make sure the cylinder can't collide with that. Shown here with an 18" log, but tested with 6" to 24".

No binding or collisions in full range of travel:

View attachment 777054

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Only potential problem I see, other than needing some more work to pick metal sizing and thicknesses, is that the thumb may tend to lift small logs off the forks due to forming a "V" with the back of the frame at small diameters:

View attachment 777056

I thought I could tune this out with some fiddling of the section lengths on the thumb, but this is the best I've been able to do without either giving up max capacity or causing a potential collision / bending metal between the cylinder and loader cross member or cylinder to thumb spine.

If someone can give me a good guess on square tube size and gauge for that thumb, it might save me some FEA simulation work. The cylinder is only 50mm bore, so around 7850 lb. at my tractor's 2500 psi working pressure. Weight is a concern, as this fork frame already weighs a lot, and I'm often fighting for more loader capacity when moving logs.

why not kink the end out at a 45 deg so that a small log would not ride up and if it is a big log the corner would catch it and pin it in?

 

[WinterDeere]

why not kink the end out at a 45 deg so that a small log would not ride up and if it is a big log the corner would catch it and pin it in?

You mean like the reverse of a hook?

 

[Sawyer Rob]

I never remove mine, even though it's fairly easy to do so, and I've picked up some tall pallets ect.. I just fold it in and go pick up whatever needs moved.

Absolutely the most versatile tool I've ever owned, even replaced the dedicated grapple.

SR

 

[DaBear3428]

You mean like the reverse of a hook?

instead of angling it in which increases the ride up effect for small logs if it is angled out for a small segment at the end, the closing thumb will push small logs down but on larger logs the longer straight segment will work as normal and for in between sized logs the corner will act as a point to pin them keeping them from riding up. one of the drawings you posted earlier had exactly the opposite.