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.

 

[dfkrug]

Looks great, Rob. I see you completely avoided the metric pin
and hole issue by avoiding the use of any of the existing bkt
linkage holes.

Nice OP welds, too. If I could do those, I would not be removing
my dipper sticks to weld on my brackets.

Unfortunately, I could not view your video as I do not have the
Flash 8 s/w. Will your new video use WMV or MPG file formats?

 

[3RRL]

Hi Dave, thanks for the compliments.
Yes, you are right. I made sure to avoid the Metric stuff. Keeping the linkage SAE means easily replacing worn parts. Sorry you could not view the videos. They're out of my Nikon "Coolpix" camera. The movement bears out what you discovered in your wooden model. I'll send you an email and maybe Loretta can convert the files for you to view?

 

[john_bud]

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

I had one of those once too. There was a twig holding the PTO cable just a hair off the stop. The safety switch was activated and the tractor wouldn't start. I didn't diddle with the PTO lever as I could plainly see that it was in the "off" position. (DUH!) Now I know. Have also had issue with "stuff" under the HST peddle keeping it from starting. Double check all levers, peddles, clutch, seat switch etc. Dumb stuff is usually cheaper to fix than broken stuff.

jb

 

[3RRL]

Dave,
I was wondering if you ever got you video of your mechanical thumb uploaded? I'd sure like to see how yours is working.
I'm going up to the property this weekend with my friend gugloils who is going to diagnose the electrical problem. He is flying in from New Mexico just to help me...can you believe that? Hopefully, he will find the problem and fix it. When I get the tractor running, the first thing I'm gonna do will be to test my thumb out. I'll be posting more photos and videos of it at work.
Keep your fingers crossed for me.

 

[tlbuser]

Dave,
He is flying in from New Mexico just to help me...can you believe that? Hopefully, he will find the problem and fix it.
Keep your fingers crossed for me.

WOW ! He must really want to see that thumb work

 

[dfkrug]

Dave,
I was wondering if you ever got you video of your mechanical thumb uploaded? I'd sure like to see how yours is working.
I'm going up to the property this weekend with my friend gugloils who is going to diagnose the electrical problem. He is flying in from New Mexico just to help me...can you believe that? Hopefully, he will find the problem and fix it. When I get the tractor running, the first thing I'm gonna do will be to test my thumb out. I'll be posting more photos and videos of it at work.
Keep your fingers crossed for me.

I can't see uploading it at all, given my limitation to dialup access. If I
put it on YouTube, it would take a while. Verizon has promised DSL for
years, but I am not holding my breath.

As for those electrical gremlins, I notice that mice will nest in any tractor
not stored in a "secure" building. They seem to chew wires just for the
h3ll of it. Rain in the starter switch had been a problem, too. My Kioti
stays indoors and has only one interlock switch, thankfully. My JD is under
a carport (tractorport?) and regularly gets mice and recalcitrant interlock
switch gremlins.

As for my articulated thumb, it has been fantastic. I have been digging
up old pipes and implements for recycling and it has worked flawlessly. I
can see my plowshare thumb tip is harder than my cast steel hoe teeth as
it has made quite an impression in the middle tooth.

 

[3RRL]

As promised, my good friend Larry (guglioLS) fixed my electrical problem in a jiffy so the first thing we did is remove the boxblade and mount the Nardi Backhoe on the tractor. I had told you guys before that the home made subframe was kinda a tight fit, but it usually takes me 10 or 15 minutes to get it on. With Larry helping, it only took about an hour.



He had his side completely pinned and mine wasn't in yet, and there's not enough play in the fits to allow that. So he and I were muscling the backhoe and subframe to get it in and connected. We finally got it on and off we went to test out the mechanical thumb.
Larry had the honors.



I'm hoping for his comments about the performance of the thumb too.
Rob-

 

[3RRL]

Here is a picture of the Kama with Grapples and Mechanical Thumb taken in the field near our food plot.



Just before that, Loretta took a video of how the mechanical thumb worked under power. Here I am checking it out while Larry operates the controls. It is working just as I was hoping it would.
Now to try it out.

 

[3RRL]

The next step was to try it on some real rocks and logs. So again, Larry worked it for the first time ever.
Here he is trying to get used to my backhoe movements, and using the mechanical moving thumb.



Just before that, he also had a chance to try out the dual grapple set up on the massive bucket. This was the first time he had operated the tractor and the backhoe.



Larry owns a beautiful Jinma 354 and has made all kinds of mods and improvements to it. So he is no stranger to hard work. He did comment on how stable the Kama 554 was with loaded tires, and that it has a lot of power, although he did not do any really heavy digging with it.

 

[3RRL]

Then it was time to see if the backhoe could pick up that frozen water laden log.
This is a photo of it.



And here is a video. The log is super heavy and was a bit too much for the Nardi.



As a matter of fact, when it was my turn to try out the backhoe thumb, I tried to get that big log (of course). I managed to test it to failure and tweak the jaws plus a couple of links ... crap!