Homemade Articulated Mechanical Thumb

[3RRL]

I couldn't help but notice that my thumb folds as neatly as most of the "stationary" thumbs I've seen. So I was pretty happy with that. I took a few more shots of the finished project.
This is from the very front showing all the pivot points welded on.



And one last one from the side.



I hope you enjoyed the project as much as I did. I was very pleased to see it all come together so nicely. When I get my tractor running, I'll show some photos or maybe a video of it picking rocks and other stuff.
Finally, here's a video of the finished "Mechanical Thumb" taken after welding but before it was re-painted. I took some videos of it but they came out too dark, so I'm showing this one instead. You can clearly see how all the articulting linkage works here. Also note the additional holes to vary the acceleration (how fast the jaw closes in relation to the bucket curl) and how wide or narrow the initial gap between the bucket and jaw can be set.



Thank you for looking.
Rob-

 

[tlbuser]

Awesome job!

 

[EddieWalker]

Rob,

Thank you for taking all those pictures and video!!!

You did an amazing job with it and until I saw all together, I wasn't sure how it would work. It's very clever and beautifuly built!!!!!!!!!

Do you have to grease each pivot point? I don't remember you puting zirk fitting on and was curious.

Thanks for sharing,
Eddie

 

[scott_vt]

Mornin Rob,
Very nice, start to finish !!! Im anxiously awaiting a video of the real deal

It almost looks like you used shoulder bolts for your pivot points ? If you did that seems like a smart way to go. Good luck with your new implement !

 

[john_bud]

Rob,

Slicker than deer guts on a door knob!

jb

 

[3RRL]

Rob,

Slicker than deer guts on a door knob!

jb

Golly John, thanks ... I think. It turned out pretty slick indeed.

Scott,
Thanks man, and yes I did use shoulder bolts for the articulating linkage pivots as well. They are Ø3/4" and hardened so they should last. I will take the action video after I get my electrical sorted out. I also have some broken pipe to repair so I'm not sure when I'll have it. But you can bet I'll post as soon as she's running.

Eddie,
Thank you also. No, I did not put zerks in this one because some of the linkage is only 1/2" thick. I thought I could just add some grease by hand every once in a while. I think the hardened washers will hold it in and keep it clean. I noticed the Andy Tatro grapple did not have fitting either so I thought it would be OK in this case too.

tlbuser,
Thanks again. I was hoping it would turn out OK and it did. I sure appreciate all the support you guys gave me throughout the project.

 

[schmism]

done any force calcs?

looks like you could really tweek the linkage when you went to bite something hard.....

 

[3RRL]

done any force calcs?

looks like you could really tweek the linkage when you went to bite something hard.....

Sorry, I didn't do the calcs. I'm too dumb for that.
LOL ... there's probably more ways to break or tweak tractor stuff than there are keeping them perfect.
I used the thickness of the grapples (they are 3/8" thick) for the jaws, which are stabilized with the plates between them. The linkage is heavier at 1/2" x 2" and the one going to the jaw is 1" x 1-1/2" thick. Although these are heavier than my grapples and most of my implements, I still wanted to keep the weight down so as not to reduce the backhoe's power too much. Plus, the linkage is being "pulled" not pushed. But if it does tweak, I'll just fix it like I do my implements when they tweak.

 

[HomeBrew2]

... my tractor isn't running right now ...

Huh

 

[3RRL]

Bro,
Electrical short somewhere ... Most probably between my ears though.